L Vibert

A Houstin

V Planas-Bielsa

P Blanchard

D Ménard

D Couet

E Schloësing

Y Le Maho

T Blasco

J Fort

N Eckbo

C Le Bohec

N A Warner

C Cornec

D Herzke

Q Schull

S Zahn

N Carrasco

Effects of individual characteristics and environmental conditions on foraging tactics of Adélie penguins »

Résumé en français

Contexte général

L'océan Austral est l'un des écosystèmes les plus productifs de notre planète et héberge les plus importantes communautés d'oiseaux marins. Néanmoins, les écosystèmes polaires montrent une vulnérabilité aux changements globaux bien plus intense que les autres écosystèmes. Le besoin de protection de l'océan Austral est plus que jamais d'actualité compte tenu de l'évolution attendue des changements globaux en l'absence de mise en oeuvre d'une politique environnementale ambitieuse.

Résultant des bouleversements environnementaux tels que l'altération des courants marins et de la circulation atmosphérique, la dégradation de la glace de mer, l'acidification des eaux ou la hausse de leur température, les répercussions attendues sur l'écologie des espèces sont multiples et variées (abondance, distribution, compétition pour l'accès à la nourriture et à l'habitat). Parallèlement, bien que régulés par la Commission pour la conservation de la faune et la flore marines de l'Antarctique (CCAMLR), le développement des activités de pêche et la possibilité d'accéder à de nouveaux espaces libérés par le retrait de la banquise sont des menaces additionnelles bien réelles.

Dans un tel contexte, il est urgent de collecter un maximum d'informations, démographiques, écologiques ou comportementales, sur les espèces constitutives de ces écosystèmes afin de disposer d'un état initial de connaissances avant que notre capacité à désentrelacer les causes des conséquences ne soit altérée.

Puisque toutes les espèces ne peuvent être étudiées, une stratégie pertinente consiste à utiliser des espèces dites « sentinelles » tels que les oiseaux de mer ou les mammifères marins. Ces prédateurs supérieurs sont affectés par la cascade de changements intégrés le long du réseau trophique. L'étude à long terme des variations affectant leurs populations (démographie, distribution, comportements) est ainsi révélatrice des changements plus globaux sous-jacents subis par le système. Néanmoins, à l'heure actuelle, le manque de données sur la dynamique spatiale et temporelle des écosystèmes et l'hétérogénéité des changements, même à des échelles spatiales relativement petites, ajoute une incertitude considérable sur les projections concernant les systèmes biologiques. L'accumulation de connaissances approfondies est donc fondamentale, et est un prérequis nécessaire à la mise en place de mesures de conservation pertinentes et efficaces, comme l'implémentation d'aires marines protégées (AMP) sur des zones identifiées comme des points chauds de biodiversité.

Les prédateurs marins sont difficilement observables en mer. Leur suivi et l'acquisition de données multiples, telles que leur localisation et leur profondeur de plongée à un instant donné, nécessitent l'utilisation d'enregistreurs de données (biologgers) déployés sur les animaux. Ces dispositifs, utilisés dans le cadre de cette thèse, peuvent stocker l'information et requièrent une récupération ou bien une transmission des données à distance par satellite. Chaque technique présente des avantages et des inconvénients, mais les informations recueillies permettent, une fois analysées, d'examiner la distribution et les activités en mer des individus équipés. Il est ainsi possible d'affiner notre compréhension des interactions existant entre une espèce et les différentes composantes (biotiques et abiotiques) de son environnement dans un souci notamment de gestion, de conservation ou d'estimation des potentialités d'adaptation future aux changements globaux.

Ces différentes problématiques, e.g. biologging, distribution et compréhension des activités en mer, enjeux de conservation, sont abordées au cours de cette thèse avec, pour espèce modèle, le manchot empereur (Aptenodytes forsteri).

Cette espèce emblématique de l'Antarctique occupe une position élevée au sein du réseau trophique marin antarctique et se situe à l'avant-garde des impacts du réchauffement climatique. En effet, les projections démographiques récentes estiment que 80% de colonies pourraient avoir disparu d'ici la fin du siècle si les émissions de gaz à effet de serre sont maintenues à leur niveau actuel.

A ce jour, 61 colonies, à la répartition circum-continentale, ont été localisées par satellite, mais peu ont été effectivement visitées et encore moins étudiées. Moins d'une dizaine de colonies ont fait l'objet de suivi en mer d'individus adultes, et seulement quatre pour des juvéniles. La connaissance effective de la distribution en mer de cette espèce est de ce fait extrêmement parcellaire et n'est connue que sur le quart du pourtour continental. Or, les colonies se répartissent sur un gradient latitudinal de 1400 km. Les individus de colonies éloignées sont donc vraisemblablement soumis à des contextes écologiques et des problématiques différents.

Unique prédateur à place centrale se reproduisant au coeur de l'hiver austral, le manchot empereur adulte alterne les allers-retours entre sites de nourrissage en mer et sa colonie tout au long de la période de reproduction et de l'élevage de son unique poussin annuel. L'espèce se caractérise également par une phylopatrie importante, i.e. les individus présentent une fidélité forte à leur site de reproduction et reviennent généralement, année après année, se reproduire au sein de la même colonie. Ces caractéristiques sont idéales pour le déploiement de biologgers puisqu'elles permettent leur récupération si besoin et la mise en place d'un suivi à long terme des individus équipés. Le déploiement d'enregistreurs de données sur ces oiseaux plongeurs permet également la collecte de données environnementales in-situ (température ou conductivité de la colonne d'eau par exemple) dans des zones inaccessibles la majeure partie de l'année (sous la banquise), offrant des informations uniques sur les écosystèmes polaires bien que le défi logistique et technique soit complexe à relever.

L'ensemble de ces critères fait du manchot empereur un modèle biologique de choix pour illustrer l'importance de la collecte de données dans l'océan Austral à des fins de conservation et de suivi à long terme de l'environnement tout en améliorant notre connaissance sur l'espèce et son rôle au sein des réseaux trophiques.

Le manchot empereur est régulièrement utilisé pour sensibiliser le public de par son statut d'espèce endémique et charismatique de l'Antarctique et d'espèce parapluie, i.e. sa vaste aire de répartition entrainerait la protection d'un grand nombre d'espèces si elle était protégée, notamment de ses proies (krill, calandre antarctique et calmar) et des réseaux trophiques inférieurs. Prédateur supérieur jouant un rôle pivot au sein des écosystèmes antarctiques, il reste cependant beaucoup à apprendre sur la répartition et les activités en mer de cette espèce. Pour combler ce manque de connaissances, j'ai co-initié et co-supervisé la mise en place d'un programme de recherche sur la colonie de manchots empereurs de la Baie d'Atka à proximité de la Station de recherche allemande Neumayer III, en bordure de la mer ouest de Weddell. La mer de Weddell abrite le tiers de la population de manchots empereurs, mais leur comportement en mer n'y avait encore jamais été étudié. Signalons que dans ce cadre, cette thèse a initié et contribué à la mise en place depuis 2017 du second observatoire à long terme de l'espèce afin d'évaluer la vulnérabilité des écosystèmes de l'Antarctique. Jusqu'à présent, la quasi-totalité des données démographiques était en effet issue d'une seule colonie répondant à un environnement particulier.

Chapitre 1-Evaluation des outils méthodologiques et nouveaux développements

Guidés par le principe de raffinement du cadre des trois R (Remplacer, Réduire, Raffiner) qui préconise de tester et d'évaluer en permanence les protocoles de recherche afin de minimiser les perturbations de la faune, dans ce premier chapitre nous décrivons et évaluons nos protocoles pour la fixation des biologgers, la capture des animaux et la récupération des dispositifs après le déploiement.

Au cours de deux sessions de terrain de quatre mois (été austraux 2017-2018 et 2018-2019), nous avons capturés/recapturés 70 adultes et 8 juvéniles afin de réaliser le déploiement et la récupération de biologgers (plateformes GPS ou ARGOS, et Time-Depth Recorder (TDR)). Afin de garantir que les données recueillies soient d'une qualité exemplaire d'un point de vue scientifique et éthique, les effets délétères potentiels des procédures de déploiement doivent être évalués et atténués.

Bien que les manchots empereurs soient l'objet d'équipements depuis près de 30 ans, nous avons revus et recapturés, pour la première fois, des manchots empereurs équipés un an auparavant juste après leur mue annuelle. Ces informations nous permettent de démontrer que la technique utilisée en routine pour des déploiements à long terme, qui consiste à coller le biologger directement sur les plumes du dos des manchots, est préjudiciable aux oiseaux. Elle provoque la perte des plumes porteuses et en conséquence des dispositifs déployés. Par conséquent, nous avons mis au point et proposons une méthode alternative d'attache sur le dos qui a conduit à des déploiements réussis. Les biologgers sont restés en place durant plus d'un an, entre les deux périodes de mue des individus équipés. Nous avons également réalisé, pour la première fois chez cette espèce, le déploiement de biologger (TDR) à la patte, au moyen d'un montage en bracelet de notre conception. Ces dispositifs ont parfaitement fonctionné jusqu'à leur récupération après 10 mois de déploiement, et comme chez les autres espèces de manchots pour lesquelles des systèmes analogues sont utilisés, aucun impact majeur de perturbation pour l'animal n'a été mis en évidence. Enfin, nous fournissons des méthodes de capture et de manipulation des manchots empereurs qui induisent un minimum de perturbation et confère un maximum de sécurité et d'efficacité. En particulier, l'utilisation d'un corral permet la capture simultanée de plusieurs individus sur le site même de la colonie. Toutes les procédures ont été documentées et partagées sous forme de vidéos et diaporamas.

Cette étude est la première à fournir des procédures aussi détaillées et éprouvées pour capturer/recapturer et déployer des dispositifs externes de télémétrie sur les manchots empereurs.

Elle est ainsi destinée à servir de ressource de base pour faciliter les futures recherches sur cette espèce sensible. Elle souligne également l'importance de surveiller les impacts potentiels, à court et long terme, des déploiements de biologgers sur les animaux dans leur milieu naturel, et la nécessité de rester critique vis-à-vis des protocoles établis.

Chapitre 2-Evaluation des outils de conservation

Après l'évaluation des outils méthodologiques employés au cours de mes recherches, l'étude de la distribution spatiale de manchots empereurs juvéniles lors de leur première année en mer, est combinée à celle de la littérature existante afin d'estimer si les outils de conservation mis en place à l'échelle de l'océan Austral sont adaptés et pertinents pour garantir la protection des manchots empereurs.

En janvier 2019, nous avons équipé huit oiseaux de 6 mois à leur départ de leur colonie de naissance, en Baie d'Atka, avec des balises ARGOS qui nous transmettaient leur localisation plusieurs fois par jour par satellite. Nous avons enregistré leur voyage au cours de cette première année en mer dans le secteur atlantique de l'océan Austral. Ces informations sont cruciales puisque la colonie de la Baie d'Atka n'est que la cinquième colonie sur les 61 recensées où des juvéniles ont été suivis. Les quatre autres colonies sont situées à plusieurs milliers de kilomètres, et ne couvrent qu'un quart du continent (mer de Ross et Antarctique de l'Est).

L'analyse des données révèle une dispersion des juvéniles sur une étendue bien plus vaste qu'enregistrée dans les autres secteurs étudiés. Leur habitat s'étend jusqu'à 48,5° de latitude Sud, soit plus de 600 km au nord que ce qui avait été observé jusqu'alors. Nous mettons ainsi en évidence que les juvéniles de manchot empereur et de manchot royal (A. patagonicus), deux espèces soeurs d'un point de vue phylogénétique, cohabitent spatialement et temporellement, alors que les adultes de chaque espèce utilisent des niches écologiques bien distinctes, une découverte d'intérêt majeur pour les chercheurs en écologie évolutive.

La méta-analyse des données de suivi en mer des manchots empereurs juvéniles suggère que, au départ de leur colonie de naissance, tous les juvéniles migrent vers le nord jusqu'à atteindre le courant antarctique circumpolaire. Ils y restent au maximum deux mois avant de repartir vers le sud et de passer le reste de leur première année dans le pack (banquise dérivante). Cette vaste amplitude de dispersion les entraine aux limites de l'océan Austral et de la juridiction de la CCAMLR. Un développement des pêcheries est, à terme, fortement envisagé dans ces zones où elles seraient alors en compétition directe pour la ressource avec les manchots empereurs juvéniles, c'est-à-dire un des stades les plus critiques de leur existence en termes de survie. Enfin, nous mettons en lumière que les juvéniles passent la grande majorité de leur première année (89,5% dans notre étude) en dehors des limites des AMP existantes ou en discussion depuis des années à la CCAMLR.

L'adjonction des données issues de la littérature aux données que nous avons collectées offre une vision d'ensemble qui révèle que les efforts de conservation existants et prévus dans l'océan Austral n'assurent pas une protection efficace des manchots empereurs. Nous soulignons également la nécessité de collecter des données de référence pour l'espèce, en particulier en Antarctique occidental, autour de la Péninsule et dans les colonies situées au plus profond de la mer de Weddell, afin d'optimiser et d'évaluer la mise en oeuvre de futures mesures de conservation.

Chapitre 3-Stratégies spatio-temporelles de prospection et de recherche alimentaire

Dans cette optique d'acquisition de données de référence, et dans le cadre des négociations concernant la mise en place d'une AMP en mer de Weddell, nous avons également équipé des manchots empereurs adultes sur la colonie de la Baie d'Atka. Au cours de deux étés, 36 individus ont été équipés de GPS-TDR en fin de période de nourrissage du poussin. Ces déploiements d'une durée de 16±6 jours ont permis un enregistrement de 1 à 3 trajets en mer selon les individus. Nous avons aussi déployé 8 balises ARGOS après la mue annuelle des adultes en janvier 2018. Elles ont fonctionné plusieurs mois (150±30 jours) jusqu'au début de l'hiver austral. Ces 8 individus portaient également chacun un TDR à la patte, dont quatre ont été récupérés après un an.

En associant les positions des individus à leur profondeur de plongées, nous sommes ainsi capables d'interpréter a posteriori leur comportement au cours de la période de déploiement afin de déterminer leurs stratégies spatio-temporelles de prospection et de recherche alimentaire.

Parallèlement, les conditions environnementales rencontrées par les individus ont été extraites des bases de données satellitaires accessibles en ligne. Nous avons alors examiné l'influence des conditions environnementales et de l'habitat (concentration en glace, distance au bord de la banquise, distance aux différents fronts, bathymétrie et pente des fonds marins) sur la distribution spatiale dans le temps des individus et sur leur comportement de plongée. Nous avons, de plus, combiné ces informations à celles d'une étude similaire réalisée au début des années 2000 sur la colonie de Pointe Géologie en Terre-Adélie1 .

Quel que soit le site d'étude, la distribution en mer des individus au fil d'une année dépend du sexe, de la concentration en glace, de la saison et de la distance à la colonie. Au cours de la période d'élevage du poussin, les adultes reproducteurs sont contraints de rester dans un rayon de 104±74 km autour de la colonie occupant un domaine vital de 26728 km². Une fois la reproduction terminée, les adultes exploitent de nouvelles zones triplant la taille de leur zone de prospection (92990 km²) alors que la zone exploitée par les juvéniles couvre 2,6 millions de km².

Les analyses préliminaires comparatives des comportements de plongée révèlent cependant des différences entre sites à des périodes spécifiques de l'année. Nous montrons que la répartition journalière des plongées est différente entre les deux sites au cours de l'été austral (novembre et décembre). Les individus équipés en Baie d'Atka présentent deux pics de plongées au cours de la journée. L'un se produit en milieu de « nuit » (bien que ce soit le jour polaire à ces latitudes) et le second à la mi-journée. Ils sont entrecoupés de périodes de moindre activité. A contrario, les plongées des individus équipés à Pointe Géologie présentent une distribution en cloche avec un maxima en milieu de journée et une faible activité de nuit. Les individus équipés de balises ARGOS en Baie d'Atka présentent cette répartition tout au long de l'année jusqu'au début de l'été austral. Un changement du comportement de plongée est alors observé et devient similaire à celui des individus équipés de GPS-TDR présentant deux pics d'activité journaliers.

Bien que préliminaires, ces analyses suggèrent un changement d'alimentation au cours de l'été austral pour les individus se reproduisant en Baie d'Atka. Les changements environnementaux (diminution de l'épaisseur et retrait de la banquise, allongement de la durée du jour) induisent potentiellement un changement dans l'abondance, la distribution nycthémérale et le type de proies disponibles dans ce secteur, entrainant un changement dans les stratégies d'approvisionnement des manchots.

Conclusion

Une connaissance plus approfondie de la niche écologique du manchot empereur est essentielle pour estimer les changements induits par les bouleversements environnementaux attendus au cours du siècle. La collecte de ces informations en mer nécessite l'équipement de quelques individus répartis sur différentes colonies afin de couvrir l'ensemble des conditions environnementales susceptibles d'être rencontrées par l'espèce à l'échelle de la population globale. Afin d'obtenir les données les plus représentatives possibles du comportement de la population, il est cependant nécessaire de disposer

Table of contents

List of figures

List of tables

32

I.1 Conservation biology

In the current context of global change (IPCC 2014(IPCC , 2019) ) and mass extinction [START_REF] Barnosky | Has the Earth's sixth mass extinction already arrived?[END_REF][START_REF] Ceballos | Accelerated modern human-induced species losses: Entering the sixth mass extinction[END_REF], conservation biology stands at the forefront. Conservation biology was formally conceptualised over the 1980s as a new field focused on understanding (description, explanation, and appreciation), protecting, and perpetuating biological diversity at all scales and all levels of biological organisation (Soulé 1985, Meffe and[START_REF] Meffe | Principles of Conservation Biology[END_REF].

This multidisciplinary science (Fig. 1), which applies the principles of ecology, biogeography, population genetics, anthropology, economics, sociology, to the maintenance of biological diversity throughout the planet [START_REF] Barbault | Écologie générale -6ème édition -Structure et fonctionnement de la biosphère[END_REF], can be represented as a pyramidal structure (Fig. 2). The base consists of documenting the extent of biodiversity, i.e. accumulate information (baseline data, for instance).

Above the base is the "knowledge" level, which is the understanding of the nature, causes, and consequences of processes and dependencies between individuals, species, and ecosystems. In other words, through the first two blocks of the pyramid, abiotic and biotic influences, including human impacts, on the functioning of the different ecosystems are assessed. Finally, at the top of the pyramid is the policy level. All the information and the knowledge gathered are compiled to develop practical methods to prevent species extinctions, and to allow for persistence of ecosystem processes and/or services [START_REF] Hunter | Fundamentals of Conservation Biology[END_REF]Gibbs 2006, Van Dyke 2008). -WCMC et al. 2018). However, doubts subsist on the real implementation and enforcement of the protection for many of them [START_REF] Rife | When good intentions are not enough … Insights on networks of "paper park" marine protected areas[END_REF][START_REF] Pieraccini | Beyond marine paper parks? Regulation theory to assess and address environmental non-compliance[END_REF][START_REF] Smith | MPAs in ABNJ: lessons from two high seas regimes[END_REF][START_REF] Riggio | How effective are the protected areas of East Africa?[END_REF], jeopardising the planet's life support systems [START_REF] Cbd | Updated Assessment of Progress Towards Selected Aichi Biodiversity Targets and Options To Accelerate Progress[END_REF].

In this context and more than ever before, our ability to understand how living organisms, amongst which top predators, will be coping with these environmental changes depends on the development of appropriate ecosystem and biodiversity management measures [START_REF] Caro | Behavioral Ecology and Conservation Biology[END_REF].

My PhD project falls within the framework of conservation biology, from the bottom (high-quality baseline data acquisition) to the top of the pyramid (evaluation of existing and planned conservation measures) through the middle part (understanding foraging strategies in relation to environmental drivers) at the scale of the polar and subpolar ecosystems.

I.2 The Southern Ocean

I.2.1. Oceanography and geography

The Southern Ocean (SO) is the vast water mass encircling the Antarctic continent. Debates still occur on its extent and delineation. The most commonly accepted definition, not recognised by all countries, fixes its northern limit at 60°S (International Hydrographic Organisation (IHO 2002), but its functional definition is usually extended at least to the Antarctic Polar Front, around 55°S [START_REF] Moore | Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data[END_REF][START_REF] Gersonde | Sea-surface temperature and sea ice distribution of the Southern Ocean at the EPILOG Last Glacial Maximum -A circum-Antarctic view based on siliceous microfossil records[END_REF]. Other limits have also been considered like the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) boundaries (Brooks et al. 2020a) or south of the 40°S [START_REF] Hindell | Tracking of marine predators to protect Southern Ocean ecosystems[END_REF].

One of the main oceanographic features in the Southern Ocean is the Antarctic Circumpolar Current (ACC), the largest ocean current, flowing clockwise (from west to east) far offshore (between 40°S and 65°S), and connecting the Atlantic, Indian and Pacific Oceans (Fig. 3; [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF]. The Southern Ocean consists of vast masses of water with different physical and chemical properties (e.g.

temperature, salinity, density). The areas where different masses meet are called "fronts". They are narrow areas having a sharp horizontal gradient of water properties (e.g. salinity, temperature; see [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF][START_REF] Sokolov | Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 1. Mean circumpolar paths[END_REF][START_REF] Talley | Descriptive Physical Oceanography[END_REF][START_REF] Kim | On the Variability of Antarctic Circumpolar Current Fronts Inferred from 1992-2011 Altimetry[END_REF]. The fronts are used as boundaries to divide the Southern Ocean in 'zones'. The fronts and zones they delineate as well as the typical meridional (north-south) circulation and water masses are summarized schematically in Fig. 4 from [START_REF] Talley | Descriptive Physical Oceanography[END_REF].

The Northern limit of the Antarctic Circumpolar Current is the non-circumpolar Subtropical Front. The ACC counts three major fronts (Fig. 3). The Sub-Antarctic Front sets the northern boundary of the circumpolar Southern Ocean. Then, comes the Polar Front (PF) characterised by an isothermal temperature of 2°C at a depth of 200 metres. Finally, the most southerly front is the Southern Antarctic Circumpolar Current Front (Fig. 3; [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF][START_REF] Talley | Descriptive Physical Oceanography[END_REF]. A fourth feature, the Southern Boundary of the Antarctic Circumpolar Current (SBACC), which marks the southern limit of the circumpolar flow (Orsi et al. 1995, Sokolov and[START_REF] Sokolov | Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 1. Mean circumpolar paths[END_REF], is defined as the southern edge of the low oxygen layer of the Upper Circumpolar Deep Water. The SBACC is not a dynamical front and is sometimes merged with the Southern Antarctic Circumpolar Current Front [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF][START_REF] Talley | Descriptive Physical Oceanography[END_REF]. The Southern Boundary separates the Antarctic Circumpolar Current from the subpolar region (Fig. 4). The fronts are important areas of nutrient mixing and act as latitudinal ecological boundaries for numerous marine species distribution [START_REF] Sokolov | Multiple jets of the antarctic circumpolar current South of Australia[END_REF]. South of the ACC and close to the Antarctic continent, the inshore Antarctic Coastal Current or Antarctic Slope Front (ASF) circulates from east to west and separates very dense cold and fresh shelf water from warmer and saltier water offshore [START_REF] Talley | Descriptive Physical Oceanography[END_REF][START_REF] Stark | Antarctic Seas[END_REF]. Both currents (i.e. ACC and ASF), influenced by the winddriven Ekman transport, form the Ross and Weddell Sea gyres [START_REF] Nicol | Krill, Currents, and Sea Ice: Euphausia superba and Its Changing Environment[END_REF], two productive areas due to the upwelling of cold, nutrient-rich water in their centre [START_REF] Stark | Antarctic Seas[END_REF]. The Southern Ocean is also one of the major thermal exchange points between the oceans, the atmosphere and the cryosphere, and a central contributor in the thermohaline circulation [START_REF] Stark | Antarctic Seas[END_REF]. As the Antarctic circumpolar surface waters cool, they become denser and plunge beneath warmer, saltier sub-Antarctic waters forming the Antarctic Bottom Waters (Deacon 1937, Freeman and[START_REF] Freeman | Mapping the Antarctic Polar Front: weekly realizations from 2002 to 2014[END_REF] that spread northwards into the abyss of the three ocean basins. Hence, at the Polar Front, the warm and deep saline waters flowing southward from other oceans upwell and are transported around Antarctica by the ACC [START_REF] Schmitz | On the interbasin-scale thermohaline circulation[END_REF][START_REF] Stark | Antarctic Seas[END_REF]) making the PF a very productive area, concentrating up to 20% of the world's marine productivity [START_REF] Laubscher | Phytoplankton production and biomass at frontal zones in the Atlantic sector of the Southern Ocean[END_REF][START_REF] Bathmann | Spring development of phytoplankton biomass and composition in major water masses of the Atlantic sector of the Southern Ocean[END_REF][START_REF] Carr | A comparison of global estimates of marine primary production from ocean color[END_REF]).

I.2.2. Sea ice I.2.2.1. Sea ice physical characteristics

Sea ice is a substrate, which, after initial freezing of seawater, is profoundly modified by interactions between physical, biological, and chemical processes [START_REF] Dieckmann | The importance of sea ice: an overview[END_REF]. Sea ice undergoes a significant yearly cycling in surface extent around Antarctica, being maximal in September and minimal in February (Fig. 3; Parkinson 2014). Sea ice is broadly classified as marginal ice zone (MIZ), pack ice, or fast ice. Fast ice is a stationary and consolidated substrate that forms in sheltered and coastal locations where it is anchored to the coastline, icebergs, glaciers and shelves and remains several years [START_REF] Massom | Fast ice distribution in Adélie Land, East Antarctica: Interannual variability and implications for emperor penguins Aptenodytes forsteri[END_REF][START_REF] Stark | Antarctic Seas[END_REF]. Pack ice is mobile, in the form of ice floes usually up to 2 m thick that are transported by wind and currents [START_REF] Stark | Antarctic Seas[END_REF]. It forms offshore and melts every year. MIZ is the area in between the pack ice and the open water, corresponding basically to loose pack ice floes (Massom andStammerjohn 2010, Stroeve et al. 2016).

Through its extent, structure and seasonality, sea ice plays a critical and highly dynamic role in the global climate system (e.g. albedo effect, physical barrier to gases, heat fluxes) as well as on the ecology of the Southern Ocean ecosystem [START_REF] Massom | Antarctic sea ice change and variability -Physical and ecological implications[END_REF].

I.2.2.2. Sea ice community

Sea ice is a major component of the biogeochemical cycles of the Southern Ocean and of the structure and dynamics of Antarctic marine ecosystems [START_REF] Massom | Antarctic sea ice change and variability -Physical and ecological implications[END_REF]. It provides food, in forms of nutrients trapped when the water froze, and habitat for various groups of organisms including bacteria, algae, fungi, and invertebrates. Sea ice retreat and melting in summer releases all the trapped nutrients and induce considerable phytoplankton blooms [START_REF] Massom | Antarctic sea ice change and variability -Physical and ecological implications[END_REF], Arrigo et al. 2014[START_REF] Stark | Antarctic Seas[END_REF]. Additionally, during winter, the sea ice and the bottom of the sea ice is colonised by algae where they can be up to three times more abundant than in the water column [START_REF] Smith | AR4 Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change[END_REF]). These algae, as the phytoplankton bloom induced in summer, is an important source of nutrition for diverse crustaceans and in particular euphausiids (e.g. Antarctic krill, (Euphausia superba)) and small fishes [START_REF] Arrigo | Sea ice algal biomass and physiology in the Amundsen Sea, Antarctica[END_REF]. In turn, these species represent a source of food for top predators and/or the prey they rely on (Fig. 5; Ainley et al. 2010). Sea ice plays also a direct role for several top predators. The two Antarctic penguin species (emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliae) penguins) as well as seal species (Ross (Ommatophoca rossii), crabeater (Lobodon carcinophaga), leopard (Hydrurga leptonyx) and Weddell (Leptonychotes weddellii) seals) are ice-obligate and associated with sea-ice year-round. Only emperor penguins and Weddell seals inhabits the fast-ice during the austral winter [START_REF] Ainley | Decadal-scale changes in the climate and biota of the Pacific sector of the Southern Ocean, 1950s to the 1990s[END_REF].

I.2.3. Threats

Polar ecosystems are substantially more vulnerable than other ecosystems and expected to experience many climate change effects within this century including ocean acidification, changes to currents and winds as well as rising temperatures and sea ice degradation [START_REF] Constable | Climate change and Southern Ocean ecosystems I: How changes in physical habitats directly affect marine biota[END_REF][START_REF] Stark | Antarctic Seas[END_REF]).

These modifications are expected to lead to multispecies effects (top-down or bottom-up), including changes to prey abundance and availability, desynchronization of trophic levels, range shifts, and thus increased competition for food and habitat [START_REF] Rintoul | Choosing the future of Antarctica[END_REF][START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF]). Measurable negative effects on wildlife have already been recorded as highlighted by the loss of an emperor penguin colony close to the West Antarctic Peninsula due to rise in local mean annual air temperature and coincident decline in seasonal sea ice duration around this colony [START_REF] Trathan | First Recorded Loss of an Emperor Penguin Colony in the Recent Period of Antarctic Regional Warming: Implications for Other Colonies[END_REF]). Climate change is also expected to result in human access to new fishing areas [START_REF] Rintoul | Choosing the future of Antarctica[END_REF][START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF], where fisheries would compete for food and habitat with marine predators, not mentioning the possibility of top predators to be part of the by-catch [START_REF] Anderson | Global seabird bycatch in longline fisheries[END_REF] or the risk of oil pollution (Culik et al. 1991[START_REF] Trathan | Pollution, habitat loss, fishing, and climate change as critical threats to penguins[END_REF], Ropert-Coudert et al. 2019). Additional pressures are also likely to come into action. Tourism in Antarctica is increasing and is likely to disturb breeding animal populations (Fig. 20; see [START_REF] Tin | Setting the Scene: Human Activities, Environmental Impacts and Governance Arrangements in Antarctica[END_REF][START_REF] Schillat | Tourism in Antarctica[END_REF], Ropert-Coudert et al. 2019), while the spreading of new pathogens or diseases as well as of invasive species is an increasing concern [START_REF] Gardner | Poultry virus infection in Antarctic penguins[END_REF][START_REF] Grimaldi | Infectious diseases of Antarctic penguins: current status and future threats[END_REF], IPCC 2019, Ropert-Coudert et al. 2019[START_REF] Hughes | Invasive non-native species likely to threaten biodiversity and ecosystems in the Antarctic Peninsula region[END_REF].

The establishment of invasive species, both fauna and flora, on land and at sea, has even already been recorded [START_REF] Olech | The first appearance and establishment of an alien vascular plant in natural habitats on the forefield of a retreating glacier in Antarctica[END_REF][START_REF] Potocka | Trichocera maculipennis (Diptera)-an invasive species in Maritime Antarctica[END_REF][START_REF] Cárdenas | First mussel settlement observed in Antarctica reveals the potential for future invasions[END_REF]. For example, in 2004, an outbreak of avian cholera that killed 2,500 to 3,000 chinstrap penguins (Pygoscelis antarctica) at Cooper Bay, South Georgia, was attributed to human visitation [START_REF] Ropert-Coudert | Happy feet in a hostile world? The future of penguins depends on proactive management of current and expected threats[END_REF], while invasive mice are attacking adult and chick seabirds in sub-Antarctic islands causing population declines [START_REF] Dilley | The effects of introduced mice on seabirds breeding at sub-Antarctic Islands[END_REF][START_REF] Jones | First evidence of mouse attacks on adult albatrosses and petrels breeding on sub-Antarctic Marion and Gough Islands[END_REF]. Scientific activities and the establishment of scientific stations for geopolitical purposes have also greatly expanded over the last few decades.

Such developments require and induce the transportation of more people and the development of facilities. For example, to increase its capacity, the Australian Antarctic Division is planning to build, near the Australian Davis research station, the first concrete airport in Antarctica2 . Wilson's storm petrels (Oceanites oceanicus) that nest at the site will be displaced while native lichens, fungi and algae will be destroyed. Additionally, Weddell seals breed within 500 metres of the proposed runway site that also counts numerous adjacent lakes3 . Finally, the accumulation of plastics/microplastics and other contaminants (e.g. heavy metal like mercury, pesticides, persistent organic pollutants) in Antarctic species and their potential long-term effects on individuals and populations has become a major concern (see Annex D4 and [START_REF] Blévin | Wide Range of Mercury Contamination in Chicks of Southern Ocean Seabirds[END_REF], Ropert-Coudert et al. 2019).

This accumulation of anthropogenic pressures on top of global warming (Fig. 6) on the fragile ecosystems of the Southern Ocean is likely to adversely impact their resilience and ability to withstand climate change [START_REF] Stark | Antarctic Seas[END_REF][START_REF] Wauchope | A snapshot of biodiversity protection in Antarctica[END_REF], Brooks et al. 2020a). In this context and despite its remoteness and pristine appearance, the urgency of the threats to the Southern Ocean and the need for protection is critical now more than ever before (Chown andBrooks 2019, Brooks et al. 2020a) and stands as a major challenge for the governing and management bodies of this ocean. The CCAMLR can then be considered as the ocean complement to the Treaty [START_REF] Brooks | Competing values on the Antarctic high seas: CCAMLR and the challenge of marine-protected areas[END_REF]. In order to have a relevant ecosystem-based approach, the administrative boundaries of the CCAMLR aim to correspond to the ecological boundaries of the Southern Ocean: therefore, the CCAMLR jurisdiction limits are roughly aligned with the Polar Front (Fig. 10). The CCAMLR is in fact the ATS body responsible for the management of the fisheries, through quota allocations and gear limitations, and for the set up and implementation of conservation measures yearly reviewed and updated within its jurisdiction 8 . However, the adoption of any measure needs a consensus between members that have different economic and political aims, which can sometimes take years of negotiations [START_REF] Sylvester | Protecting Antarctica through Co-production of actionable science: Lessons from the CCAMLR marine protected area process[END_REF].

7 An acceding State is a Contracting Party bound by the provisions of the CAMLR Convention but is not a CCAMLR Member. Acceding States do not contribute financially to the organisation, participate in decision-making and are not permitted to fish in the CCAMLR Area.

8 See https://www.ccamlr.org/

Although the Statutes of the CCAMLR distinguish it from a simple Regional Fisheries Management Organisations (RFMO), CCAMLR's main focus is on fisheries management, and most of the conservation measures adopted by the CCAMLR are fisheries management related [START_REF] Nicoll | Correct application of the IUCN protected area management categories to the CCAMLR Convention Area[END_REF]. Currently, four commercial fisheries occur within the CCAMLR boundaries: fisheries for Antarctic krill (Euphausia superba), mackerel icefish (Champsocephalus gunnari), Patagonian and Antarctic toothfish (Dissostichus eleginoides and D. mawsoni). They are under the regulation of the CCAMLR and must comply with the regulatory framework enforced. Conservation measures can be divided in two mains parts: the compliance and fisheries regulation, and the protected areas.

(i) Compliance and fisheries regulation overview

The CCAMLR area is divided in domains and units management zones where quotas are allocated by units and species every year. The aim is to minimise the impact harvesting activities may have on the sustainability of target species. To avoid competition and mitigate by-catch of top predators, a spatiotemporal regulation is applied in accordance with top-predator species' biology to limit their disturbance during the breeding period. Additionally, to limit by-catch, for several species, by-catch Total Allowable Catches (TACs) are fixed. If this by-catch TAC is reached, then the fishery has to move in another area or to stop even though the TACs for fishable species have not been reached [START_REF] Schiffman | CCAMLR Fisheries: Challenges to Effective Conservation and Management[END_REF]. Other regulations apply to the type and size of gear to use (e.g. weighted lines, bird exclusion devices, night setting), notably to preserve the benthic ecosystem and to reduce mammal and seabird (mainly albatrosses and petrels; [START_REF] Kock | Understanding CCAMLR's Approach to Management[END_REF] mortality and injury during longline and trawl fishing.

To fight against illegal, unreported and unregulated fishing (IUU fishing), estimated in the 90's to be six times more important than legal fishing inside the CCAMLR area 9 [START_REF] Stark | Antarctic Seas[END_REF], and thus exceeding sustainable limits, the CCAMLR adopted a set of measures. The CCAMLR implements a Vessel Monitoring System (VMS), i.e. each vessel is equipped with an automatic location communicator (ALC) to transmit its position and must report fine-scale catch data. Vessels can be inspected at sea or at port. Additionally, the CCAMLR introduced in 2000 a Catch Documentation Scheme (CDS) for toothfish (the most valuable fishery, see Fig. 9). This document makes it possible to trace the origin and the trade cycle of catches in order to prohibit the trade of non-verified catch. As a result, IUU fishing has significantly reduced (Agnew et al. 2009, Chown and[START_REF] Chown | The State and Future of Antarctic Environments in a Global Context[END_REF]) but still remains a concern (CCAMLR website) since the CCAMLR does not impose any legal obligations against non-party states [START_REF] Bender | A state of necessity: IUU fishing in the CCAMLR zone[END_REF]. However, the CCAMLR is more than a RFMO since its mandate goes beyond the simple management of fisheries and includes the notion of conservation and sustainable management of deep-sea species. (ii) Towards a representative system of marine protected areas in the Southern Ocean

The establishment of marine protected areas (MPAs) is another approach to efficiently safeguard the marine biodiversity [START_REF] Sciberras | Evaluating the biological effectiveness of fully and partially protected marine areas[END_REF][START_REF] Speed | Evidence for rapid recovery of shark populations within a coral reef marine protected area[END_REF][START_REF] Laffoley | Marine Protected Areas[END_REF]. According to the International Union for Conservation of Nature (IUCN), a protected area is a "clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values"

(WCPA/IUCN 2013). This description encompasses MPAs. They aim to conserve biodiversity by mitigating ocean threats, to preserve and to restore ecosystems, and to regulate fisheries in order to ensure sustainable use of the resources. Six different categories of MPAs exist depending on the management and governance type, from a strict "no-take" policy to a sustainable use of natural resources (WCPA/IUCN 2013). Herein, we consider MPAs in its broad meaning of being a marine area that provides protection for all or part of the natural resources it contains (CCAMLR website).

Noteworthy, the definition of the CCAMLR is slightly different than from the IUCN and does not include the "long-term" notion (CCAMLR 1980). Thus, the CCAMLR area as a whole cannot be considered as a MPA [START_REF] Nicoll | Correct application of the IUCN protected area management categories to the CCAMLR Convention Area[END_REF] 10 See also https://www.ccamlr.org/en/science/marine-protected-areas-mpas

These areas are managed in compliance with the CCAMLR legislation (CCAMLR 1980). As a result, currently, 12% of the waters inside the CCAMLR boundaries are protected but they are not representative of the full range of ecosystems existing in the Southern Ocean (Fig. 10; Brooks et al. 2020a). In the coming years, three new MPAs adjacent to the continent might be established (Table 1).

If the current proposals were adopted, then 22% of the CCAMLR waters would be under protection (Fig. 10; Brooks et al. 2020a). The marine environment, which covers 71% of the Earth surface, is highly dynamic and heterogeneous.

As such, monitoring its change over time and 3-dimensional space represents a tremendous challenge.

In order to overcome this challenge, a strategy is to use so-called "sentinel" species such as seabirds or marine mammals [START_REF] Durant | Pros and cons of using seabirds as ecological indicators[END_REF], Le Bohec et al. 2013, Hazen et al. 2019). Those species are often far ranging and stand near the top of the trophic networks [START_REF] Burger | Bioindicators: A Review of Their Use in the Environmental Literature 1970-2005[END_REF], Hazen et al. 2019), which are relatively short in the Southern Ocean [START_REF] Smith | Marine Ecosystem Sensitivity to Climate Change[END_REF]. They are also easier to monitor than lower trophic level organisms and integrate information from the bottom to the top of the trophic networks (bottom-up control) over multiple spatiotemporal scales [START_REF] Croxall | Environmental change and Antarctic seabird populations[END_REF], Frederiksen et al. 2007).

In other words, they are subject to variations in the structure of trophic networks, which are themselves subject to environmental changes.

Most of the apex predators are long-lived species, thus long-term monitoring of the variations affecting their populations (e.g. demographic, distribution, behaviour) is indicative of the more global underlying changes in the system [START_REF] Durant | Pros and cons of using seabirds as ecological indicators[END_REF], Hazen et al. 2019). This characteristic makes them also suitable for studying whether the effects of climate change can be mitigated by phenotypic plasticity (e.g. morphological, physiological, behavioural traits) and microevolutionary changes (Le [START_REF] Bohec | Polar Monitoring: Seabirds as Sentinels of Marine Ecosystems, in "Adaptation and Evolution in Marine Environments[END_REF]. These reasons explain why several species of penguins, such as the Emperor penguin or pinnipeds, such as the southern elephant seal (Mirounga leonine), are therefore the focus of long-term monitoring programs.

As a result, marine predators have been recognised as a crucial component of spatial and ecosystembased management, such as MPA design and systematic conservation planning [START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF].

Their protection would encompass a wide range of habitats and would be beneficial to many ecological structures and species ("umbrella" species concept11 ; [START_REF] Roberge | Usefulness of the Umbrella Species Concept as a Conservation Tool[END_REF].

Nevertheless, due to the remoteness and harsh environmental conditions of the Polar Regions, which imply technical and logistical constraints for data collection, their physical environment and ecosystems are still under-sampled [START_REF] Fedak | The impact of animal platforms on polar ocean observation[END_REF]. However, baseline data on species distribution, demography and ecology, as well as their environmental main drivers, are crucial to set up an efficient monitoring of climate change impacts on these ecosystems [START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF], Trathan et al. 2018), and a necessary prerequisite for the establishment of relevant and effective conservation measures in the Southern Ocean [START_REF] Ropert-Coudert | The retrospective analysis of Antarctic tracking data project[END_REF]). The study of the distribution and demography of marine predators is thus of primary interest to fill part of these gaps [START_REF] Hindell | Tracking of marine predators to protect Southern Ocean ecosystems[END_REF].

Marine top predators are long-lived species, iteroparous (i.e. breed several times during life), with a low fecundity per reproductive episode and a late sexual maturity, but they present a very high parental investment [START_REF] Stearns | Life-history tactics: a review of the ideas[END_REF], 1992, Le Bohec et al. 2013). Therefore, from an evolutionary perspective, they correspond to the organisms that are expressing the K-selection strategy (MacArthur and Wilson 1967) of the so-called r-K gradient [START_REF] Pianka | On r-and K-Selection[END_REF], and the survival of adults primes over the one of their offspring. Their life-history traits make them particularly sensitive to the rapidity of current environmental changes [START_REF] Burrows | The pace of shifting climate in marine and terrestrial ecosystems[END_REF][START_REF] Mahlstein | Pace of shifts in climate regions increases with global temperature[END_REF][START_REF] Poloczanska | Global imprint of climate change on marine life[END_REF].

Indeed, their long generation time (e.g. 16 years for the emperor penguin [START_REF] Jenouvrier | Projected continent-wide declines of the emperor penguin under climate change[END_REF]) but see review for penguins in [START_REF] Forcada | Penguin responses to climate change in the Southern Ocean[END_REF]) makes evolutionary adaptability unlikely (Forcada andTrathan 2009, Cristofari 2016). This mismatch between the time they would require to adapt and the velocity of the changes is seriously threatening their future [START_REF] Trathan | Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability[END_REF], Jenouvrier et al. 2019[START_REF] Tulloch | Future recovery of baleen whales is imperiled by climate change[END_REF][START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF]) even though populations of the same species disseminated around Antarctica may not respond uniformly due to regional differences in changes to the physical environment [START_REF] Constable | Climate change and Southern Ocean ecosystems I: How changes in physical habitats directly affect marine biota[END_REF], Jenouvrier et al. 2019).

I.3.2. General use of biologging

Marine predators are challenging to observe at sea [START_REF] Hooker | Bio-logging science: Logging and relaying physical and biological data using animalattached tags[END_REF]). As a result, electronic devices called biologgers -are deployed on animals to measure a variety of parameters using sensors [START_REF] Kays | Terrestrial animal tracking as an eye on life and planet[END_REF][START_REF] Hays | Key Questions in Marine Megafauna Movement Ecology[END_REF]). This approach is referred as Biologging: the "use of miniaturised animalequipped tags for logging and/or relaying data about an animal's movements, behaviour, physiology and/or environment" [START_REF] Rutz | New frontiers in biologging science[END_REF]. Since its beginning in the 1940s [START_REF] Scholander | Experimental Investigations on the Respiratory Function in Diving Mammals and Birds. I kommisjon hos Jacob Dybwad[END_REF], the collection of telemetry data has been steadily expanding (Fig. 11;[START_REF] Mcintyre | Trends in tagging of marine mammals: a review of marine mammal biologging studies[END_REF][START_REF] Forin-Wiart | Why implantation of bio-loggers may improve our understanding of how animals cope within their natural environment[END_REF]. This technique benefits from technological advances (e.g. miniaturisation, design optimisation, storage capacity, power consumption) that permit to collect an increasing amount of varied data at finer spatial and temporal scales (Ropert-Coudert et al. 2009b[START_REF] Bograd | Biologging technologies: new tools for conservation[END_REF][START_REF] Wilmers | The golden age of bio-logging: how animal-borne sensors are advancing the frontiers of ecology[END_REF]. Biologgers can record data related to physiological (e.g. heart rate, blood flow, stomach-pH) or behavioural (e.g. movement, speed, acceleration) parameters as well as environmental data (e.g.

pressure, temperature, salinity, light, sound, imagery), (see references in [START_REF] Cooke | Biotelemetry: A mechanistic approach to ecology[END_REF], Ropert-Coudert et al. 2009a[START_REF] Hussey | Aquatic animal telemetry: A panoramic window into the underwater world[END_REF][START_REF] Börger | Biologging Special Feature[END_REF]. These data enable scientists to assess the relationships between marine organisms and their environment from a new perspective. For instance, in the marine environment, Time-Depth Recorders (TDRs) are used to track diving behaviour with the timeframe of a second, and to gain insight into foraging tactics of seabirds and pinnipeds [START_REF] Bost | Changes in dive profiles as an indicator of feeding success in king and Adélie penguins[END_REF][START_REF] Pichegru | Diving patterns of female macaroni penguins breeding on Marion Island, South Africa[END_REF][START_REF] Vacquié-Garcia | Predicting prey capture rates of southern elephant seals from track and dive parameters[END_REF]; see Chapter V). The combination of magnetometers and accelerometers recording data at frequencies of several tens of Hz makes it possible to reconstruct the movements of individuals underwater in 3-D [START_REF] Wilson | All at sea with animal tracks; methodological and analytical solutions for the resolution of movement[END_REF][START_REF] Shiomi | Distribution of emperor penguins ' dive directions under the fast sea ice[END_REF]. More broadly, biologging provided new insights in a lot of domains: in the spatiotemporal distribution of species [START_REF] Block | Tracking apex marine predator movements in a dynamic ocean[END_REF], Hindell et al. 2020) and their habitat use [START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF], Evans et al. 2019), in the allocation of time-budget [START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF][START_REF] Jeanniard-Du-Dot | Accelerometers can measure total and activity-specific energy expenditures in free-ranging marine mammals only if linked to timeactivity budgets[END_REF]) and the construction of energy landscapes [START_REF] Shepard | Derivation of body motion via appropriate smoothing of acceleration data[END_REF][START_REF] Wilson | Technological innovation in archival tags used in seabird research[END_REF], in the understanding of various physiological parameters (see review in [START_REF] Ponganis | Bio-logging of physiological parameters in higher marine vertebrates[END_REF]) and the ontogeny of some behaviours, in the understanding of movement tactics and foraging strategies [START_REF] Pütz | Foraging strategy of king penguins during summer at the Crozet islands[END_REF], Heerah et al. 2014), and also in oceanography by sampling remote and inaccessible areas of the oceans [START_REF] Boyd | Can marine mammals be used to monitor oceanographic conditions?[END_REF][START_REF] Fedak | The impact of animal platforms on polar ocean observation[END_REF].

I.3.3. Biologging as a tool for conservation

In addition to providing critical fundamental information on the movements and behaviours of a variety of species over a long period of time, biologging data are a suitable tool for conservation [START_REF] Bograd | Biologging technologies: new tools for conservation[END_REF][START_REF] Heylen | Bio-telemetry as an Essential Tool in Movement Ecology and Marine Conservation[END_REF], Hays et al. 2019). For instance, the utilisation distributions, i.e. the probability of space use [START_REF] Fieberg | Quantifying homerange overlap: the importance of the utilization distribution[END_REF] derived from the tracks, permit to assess the spatiotemporal distribution of marine predators and, consequently, to highlight overlap with threats [START_REF] Pichegru | Overlap between vulnerable top predators and fisheries in the benguela upwelling system: Implications for marine protected areas[END_REF][START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF][START_REF] Oppel | Spatial scales of marine conservation management for breeding seabirds[END_REF]. Alternatively, areas where predators concentrate are indicators of abundant presence of lower trophic level communities and thus are areas of high ecological importance, known as "hotspot of biodiversity" [START_REF] Myers | Threatened biotas:hot spots in tropical forests[END_REF][START_REF] Myers | The biodiversity challenge: Expanded hotspots analysis[END_REF]. Identified hotspots of biodiversity of the Southern Ocean are presented in Fig. 12. Therefore, they are of major importance for conservation and require specific management attention in regards of the threats (rapid environmental changes, fishing, pollution, and many other anthropogenic disturbances) to these high priority areas. However, many marine predators are far-ranging species, sometimes at the ocean basin scale [START_REF] Weimerskirch | Lifetime foraging patterns of the wandering albatross: Life on the move![END_REF][START_REF] Reisinger | Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean[END_REF], at least during some of their life stages (juvenile, immature or adult, breeder or non-breeders; see [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]. For instance, juvenile king penguins ((Aptenodytes patagonicus); see [START_REF] Orgeret | Exploration during early life: distribution, habitat and orientation preferences in juvenile king penguins[END_REF]) and juvenile or sabbatical wandering albatrosses ((Diomedea exulans); see [START_REF] Weimerskirch | Lifetime foraging patterns of the wandering albatross: Life on the move![END_REF][START_REF] Reisinger | Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean[END_REF]) have a much greater home range than breeding adults. As such, they are a challenge for spatial management [START_REF] Hyrenbach | Viewpoint: Marine protected areas and ocean basin management[END_REF][START_REF] Game | Pelagic protected areas: the missing dimension in ocean conservation[END_REF]. Biologging is thus a valuable tool to identify migration routes and possibly determine where to establish corridors that link the breeding and foraging grounds of migratory species or habitats used at different stages of the life-history [START_REF] Harrison | The political biogeography of migratory marine predators[END_REF], Dunn et al. 2019[START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]. It can also reveal important habitats for specific life-history stages and their potential overlap with threats [START_REF] Dunn | The importance of migratory connectivity for global ocean policy[END_REF][START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF], especially for juveniles that remain outside of hotspot regions, since they often target less productive waters than adults (Riotte-Lambert and [START_REF] Riotte-Lambert | Do naive juvenile seabirds forage differently from adults?[END_REF][START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF].

Recently, tracking data have also been used to track illegal fishing poaching in sub-Antarctic waters [START_REF] Weimerskirch | Ocean sentinel albatrosses locate illegal vessels and provide the first estimate of the extent of nondeclared fishing[END_REF]. Wandering albatrosses were equipped with specific devices made to track vessels, including the ones that switched off their compulsory transmitter and thus suspected of illegal fishing. If this is of great interest, we have to keep in mind that this could also expose "wildlife-spies", and other seabirds in this case, to retaliation given the economic stakes. Several examples have been reported in the literature. In Africa, carcasses are being poisoned to eliminate vultures, whose overhead circling could reveal the poachers' presence [START_REF] Ogada | Ivory poachers and poison: drivers of Africa's declining vulture populations[END_REF]) while around Crozet archipelago killer whales where being killed to prevent them from feeding on longlines [START_REF] Tixier | Demographic consequences of fisheries interaction within a killer whale (Orcinus orca) population[END_REF]).

Long-term biologging observations are and continue to be used to understand the influence of climate variations and to predict the impacts of climate change on ecosystems (Costa et al. 2010a). Indeed, tracking data can be included in predictive models in which different scenarii can be anticipated due to the variation of parameters related to the animals, the environment or anthropogenic activities [START_REF] Bestley | Integrative modelling of animal movement: incorporating in situ habitat and behavioural information for a migratory marine predator[END_REF][START_REF] Stillman | Making Predictions in a Changing World: The Benefits of Individual-Based Ecology[END_REF], Van der Vaart et al. 2016), giving cues for future management priorities. A last aspect not to neglect is the huge potential of tracking data in terms of outreach, public education, and communication [START_REF] Hazen | Ontogeny in marine tagging and tracking science: technologies and data gaps[END_REF]. They can be presented in a highly attractive way (e.g. animated maps, videos, Graphical Interchange Formats (GIFs), 3D visualisation or used in virtual reality; see Fig. 13) to raise awareness, to deliver a message to the governing bodies responsible for the decisions in conservation policy and management, and also to stakeholders [START_REF] Heylen | Bio-telemetry as an Essential Tool in Movement Ecology and Marine Conservation[END_REF].

I.3.4. Ethical consideration

Biologging data are of particular importance for conservation purposes. However, equipping animals with devices raises ethical questions since it involves adverse effects for the carrying individuals [START_REF] Wilson | Diel dive depth in penguins in relation to diel vertical migration of prey: whose dinner by candlelight?[END_REF]McMahon 2006, McMahon et al. 2012). This is not a trivial paradox. Capture is not always required to deploy a biologging device on a wild animal, e.g. for cetaceans [START_REF] Mul | Implications of tag positioning and performance on the analysis of cetacean movement[END_REF]). However, the act of deploying is in itself a disturbance [START_REF] Wilson | Measuring Devices on Wild Animals: What Constitutes Acceptable Practice?[END_REF]. Several studies have highlighted that biologgers cause discomfort to tagged animals and may even impede their movements or reduce their fitness (Culik and Wilson 1991[START_REF] Ropert-Coudert | Impact of Externally Attached Loggers on the Diving Behaviour of the King Penguin[END_REF], 2007[START_REF] Wilson | Measuring Devices on Wild Animals: What Constitutes Acceptable Practice?[END_REF], Beaulieu et al. 2009[START_REF] Vandenabeele | Excess Baggage for Birds: Inappropriate Placement of Tags on Gannets Changes Flight Patterns[END_REF]. Such disruption can lead to biases in the behaviour of equipped animals, resulting in misinterpretation (Culik andWilson 1991, Saraux et al. 2011a). To minimise the perturbation, protocols of capture, equipment and recapture, need to be optimised and continuously enhanced. Impacts of biologging studies can be reduced by applying the Three Rs principles (Replacement, Reduction, Refinement) defined in 1959 by Russel and Burch in the context of animal testing [START_REF] Russel | Page The principles of humane experimental technique[END_REF] to biologging studies (Horning et al.

2019):

-Chapter I -52 1) Replacement alternatives refer to methods that avoid or replace the use of animals. It is not always achievable. The use of old data with more advanced modelling techniques is a form of replacement as well as passive monitoring techniques (e.g. acoustic or video recordings) and genetic studies (e.g. biopsy on dead individuals, scat collection).

2) Reduction alternatives refer to the use of the lowest possible number of individuals to answer the research questions. The collection of higher resolution data, of multisensory logger, and the collaboration between projects are good practices to achieve this goal. Animal-borne devices can sample otherwise inaccessible areas and benefit to other disciplines. For instance, the Conductivity-Temperature-Depth-profiles collected by seals are also used by oceanographers [START_REF] Boehlert | Autonomous Pinniped Environmental Samplers: Using Instrumented Animals as Oceanographic Data Collectors[END_REF][START_REF] Fedak | The impact of animal platforms on polar ocean observation[END_REF].

3) Refinement alternatives are interpreted as the enhancement of experimental procedures to minimise negative effects on animals. Size, mass, shape, and positioning of biologgers were identified as the main parameters to work on to optimise tags [START_REF] Hawkins | Bio-logging and animal welfare : practical refinements[END_REF]). Great advances have been made in terms of miniaturisation, design optimisation, storage capacity, and power consumption, and biologging continue to progress [START_REF] Wilmers | The golden age of bio-logging: how animal-borne sensors are advancing the frontiers of ecology[END_REF], Kay et al. 2019).

In the absence of other alternatives, biologging data are of such importance for the understanding of wildlife movements and behaviour, and in the establishment of conservation measures and protective policies, that the benefits outweigh the risks and justify its use [START_REF] Mcmahon | Animal welfare and decision making in wildlife research[END_REF][START_REF] Wilmers | The golden age of bio-logging: how animal-borne sensors are advancing the frontiers of ecology[END_REF]. However, it is still crucial to monitor and report potential impacts of biologger deployments on animals, and scientists need to remain critical towards established protocols as implied in the Three Rs framework.

I.4 Habitat concepts and foraging ecology of marine top predators I.4.1. Habitat selection

In the simplest form, the habitat of an organism is the place where it lives [START_REF] Odum | Fundamentals of ecology[END_REF]. Since then, a habitat has been more explicitly defined as being the sum of the resources and conditions leading to the occupancy of an area by a given organism to ensure its reproduction and survival [START_REF] Block | The Habitat Concept in Ornithology Theory and Applications[END_REF][START_REF] Hall | The Habitat Concept and a Plea for Standard Terminology[END_REF][START_REF] Krausman | Some Basic Principles of Habitat Use[END_REF].

The notion of habitat is scale dependent, and several levels can be considered in time and space [START_REF] Krausman | Some Basic Principles of Habitat Use[END_REF]. Understanding the whole distribution of a species as well as the differential use of habitat is crucial to implement adequate conservation measures at the relevant location. [START_REF] Johnson | The Comparison of Usage and Availability Measurements for Evaluating Resource Preference[END_REF] was the first to establish a habitat selection scale, and he defined four natural ordering habitat selection processes. The first-order selection (macroscale) refers to the geographical or physical range of a species (distribution area). The second-order selection corresponds to the home range of an individual within the population range. The third-order selection identifies how the habitat components (i.e. physical and biological resources) are used within the home range to meet the life requisites such as foraging or nesting. This order corresponds to the classical definition of 'habitat use'

given by [START_REF] Block | The Habitat Concept in Ornithology Theory and Applications[END_REF]. The fourth-and last order selection (microscale) refers to how the components of a habitat are used. For instance, if the third-order selection corresponds to a foraging area, then the fourth order would be the acquisition of food items from those available at that site [START_REF] Johnson | The Comparison of Usage and Availability Measurements for Evaluating Resource Preference[END_REF][START_REF] Krausman | Some Basic Principles of Habitat Use[END_REF].

In this context, the habitat selection by an individual is an active behavioural process that results from a compilation of innate and learned behaviours [START_REF] Hutto | Habitat selection by nonbreeding, migratory land birds[END_REF]. This process allows an individual to distinguish among various components of its environment and leads to the disproportional use of environmental conditions to influence its fitness and survival [START_REF] Block | The Habitat Concept in Ornithology Theory and Applications[END_REF]. According to the life-history theory, organisms tend to optimise their individual fitness, i.e. maximise their genetic contribution to future generations [START_REF] Stearns | The Evolution of Life Histories[END_REF]. However, throughout their lives, individuals are facing constraints that affect their survival and/or reproduction and to which they must adjust [START_REF] Mcnamara | Statedependent life histories[END_REF]. Under the process of natural selection, behavioural and physiological traits have been selected and result in a set of behavioural strategies observable at different spatiotemporal scales (e.g. foraging at the seasonal or daily scale, habitat selection) for all activities of an individual (e.g. breeding, resting, foraging, migrating, dispersing). Among all the activities that an animal exhibits, foraging appears to be the most crucial since collecting sufficient food supply is a basic requirement of all other life-history traits [START_REF] Stevick | Patterns of Movement[END_REF].

I.4.2. Foraging ecology

Resource acquisition is a central activity throughout the life of organisms and is the corner point for successful reproduction. Behaviours associated with food search and food intake are strongly subject to the mechanisms of natural selection and have a high selective value [START_REF] Bell | Habitat use and response to patches of prey by desert insectivorous bats[END_REF]. The optimal foraging theory predicts that, in a complex environment, animals should forage so as to maximise the "benefit/cost" ratio of feeding behaviours (i.e. energy gain; MacArthur and [START_REF] Macarthur | On Optimal Use of a Patchy Environment[END_REF][START_REF] Schoener | Theory of Feeding Strategies[END_REF][START_REF] Stephens | Foraging Theory[END_REF]Fig. 14). However, the environmental characteristics of a habitat vary at different spatial and temporal scales that directly influence the distribution, abundance, and thus availability of resources [START_REF] Hunt | Physical processes, prey abundance, and the foraging ecology of seabirds[END_REF], Weimerskirch et al. 2005, Bost et al. 2009a). As such, resources are heterogeneously distributed and aggregated in "patches" of various sizes and densities [START_REF] Fauchald | Scale-dependent predator-prey interactions: the hierarchical spatial distribution of seabirds and prey[END_REF][START_REF] Fauchald | Hierarchical patch dynamics and animal movement pattern[END_REF]. Adapted from [START_REF] Charnov | Optimal foraging, the marginal value theorem[END_REF]). The optimal time spent in a patch is given by the tangent to the cumulative food intake curve. The predator needs to spend enough time in the patch to cover the energy expenditure of moving from one patch to another but also to leave the patch before the resource is too depleted as resource intake within a patch diminishes with time.

Predators have to perpetually adapt their foraging behaviour according to the distribution and availability of prey [START_REF] Charnov | Optimal foraging, the marginal value theorem[END_REF][START_REF] Fauchald | Scale-dependent predator-prey interactions: the hierarchical spatial distribution of seabirds and prey[END_REF]. The predictability of prey patches at finer scales is lower than at coarser scales [START_REF] Weimerskirch | Prey Distribution And Patchiness: Factors In Foraging Success And Efficiency Of Wandering Albatrosses[END_REF]. At large scales, prey may be aggregated in predictable areas (e.g. seamount region, front), while at smaller scale they might congregate in refuges or in one dense and compact swarm difficult to locate (Fauchald andTveraa 2006, Bost et al. 2009a). Yet, to maximise the resource acquisition, the optimal foraging theory suggests that predators will maximise the time spent in the vicinity of a successful prey patch by decreasing their displacement speed and increasing their turning frequency [START_REF] Kareiva | Swarms of predators exhibit "preytaxis" if individual predators use area-restricted search[END_REF]Odell 1987, Fauchald and[START_REF] Fauchald | Using First-Passage Time in the Analysis of Area-Restricted Search and Habitat Selection[END_REF]. As such, they minimise the travelling and associated energetic expenditure between patches (MacArthur and [START_REF] Macarthur | On Optimal Use of a Patchy Environment[END_REF]. In other words, predators tend to maximise the time spent in a profitable area, and they concentrate their search activity in an area with a high density of prey. This behaviour is known as 'Area Restricted Search' (ARS) behaviour [START_REF] Kareiva | Swarms of predators exhibit "preytaxis" if individual predators use area-restricted search[END_REF]Fig. 15).

This behaviour has been observed in many taxa in the horizontal dimension, including seabirds [START_REF] Scheffer | Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia[END_REF][START_REF] Sommerfeld | Foraging Parameters Influencing the Detection and Interpretation of Area-Restricted Search Behaviour in Marine Predators: A Case Study with the Masked Booby[END_REF][START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF][START_REF] Jouma'a | Threedimensional assessment of hunting strategies in a deep diving predator, southern elephant seal Mirounga leonine[END_REF]). However, depending on the species and environmental conditions, the detection of foraging areas with this method is not always reliable [START_REF] Robinson | A comparison of indirect measures of feeding behaviour based on ARGOS tracking data[END_REF], Weimerskirch et al. 2007[START_REF] Bastille-Rousseau | Inference from habitat-selection analysis depends on foraging strategies[END_REF]. Noteworthy, results are particularly misleading for species diving in ice-covered areas [START_REF] Bailleul | Assessment of scale-dependent foraging behaviour in southern elephant seals incorporating the vertical dimension: A development of the First Passage Time method[END_REF]) like, for instance, Weddell seals and emperor penguins. For such species, haul-out behaviour as well as resting or slow and meandering movements at the surface could lead to the inaccurate detection of ARS. However, for diving animals, resources are distributed heterogeneously in 3 dimensions, i.e. both in the horizontal and vertical dimensions. As such, marine predators adopt ARS behaviour not only along their track, but also at depth during their dive (Fig. 15; Zimmer et al. 2007[START_REF] Bailleul | Looking at the unseen: Combining animal bio-logging and stable isotopes to reveal a shift in the ecological niche of a deep diving predator[END_REF]. When diving, marine predators usually spend some time at particular depth and increase their vertical sinuosity by performing undulations called wiggles, making an identifiable ARS vertical behaviour (Fig. 15; [START_REF] Heerah | A new method to quantify within dive foraging behaviour in marine predators[END_REF]. Thus, by studying simultaneously spatial locations of animals' as well as the depth ranges they move in, it is possible to determine favourable habitats for foraging marine predators. Studying foraging activities is fundamental in ecology since foraging controls the energy intakes and as such the fitness of individuals. Understanding the foraging strategies (where, how, and when) of marine top predators is a necessity to identify profitable areas, to set up an efficient monitoring of the effects of environmental changes (i.e. natural and anthropogenic) on individuals and population dynamics, and to implement conservation measures when relevant.

-Chapter I -

57

I.5 Structure and aim of the thesis

My PhD project is part of a global framework, which is the setting up of the second Life Observatory of emperor penguins worldwide. This Life Observatory that I co-initiated and co-supervised, will help to predict how this species copes with environmental changes. With my work, I specifically aim to contribute to a better understanding of the distribution and ecology at sea of the Emperor penguin with conservation purposes in mind.

Chapter III aims to provide the description and assessment of the different techniques of capture, handling, and equipment we used on-site on emperor penguins. Indeed, there was no dedicated paper on this topic in the current literature. To fill this gap, we produced a publication with an exhaustive documentation to provide a standardised framework for future deployments on adults and juveniles of this species. Some of the techniques and conclusions are applicable to other penguin species.

Little is known about the early life at-sea of emperor penguins, even though this is a critical phase in their life and a crucial one for the viability of the global population. As such, in Chapter IV, we assessed the distribution of juvenile emperor penguins in the Weddell Sea region and the Atlantic sector of the Southern Ocean, home to a more than a third of the species' global population, but where the species distribution at sea had never been studied. Through a meta-analysis including our and previous and rare tracking data on juvenile emperor penguins available in the literature, we further investigated if they make use of the existing or proposed MPAs around Antarctica.

In Chapter V, we assessed the distribution in the Atlantic sector of the Southern Ocean of adult emperor penguins in various breeding phases and status. Together with the juveniles' information (Chapter IV), it exposes for the first time a global picture of the species at-sea distribution in this area.

We additionally explored the environmental factors (e.g. sea ice, bathymetry) influencing their movements and habitat use and preference. Finally, we also investigated and compared the fine-scale vertical foraging behaviour of adults from two localities, birds from Atka Bay colony foraging in the Weddell Sea and Atlantic sector of the Southern Ocean, and Pointe Géologie colony and their use of the d'Urville Sea.

In addition, over the course of my PhD project, I was also involved in other research works on Antarctic (i.e. emperor and Adélie) penguin ecology. These studies, in which I appear as a co-author, can be found as Annexes of this thesis in the form of articles, either already published or in preparation.

Annex A(published) and Annex B (published) relate to the use of remote-controlled and energetically self-sufficient observatories to investigate the spatio-temporal dynamics of penguin movements on land and colony structuring. Annex C (in preparation) is a study that I co-initiated and co-supervised, and that explores the foraging behaviour of Adélie penguins in the d'Urville Sea. Annex D (ready to submit) focuses on the contaminant accumulation on Adélie penguins.

II.1 The species II.1.1. General biology

The Emperor penguin (Aptenodytes forsteri) belongs to the order of the Sphenisciformes (family: Spheniscidae) and, together with the king penguin, to the genus Aptenodytes (etymology from ancient Greek: "A" for "without", "pteno" for "wing" or "feather", and "dytes" for "diver"). They are the tallest (ca. 80 cm -120 cm when the neck is fully stretched) and heaviest (up to 45 kg) living penguins [START_REF] Stonehouse | The Emperor Penguin breeding behaviour and development -FIDS Scientific Report[END_REF], and their lifespan remains still unknown but estimated to be around 35-40 years [START_REF] Jenouvrier | Projected continent-wide declines of the emperor penguin under climate change[END_REF]).

The population is currently estimated to count around ca. 270 000 breeding pairs [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF], Trathan et al. 2020, Fretwell and Trathan 2020). The 61 known colonies have a circum-continental distribution along the shoreline of mainland Antarctica, at latitudes comprised between 64°S and 78°S (Fig. 16) and are in average 300 km apart [START_REF] Ancel | Looking for new emperor penguin colonies? Filling the gaps[END_REF]. A single colony counts few hundreds to 25 000 breeding pairs [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF]. Several new colonies have been discovered only recently [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF][START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF][START_REF] Ancel | Emperors in hiding: When ice-breakers and satellites complement each other in Antarctic exploration[END_REF], Fretwell and Trathan 2020), and some might still remain undiscovered until now [START_REF] Ancel | Looking for new emperor penguin colonies? Filling the gaps[END_REF].

Intensive debates are currently taking place regarding the existence of a single panmictic population [START_REF] Cristofari | Full circumpolar migration ensures evolutionary unity in the Emperor penguin[END_REF] or the existence of several (estimated to be at least four) metapopulations [START_REF] Younger | The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins[END_REF]. Additionally, the Emperor penguin has long been considered as a highly philopatric species [START_REF] Prévost | Ecologie du manchot empereur[END_REF], Ancel et al. 2013a) and the location of the colonies stationary.

Recent works [START_REF] Fretwell | Emperor Penguins Breeding on Iceshelves[END_REF][START_REF] Larue | Emigration in emperor penguins: Implications for interpretation of long-term studies[END_REF][START_REF] Fretwell | Emperors on thin ice: three years of breeding failure at Halley Bay[END_REF] suggest that this pattern might not be exclusive and that colony location appears more dynamics than previously thought [START_REF] Larue | Emigration in emperor penguins: Implications for interpretation of long-term studies[END_REF]. 2020) and counts from [START_REF] Fretwell | Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins[END_REF]. Recent movement between Halley Bay and Dawson-Lambton colonies are not accounted for [START_REF] Fretwell | Emperors on thin ice: three years of breeding failure at Halley Bay[END_REF]. Colonies where tracking occurred are underlined in violet.

II.1.2. Life-history and breeding traits

The Emperor penguin shares common life-history traits with other seabirds. They are long-lived species with a long generation time, a late sexual maturity; they breed in colony and produce few offsprings but invest (time and energy) in the quality of their one and only annual chick [START_REF] Stonehouse | The Emperor Penguin breeding behaviour and development -FIDS Scientific Report[END_REF][START_REF] Prévost | Ecologie du manchot empereur[END_REF]. Also similarly to other seabirds, the breeding cycle of the Emperor penguin can be divided into three main phases: breeding, moulting, and interbreeding period [START_REF] Hamer | Breeding biology, life histories, and life history-environment interactions in seabirds[END_REF]).

However, variations in phenotypic and life-history traits and strategies are expected and can be observed: for instance, the phenology can greatly differ due to the latitude of the colony (e.g. 2-4 weeks of delay in the arrival, laying, fledging dates between Atka Bay and Pointe Géologie; Houstin, Le Bohec, Zitterbart, unpublished observations). However, a classical annual breeding cycle can be described as follows (Fig. 17). In late March beginning of April, males and females gather at their colony site, mostly located on stable fast-ice, but occasionally on lands or shelves [START_REF] Fretwell | Emperor Penguins Breeding on Iceshelves[END_REF]. The colony site should provide a stable ground up to the end of the breeding season in December-January. After a period of courtship which can last up to 6 weeks [START_REF] Prévost | Ecologie du manchot empereur[END_REF][START_REF] Isenmann | Contribution à l'éthologie et à l'écologie du manchot empereur (Aptenodytes forsteri Gray) à la colonie de pointe Géologie (Terre Adélie)[END_REF], Ancel et al. 2013b), pairs are forming and copulating, and a unique egg is laid at the beginning of the austral winter. Females then leave the colony to forage at sea, while males incubate the egg during 64 days in average [START_REF] Stonehouse | The Emperor Penguin breeding behaviour and development -FIDS Scientific Report[END_REF][START_REF] Prévost | Ecologie du manchot empereur[END_REF], enduring a fast of ca. 4 months [START_REF] Maho | The Emperor Penguin: A Strategy to Live and Breed in the Cold: Morphology, physiology, ecology, and behavior distinguish the polar emperor penguin from other penguin species, particularly from its close relative, the king penguin[END_REF]. Chicks hatch in the middle of the winter (July-August). In the following 6-7 weeks, chicks are not thermally independent, hence one parent always accompanies their offspring, while the other is foraging in the pack-ice (Labrousse et al. 2019a). By November, chicks become thermally independent and are left on their own on the colony site, while both parents alternate independently between foraging at sea and return to feed their chick. These commuting trips occur until chicks fledge in December or January [START_REF] Stonehouse | The Emperor Penguin breeding behaviour and development -FIDS Scientific Report[END_REF][START_REF] Prévost | Ecologie du manchot empereur[END_REF], Ancel et al. 2013a). In December or January, depending on the latitude of the colony, chicks moult and fledge. By the end of the austral summer, the adult emperor penguins also perform their annual moult. The moulting process lasts on average 30 days [START_REF] Groscolas | Study of molt pasting followed by an experimental forced fasting in the emperor penguin Aptenodytes forsteri: Relationship between feather growth, body weight loss, body temperature and plasma fuel levels[END_REF] during which birds need to remain out of water on ice floes or coastal fast ice (Kooyman et al. 2004). After few weeks spent foraging at sea to replenish their body reserves (Kooyman et al. 2004), adults will mostly come back breeding, the proportion of adults skipping a breeding season being unknown [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]).

Juveniles will not return to their colony of origin and spend their first years of life at sea. Female emperor penguins will start breeding at 3-6 years of age, while males between 4-8 years [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF][START_REF] Jenouvrier | Projected continent-wide declines of the emperor penguin under climate change[END_REF].

II.1.3. Foraging behaviour II.1.3.1. Distribution at sea

Like all the seabirds and pinnipeds of the Southern ocean, the Emperor penguin is a central-place forager [START_REF] Orians | On the theory of central place foraging[END_REF], i.e. these predators have to commute between their breeding colony to feed their offspring and their feeding areas. The species is even the only central-place predator breeding in the middle of the austral winter [START_REF] Ainley | Decadal-scale changes in the climate and biota of the Pacific sector of the Southern Ocean, 1950s to the 1990s[END_REF]. So far, all the emperor penguins tracked since the 80s were from colonies located in the Ross Sea (several colonies between research stations in East Antarctica, covering approximately a third of the continental perimeter (Fig. 16). The distribution at sea of the Emperor penguin around the rest of Antarctica remains unknown.

However, all the tracking studies (Table 9) revealed similar distribution patterns between sites to date.

During the chick-rearing period, constrained by the highly-demanding chick provisioning, breeding adults are staying in the vicinity of the colony (within a ca. 150 km radius in average) foraging in cracks, flaw leads, ephemeral and persistent polynyas, i.e. areas of open water, or persistently loose sea ice [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Rodary et al. 2000a, Zimmer et al. 2007b[START_REF] Massom | Fast ice distribution in Adélie Land, East Antarctica: Interannual variability and implications for emperor penguins Aptenodytes forsteri[END_REF], Labrousse et al. 2019a). In the only study carried out on nonbreeding adults, Goetz and colleagues (2018) revealed that, on the contrary, an unknown proportion of the non-breeding birds spend this time-period a thousand kilometres away from any colony in the pack ice. When breeding is over and the chick is left alone to fledge, adults range a bit further (~350 km) during their pre and/or post-moult period extending from December to March (Kooyman et al. 2004[START_REF] Wienecke | Premoult foraging trips and moult locations of Emperor penguins at the Mawson Coast[END_REF], Zimmer et al. 2007b).

During their first year at sea, juveniles appear to venture north of the 60 th parallel, i.e. out of the classical Southern Ocean delineation, at the beginning of their journey, before spending the winter in the pack ice [START_REF] Kooyman | Penguin dispersal after fledging[END_REF][START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF], Thiebot et al. 64 2013, Labrousse et al. 2019b). Nothing is known about their moulting area [START_REF] Fretwell | Penguins from space: faecal stains reveal the location of emperor penguin colonies[END_REF] and their following years at sea before their return for breeding.

Whether similar patterns exist for juvenile and adult emperor penguins in the Atlantic sector is

nonetheless still an open question, while a better understanding of this species within the Weddell Sea is a priority (Teschke et al. 2016a, Labrousse et al. 2019b, Trathan et al. 2020).

II.1.3.2. Diving

The knowledge of the horizontal distribution at sea of the Emperor penguin is not sufficient to determine its feeding grounds. Their energetic supply requires both horizontal and vertical transit phases to access resources. The concomitant use of biologgers to record marine predator locations and their behaviour while foraging at sea, can give us insights about the spatio-temporal distributions of the food web [START_REF] Wilson | Diel dive depth in penguins in relation to diel vertical migration of prey: whose dinner by candlelight?[END_REF], Ropert-Coudert et al. 2001[START_REF] Pichegru | Foraging behaviour and energetics of Cape gannets Morus capensis feeding on live prey and fishery discards in the Benguela upwelling system[END_REF][START_REF] Elliott | Seabird foraging behaviour indicates prey type[END_REF].

Emperor penguins are the deepest diving species of seabirds: they can dive as deep as 564 m [START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF]) for as long as 32 minutes [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]). However, the vast majority of the dives occurs below 150 m and lasts less than 10 minutes with less than 2-min recovery between consecutive dives [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF][START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF].

As other penguin species [START_REF] Williams | The Penguins: Spheniscidae. Page The penguins. Bird families of the world[END_REF], Halsey et al. 2007), most of the emperor penguin dives consist of three distinct phases: i) a constant descent phase, followed by ii) a bottom phase, with a horizontal trend that can still be slightly ascending, and iii) a steeper ascent phase. After a dive, there is a period of recovery, called post-dive duration, preceding the next dive (Fig. 18). According to the current literature, the majority of the feeding events occurs during the bottom phase [START_REF] Chappell | Diving Behavior During Foraging in Breeding Adelie Penguins[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Zimmer et al. 2007b). These feeding events are indicated by undulations known as wiggles and common in all penguin species (Rodary et al. 2000b[START_REF] Simeone | In-depth studies of Magellanic penguin (Spheniscus magellanicus) foraging: Can we estimate prey consumption by perturbations in the dive profile?[END_REF][START_REF] Ropert-Coudert | Foraging strategies and prey encounter rate of free-ranging Little Penguins[END_REF], Halsey et al. 2007, Zimmer et al. 2007b). However, two main types of foraging behaviour of emperor penguins emerge in the literature. If most of the birds and dives are pelagic, i.e. occurring in the water column, emperor penguins have also been reported to perform benthic dives over the shelf area (Rodary et al. 2000a[START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]. Benthos prey items have been found to be part of the diet of emperor penguins from Auster (Robertson et al. 1994, Kirkwood andRobertson 1997), revealing that adult emperor penguins are also able to feed on benthic prey where and when the sea-floor is accessible (sea ice presence can prevent access to areas). Sub-ice foraging has been documented on tape [START_REF] Ponganis | Sub-ice foraging behavior of emperor penguins[END_REF], however, the importance of this behaviour has not been quantified yet.

In definitive, such information indicates that emperor penguins hunt opportunistically for available prey throughout the water column [START_REF] Kooyman | Diving Behavior of Emperor Penguins Nurturing Chicks at Coulman Island, Antarctica[END_REF], Zimmer et al. 2007b[START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF].

II.1.3.3. Diet

The diet of the Emperor penguin has been investigated by different techniques: stomach flushing [START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF][START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF][START_REF] Ainley | Does prey preference affect habitat choice in Antarctic seabirds?[END_REF][START_REF] Piatkowski | Squid diet of emperor penguins ( Aptenodytes forsteri ) in the eastern Weddell Sea, Antarctica during late summer[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Zimmer et al. 2007a), scat analysis [START_REF] Green | Food of the emperor penguin Aptenodytes forsteri on the Antarctic fast ice edge in late winter and early spring[END_REF], Kooyman et al. 2004), stable isotopes (Zimmer et al. 2007b[START_REF] Cherel | Isotopic niches of emperor and Adélie penguins in Adélie Land, Antarctica[END_REF], and once by camera [START_REF] Ponganis | Sub-ice foraging behavior of emperor penguins[END_REF].

Their diet is composed of fish, mostly nototheniids and particularly Antarctic silverfish ((Pleuragramma antarcticum), see detailed description in [START_REF] Mintenbeck | Impact of Climate Change on the Antarctic Silverfish and Its Consequences for the Antarctic Ecosystem[END_REF] The diet composition and prey item proportions vary enormously among studies with time of year and location (Table 2; Ratcliffe and Trathan 2012).

For instance, emperor penguins from Pointe Géologie colony in Adélie Land (our second study site, see page 71) have been mostly described as ichthyophagous by two studies that occurred 20 years apart [START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF]Ridoux 1986, Cherel 2008). In addition to Antarctic silverfish, they also consume squids (Zimmer et al. 2007a), and adults fed for themselves on the same prey as those given to their chicks [START_REF] Cherel | Isotopic niches of emperor and Adélie penguins in Adélie Land, Antarctica[END_REF], at least during the chick-rearing period. On the contrary, in the Weddell Sea, at Drescher inlet colony (~650 km south-west of Atka Bay, our first study site, see page 70), iceassociated Antarctic krill was the main prey item during the breeding season [START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF]) but was supplanted by the consumption of squids and fish in the post-moult diet (Piatkowski andPütz 1994, Pütz 1995).

Noteworthy, for a same site in East Antarctica (at both Auster and Taylor colonies), diet composition greatly varied between years, switching from fish and squid in 1988 [START_REF] Robertson | Diet composition of Emperor Penguin chicks Aptenodytes forsten' at two Mawson Coast colonies[END_REF] to krill in 1993 [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF]. The presence of demersal and bentho-pelagic fish in the diet has also been reported at these colonies (Robertson et al. 1994, Kirkwood andRobertson 1997).

II.1.4. Threats and conservation status

The Emperor penguin is a sea ice obligate species, i.e. birds are found year-round in association with sea ice (Ainley et al. 2010b, 2016, Trathan et al. 2011). They depend on sea ice as breeding ground (fast ice) for the vast majority of the colonies [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF], for feeding [START_REF] Trathan | First Recorded Loss of an Emperor Penguin Colony in the Recent Period of Antarctic Regional Warming: Implications for Other Colonies[END_REF], Labrousse et al. 2019a), for moulting (Kooyman et al. 2004) as well as for resting and as a shelter from predators (leopard seals and killer whales (Orcinus orca) when foraging at sea [START_REF] Ainley | Birds and Antarctic sea ice[END_REF]).

Specific environmental conditions at each emperor penguin colony (e.g. distance to oceanic fronts, persistence of sea ice in time and space, seaward extent of Antarctic continental shelf, presence of specific oceanic currents like gyres) may be affected differently by the ongoing and future impacts of climate change. However, most climate models agree that future global climate change will lead to reduction in sea ice area of ca. 30 to 40% over the 21 st century, depending on the emission scenario under consideration [START_REF] Bracegirdle | The importance of sea ice area biases in 21st century multimodel projections of Antarctic temperature and precipitation[END_REF][START_REF] Palerme | Evaluation of current and projected Antarctic precipitation in CMIP5 models[END_REF]. Late formation and early retreat are also expected to occur, while emperor penguins need a stable sea ice during nine months for the completion of their breeding cycle. The most recent projections under different climate change scenarios have concluded that the species faces the risk to be nearly extinct (80% of colonies lost and a population decline of 81%) within the next 100 years [START_REF] Jenouvrier | The Paris Agreement objectives will likely halt future declines of emperor penguins[END_REF] in the absence of an ambitious policy to limit greenhouse gas emissions. These projections considered only the demographic parameters of adult emperor penguins due to the lack of long-term demographic data on juvenile and immature populations. It is likely that the integration of such data would make forecasts of survival even more pessimistic (Trathan et al. 2020).

In addition to sea ice degradation (in extent and persistence) through changes to currents and winds, rising temperatures and ocean acidification, climate change is expected to lead to multispecies effects, including changes to prey abundance and availability, range shifts and competition with other Antarctic predators (IPCC 2019[START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF].

Currently, the fisheries are not considered as being a direct threat for emperor penguins since the Antarctic krill fisheries operate relatively far from emperor breeding sites (Trathan et al. 2020).

However, the sea ice retreat will soon give access to new fishing areas and may change the spatiotemporal repartition of krill stocks [START_REF] Rintoul | Choosing the future of Antarctica[END_REF][START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF]. If these new ice-free areas were to be exploited, the competition with fisheries for accessing the resources together with the risk of potential by-catch events would be additional threats for the species. Nevertheless, it is important to keep in mind that we still know very little about the distribution of juveniles (4 studies) and nonbreeding birds (1 study) which, unlike breeding birds, venture thousands of kilometres ashore [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b). A better understanding of these life-history stage is notwithstanding critical since their ignorance when assessing overlap with threats is likely to bias estimates of the risks, as shown by Carneiro and colleagues (2020) on 22 species of albatrosses and petrels.

Direct anthropogenic threats at breeding sites might also occur and must continue to be regulated and rules enforced by the Antarctic Treaty System to ensure that colonies are not affected by future developments such as tourism (Fig. 20), new aircraft runways, and new or enhanced research facilities. Red List of threatened species (Birdlife International 2018). The IUCN Red List classifies species under different categories (Fig. 21) that indicate an estimated risk of extinction. Classified as 'NT', means that the species is considered close to being at high risk of extinction in the near future. Noteworthy, several researchers, specialists of the Emperor penguin, consider that the species require an IUCN designation of, at least, Vulnerable (VU) to properly reflect the species' status (Trathan et al. 2020).

Such a classification would provide an opportunity to increase the protection level of the species through the ATS and ensure that regional management actions decided by the CCAMLR would take into consideration any activity that might affect emperor penguins (Trathan et al. 2020). For instance, any breeding colonies would be protected according to the same set of rules (e.g. approach distances, number of people, vehicles allowed close by and distances), not only the few existing rules that are currently specifically designated as Antarctic Specially Protected Area (ASPA) through the ATS. AB is situated in waters where the main oceanographic feature is the cyclonic (clockwise rotating)

Weddell Sea Gyre that drives the currents from west to east [START_REF] Vernet | The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges[END_REF]. The Pointe Géologie (PG) archipelago is made of several islands located aside the Antarctic continent and the Astrolabe glacier. The sea ice is very stable and may remain several years, providing a perfect ground for the emperor penguin colony. Given the proximity of the research station, PG has been monitored continuously since 1956 (Prévost 1961, Barbraud and[START_REF] Barbraud | Emperor penguins and climate change[END_REF]. The breeding behaviour of the species is mostly known through observations made on this colony [START_REF] Jouventin | Comportement et structure sociale chez le manchot empereur[END_REF], Ancel et al. 2009, Jenouvrier et al. 2009a[START_REF] Matthysen | Multicausality of dispersal: a review[END_REF], 2017), which is the 1 st Life Observatory of the species.

The colony counts currently around 4000 breeding pairs [START_REF] Barbraud | Population trends of penguins in the French Southern Territories[END_REF]. PG is located at the eastern edge of East Antarctica in the Indian sector of the Southern Ocean. The Antarctic continental shelf is about 100 km wide and marked by two plateau 100-300 m deep (Adélie and Mertz banks) separated by two big depressions (Adélie Depression and d'Urville Trough) and canyons up to 1000 m depth (Fig. 23; [START_REF] Beaman | A new high-resolution bathymetry model for the Terre Adélie and George V continental margin, East Antarctica[END_REF]. The bathymetric features play a crucial role on the hydrological circulation over the Antarctic shelf in the region [START_REF] Williams | Antarctic Bottom Water from the Adélie and George V Land coast, East Antarctica (140-149[END_REF].

II.2.2. Biological data collection II.2.2.1. Fieldwork at Atka Bay

During two 4-months field sessions that occurred in the austral summers 2017-2018 and 2018-2019 13 at the Atka Bay emperor penguin colony (Fig. 16), we captured/recaptured 70 adults and 8 juveniles in order to carry out the deployment and recovery of biologgers. We deployed tracking devices (ARGOS platforms, GPS devices), TDR, and accelerometers.

(i) Choosing the tracking devices

Two different types of tracking devices with specific capacities can be used to track marine wildlife with accuracy and during the polar day14 :

- passes. This precision varies from a hundred metres to several tens of kilometres [START_REF] Lopez | Improving Argos Doppler Location Using Multiple-Model Kalman Filtering[END_REF], CLS 2016). With this system, the data are transmitted to the user who does not need to retrieve the beacon.

-The Global Positioning System (GPS):

Contrary to ARGOS, GPS devices do not emit any signal, but satellites are sending messages received by a beacon. By triangulating signals received from different satellites, the GPS device can calculate its position with a very high spatial accuracy, most of the time less than 100 m (Costa et al. 2010b). With this system, the data are not transmitted, the GPS device needs to be recovered to get access to the data.

In other words, ARGOS platforms are less accurate but do not need to be recovered, while GPS devices are more accurate but need to be recovered to access the data.

Our choice has been mainly determined by 1) our research questions and the degree of precision required to address them (e.g. Where and how far do chick-rearing adult emperor penguins from the Atlantic sector of the SO travel to forage? What are the foraging grounds of the adults during the winter?), 2) the constraints linked to the biology of the Emperor penguin (e.g. annual moult in January), but also 3) some logistical constraints to perform our study, as we were having access to the penguin colony only from November to January. During late chick-rearing period, just before their annual moult, adult emperor penguins alternate trips at sea and return at the colony for feeding their chick. These recurring returns of the adult to feed its chick, approximately once per week, make this period ideal for captures, deployments, and recaptures for data logger retrieval. As such, we chose to use GPS devices with a high frequency sampling for this period (November-December). On the contrary, after their annual moult, the majority of the juveniles will not come back at the colony for at least two years [START_REF] Mougin | Structure et dynamique de la population de Manchots empereurs de la colonie de l'archipel de Pointe Géologie[END_REF], and studies suggest that most of the adults moult in the pack ice [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF][START_REF] Hawkins | Bio-logging and animal welfare : practical refinements[END_REF][START_REF] Wienecke | Premoult foraging trips and moult locations of Emperor penguins at the Mawson Coast[END_REF], 2010). There is also no certainty that adults moulting at a colony are actual breeders from that particular colony, and that they will return for the next season. Therefore, successfully retrieving the devices is unlikely and the use of transmitting devices (ARGOS platform) is by far the most prevalent technique after the moult to ensure data recovery over the winter.

(ii) Time-Depth Recorders (TDR)

TDR are archival data loggers that measure and store pressure and temperature as a function of time.

Obtaining at high frequency (usually 1 Hz) the depth reached per unit of time of a diving predator allows to efficiently reconstruct the animal's diving behaviour during its foraging trips at sea (e.g. [START_REF] Charrassin | Seasonal changes in the diving parameters of king penguins (Aptenodytes patagonicus)[END_REF][START_REF] Dragon | Horizontal and vertical movements as predictors of foraging success in a marine predator[END_REF]. The use of these devices does not provide indications on geographical movements, but only information in the water column. However, by combining the positions of individuals recorded by the tracking devices with the diving depth simultaneously recorded by the TDR, we are able to interpret a posteriori birds' behaviour during the deployment period and determine the spatio-temporal prospecting and foraging strategies. These devices provide valuable information on the feeding behaviour, exploration effort and hunting success of the diving predators (e.g. [START_REF] Wienecke | Foraging areas of king penguins from Macquarie Island in relation to a marine protected area[END_REF][START_REF] Scheffer | Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia[END_REF], Zimmer et al. 2010a[START_REF] Evans | Foraging behaviour of common murres in the Baltic Sea, recorded by simultaneous attachment of GPS and time-depth recorder devices[END_REF][START_REF] Viviant | Can we predict foraging success in a marine predator from dive patterns only? Validation with prey capture attempt data[END_REF][START_REF] Heerah | From high-resolution to low-resolution dive datasets: a new index to quantify the foraging effort of marine predators[END_REF][START_REF] Carter | Navigating uncertain waters: a critical review of inferring foraging behaviour from location and dive data in pinnipeds[END_REF]).

(iii) Deployments

In total, we performed 3 types of deployments (Table 3), by equipping:

-breeding adults for short-term period (few weeks) to monitor their foraging activities during the late-chick-rearing period with GPS devices and an extra TDR,

-adult birds at the end of their annual moult to monitor their distribution and diving behaviour over a full year (long-term period) with ARGOS platform and an extra TDR, -5-months old fledged chicks to track them during their first year at sea (long-term period)

with ARGOS platform only, because of their multi-year dispersal behaviour [START_REF] Mougin | Structure et dynamique de la population de Manchots empereurs de la colonie de l'archipel de Pointe Géologie[END_REF]) that would prevent device retrieval the next field season.

Monitored period 1 to 3 weeks between Nov-Dec Year Year

Illustration of the instrumentation performed

Adults were also equipped with accelerometers (acc), as an extra device for long-term deployment, or included in the Axy-Trek logger for short-term deployment. Note that the analysis of these data will not be presented in this thesis. a. An adult emperor penguin equipped with TDR in the middle of the back and a GPS underneath. b. An adult emperor penguin equipped with an accelerometer in the middle of the back, an ARGOS platform underneath, and a leg-banded TDR on its right ankle. c. Two juvenile emperor penguins both equipped with an ARGOS platform.

Over the two summer seasons, we deployed 36 GPS Axy-Trek from TechnoSmArt (Table 4) on latechick-rearing adults (short-term deployments). To remotely monitor the presence/absence of the birds in the colony and to facilitate the device recovery, GPS devices were combined with VHF beacon that could last 6 months. To ensure a one month functioning of the GPS battery, one location was collected every 15 minutes. In 2017-2018, locations were collected every three minutes. However, the water switch unit did no function correctly and the GPS kept trying to get a signal under water.

Consequently, the battery power diminished faster than expected and the tracking duration lasted only around a week. To prevent such issue, in 2018-2019, we changed the sampling frequency and collected one location every 15 minutes. As a result, the batteries lasted around a month.

Right after their moult, 8 juveniles and 8 adults were equipped with SPOT-367 ARGOS platforms from Wildlife Computers (Table 4, long-term deployments). The platforms were programmed to transmit their locations every day at 4, 6, 10, 16, 19 and 21:00 GMT, to be synchronized with the best ARGOS satellite coverage. With such a programming, the batteries were expected to last around 15 months.

We also used two different TDR devices according to their memory size and thus the amount of data they could store. 'Cefas g5+' were used for short-term deployments and 'Lotek Lat 1800' for long-term deployments (Table 4). They were both programmed to record depth and temperature at 1 Hz frequency with a 30 cm resolution and 1% accuracy. Birds' capture and handling procedures, logger deployment techniques, birds' release and ethical matters in biologging studies are reported in details in Chapter III of this thesis.

II.2.2.2. Data previously collected at Pointe Géologie

We used tracking data from 33 individuals equipped with ARGOS platforms at the Pointe Géologie colony in Adélie Land (see page 71) between 1998 and 2005 (see Table 5 for details). Tracking data from 2005 were previously published in Zimmer and colleagues (2007b). In 1998 and 2001, locations were collected every 100 minutes except between 9h -13h local time. In 2005, the loggers were duty cycled to be 6h on and 6h off. Amongst the birds monitored in November 2005, 4 birds were equipped with Splash ARGOS platforms, which also recorded the diving depth every 2 seconds with a 0.5 m resolution. The dive data were already published in [START_REF] Zimmer | Constraints on Foraging and their Consequences for Emperor Penguins PhD[END_REF]colleagues (2008, 2010).

II.2.3. Conservation management policy and environmental variables

The distribution at sea of our tracked emperor penguins was investigated in relation to the geographical coverage of planned and existing conservation efforts in the Southern Ocean (see Fig. 36). We also aimed to evaluate the influence of environmental variables on the distribution at sea and the foraging activities of our equipped birds.

II.2.3.1. Main conservation and management bodies

The Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) is the main policymaker of the Southern Ocean (CCAMLR 1980). The boundaries of the CCAMLR jurisdiction are therefore the main limits defining the potential implementation of conservation efforts in this circumpolar area. In addition to the CCAMLR limits, we also considered the existing and proposed Marine Protected Areas (MPAs) around the Antarctic continent and around sub-Antarctic islands (Brooks et al. 2020a). Moreover, given the role of primary importance played by the International The maximum and minimum median sea ice extent 1981-2010 used for visualisation purposes on Fig. 36 and Fig. 39 were obtained from the National Snow and the Ice Data Center NSDIC [START_REF] Fetterer | Sea Ice Index, Version 2, updated daily[END_REF]). The sea ice edge defined by the 15% sea ice concentration isocline (Cavalieri 1991, Stammerjohn and[START_REF] Stammerjohn | Opposing Southern Ocean climate patterns as revealed by trends in regional sea ice coverage[END_REF]) was extracted daily. Contours corresponding to outlying floes or polynyas were removed from the datasets to prevent bias in the sea ice edge distance computation with QGIS 'r.contour.step' tool.

To account for spatial variability of sea ice, at each location, we additionally computed the sea ice concentration over an area bounded by a radius corresponding to the kernel smoothing factor. We also computed the percentage of sea ice > 90% over the bounded area to take into account the absence of cracks and daily polynyas that emperor penguins use to dive and forage.

(ii) Oceanographic features

The Southern Ocean fronts and the Southern Boundary of the Antarctic Circumpolar Current [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF] were downloaded from https://gis.ccamlr.org.

The bathymetry covariate at one-minute horizontal spatial resolution was obtained from the ETOPO1

Global Relief Model provided by the NOAA National Geophysical Data Center [START_REF] Amante | ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis[END_REF]. The bathymetry indicates whether the birds are located in neritic or oceanic waters, and if they perform benthic dives (Rodary et al. 2000a).

The bathymetric grid was used to compute a gradient of bathymetry (or slope) grid with the 'terrain' function from the R package 'raster' [START_REF] Hijmans | raster: Geographic analysis and modeling with raster data[END_REF]. The slope value of each cell in degree was computed from the bathymetric value of eight neighbouring cells.

(iii) Habitat features

We divided the Southern Ocean in 3 habitat types to take into account the effect of bathymetry and water movements: 1) The continental shelf break was considered as the area along the continent below the 1000 m isobaths [START_REF] Knox | Biology of the Southern Ocean[END_REF][START_REF] Nicholls | Ice-ocean processes over the continental shelf of the southern Weddell Sea, Antarctica: A review[END_REF]). We then used the classification of Douglass and colleagues (2014) to segregate 2) the Antarctic continental slope area (roughly areas around the continent with ranging between 1000 and 4000 m) from 3) the deep ocean (abyssal plain)

characterised by a low bathymetry slope and depth > 4000 m.

II.3 Data analysis

Analyses were performed using the software R v. 3.5.0 (R Core Team 2018) and QGIS v. 2.18.18 (QGIS Development Team 2017) with the data package 'Quantarctica3' [START_REF] Matsuoka | Quantarctica[END_REF].

II.3.1. Spatial analysis

Spatial datasets always contain some aberrant points. Moreover, due to the difference in sampling frequencies and of accuracy between GPS and ARGOS locations, our datasets needed to be standardised to make comparisons feasible and meaningful. Once the location datasets are cleaned and standardised, the distribution at sea and the habitat used by the birds can therefore be estimated.

In this thesis, data were divided into 5 study groups according to the study site and the period of deployment (Table 7). Each group was processed with the same routine, but with some particularities (e.g. presence of several foraging trips for some birds, different sampling frequencies between devices).

II.3.1.1. Location cleaning and filtering

Erroneous locations were filtered out using a speed filter from the R package 'argos filter' [START_REF] Freitas | A simple new algorithm to filter marine mammal Argos locations[END_REF] with the maximum travel speed fixed at 15 km.h -1 following previous studies on emperor penguins [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 1997, Labrousse et al. 2019b). As such, all locations requiring unrealistic swimming speed were removed.

Tracking datasets for each individual were divided into foraging trips when relevant (Table 7).

Locations within 5 km from the deployment site were considered as the bird having returned to the colony and subsequent locations distant to more than 5 km from the colony were considered as a separate foraging trip. The risk of pseudo-replication, by the use of trips from the same individuals as independent samples, was investigated by comparing within-and between-individual variances as described in Lascelles and colleagues (2016). Since the variance between individuals from each study group was not greater than within individuals, each single trip per individual was considered as independent.

II.3.1.2. Interpolation of locations at a regular time step

To correct the different sampling frequencies within and between study groups (from several minutes to several hours), we chose to interpolate locations at every hour [START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF]). To do so, we used a state-space modelling approach [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF]) in order to estimate hourly locations with respect to the uncertainty of transmitted locations. Concretely, a 'Kalman filter', which accounted for location errors, was applied using the R package 'crawl' [START_REF] Johnson | Fit continuous-time correlated random walk models to animal movement data[END_REF], and the Continuous-time Correlated Random Walk (CRW) models were used to predict locations at a regular hourly time step interval [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF]; see Fig. 29 to visualise an example of interpolations). It is then possible to draw contours of differential intensity of space use by the animals. The area of interest is then defined as the area included by the contour of the UD so that the volume below the distribution and within the contour represents a certain percentage of the total volume [START_REF] Worton | Kernel Methods for Estimating the Utlization Distribution in Home-Range Studies[END_REF][START_REF] Calenge | Des outils statistiques pour l'analyse des semis de points dans l'espace Ecologique -PhD[END_REF]): the 90% contour reflects the general distribution of the group or 'home range', while the 50% contour delineates the more intensively used territory and is referred as 'core area' [START_REF] Börger | Effects of sampling regime on the mean and variance of home range size estimates[END_REF].

II.3.1.3. Estimation of distribution at sea

In order to define the smoothing factor, i.e. the width of the kernel function, we used a first passage time (FPT) analysis [START_REF] Fauchald | Using First-Passage Time in the Analysis of Area-Restricted Search and Habitat Selection[END_REF][START_REF] Scheffer | Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia[END_REF][START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF][START_REF] Vacquie-Garcia | Hooded seal Cystophora cristata foraging areas in the Northeast Atlantic Ocean-Investigated using three complementary methods[END_REF]. FPT is defined as the time taken by an individual to cross the area of a circle with a given radius. FPT is computed over each location and for an increasing range of radii (from 2 to 150 km and incremented by 2 km in our study). The maximum peak in relative variances across the range of radii values indicates the optimal scale of interaction of the birds of each group with the environment [START_REF] Bailleul | Assessment of scale-dependent foraging behaviour in southern elephant seals incorporating the vertical dimension: A development of the First Passage Time method[END_REF]) and corresponds to the smoothing factor of the kernel analysis [START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF]. Kernels (Fig. 39) were computed with the R package 'adehabitatHR' [START_REF] Calenge | Package ' adehabitatLT[END_REF].

Additionally, in order to compare our data with previous results from the literature, we used a traditional technique to delineate the extensive distribution of the birds from each study site. We drew with GIS software polygons encompassing the whole tracks of the birds from each study site (see Fig. 27 to visualise an example of a resulting polygon, referred as 'Distribution area' and page 126 for the details of the method). The size of each kernel and polygon was calculated with the R package 'raster'

(Hijmans and van Etten 2020) for comparisons. Since locations were interpolated on a regular time step, the values of FPT at each location are a measure of occupancy. For several species like elephant seals or king and Adélie penguins, FPT can be used as a proxy to identify foraging areas [START_REF] Scheffer | Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia[END_REF][START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF][START_REF] Vacquie-Garcia | Hooded seal Cystophora cristata foraging areas in the Northeast Atlantic Ocean-Investigated using three complementary methods[END_REF]) through the concept of Area Restricted Search (ARS; [START_REF] Kareiva | Swarms of predators exhibit "preytaxis" if individual predators use area-restricted search[END_REF]Odell 1987, Fauchald and[START_REF] Fauchald | Using First-Passage Time in the Analysis of Area-Restricted Search and Habitat Selection[END_REF]. Marine predators are supposed to maximise their research behaviour of prey. Areas with high FPT values are therefore considered as foraging areas, and areas with lower FPT values as transiting zones between foraging areas. However, the differentiation is not so binary for emperor penguins. Indeed, when out at sea, adult and juvenile emperor penguins do not spent all their time diving. They also rest on sea ice especially during the wintertime (see Fig. 28 from our study, but also [START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Labrousse et al. 2019a). Consequently, the FPT values from our tracked birds rather segregate areas of residence (resting and foraging) characterised by high FPT values, from areas or periods of travel characterised by low FPT values.

The environmental drivers of FPT values were investigated (see page 147) with Generalized Additive Mixed (GAMMs) given their flexibility to identify nonlinear functional relationships between species distribution and environmental conditions [START_REF] Zuur | Mixed effects models and extensions in ecology with R[END_REF].

II.3.1.4. Environmental variables at the exact locations

To account for location error when extracting environmental variables, we used the fitted CRW model to create a dataset of 100 simulations of each location and individual bird [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF]. The 100 values for the bathymetry, the gradient of bathymetry and sea ice concentration covariates, and the distance covariates associated with each possible location, were first extracted and then averaged, giving a mean value and its standard deviation for each location along the mean track (Fig. 29 and also [START_REF] Heerah | Contrasting behavior between two populations of an ice-obligate predator in East Antarctica[END_REF].

II.3.1.5. Estimation of distances

The distance from the locations of the birds to the sea ice edge, to the colony location or to the oceanic fronts was computed with the R package 'geosphere' [START_REF] Hijmans | Package ' geosphere[END_REF].

II.3.1.6. Residence time in management bodies and environmental features

To assess the intensity of use of features related to conservation management in the Southern Ocean by the tracked birds, we averaged the proportion of time they spent monthly inside each feature, referred hereafter as 'residence time'. We also computed the residence time per individual over the total tracking duration of each bird. Additionally, for each study site and each management feature, we computed the proportion of the distribution area falling inside the boundaries of a particular feature with the R package 'raster' (Hijmans and van Etten 2020).

We tested the statistical effect of the individuals and of the months on these proportions using Kruskal-Wallis rank sum tests. When a significant difference was measured among individuals or months, the Tukey's 'Honest Significant Difference' multiple comparison of means test was used to identify which individual(s) or month(s) differed from others [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF][START_REF] Thiebot | Adélie penguins' extensive seasonal migration supports dynamic Marine Protected Area planning in Antarctica[END_REF].

II.3.2. Dive analysis

Dive extraction was carried out with the MT-Dive software (Multi Trace-Dive, Jensen Software Systems, Laboe, Germany). The software split the pressure recordings into dives by looking at the inflexion points near the surface and allows for Zero Offset correction between dives to correct for drifting recordings while extracting various metrics (see below). Start and end of dives were considered from the last record at the surface, and dive duration as the time between dive start and end. The data processing is not perfect and some artefacts need to be corrected after extraction. For instance, some dives might be duplicated, other might not be correctly split resulting in too long dives.

This analysis considers for the moment only the dives deeper than 5 m.

Wiggles were defined as deviation of the depth at 3 points on which the vertical speed drops below 0 m/s (inflexion points) and with a change of depth above a threshold depending on the resolution of the TDR used (Fig. 30; [START_REF] Simeone | In-depth studies of Magellanic penguin (Spheniscus magellanicus) foraging: Can we estimate prey consumption by perturbations in the dive profile?[END_REF]. The definition of the bottom phase is less homogenous in the literature. In most studies on emperor penguins, the bottom phase is defined as the part of the dive deeper than 85% of the maximum depth [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Zimmer et al. 2007b, 2008, 2010[START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF], which was the default set up of the software from Wildlife Computers [START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF]). Other values have also been used in other species (90% [START_REF] Charrassin | Seasonal changes in the diving parameters of king penguins (Aptenodytes patagonicus)[END_REF], Bost et al. 2007) or 75% [START_REF] Enstipp | The dive performance of immature king penguins following their annual molt suggests physiological constraints[END_REF]) in king penguins, for instance).

Halsey and colleagues [START_REF] Halsey | A thorough and quantified method for classifying seabird diving behaviour[END_REF] and [START_REF] Hanuise | Optimization of transit strategies while diving in foraging king penguins[END_REF] defined the bottom phase as starting with the first wiggle that occurs deeper than a particular threshold and ending with the last wiggle that finishes deeper than this threshold. Others used various speed threshold (Rodary et al. 2000b, Ropert-Coudert et al. 2007[START_REF] Preston | Foraging behaviour of little penguins Eudyptula minor in an artificially modified environment[END_REF]. The start and end of bottom phases were defined as the first and last time the rate of change of depth became <0.5 m/s during a dive associated with a slimness parameter fixed at 0.1. The choice of these values was confirmed with visual inspection of thousands of dives. Such parameters allow maximising the detection of wiggles occurring during the part of the dive slightly ascending. The definition of the bottom phase we used is thus flexible to changes in the depths of the dives during which the majority of feeding events may occur. The Emperor Penguin (Aptenodytes forsteri) is regularly used to raise awareness, and, as key top predator and umbrella species, plays a central role in the Antarctic ecosystem but much remains to be learned about the distribution and activities at sea of the species. To fill parts of this gap, we equipped adults for short-term (GPS, Time-Depth Recorder (TDR)) and long-term (i.e. planned for one year) deployments (ARGOS platforms, TDR), as well as juveniles for long-term deployments (ARGOS platforms) in the Weddell Sea region and in the Atlantic sector of the Southern Ocean where they had not been studied yet.

In this report, we describe and evaluate our protocols for the attachment of biologgers on-site, the capture of the animals and the recovery of the devices after deployment. Our unprecedented recaptures of long-term equipped emperor penguins demonstrated that the traditional technique gluing the biologgers directly to the back feathers is detrimental to the birds. It causes excessive feather breakage and the loss of the devices. We propose an alternative method of attachment for back-mounted devices that led to successful year-round deployments on juveniles and evaluate the first deployments of leg-bracelet mounted TDRs on emperor penguins.

Our findings highlight the importance of monitoring potential impacts of biologger deployments on the animals and the need to remain critical towards established protocols. We propose alternative techniques and a standardised study design for emperor penguins capture and on-site logger deployment that help mitigate the potential negative impacts of logger deployment on these birds.

III.2 Introduction

Over the last decades, biologging technologythe "use of miniaturised animal-equipped tags for logging and/or relaying data about an animal's movements, behaviour, physiology and/or environment" [START_REF] Rutz | New frontiers in biologging science[END_REF]) -has rapidly progressed and led to fundamental advances in ecology of e.g. terrestrial [START_REF] Fortin | WOLVES INFLUENCE ELK MOVEMENTS: BEHAVIOR SHAPES A TROPHIC CASCADE IN YELLOWSTONE NATIONAL PARK[END_REF][START_REF] Marker | Spatial ecology of cheetahs on north-central Namibian farmlands[END_REF][START_REF] Kays | Terrestrial animal tracking as an eye on life and planet[END_REF] and marine predators (Ropert-Coudert et al. 2009a[START_REF] Bograd | Biologging technologies: new tools for conservation[END_REF][START_REF] Mcintyre | Trends in tagging of marine mammals: a review of marine mammal biologging studies[END_REF] including seabirds [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Clarke | Sex differences in Adelie penguin foraging strategies[END_REF][START_REF] Sato | Buoyancy and maximal diving depth in penguins: do they control inhaling air volume?[END_REF], Wilson et al. 2002[START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Massom | Fast ice distribution in Adélie Land, East Antarctica: Interannual variability and implications for emperor penguins Aptenodytes forsteri[END_REF], Bost et al. 2009b, Weimerskirch et al. 2014, Pistorius et al. 2017[START_REF] Chimienti | Taking movement data to new depths: Inferring prey availability and patch profitability from seabird foraging behavior[END_REF]. This technical evolution that included miniaturisation, design optimisation, storage capacity and power consumption, was supported by the development of new analytical techniques and processing software [START_REF] Hussey | Aquatic animal telemetry: A panoramic window into the underwater world[END_REF][START_REF] Carter | Navigating uncertain waters: a critical review of inferring foraging behaviour from location and dive data in pinnipeds[END_REF].

Biologgers can cause discomfort to the tagged animals and may even impede their movements, especially in the case of diving seabirds like penguins where the increased water drag can increase the energy expenditure (Culik and Wilson 1991[START_REF] Ropert-Coudert | Impact of Externally Attached Loggers on the Diving Behaviour of the King Penguin[END_REF], 2007, Beaulieu et al. 2009[START_REF] Vandenabeele | Tags on seabirds; how seriously are we considering instrumentinduced behaviors?[END_REF]). However, by collecting high-resolution data on a small number of animals, biologging can comply with the Reduction principle of the Three Rs framework (Replacement, Reduction, Refinement; [START_REF] Russel | Page The principles of humane experimental technique[END_REF]. The miniaturisation of devices [START_REF] Wilmers | The golden age of bio-logging: how animal-borne sensors are advancing the frontiers of ecology[END_REF], the establishment of guidelines [START_REF] Kenward | A Manual for Wildlife Radio Tagging[END_REF], CCAMLR 2014) and the activities of study review boards that oversee the ethical treatment of animals in scientific studies [START_REF] Wilson | Measuring Devices on Wild Animals: What Constitutes Acceptable Practice?[END_REF][START_REF] Casper | Guidelines for the instrumentation of wild birds and mammals[END_REF][START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF], Williams et al. 2019) also help to mitigate adverse impacts.

Yet, especially in the case of penguin tracking studies, the inability to observe the animals carrying the devices at sea bears the risk that deleterious effects may not be obvious [START_REF] Vandenabeele | Tags on seabirds; how seriously are we considering instrumentinduced behaviors?[END_REF] or may even remain unnoticed if birds are not resighted. For instance, after decades of flipper banding of thousands of penguins [START_REF] Wanless | Sixth review of data held by the central data bank for antarctic bird banding[END_REF] and see references in [START_REF] Jackson | The potential costs of flipper-bands to penguins[END_REF], it was only in the 2000's that studies [START_REF] Gauthier-Clerc | Long-term effects of flipper bands on penguins[END_REF][START_REF] Dugger | Effects of flipper bands on foraging behavior and survival of adélie penguins (pygoscelis adeliae)[END_REF], Saraux et al. 2011a, Le Maho et al. 2011) assessed its long-term effect, and showed that flipper bands dramatically decreased the survival and breeding success of their carrier. This finding raised important questions about ethics and bias in scientific studies; an issue already highlighted by [START_REF] Wilson | Recording Devices on Free-Ranging Marine Animals: Does Measurement Affect Foraging Performance?[END_REF]. Flipper banding of penguins is a prime example why it is necessary to study potential impacts of device deployments on animals, as well as to remain critical towards -and keep testing -new methods to minimise wildlife disturbance. It has to be noted that of the five studies [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Kooyman et al. 2015[START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Labrousse et al. 2019b) where emperor penguins (Aptenodytes forsteri) have been tagged with external biologgers for a year-round deployment duration, none has reported the recovery of the device or a sighting of an equipped bird after deployment. The causes of signal loss remained unclear [START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF]Ponganis 2004, Kooyman et al. 2015) and the fate of the device-carrying birds uncertain.

Nonetheless, data obtained from biologgers are often of such importance for conservation biology that the benefits may outweigh the risk for the animals. For example, tracking studies that determine the home range and movement corridors of species are often a prerequisite for conservation management policies [START_REF] Block | Physiological Ecology in the 21st Century: Advancements in Biologging Science[END_REF] were chosen according to our research questions and subject to seasonal constraints. We document for the first time the resighting and recapture of long-term equipped emperor penguins as well as device recovery. Indeed, while back-mounted loggers have already been successfully used for longterm deployments on emperor penguins [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Labrousse et al. 2019b), their physical impact has never been assessed presumably due to the logistical difficulties in resighting the birds before the annual moult.

Furthermore, we present the first leg-band biologger attachment and deployment on emperor penguins. Several leg-band devices had been successfully tested and deployed on other penguin species (Adélie and macaroni (Eudyptes chrysolophus) penguins, see Bost et al. 2009a[START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF][START_REF] Thiebot | Adélie penguins' extensive seasonal migration supports dynamic Marine Protected Area planning in Antarctica[END_REF]) and it was shown that the leg-band devices minimised drag, induced little behavioural disturbance and did not jeopardize birds' survival. To date, no such deployment had been documented on emperor penguins. Additionally, we describe and discuss methods for catching, handling or retrieving (resight and recapture) emperor penguins. These necessary procedures lack standardisation across studies. Some use a rugby-like catch method [START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF][START_REF] Zimmer | Constraints on Foraging and their Consequences for Emperor Penguins PhD[END_REF], others would use a crook [START_REF] Cockrem | Corticosterone Responses to Capture and Restraint in Emperor and Adelie Penguins in Antarctica[END_REF], Kooyman et al. 2015)) or a fixed enclosure (Kooyman et al. 1992b[START_REF] Williams | What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins[END_REF]) and the impacts of these procedures on the targeted bird are rarely reported.

Summarising, in this manuscript, we describe and review protocols for on-site capture, handling and release of emperor penguins, biologger attachment and recovery techniques that minimise the impacts on the birds' welfare. These protocols could be used to standardise and facilitate further studies on emperor penguin movement ecology of highest ethical standards. [START_REF] Ponganis | Sub-ice foraging behavior of emperor penguins[END_REF], Zimmer et al. 2007b, 2010[START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF] are referred to as "short-term", while year-round planned monitoring that include austral winter are referred to as "long-term" [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Rodary et al. 2000a, Zimmer et al. 2007b).

III.3 Material and Methods

The deployment protocols to use on emperor penguins largely depend of the species' phenology (and of logistic constraints). The Emperor penguin is the only bird species breeding during the austral winter [START_REF] Prévost | Ecologie du manchot empereur[END_REF], almost exclusively on sea ice [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF]) all around Antarctica [START_REF] Ancel | Looking for new emperor penguin colonies? Filling the gaps[END_REF]. After a courtship period in March and April, depending on the colony's latitude, and an incubation period of around 64 days, the chicks hatch in the middle of the austral winter. As central place foragers [START_REF] Orians | On the theory of central place foraging[END_REF], male and female do alternate trips at sea to find food for their sole offspring. By October, the chick becomes thermally independent and is left on its own while both parents go foraging at sea and return to feed their chick independently [START_REF] Stonehouse | The Emperor Penguin breeding behaviour and development -FIDS Scientific Report[END_REF][START_REF] Prévost | Ecologie du manchot empereur[END_REF]). These recurring returns of each adult to feed its chick, approximately once per week, allow for the deployment and retrieval of short-term data loggers. In December or January, chicks moult and fledge. By the end of the austral summer, the adult emperor penguins moult. For both moulted chicks (i.e. juveniles) and adults, a reliable attachment of long-term logging devices on their backs is only possible after moulting is largely completed. The majority of the juvenile penguins will not return to the colony for at least two years [START_REF] Mougin | Structure et dynamique de la population de Manchots empereurs de la colonie de l'archipel de Pointe Géologie[END_REF] and previous studies suggest that most of the adults moult on the pack ice [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF][START_REF] Hawkins | Bio-logging and animal welfare : practical refinements[END_REF][START_REF] Wienecke | Premoult foraging trips and moult locations of Emperor penguins at the Mawson Coast[END_REF], Zimmer et al. 2007b). There is also no certainty that adults moulting at the colony are actual breeders from that particular colony and that they will return for the next season. Therefore, successfully retrieving the devices is unlikely and the use of transmitting devices is by far the most prevalent technique to ensure data collection.

In this study, we used two methods of capture (corral or crook, see the capture protocols section for details) to catch three categories of birds (a pair of an adult with its chick in November/December, juveniles and moulted adults in January) in order to deploy and/or recover six different types of loggers (Table 4). Depending on the duration (short-or long-term) of planned equipment, biologgers were attached by one of four techniques (back-attachment-tape/-cyanoacrylate-glue/-tape-epoxy and leg-band). The four deployment protocols are briefly presented below and summarised in Table 8.

Additionally, all birds, i.e. adults and chicks, were marked with subcutaneous passive integrated transponder (PIT of 3.85 × 32 mm and 0.8 g, Texas Instruments Remote Identification System, TIRIS, Texas, USA) implanted between the tail and left leg (Additional file 2) allowing remote identification of individuals with automatic reading systems. All protocols adhered to current best-practise standards to reduce the risk of physical harm and stress to individuals and the colony. (Culik andWilson 1991, Bannasch et al. 1994), we followed the recommendations of previous studies. The hydrodynamically-shaped devices represented less than 1% of the penguin's cross-sectional area, weighed less than 3% of the bird's mass [START_REF] Kenward | A Manual for Wildlife Radio Tagging[END_REF]) and were attached on the lower back of the birds with adhesive tape.

III.3.1.2. Long-term deployment: back-glued loggers

In January 2018 we equipped 8 adults that had completed their moult with an Advanced Research and Global Observation Satellite (ARGOS) platform and a separate accelerometer. ARGOS platforms sent the locations of the birds through the Collecte Localisation Satellites (CLS) ARGOS service (Toulouse, France). The streamlined devices were attached by direct contact between cyanoacrylate glue and the feathers in the middle of the lower back of birds (Wilson et al. 1997b[START_REF] Casper | Guidelines for the instrumentation of wild birds and mammals[END_REF].

III.3.1.3. Long-term deployment: back-taped-epoxied loggers

In January 2019, we equipped 8 juveniles with ARGOS platforms. The devices were attached to the lower back of birds with adhesive tape that was secured with epoxy glue. Importantly, the epoxy glue did not come in contact with the back feathers.

III.3.1.4. Long-term deployment: leg-banded loggers

In January 2018, the same 8 birds equipped with ARGOS loggers (see section III.3.1.2 above) were also equipped with an additional TDR sensor that was attached with a leg-bracelet. Similar leg-bracelets had been successfully deployed on other penguin species (Bost et al. 2009a, Thiebot et al. 2011b[START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF][START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF] and Houstin, Fournier, Le Bohec, unpublished observations on Adélie penguins).

III.3.2. Capture protocols

A very limited number of scientists have ever handled a non-anaesthetised adult emperor penguin.

Handling such an animal can be difficult as they are strong but fragile birds (especially the flippers) with a body mass ranging from 15 (this study) to ca. 40 kg depending on age, sex, season and location [START_REF] Prévost | Ecologie du manchot empereur[END_REF][START_REF] Maho | Thermoregulation in fasting emperor penguins under natural conditions[END_REF]). While it is always better to transfer such skills directly in the field, this may not always be possible due to the limited number of qualified and experienced persons able to train others. Therefore, our study and the associated protocols aim to fill part of this gap.

The techniques developed in this study to approach, capture and handle an adult emperor penguin require only (in our experience this is a minimum) two qualified and empowered field staff (referred to hereafter as specialists). While at least one of the specialists should have prior field experience with emperor penguins, it is sufficient for the other specialist to have experience in handling other wildlife species and a thorough understanding of the protocols and guidelines. In addition to the two specialists, at least one, but better two, assistants with general fieldwork experience are required to support the capture and handling of the penguins.

III.3.2.1. Adult-Chick capture protocol

Here, we present a technique to capture an adult emperor penguin with its thermally independent chick during the late chick-rearing period. Catching a duo can be of interest for research questions concerning demography, kinship, evolutionary ecology or ecophysiology. To avoid larger disturbances it is ideal to capture birds at the outer rim. Therefore, the first step is to observe the outermost 3-4 rows of animals from a distance, to locate adults that are feeding the same chick several times and that are either stationary or moving towards the outer edge of the colony. Note that allofeeding behaviour is quite common in emperor penguins [START_REF] Jouventin | Adoption in the emperor penguin, Aptenodytes forsteri[END_REF]) but allofeeders usually do not stay with the same chick at this time of the season (Houstin, Le Bohec, unpublished observations).

(i) Capture equipment

Three main tools are required:

-One 2 to 3 m long stick (e.g. lightweight bamboo sticks) used to direct targeted birds out of the colony (Fig. 31a).

-One 2.5 m long light crook made of stainless steel or aluminium, bent at 50 cm from one end by an angle of approximately 135 degrees (Fig. 31a), used to direct birds and catch them if necessary. Note that a crook is more efficient than a hook from which penguins manage to escape by twisting their neck.

-A corral made of three separate panels (Fig. 31a). Each panel consists of plastic pipes joined together to form a 3 m by 0.8 m frame. For every metre in length, a vertical plastic tube is added for stability. A polypropylene net (aviary net with a mesh size of 2 cm) is connected to the frame using cable ties. This construction results in lightweight (e.g. 4.5 kg), sturdy and field serviceable panels. When the panels are connected (Fig. 31b), the triangle formed can be closed with two large reusable cable ties at each of the three joints. We suggest covering one of the panels with a plain fabric, even if this makes the panel more difficult to handle when there is wind. The fabric reinforces the corral, provides shade to the birds and prevents them from attempting to go through the net. It also protects the fieldworkers from wind and allows them to hide behind the panel to calm the birds before release. Once the pair is ~30-40 m outside the colony, one assistant hands one of the panels to the specialist with the bamboo stick, and returns to his/her own position. Once the panels have been placed equidistantly (~30 m) around the penguin pair, everybody moves closer to the pair and close the corral around it. It is to be noted that the last few metres (< 5 m) before the corral is fully closed, the team has to move in a smooth, swift and highly coordinated manner, so that no escape route is presented. If executed correctly, the penguins will remain stationary, looking for the best escape route, and find themselves in the closed corral before an escape is attempted. The specialist with the crook helps to close and secure the corral with reusable cable ties. If the adult attempts to escape, use the crook to catch the bird and prevent the escape (see section III.3.2.2 below). Four persons are the optimal number to carry out this capture protocol. If everybody is experienced, it can be executed comfortably, for the animals as well as for the scientists, with three people. The whole procedure is presented in detail in Additional file 3. After capture and manipulation, we recommend to let parent and chick rest and calm down for a few minutes in the corral to increase the chance that they stay together upon release. To release the birds in a particular direction, the cable ties of the edge facing the desired exit direction are unzipped and the corral sufficiently opened to allow the birds to go through (Additional file 5).

We used this method to capture an adult with its not-yet-moulted chick to increase our chances of recapture. Indeed, breeders with moulted chicks ready to fledge or with chicks having sufficient reserves to perform their moult and fledge on their own are more prone to end their breeding cycle, defined by the "abandon" of their chick [START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF]. Devices were recovered after one to three foraging trips.

Please note that this corral capture procedure was also used to capture flock of chicks at the beginning of their moult to mark them with subcutaneous PIT in order to perform long-term population monitoring of the colony. Body mass and mortality rate of PIT-tagged chicks from equipped adults will be compared to these annual cohorts of 300 random chicks PIT-tagged each summer.

III.3.2.2. Single adult capture protocol

Two techniques can be used to capture a single adult emperor penguin, the choice depends on the behaviour of the bird while approaching, the availability of assistants, and the weather conditions.

As described above for the pair of an adult and its chick, the corral can be used to trap a single adult in a very similar way. Nonetheless, due to the fact that solitary birds are more mobile and usually more vigilant to their environment the corral method may be difficult, which is especially true during heavy winds or a blizzard.

An alternative and efficient technique is to use a crook to catch the bird (Additional file 6) as mentioned in [START_REF] Cockrem | Corticosterone Responses to Capture and Restraint in Emperor and Adelie Penguins in Antarctica[END_REF]. The crook capture requires two people and in contrast to the corral protocol and the deployment of loggers can also be conducted in bad weather. Once the bird is isolated, one specialist places the crook around the neck of the bird preventing the penguin to escape by tobogganing, i.e. moving on its belly. Meanwhile, the other specialist grabs the tibiotarsi of the bird and holds them firm. The crook is gently removed and placed away from the capture site, and the penguin secured by the two specialists, one in front of the bird and one at the back. The crook-carrying specialist should be carrying the necessary supplies for manipulation in his/her backpack, because, after the capture, he/she will have his/her hands free, while the other specialist is still holding the bird.

We used this technique to recapture adults for device recovery or to capture non-breeding (e.g. moulting or post-moulting) adults.

III.3.2.3. Fledging juvenile capture protocol

For their first departure at sea, juvenile emperor penguins usually leave the colony in small groups. A group capture with the corral is, therefore, more efficient and potentially less stressful for the birds.

The protocol is similar to the adult-chick-pair capture, but here an entire group of juveniles is slowly encircled by three corral bearers. As emperor penguins are social animals, it is likely that keeping the group together reduces the stress of manipulated individuals and facilitates the remainder of their travel towards the sea after release. Juveniles of interest are removed individually from the corral for the manipulation and returned afterwards. All juveniles are released together after all target animals have been handled.

III.3.3. Adult emperor penguin handling protocol

One specialist (S1) grabs the penguin's neck with his/her arm always above the beating flippers and, while kneeling down, pulls the penguin towards his/her body. The second arm goes above the junction between flippers and the body, against the penguin's chest, holding the bird firmly. It is crucial to always contain the head-beak-neck of the penguin, to prevent the bird from trying to strike with its beak. This procedure can be seen in detail in the Additional file 7. Once the bird is secured in this position, the second specialist (S2) approaches and bends the penguin's head towards the ground while S1 grabs the legs above the ankles to lay the bird on its belly. When the bird is laying on the ground, S2 kneels over the bird with its head between (below) the legs of S2. In this position, the bird is immobilised. It is crucial that the flippers, the most fragile part of the bird, are unrestrained and untouched, throughout the whole process. If an assistant is available, he/she can hold the legs of the birds and stretch them (foot soles pointing towards the sky). Working with three people allows S1 to deploy the loggers seated next to the penguin and reduces manipulation time. Most penguins stay quiet in this position with some few second long bursts of intense activity: a gentle but firm pressure on the back and pulling the foot soles upper and further from the ground helps to calm the bird.

III.3.4. Equipment protocols

During manipulation, the bird's eyes were always covered with a hood to reduce stress level [START_REF] Casper | Guidelines for the instrumentation of wild birds and mammals[END_REF]) and birds were handled at distance from the edge of the colony to avoid conspecifics' disturbance (usually > 40 m, thus well above the 5 m limit recommended in the General guidelines produced by the Antarctic Treaty Consultative Meeting (ATS 2020)).

III.3.4.1. Short-term deployment: back-taped loggers

Before starting with the attachment, we recommend to use a cardboard stencil and waterproof tape that is a bit larger than the logger to demarcate the precise location of the equipment and the placement of the strips of adhesive tape on the penguin (see this in detail Additional file 8). Following studies from [START_REF] Wilson | Tape: A Package-Attachment Technique for Penguins[END_REF]Wilson et al. ( , 1997b) ) on the logger characteristics. Some glue is applied to secure their lock, which should be positioned on the side of the logger, near the lower end, to reduce drag. For a deployment period of more than one month, we recommend to add glue on top of the tapes. After manipulation is completed, we recommend to mark the bird before release with a hair-dye painted number that will last until the following moult (e.g. Schwarzkopf, Palette dark-blue N°909, Henkel AG., Düsseldorf, Germany; Fig. 32). We used this technique to deploy GPS-Acc-VHF (Axy-Trek from TechnoSmArt) and TDR (g5+ from Cefas) devices (see Table 4 for technical details and Fig. 33a to view an equipped bird) on adult emperor penguins at the end of their breeding cycle. It took 7 and 3 minutes respectively to deploy them (see respective movies of deployments in Additional files 8 and 10). We used four strips of tape and two cables ties (PLT1.5M-C0 142*2.6 mm) for the GPS-Acc-VHF and two strips of tape and two cable ties (PLT1M-C0 99*2.5 mm) for the TDR. The shape of the Axy-Trek logger was customised by the manufacturer to include two thin promontory ends, at the head and at the tail of the device, which facilitate cable tie attachment.

III.3.4.2. Long-term deployment: back-glued loggers

According to protocols from previous studies [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Kooyman et al. 2015), that conducted long-term deployment of biologgers on the back of penguins, we fixated the lower side of the loggers directly to the feathers using cyanoacrylate glue (Loctite 401). The attachment was secured with polyamide cable ties as described above (Fig. 33b).

We used this technique to deploy Spot-367 ARGOS loggers from Wildlife Computers and accelerometer (WACU) from MIBE-IPHC-CNRS on adults close to finishing their moult (Fig. 34). In an attempt to increase the duration deployment of the ARGOS logger, a rubber cable tie (Panduit, ERTM-C20), flexible and resistant to cold and pressure was added and positioned at the middle of the device.

The accelerometer was positioned higher on the back of the penguin with approximately 3 cm between both loggers. Each deployment took about 8 minutes. Similar to the short-term deployment protocol, the logger is attached to the feathers using pre-cut lengths of Tesa® tape on the entire logger length (sparing exposed sensors if any). The overlap between tape strips is reinforced with cyanoacrylate glue (Loctite 401). We recommend using two polyamide cable ties around the head and one at the bottom of the logger to secure the attachment.

The supernumerary cable tie on the head is added for extra safety. Once all the adhesive strips and cable ties were fixated, we applied epoxy adhesive (Loctite EA 3430) on the mounting (sparing exposed sensors if any) to reinforce the waterproofness and robustness, adapting methods from other studies (Wilson et al. 1997a[START_REF] Pütz | Post-Fledging Dispersal of King Penguins (Aptenodytes patagonicus) from Two Breeding Sites in the South Atlantic[END_REF]. This manipulation takes approximately 20 minutes, but it prevents the use of glue directly onto the animal and its feathers. The attachment procedure is shown in the Additional file 12.

We performed this deployment on fledging chicks. We selected the individuals most advanced in their moult, i.e. presenting no more down on their back (Fig. 33c). The lower survival rate of the juveniles during the first year at sea compared to adults [START_REF] Williams | The Penguins: Spheniscidae. Page The penguins. Bird families of the world[END_REF], their non-return to breeding colonies before several years [START_REF] Mougin | Structure et dynamique de la population de Manchots empereurs de la colonie de l'archipel de Pointe Géologie[END_REF] We designed two similar types of bracelet, a first version that we deployed (Fig. 33b), and a second version incorporating slight changes and improvements. A detailed manual of the mounts is provided in Additional file 13. We designed the bracelet to mount a Lotek Lat 1800 TDR (see Table 4 for specifications) but the bracelet can be easily adapted to other types of TDR.

The TDR is fixed to a rubber cable tie (Panduit, ERTM-C20) covered with heat-shrinkable sheath and attached around the bird tibiotarsus by closing the cable tie just above the ankle, like a bracelet. A built-in lock prevents the cable tie to tighten itself after deployment. The bracelet fits loosely with ~1 cm space between the bracelet and the leg. The shape of emperor penguin's legs prevents the bracelet from spinning around the leg. When properly set up and attached (Additional file 13), the attachment does not interfere with egg or chick placement on the bird feet during the breeding season. Deployment time is less than 3 minutes. On retrieval, the bracelet is easy and quick to remove (within a few seconds) by cutting the rubber cable tie with pliers.

III.4 Results

III.4.1. Short-term deployment: back-taped loggers

In 2017-2018, 16 deployments were performed: 10 between November 27 th and December 2 nd , of which 6 devices were recovered and redeployed between December 10 th and 12 th . None of the devices of the second deployment session were recovered, resulting in 38% recovery.

In 2018-2019, 20 deployments were performed, 10 between November 05 th and 07 th , which all were recovered and redeployed between November 25 th and December 6 th . Six devices of the second deployment were recovered, resulting in 83% recovery. We conducted intense VHF and visual (binocular) surveys for equipped birds (ca. every 4 hours), thus we are confident that we retrieved all the loggers from returning birds. All VHF units of recaptured birds were working and unequipped birds have been regularly identified afterwards by their hair-dye painted number on their chest.

Bird feathering on recovery was intact and no physical damage on the bird or on the device was apparent. All loggers were still securely attached, even after the longest deployment of 25 days (Table 9). Our recovery rate for November (90%) is similar (z-test, p-value > 0.05) to those of previous studies at this period ( Only post-moult long-term deployments, i.e. pre-nuptial/pre-winter travels (beginning in Jan-Feb-Mar) and breeding short-term deployments, i.e. Nov-Dec, are considered in this table. Other studies have deployed devices specifically between May and October, i.e. breeding period only [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Rodary et al. 2000a, Zimmer et al. 2007b, Labrousse et al. 2019a) or at the end of austral summer (end of December-January) trying to locate moulting areas [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF][START_REF] Wienecke | Premoult foraging trips and moult locations of Emperor penguins at the Mawson Coast[END_REF]). W-Mon = Winter-month of deployment, S = summer, ad = adult, juv = juvenile. NA = not available. For studies on juveniles, duration below 30 days have been removed since those short periods of deployment are mostly thought to be due to predation.

For [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF], only not hand-fed chicks have been considered. The corrected numbers of deployments are indicated by a star (*). In bold, the greatest values within a category of deployment. In italic, data from other studies.

The average mean mass of PIT-tagged chicks from the annual cohort and chicks from equipped adults were similar (Table 10). The mean mass of PIT-tagged chicks from the annual cohort in the second year was significantly lower (p-value < 0.05) than the mean mass of PIT-tagged chicks from the annual cohort in the first year. Albeit the mean mass of chicks from equipped adults in the second year was also lower than the mean mass of chicks from equipped adults in the first year, there were no statistical differences (p-value > 0.05) due to the small sample size (ANOVA were carried out after a log-transformation of the data to meet the assumptions of normality). Concomitantly to the deployments, the survival rate of chicks was assessed both summers (Table 11).

Dead chicks were counted on-site throughout the summer seasons, while alive chicks were counted using ClickPoints software [START_REF] Gerum | ClickPoints : an expandable toolbox for scientific image annotation and analysis[END_REF] at the end of December on ultra-high resolution panoramic pictures obtained with the SPOT penguin observatory (Richter et al. 2018a The number of dead (CEB, PIT, Total) and alive (Total) chicks over the two summer seasons at Atka Bay colony are provided. Dead chicks: CEB = chicks of equipped birds, PIT = Passive-Integrated-Transponder-tagged chicks not including the CEB, Total = total number of dead chicks found on the colony during the summer seasons (from November to January), Alive chicks: Total = number of alive chicks counted end of December on pictures. Numbers in brackets are the number of individuals manipulated for each study.

III.4.2. Long-term deployment: back-glued loggers

Our study is the first to report recapture of emperor penguins after a whole-winter deployment (January to November). Identified by the number painted on their chest (Fig. 32), 4 of the 8 birds equipped in January 2018 were resighted and recaptured in November 2018 (Table 9). All of them had lost the devices on their back. Instead, there was a line of missing/broken feathers (Fig. 35). No injury was detected.

This finding explains why contact with all ARGOS devices was lost during the winter. The mean transmission period was 150 ± 30 days (range 118-201 days, Table 9), significantly exceeding the previous average deployment durations of 66 [START_REF] Kooyman | Why do satellite transmitters on emperor penguins stop transmitting?[END_REF]) (p-value > 0.05, ANOVA) and 114 days [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]) (p-value < 0.05, ANOVA) from all previous similar studies. III.4.3. Long-term deployment: back-taped-epoxied loggers Noteworthy, three of the 8 juveniles equipped in January 2019 transmitted until their annual moult in January 2020. None of the birds did return to their native colony for moult; an observation congruent with the conjecture that juveniles of 1.5-years of age do not come back to moult at their colony of origin for the first year [START_REF] Mougin | Structure et dynamique de la population de Manchots empereurs de la colonie de l'archipel de Pointe Géologie[END_REF]Van Beveren 1979, Labrousse et al. 2019b). This tracking period of a full year, from January 2019 to January 2020 (

III.4.4. Long-term deployment: leg-banded loggers

Our study is the first to perform a year-round deployment and data collection on emperor penguins.

The 4 adults recaptured without their back-mounted loggers were still carrying their leg bracelet mounted TDR, providing an unprecedented record of an entire year of high frequency (1 Hz) depth and temperature logs for emperor penguins.

For all recaptured birds, the leg-bracelet mounting did not present any damage, the bracelet and the TDR were at the same position of their deployment, suggesting that the device did not rotate around the leg during the deployment period. However, all recaptured birds had lost a few feathers especially on the inside part of the leg and showed signs of abrasion in the form of a slight reddening of the skin and peeling under the bracelet area. Two of them had small sore spots on their tarsi. No limping was observed before or after removal. An illustrated comparison between an equipped and an unequipped leg after recovery can be found in the Additional file 14.

III.5 Discussion

We presented three techniques to capture and/or recapture emperor penguins, as well as four different procedures to externally attach various biologging devices on an emperor penguin. To our knowledge, the two methods of capture/recapture using a corral have not been described in the scientific literature. Two of the four deployment methods presented, the back-taped-epoxied logger and the leg-banded logger, are new developments for this species. With the description of those new or refined methods and detailed assessment of their impacts on the birds wellbeing, paired with an exhaustive documentation (pictures, movies and slideshows exposed in the multiple additional files), we aim to facilitate, standardise and thus enhance future research on this species.

III.5.1. Capture and handling

All capture techniques presented in this study yield minimal colony disturbance regardless of the period of the breeding cycle. The described handling is safe for birds and handlers, and only a minimal number of trained personnel is required, which is an important consideration when conducting fieldwork in remote places like Antarctica.

We recommend using those techniques to capture and manipulate emperor penguins at a breeding site and urge users to share their improvements and modifications. We also recommend the use of the corral if no member in the field team is accustomed to handling a crook or a hook on at least one penguin species.

We are confident that the use of an easy-removable corral opens new perspectives for research in different fields (demography, comparative physiology, evolutionary ecology) that require, for instance, catching pairs of breeding adults at the beginning of the austral winter.

III.5.2. Deployments III.5.2.1. Short-term deployment: back-taped loggers

Our study is the first to report the deployment of GPS devices on emperor penguins. GPS devices have already been deployed on penguins [START_REF] Mattern | How to get the most (or anything) out of GPS loggers: a case study with Snares penguins[END_REF][START_REF] Trathan | Linear tracks and restricted temperature ranges characterise penguin foraging pathways[END_REF][START_REF] Poupart | Variability in the foraging range of Eudyptula minor across breeding sites in central New Zealand[END_REF][START_REF] Le Guen | Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins ( Pygoscelis adeliae )[END_REF]), yet never on emperor penguins on which only ARGOS devices (Zimmer et al. 2007b, 2010[START_REF] Sato | Stroke rates and diving air volumes of emperor penguins: implications for dive performance[END_REF][START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF] or dive-pattern-analysis related loggers [START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF][START_REF] Sato | Stroke rates and diving air volumes of emperor penguins: implications for dive performance[END_REF][START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF] 10) suggest that the environmental conditions were harsher the second summer, explaining the higher number of dead chicks from equipped birds in the second year of this study.

To optimise the recovery rate of devices deployed at the end of the breeding season and minimise potential impact on chicks, we recommend to deploy devices on adults with medium-sized chicks at the very beginning of chick moult. Supported by the secure attachment of the presented technique, we furthermore suggest increasing deployment time rather than to recover loggers and redeploy them.

III.5.2.2. Long-term deployment: back-glued loggers

Our study is the first to document the recapture of a long-term equipped emperor penguin and thus the first able to assess (i) the state of the bird, (ii) the state of devices, and (iii) provide evidence explaining the loss of signal from communicating-satellite-relayed loggers reported in previous studies.

Until now, five studies had performed long-term deployments on emperor penguins right after the moult (Table 9), all using ARGOS platforms and cyanoacrylate glue to attach the logger directly to the back-feathers of the birds. None of the birds were resighted. Two deployments were made on adults [START_REF] Kooyman | Why do satellite transmitters on emperor penguins stop transmitting?[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], three on chicks [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b).

Our results show that both glued devices, the ARGOS transmitter and the small accelerometer, which vary substantially in size and weight (Table 4), were lost in the same manner on all birds. We speculate that the cyanoacrylate glue rigidifies the feathers, which then become brittle and break with either the continuous birds' movements and/or their attempts to remove the device. Wilson et al. (1997b) also observed this device-sized hole in the feather layer after winter deployment on four Magellanic penguins (Spheniscus magellanicus) using epoxy instead of cyanoacrylate glue. In our study, five of the eight ARGOS signals were lost while birds were on fast ice at the breeding side, thus not in the water for several weeks. The longest duration of deployment (201 days, Table 9) was recorded for the only bird that did not spend any extended time on ice. When the birds remain on the fast ice at their breeding colony, they are exposed to extremely cold temperatures, up to -50°C in Atka Bay (Richter et al. 2018a). We assume that, such cold temperature could have two different effects. Either the cyanoacrylate induced brittle feathers become very weak when exposed to such cold temperatures and, therefore, are easier to break during the penguins' movement, or the brittle feathers do not provide the proper isolation against the cold, thus altering the heat transfer and/or thermoregulation of the bird (as observed on pup grey seals (Halichoerus grypus) by [START_REF] Mccafferty | The effect of instrument attachment on the surface temperature of juvenile grey seals (Halichoerus grypus) as measured by infrared thermography[END_REF]). This could lead to the animal preening their feathers fiercely and thereby removing the logger by breaking/removing the brittle glued feathers. In addition, blizzards may have caused the accumulation of ice around the loggers, amplifying the above effects and tearing the device off [START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF]Ponganis 2004, Kooyman et al. 2015). However, we suggest that the huddling behaviour of emperor penguins [START_REF] Prévost | Ecologie du manchot empereur[END_REF][START_REF] Gilbert | Huddling behavior in emperor penguins: Dynamics of huddling[END_REF]) would prevent ice accumulation in the middle of the winter. Another possible explanation could be the timing of deployment. Devices were attached just at the end of the moult, a time when feathers may not yet be fully developed despite a meticulous bird selection process (Fig. 34). Their growth after deployment could potentially have added some slack and thus reinforced the pull on the feather shafts, ultimately leading to their breakage after few months. The loss of back feathers undoubtedly leads to a diminution of insulation that causes a greater heat loss. The resulting increase in energetic needs reduces fasting capabilities and forces the birds to compensate by finding more prey items when they return at sea to forage in order to replenish their reserves while accumulating food for their chick. As body reserves management is critical for this species, any significant heat loss is likely to impact breeding success.

The ARGOS locations of the birds throughout the year allow to determine if an animal attempted to breed (according to its location and behavioural pattern at sea and at the breeding site during the winter breeding period). Three of the four recaptured birds attempted to breed. Amongst those, only one succeeded and was observed several times with its chick during the summer season. The fourth recaptured bird did not attempt to breed in that year. Two of the four birds that were not recaptured, did not return to Atka Bay colony in that year and did not attempt to breed at another colony. The remaining two birds did return to Atka Bay colony for breeding. These two non-recaptured breeders were not resighted despite intensive searching efforts throughout the season (two daily checks of two hours each per day with two specialists screening the colony with binoculars). The risk of premature death is unlikely as survival is high on adult emperor penguins [START_REF] Jenouvrier | Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models[END_REF]. This suggests that they either skipped or failed breeding and, therefore, were not present at the colony in November/December 2018. Nevertheless, the possibility that these two breeding birds were successful breeders that we did not detect and recapture cannot be excluded. First, the colony counts at least 12500 breeding pairs [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF], Richter et al. 2018a), which makes visual detection difficult. Second, days of harsh weather conditions prevent binocular checks, sometime for several days in a row. Late chick-rearing emperor penguins spend only few hours at the colony [START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF], 22.5 hours in average for birds from this study, thus it is possible that we did not manage to recapture birds that were actually successful breeders.

We interpret the low number of successful breeders (1 over 3 or 5 that attempted a reproduction) amongst equipped birds as the consequences of the additional costs induced by the attachment technique to glue the device directly on the feathers, and thus reduced chance for successful breeding.

In tagging procedures, the ethical principle of Refinement from the Three Rs [START_REF] Russel | Page The principles of humane experimental technique[END_REF],

i.e. the use of methods which decrease any adverse effect, should apply. Thus, we claim that the loss of the device and resulting consequences for the birds are unacceptable and that our findings combined with the ones from Wilson et al. (1997b) should prevent further use of glue directly on the birds feathers for long-term deployment on penguins as it is currently practiced. Instead, we propose an alternative technique.

III.5.2.3. Long-term deployment: back-taped-epoxied loggers

Due to the results of the long-term deployment performed in 2018 as highlighted above, we adapted the deployment methodology for the 2019 deployment. Logistical constraints forced us to leave the field before the first moulting adult emperor penguin on site had fully moulted. We therefore focused on a second long-term deployment objective of our research project on the distribution at sea according to the age-class. We employed the back-taped-epoxied technique on juveniles, who so far had only been tagged using the back-glued method so far (Table 9).

Three of the juveniles (40%) retained their device for an entire year, thus achieving the longest duration of back-mounted logger deployment possible in penguins. The previous longest durations recorded for juvenile emperor penguins were of 344, 298 and 271 days (Labrousse et al. 2019b) with one bird (6% of the deployments) approaching the one year length duration. The mean duration of our long-term deployments (233 ± 108 days) with the taped-epoxied technique is longer than any previously reported on juvenile or adult emperor penguins (Table 9). Therefore, we are confident that the technique presented is a significant improvement for tracking of penguins and understanding their activities at sea. Some of the previous studies using glue on juveniles approached long-term attachment duration.

Nevertheless, in addition to the possible loss of feathers and insulation previously discussed, the glue has the potential to cause thermal skin burns [START_REF] Walker | A review of the effects of different marking and tagging techniques on marine mammals[END_REF]. Juveniles are more vulnerable than adults as their foraging skills (including their ability to dive, to capture prey, and to find productive feeding grounds)

are not yet fully developed, and their experience to escape predators is also minimal [START_REF] Wanless | Black-legged kittiwakes as indicators of environmental change in the North Sea: Evidence from long-term studies[END_REF][START_REF] Orgeret | Early diving behaviour in juvenile penguins: improvement or selection processes[END_REF][START_REF] Enstipp | Apparent changes in body insulation of juvenile king penguins suggest an energetic challenge during their early life at sea[END_REF]. The additional cost induced by a glued device may negatively impact the survival of the juveniles during their first months in their new marine environment that they experience for the first time. As a result, for studies requesting the deployment of back-mounted devices on penguins for long-term duration, the use of glue on feathers should be entirely avoided, and we recommend to use instead a mix of Tesa® tape strips (feathers' side) and epoxy (on the strips covering the device) to reinforce adhesion.

We did not show that this attachment will last on adult emperor penguins as long as for juveniles. An early departure from the field due to logistical constraints prevented us to deploy this new technique on fully moulted adult emperor penguin. Adult emperor penguins experience very harsh environmental conditions on the sea ice, especially at their breeding site, during winter with temperatures below -50°C and wind speeds above 150 km/h at Atka Bay (Richter et al. 2018a). Mean deployment durations on adults are less than six months (Table 9) and need to be improved to cover the entire breeding cycle to justify the disturbance. We are convinced that new techniques should be tested such as the more efficient and less impacting one presented in this study for juveniles.

III.5.2.4. Long-term deployment: leg-banded loggers

We developed and tested a leg-band TDR mount to enable year-round deployments on adult emperor penguins. The deployed leg-band TDR mount was the first to successfully collect high frequency (1 Hz), pressure and temperature data in this species during the whole year. This data will allow a detailed analysis of foraging activities and water column exploitation over a full year for the same birds.

Leg-band mounted devices had already been deployed on penguins (Bost et al. 2009b[START_REF] Thiebot | Quantitative method to estimate species habitat use from light-based geolocation data[END_REF], Ballard et al. 2010, Dunn et al. 2011[START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF][START_REF] Thiebot | Adélie penguins' extensive seasonal migration supports dynamic Marine Protected Area planning in Antarctica[END_REF]), but not yet on the emperor penguin species. Often, the condition of the birds at retrieval are not mentioned, however, some of the studies reported similar leg irritations [START_REF] Dunn | Postbreeding dispersal of Adélie penguins (Pygoscelis adeliae) nesting at Signy Island, South Orkney Islands[END_REF][START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF]; T.

Raclot pers. com.; Houstin, Fournier, Le Bohec, unpublished observations) as the ones we observed in this study. The commonly accepted flying bird banding technique is also known to cause unintentional damage like sores, inflammation, or even loss of feet in extreme cases [START_REF] Pierce | Plastic colour rings and the incidence of leg injury in flycatchers (Muscicapidae, Monarchidae)[END_REF][START_REF] Griesser | Causes of Ring-Related Leg Injuries in Birds -Evidence and Recommendations from Four Field Studies[END_REF][START_REF] Costantini | A meta-analysis of the effects of geolocator application on birds[END_REF], thus the irritations observed here can be considered as a minor impact.

We suggest that the use of a non-continuous heat-shrink tubing and the glue around the head of the rubber cable tie created a small ledge in the otherwise smooth surface that irritated the birds' leg-skin.

From this observation, we have designed an improved version for the second season (Additional file 13), which could not be tested due to early departure from the field site. The continuous heatshrinkable sheath in the updated bracelet attachment will likely reduce friction between the leg and the bracelet and ideally avoid skin irritation. If feathers are still lost, we expect the tibiotarsus to be less irritated and the occasional development of sores prevented. To prevent the formation of glue flakes, glue will only be applied inside the cable tie's closure, with parsimony, and not around the whole head.

At retrieval, the mounting did not show any damage or sign of wears and is expected to last several years before the elastomeric cable tie breaks. Consequently, before deploying such a system, a strategic plan for its retrieval is crucial. Emperor penguins are non-nesting seabirds, breeding freely on sea ice within a mobile colony (Richter et al. 2018a), which makes the recapture of birds difficult, especially after more than one year when the annual moult removed any externally painted-markings.

Due to their PIT-tag, all birds manipulated can be life-long identified by automatic detection systems, without requiring recapture or visual observation [START_REF] Gendner | Automatic weighing and identification of breeding penguins[END_REF][START_REF] Gendner | A new application for transponders in studying penguins[END_REF] ). Such a system will be deployed at Atka Bay colony the next coming season to improve our retrieval ratio of 50%, while the ones for nesting birds stand between 60 to 90% (Bost et al. 2009b, Ballard et al. 2010, Thiebot et al. 2011a, 2015, Dunn et al. 2011[START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF]. This technological improvement will allow us in the years to come to recapture birds even after several years of deployment like for nesting birds [START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF], T.

Raclot pers. com.; Houstin, Fournier, Le Bohec, unpublished observations).

Specifically with this bracelet technique, multi-year deployments might be considered. Scientific programmes running in Antarctica are not always able to return several years in a row, and this technique of deployment offers some flexibility. Solutions still need to be developed for communicating devices that need to get out of water regularly to send or receive telemetry (GPS, ARGOS) or for biologgers that would record too noisy data when positioned on the leg. However, for small data loggers, that are able to record environmental variables (e.g. hydrostatic pressure, water conductivity and temperature, environmental luminosity) on a multi-year scale [START_REF] Enstipp | Apparent changes in body insulation of juvenile king penguins suggest an energetic challenge during their early life at sea[END_REF][START_REF] Enstipp | The dive performance of immature king penguins following their annual molt suggests physiological constraints[END_REF], the leg-band technique is an interesting alternative.

III.6 Conclusions

The deployments presented in this study deliver long-term biologging data that provide highly valuable insights about emperor penguins' distribution in the Weddell Sea and in the Atlantic sector of the Southern Ocean, where they had never been studied before and are essential for assessing the adaptive potential of the species globally. Ethical concerns raised by the use of measuring devices on wild animal are not new [START_REF] Wilson | Measuring Devices on Wild Animals: What Constitutes Acceptable Practice?[END_REF]) and a recent review [START_REF] Forin-Wiart | Why implantation of bio-loggers may improve our understanding of how animals cope within their natural environment[END_REF] addressed the current pros and cons on attachment issues. To ensure data is of exemplary quality from a scientific and ethical point of view, the potential deleterious effects of deployment procedures (capture-attachment-recapture) must be assessed and mitigated.

Emperor penguins have been equipped with loggers over the last thirty years, however, there is no specific methodological publications either on the critical "how" question nor on detailed capture and recapture processes. Attachment procedures are occasionally more detailed but with contrasting results of deployment durations and no conclusions about the outcomes for the birds and the devices.

This study is the first to provide such highly detailed and proven procedures to capture/recapture and externally attach telemetry devices on emperor penguins. We, therefore, consider this study as major advancement by (i) stating clearly the impact of using glue for biologging device attachment on penguins, not only emperor penguins, (ii) helping to assess long-term loggers loss reasons (notably ARGOS transmitters), (iii) presenting two customised less invasive attachment techniques of biologging devices on emperor penguins in detail, and (iv) explicitly providing techniques to capture and handle emperor penguins with a limited amount of disturbance as well as a maximum of safety and efficiency.

This publication is intended to serve as a resource to facilitate future research on this iconic species, and urge researchers to share their improvements in order to keep implementing a high standard framework for the study of emperor penguins.

This study also encourages researchers and journals to give more exposure to fieldwork methodology in scientific publications not specifically methodology oriented, in particular to techniques developed and tested but not successful in the field. We are convinced that too much time and resources are allocated to the development of techniques already tested but not shared because of their failure.

Tests, errors and failures are inherent of research and should be, to some extent, valued as significant results; a practice that would benefit to both scientists and animals.

Chapter IV. Juvenile emperor penguin range calls for extended conservation measures in the Southern Ocean

IV.1 Abstract

To protect the unique and rich biodiversity of the Southern Ocean, conservation measures such as marine protected areas and fishery management zones have been implemented. Based on the known habitat distributions of key species of the ecosystems including emperor penguins and other top predators, the establishment of several additional protection zones are currently being considered.

However, the presence of such species at sea is often insufficiently sampled. Indeed, current distribution models focus on the habitat of adult animals and neglect that immatures and juveniles can inhabit vastly different areas. Here, we show that conservation efforts in the Southern Ocean are insufficient for ensuring the protection of highly mobile species like the Emperor penguin. We find that juvenile emperor penguins spend the vast majority (~90%) of their time outside the boundaries of proposed and existing marine protected areas, and that their distribution extends up to 1500 km north of the habitat range as defined by the International Union for Conservation of Nature (IUCN) that curates the Red List of Threatened Species. We argue that for successful strategic conservation planning based on long-lived sentinel and umbrella species such as seabirds and marine mammals, the habitat range of all age classes must be considered.

IV.2 Introduction

Anthropogenic environmental changes lead to upheaval even in remote and apparently untouched ecosystems such as the Antarctic and its circumpolar Southern Ocean. Top marine predators such as seabirds and marine mammals play a pivotal role in marine ecosystems [START_REF] Hammerschlag | Ecosystem Function and Services of Aquatic Predators in the Anthropocene[END_REF][START_REF] Pimiento | Functional diversity of marine megafauna in the Anthropocene[END_REF], and any disruptions in their abundance and distribution have a major impact on the ecosystem functioning and resilience [START_REF] Myers | Cascading effects of the loss of apex predatory sharks from a coastal ocean[END_REF][START_REF] Graham | Seabirds enhance coral reef productivity and functioning in the absence of invasive rats[END_REF]. At the same time, top predators are key indicators of the ecosystem's health because of their high position in the trophic cascade and the vast, ocean basin-scale habitat of individual animals [START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF], Hazen et al. 2019, Hindell et al. 2020). Thus, they react particularly sensitive to disturbances in the food web and are therefore important bioindicators of environmental changes. The health, abundance and distribution of top marine predators are consequently key metrics in ecosystem-based management, e.g. for the designation and the design of marine protected areas and systematic conservation planning [START_REF] Ronconi | The role of seabirds in Marine Protected Area identification, delineation, and monitoring: Introduction and synthesis[END_REF], Ballard et al. 2012[START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF], Hays et al. 2019).

Effective conservation plans require comprehensive consideration of the complete at-sea distribution of the species, including each life-history stage [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]). However, the distribution of juvenile and immature animals, which are an essential part of the total population, is difficult to assess and is therefore often neglected. This is especially true for polar ecosystems, where remoteness and the extreme environmental conditions induce technical and logistical constraints for data collection [START_REF] Fedak | The impact of animal platforms on polar ocean observation[END_REF].

Polar ecosystems currently experience significant impact due to global changes [START_REF] Stark | Antarctic Seas[END_REF].

Measurable negative effects on polar wildlife have already occurred, such as population decreases of numerous seabird species [START_REF] Trivelpiece | Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica[END_REF][START_REF] Barbosa | Population decline of chinstrap penguins (Pygoscelis antarctica) on Deception Island, South Shetlands, Antarctica[END_REF], Ropert-Coudert et al. 2018), including the complete loss of colonies of one of the most emblematic species of the Antarctic, the Emperor penguin ((Aptenodytes forsteri); Trathan et al. 2011a, Fretwell andTrathan 2019). The vanishing of these colonies has been attributed to strong El Niño events, rise in local mean annual air temperature, strong winds, and/or decline in seasonal sea ice duration. Climate change is also expected to result in human access to new ice-free fishing areas [START_REF] Rintoul | Choosing the future of Antarctica[END_REF][START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF], whereby seabirds and marine mammals will have to compete for food with industrial fisheries and may even become by-catch (González-Zevallos and Yorio 2006, [START_REF] Trathan | Pollution, habitat loss, fishing, and climate change as critical threats to penguins[END_REF], Crawford et al. 2017). The accumulation of anthropogenic pressures on these fragile ecosystems urgently requires effective protective measures (Chown andBrooks 2019, Brooks et al. 2020a).

123

The Southern Ocean is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The CCAMLR's mandate includes the implementation of direct conservation measures such as the establishment of Marine Protected Areas (MPAs) and the regulation of the fishing industry, through quota allocations and gear limitations. Conservation measures within the CCAMLR are adopted on the basis of the best scientific data available, amongst which are the distribution and demography of marine predators (CCAMLR 2018a, 2019a[START_REF] Teschke | An integrated data compilation for the development of a marine protected area in the Weddell Sea[END_REF].

Similarly, the International Union for Conservation of Nature (IUCN)'s Red List of Threatened Species is built upon a range of scientific data that help to define the habitat range of each species, which serves as a reference for political decisions on the implementation of conservation measures. Consequently, an uncertain distribution range might lead to inadequate decisions for the future protection of the species.

As of today, 12% of the waters inside the CCAMLR boundaries are protected (Brooks et al. 2020a). For The emperor penguin population is currently estimated at ca. 270 000 breeding pairs spread over 61 identified colonies around the Antarctic continent [START_REF] Trathan | The emperor penguin -Vulnerable to projected rates of warming and sea ice loss[END_REF]Trathan 2020).

The species is severely threatened by global warming and expanding fishing activities in the Southern Ocean [START_REF] Trathan | Pollution, habitat loss, fishing, and climate change as critical threats to penguins[END_REF](Trathan et al. , 2020)), facing the risk to be nearly extinct within this century 100 years [START_REF] Jenouvrier | The Paris Agreement objectives will likely halt future declines of emperor penguins[END_REF]. The most effective action to protect emperor penguins from impacts of climate change would be a reduction in anthropogenic greenhouse gas emissions [START_REF] Jenouvrier | The Paris Agreement objectives will likely halt future declines of emperor penguins[END_REF], Trathan et al. 2020). Also the establishment of marine protected areas across its range would help to mitigate the anthropogenic impact (Trathan et al. 2020).

Marine conservation efforts need spatially-explicit movement data throughout each life-history stage, but little is known about the early life at sea of emperor penguins, even though this is a critical phase in their life and crucial for the viability of the global population [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF]. To date, only 48 juvenile emperor penguins have been tracked in total, and at-sea distribution data of juveniles are available only for the Ross Sea (10 animals; [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF]) and for East Antarctica (38 animals; [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b). However, for the designation of MPAs, it is fundamental to know their distribution at the circum-Antarctic scale (Hays et al. 2019[START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF], Hindell et al. 2020).

To bridge this gap in knowledge, we equipped eight 6-months-old emperor penguin chicks with ARGOS satellite platforms that sent the locations of the birds several times each day. We also incorporated into our analysis the distribution of all previously tracked juvenile emperor penguins [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b) in order to assess the habitat used by the juvenile emperor penguin at a global scale and contribute towards a fuller assessment of the species distribution to be incorporated into conservation planning.

IV.3 Material and Methods

IV.3.1. Study site and instrumentation

Our study was conducted at the Atka Bay emperor penguin colony (70°37'S, 08°09'W) in close vicinity Fledglings with no more down on their back (Fig. 33c) were captured on their departure to sea with a corral (Fig. 31).

To minimize drag, ARGOS platforms (107*18*21 mm, 45g, Table 4) were deployed on the lower back of the birds (Culik andWilson 1991, Bannasch et al. 1994). The streamlined devices were attached to the feather with adhesive tape (Tesa® tape 4651, Beiersdorf AG, Hamburg, Germany) and secured with three cable ties (Panduit PLTM1.5M-C0 142*2.6mm, Panduit Corp, Illinois, USA). We then applied epoxy glue (Loctite EA 3430, Loctite, Henkel AG., Düsseldorf, Germany) on the mounting to increase waterproofness and robustness (Wilson et al. 1997b[START_REF] Pütz | Post-Fledging Dispersal of King Penguins (Aptenodytes patagonicus) from Two Breeding Sites in the South Atlantic[END_REF].

IV.3.2. Estimation of the at-sea distribution of juvenile emperor penguins from the Atka Bay colony IV.3.2.1. Location filtering ARGOS locations are associated with spatial error ellipses. These spatial errors can range from a few hundred metres to several kilometres (Costa et al. 2010b, CLS 2016). Erroneous locations were filtered out using a speed filter from the R package 'argos filter' [START_REF] Freitas | A simple new algorithm to filter marine mammal Argos locations[END_REF] with the maximum travel speed fixed at 15 km/h following similar studies on emperor penguins [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 1997, Labrousse et al. 2019b).

IV.3.2.2. Interpolation of locations at a regular time step

We used a state-space modelling approach [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF] to estimate hourly locations.

Specifically, a Kalman filter, which accounted for location error, was applied using the R package 'crawl' [START_REF] Johnson | Fit continuous-time correlated random walk models to animal movement data[END_REF], and Continuous-time Correlated Random Walk (CRW) models were used to predict locations at a regular time step interval of 1 h [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF].

IV.3.2.3. Estimation of the colony-specific distribution area for juvenile emperor penguins

In addition to the eight birds tracked in our study, 48 juvenile emperor penguins from four different colonies have previously been tracked [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b); see Table 12 for the details on the colonies. Data of these previously acquired bird journeys are available as maps in the respective publications. We georeferenced these tracking maps using the QGIS software. We subsequently plotted the main corner points encompassing the tracks of all birds from each colony. We obtained the distribution of juvenile emperor penguins by computing the concave hull envelope for each dataset (Fig. 27) using the 'ConcaveHull' plugin [START_REF] Moreira | Concave hull: a k-nearest neighbours approach for the computation of the region occupied by a set of points[END_REF]. Envelopes from the same colony [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b) were merged to consider only one polygon per colony (referred to as distribution area), including one for the Atka Bay colony. The size of each distribution area was calculated with the 'raster' function from the R package (Hijmans and van Etten 2020) and is reported in Table 12. Due to the significant overlap of Auster and Taylor Glacier juvenile distribution [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF]) and the close (132 km) vicinity of the two sites [START_REF] Ancel | Looking for new emperor penguin colonies? Filling the gaps[END_REF], for visualization purposes, the tracks of the birds from Auster and Taylor Glacier colonies are shown in the same polygon in Fig. 36. However, the distribution areas were computed separately for each colony.

IV.3.3. Ecological features

The locations of the Southern Ocean fronts and the Antarctic Circumpolar Current boundaries (ACC; [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF] were downloaded from https://gis.ccamlr.org (CCAMLR 2019b).

The bathymetry at one-minute horizontal spatial resolution was obtained from the ETOPO1 Global Relief Model provided by the NOAA National Geophysical Data Center [START_REF] Amante | ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis[END_REF].

Sea ice concentrations (ranging from 0 to 100%) were obtained from Advanced Microwave Scanning Radiometer (AMSR-2) satellite estimates of daily sea ice concentration at 3.125 km resolution from the University of Bremen (https://seaice.uni-bremen.de/data/amsr2/, Spreen et al. 2008b). The sea ice

IV.4 Results

Tracking data from our study show that juvenile emperor penguins from the Atka Bay colony commonly travel beyond 50°S (the lowest recorded latitude was 48.37°S), which is 600 km further north than previously recorded (Table 12). Two birds reached the sub-Antarctic South Georgia and South Sandwich Islands' region in late June and stayed there at least until July when their ARGOS platforms stopped transmitting, demonstrating that the presence of juvenile emperor penguins in sub-Antarctic area should be considered not an extreme but regular behaviour, at least in the Atlantic sector of the Southern Ocean. All tagged juveniles reached the Southern Boundary of the Antarctic Circumpolar Current (ACC), and 5 of out of 8 birds remained for prolonged time periods (> 46 days) between the southern ACC boundary and the Antarctic Polar Front where Antarctic waters meet the relatively warmer sub-Antarctic waters. One bird even travelled north of the Polar Front. The penguin tracks over a full year (polygon encompassing the area covered by the tracks) covered an area of 5.1 millions km² (Fig. 36 and Fig. 37, Table 12), nearly 1.4 times larger than the largest previously reported distribution of juvenile emperor penguins from a breeding colony Table 12). 59.9 707.9 1.4 25.9 7.6 17.7 11.6 4.9 Colony details (location and size), tracking survey metrics (duration, distance, distribution), percentage of the distribution area that is falling within the main conservation and management areas (IUCN, CCAMLR, MPAs), and oceanographic features of the Southern Ocean (SO/Treaty limit, ACC). * Number of breeding pairs [START_REF] Fretwell | Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins[END_REF]. ACC: Antarctic Circumpolar Current; SO: Southern Ocean (i.e. at the parallel of 60°S as defined in the Antarctic Treaty); CCAMLR: Commission for the Conservation of Antarctic Marine Living Resources; IUCN: International Union for Conservation of Nature; MPAs: Marine Protected Areas. The seasonal travel pattern of the juvenile penguins from our data set resembles those of the other colonies. At the end of the summer, after leaving their colony of origin, juveniles migrate northward towards and into the Antarctic Circumpolar Current where, in our study, they remained on average for 37 ± 24 days (mean ± SD). Juvenile emperor penguins commonly range outside the limits of the Southern Ocean (i.e. the parallel of 60°S as defined in the Antarctic Treaty, hereafter referred to as SO-Treaty) with some birds wandering outside the CCAMLR boundaries (Fig. 36 and Table 13). In late fall, i.e. end of March/April, they migrate southward towards the pack-ice where they spent the winter (Fig. 37).

The individual juvenile emperor penguins from our study spent only 51.1 ± 13.3 % of their time inside the species' habitat range defined by the IUCN, which has been established based on the estimated adult distribution. Moreover, the percentage of time spent inside the designated habitat range showed large and highly significant variations across months (p<1e-05; Fig. 37). In deep winter (in August), all tracked juvenile penguins were outside the IUCN range, whereas in January and May, they were mostly within the IUCN range. The most distant location occurred at 1260 km north of the IUCN range. Data from other colonies followed a similar pattern (Table 12), whereby 38.8 ± 19.4% of the distribution areas of juvenile emperor penguins fall within the IUCN range. Juveniles from Cape Washington colony in the Ross Sea reached the furthest distance ever recorded (1500 km) outside the IUCN range. Based on our and previous tracking data, the habitat range defined by the IUCN is severely underestimated. A similar argument can be made also for the current and planned Marine Protected Areas discussed by the CCAMLR, as on average only 10.0 ± 4.9% of the estimated distribution areas fall within the MPAs' boundaries (Table 12). For instance, juvenile emperor penguins from the Atka Bay colony, which is located inside the proposed Weddell Sea Marine Protected Areas (WSMPA, the largest currently proposed MPA in the Southern Ocean), left the MPA's boundaries after 9 ± 4 days of northward migration in January and remain only 10.6 ± 7.5% of their time inside the boundaries with significant variations across months (p<1e-04; Fig. 37). Only in January before they left the colony, and in December, when they returned to the Antarctic continent to moult, did they spend a significant amount of time inside the WSMPA (47.9 ± 23.8 % and 31.1 ± 13.4 %, respectively). All tagged penguins were outside the WSMPA's boundaries in February and between July and November (Fig. 37).

IV.5 Discussion

As a top marine predator, emperor penguins are a key umbrella species of the Southern Ocean's ecosystem (Le [START_REF] Bohec | Polar Monitoring: Seabirds as Sentinels of Marine Ecosystems, in "Adaptation and Evolution in Marine Environments[END_REF]. Monitoring their population size and distribution at sea is therefore essential for the planning of biodiversity conservation measures. The common approach for designating boundaries of marine protected areas focus on protecting breeding birds and colonies [START_REF] Sherley | The initial journey of an Endangered penguin: implications for seabird conservation[END_REF], Boersma et al. 2019). However, we argue that this is not sufficient and point out that the habitat range of juvenile penguins requires a particularly high level of protection. Juveniles are more vulnerable than adult animals as their foraging skills (including their ability to dive, to capture prey, and to find productive feeding grounds)

are not yet fully developed, and their experience to escape predators is minimal [START_REF] Wanless | Black-legged kittiwakes as indicators of environmental change in the North Sea: Evidence from long-term studies[END_REF][START_REF] Orgeret | Early diving behaviour in juvenile penguins: improvement or selection processes[END_REF][START_REF] Enstipp | Apparent changes in body insulation of juvenile king penguins suggest an energetic challenge during their early life at sea[END_REF]. Moreover, juvenile survival can have a critical impact on the population dynamics especially in long-lived species [START_REF] Stearns | The Evolution of Life Histories[END_REF]. Emperor penguins start breeding at the age of 4-5 years old at the earliest, lay only one egg per pair and year, and only have an annual 55% chance to bring a chick to fledging (Jenouvrier et al. 2010). This low fecundity makes the survival of immature individuals, which represent only about one quarter of the total population [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF], particularly critical for the recruitment into the breeding population and thus the species viability [START_REF] Abadi | Integrated population modeling reveals the impact of climate on the survival of juvenile emperor penguins[END_REF]. Moreover, the dispersal behaviour of juveniles -in contrast to adults -is one of the main processes by which long-lived species will be able to adapt to the ongoing rapid environmental change and allow them to explore possible alternative feeding and breeding grounds [START_REF] Gienapp | Evolutionary Responses to Climate Change[END_REF]. Therefore, for successful strategic conservation planning, the habitat range of all age classes must be considered.

Our tracking data are the first of its kind in the Atlantic sector of the Southern Ocean and in West

Antarctica. Together with the tracking data from four other emperor penguin colonies distributed across Eastern Antarctica (Fig. 36; [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b), our findings reveal that juveniles spend a considerable amount of time outside the species' IUCN range and outside the limits of existing or planned MPAs in the Southern Ocean (Fig. 36, Table 12 andTable 13). Consequently, if protection measures would be based on the current IUCN range, as it stands, it would lead to inadequate and inefficient decisions for the future protection of the species. Furthermore, all studies including ours have found that the ACC area is visited by the vast majority of the tagged juveniles during their first journey after hatching, with some birds swimming as far north as the Antarctic Polar Front, which appears to act as an ecological constraint. The penguins' dispersive behaviour, tied to the most vulnerable stage of their life, leads them outside the SO-Treaty and CCAMLR limits in waters where they are more likely to encounter and compete with fisheries (Fig. 36). In accordance with the CCAMLR's ecosystem-based fisheries management approach, whose effectiveness has been recently questioned [START_REF] Watters | Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution[END_REF], the presence of this critical fragment of the emperor penguin population must be considered by the CCAMLR when allocating fishing quotas and zones. Noteworthy, several CCAMLR fishing states are lobbying for an increase of the spatial and temporal distribution of catches and fisheries (Cordonnery and Kriwoken 2015[START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], Trathan et al. 2018).

From an evolutionary perspective, it is noticeable that the fledglings of the two sister species from the Aptenodytes genus are aiming for the same feeding ground during their first year of life while adults forage in separate ecological niches [START_REF] Williams | The Penguins: Spheniscidae. Page The penguins. Bird families of the world[END_REF]. Our tracking data show that the northern part of the range of juvenile emperor penguins overlaps in time and space with the range of juvenile king penguins ((Aptenodytes patagonicus); see [START_REF] Orgeret | Exploration during early life: distribution, habitat and orientation preferences in juvenile king penguins[END_REF] for tracking details of juvenile king penguins). It is reasonable to think that these findings apply for other sectors of the Southern Ocean with sub-Antarctic islands (Fig. 52).

Most of our current knowledge about the breeding behaviour, life-history and demographic parameters of emperor penguins is based on the monitoring of a single colony at Pointe Géologie, Terre Adélie [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF]. This and our findings on the distribution at sea highlight the necessity to further compile baseline data for the species and all its life-history stages in presently uncharted regions (especially in West Antarctica, around the Peninsula, and in other parts of the Weddell Sea), to optimize and assess the implementation of future conservation measures on emperor penguins. Such pan-Antarctic data could also answer the current debate about the panmictic status of the Emperor penguin species, i.e. the connectivity between breeding colonies [START_REF] Cristofari | Full circumpolar migration ensures evolutionary unity in the Emperor penguin[END_REF][START_REF] Younger | The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins[END_REF]). The existence of several metapopulations or of a unique population connected around the whole of Antarctica could imply different conservation strategies.

While growing body of evidence indicates the ongoing and near future extinction threats, Trathan and colleagues (Trathan et al. 2020) recently advocated for a reclassification of the Emperor penguin on the IUCN Red List from the current "Near Threatened" status to "Vulnerable" or "Endangered", as well as a classification of the Emperor penguin as an "Antarctic Specially Protected Species" by the Antarctic Treaty. Our data emphasize the need to include all age-classes and age-specific threats into the classification assessment and into the design of a new strategic framework for conservation in the Southern Ocean [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF], Hindell et al. 2020). In the context of the vast habitat range of emperor penguins and also other marine top predators [START_REF] Raymond | Important marine habitat off east Antarctica revealed by two decades of multi-species predator tracking[END_REF][START_REF] Staniland | Long term movements and activity patterns of an Antarctic marine apex predator: The leopard seal[END_REF], Hindell et al. 2020), we furthermore argue in favour of globally integrated systems of marine protected areas [START_REF] Hannah | A Global Conservation System for Climate-Change Adaptation[END_REF]. This can be achieved by combining migratory corridors with static and dynamic MPAs (i.e. MPAs that rapidly evolve in space and time in response to changes in the ocean and its users; see details in [START_REF] Maxwell | Dynamic ocean management: Defining and conceptualizing real-time management of the ocean[END_REF], in order to create an ecological connected network that 135 would provide a robust protection to the Southern Ocean (Brooks et al. 2020a). Without an aggressive effort to introduce effective dynamic management of the Southern Ocean it is virtually certain that Antarctica's biodiversity and its most iconic species will be irrecoverably lost. Contrary to Chapters 3 and 4, the work from Chapter 5 is still in preparation and has not been submitted yet. Here, we present preliminary results and ongoing analyses that will be completed and confirmed.

ZI1525/3-

V.2 Introduction

The abundance and distribution of marine organisms is highly heterogeneous over a wide range of spatial and temporal scales [START_REF] Mann | Dynamics of Marine Ecosystems[END_REF]. Global change leads to many environmental disruptions for marine organisms (IPCC 2019) that are expected to result, for the very least, in shifts in species' distribution and interaction [START_REF] Cheung | Projecting global marine biodiversity impacts under climate change scenarios[END_REF][START_REF] Poloczanska | Global imprint of climate change on marine life[END_REF], Constable et al. 2014, IPCC 2019). However, monitoring changes of all the species that composed an ecosystem is logistically difficult. To address this challenge, ecologists use sentinel species, especially meso-and top predators such as seabirds and marine mammals [START_REF] Burger | Bioindicators: A Review of Their Use in the Environmental Literature 1970-2005[END_REF][START_REF] Durant | Pros and cons of using seabirds as ecological indicators[END_REF], Hazen et al. 2019), because they often forage over very large oceanic areas and stand near the top of the trophic networks. As such, they are exposed to a wide range of environmental conditions and integrate and amplify the changes occurring at lower levels of the food web over multiple trophic and spatio-temporal scales [START_REF] Croxall | Environmental change and Antarctic seabird populations[END_REF], Frederiksen et al. 2007). The monitoring of top predator species can also help to identify and provide valuable insights into the zones of ecological importance [START_REF] Block | Tracking apex marine predator movements in a dynamic ocean[END_REF], Raymond et al. 2015[START_REF] Reisinger | Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean[END_REF], Maxwell et al. 2020, Hindell et al. 2020). As a result, marine predators have been recognised as a crucial component of spatial and ecosystem-based management, such as Marine Protected Area (MPA) design and systematic conservation planning [START_REF] Ronconi | The role of seabirds in Marine Protected Area identification, delineation, and monitoring: Introduction and synthesis[END_REF][START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF], Hays et al. 2019). Assessing and understanding how marine top predators exploit their environment is therefore of particular interest.

Marine predators are challenging to observe at sea [START_REF] Hooker | Bio-logging science: Logging and relaying physical and biological data using animalattached tags[END_REF]. Their underwater behaviour cannot be easily observed while they move in three dimensions (i.e. horizontally and vertically by diving) and over time. As a result, accessing and assessing their movements to investigate their habitat use and preference or their foraging behaviour, require the use of animal-borne devices. The rapid and ongoing progress of biologging technology [START_REF] Rutz | New frontiers in biologging science[END_REF] in terms of miniaturisation, design optimisation, storage capacity and power consumption (Ropert-Coudert et al. 2009a, Portugal and White 2018) as well as the improvement of the quantity, the quality and the accessibility of remotely sensed data [START_REF] Palumbi | New Wave: High-Tech Tools to Help Marine Reserve Research[END_REF]) has led to fundamental advances in ecology of marine predators [START_REF] Bograd | Biologging technologies: new tools for conservation[END_REF][START_REF] Mcintyre | Trends in tagging of marine mammals: a review of marine mammal biologging studies[END_REF][START_REF] Roncon | View From Below: Inferring Behavior and Physiology of Southern Ocean Marine Predators From Dive Telemetry[END_REF]. Marine top predators generally feed on patchily-distributed prey resources over a range of spatial scales [START_REF] Young | The trophodynamics of marine top predators: Current knowledge, recent advances and challenges[END_REF]. By studying simultaneously spatial locations of animals as well as the depth ranges they move in and tied them to the environmental conditions encountered, it is possible to determine the characteristics making areas profitable for foraging predators [START_REF] Turchin | Translating Foraging Movements in Heterogeneous Environments into the Spatial Distribution of Foragers[END_REF]. Advances in technology now allow to examine small-scale movements and fine scale-vertical behaviour that are crucial to apprehend scale-dependent adjustments and foraging decisions of far-ranging predators [START_REF] Dragon | Horizontal and vertical movements as predictors of foraging success in a marine predator[END_REF].

Living and feeding from the oceans, seabirds play a major role in the ecosystems, consuming several hundred tons of prey per year [START_REF] Ballerini | Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf[END_REF][START_REF] Southwell | Large-scale population assessment informs conservation management for seabirds in Antarctica and the Southern Ocean: A case study of Adélie penguins[END_REF]). Among them, penguins constitute the dominant component of the avian biomass of the Southern Ocean [START_REF] Llano | Ecology of the Southern Ocean Region[END_REF]). Despite being one of the most iconic seabird species of Antarctica, the knowledge on emperor penguins distribution and foraging behaviour is still fragmented. For instance, in the Weddell Sea area, home of 33% of the population [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF], Teschke et al. 2016b), apart from the presence and locations of breeding colonies, very little is known about the horizontal distribution at sea and the finescale vertical foraging behaviour of the species [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kooyman | Diving Behavior of Emperor Penguins Nurturing Chicks at Coulman Island, Antarctica[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Zimmer et al. 2007b). As a sea-ice obligate species [START_REF] Ainley | Decadal-scale changes in the climate and biota of the Pacific sector of the Southern Ocean, 1950s to the 1990s[END_REF], emperor penguins are particularly threatened by global change [START_REF] Jenouvrier | Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models[END_REF], 2014[START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF], Trathan et al. 2020), notably to changes in the dynamic of sea ice and its associated food web (Ainley et al. 2010b, Trathan et al. 2011, Constable et al. 2014[START_REF] Fretwell | Emperors on thin ice: three years of breeding failure at Halley Bay[END_REF].

How the species will respond to global change is still uncertain [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Jenouvrier et al. 2019, Trathan et al. 2020). To refine our understanding and improve the power of predictive models, it is necessary to acquire baseline data on the current behaviours and strategies at sea and on land of emperor penguins through the entirety of their life cycle, across all life-history stages, and also at different breeding locations spanning around the continent [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Trathan et al. 2020).

Indeed, specific environmental conditions exist at each emperor penguin colony (i.e. distance to oceanic fronts, persistence of sea ice in time and space, seaward extent of Antarctic continental shelf, presence of specific oceanic currents like gyres, local weather like air temperature, snowfall, wind speed and direction) and may be affected differently by the ongoing and future impacts of climate change. Such heterogeneity is likely to lead to dissimilar responses and various population trajectories between sites [START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF]Ponganis 2017, Jenouvrier et al. 2019). Such information could also serve as science-based add-ons for the proposed MPAs around the continent (i.e. in the Weddell Sea and Dronning Maud Land region, in East Antarctica and in Peninsula) that have been under intense negotiations from years (Brooks et al. 2020a) as well as for the establishment of relevant and effective conservation measures in the Southern Ocean for an uncertain future (Teschke et al. 2016a, Trathan et al. 2020[START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF].

Studies on the emperor penguins' diet suggest an opportunistic feeder through time and space since diet composition varies enormously with time of year and location (see references in Trathan et al. 142 2020). They can dive up to 564 m [START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF]) for as long as 32 minutes [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF] to prey on pelagic and/or benthic fishes (especially the Antarctic silverfish (Pleuragramma antarcticum)), squids (mainly the arrow squid (Psychroteuthis glacialis) and the Antarctic neosquid (Alluroteuthis antarcticus)), and crustaceans (particularly Antarctic krill (Euphausia superba)) [START_REF] Green | Food of the emperor penguin Aptenodytes forsteri on the Antarctic fast ice edge in late winter and early spring[END_REF][START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF][START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF][START_REF] Piatkowski | Squid diet of emperor penguins ( Aptenodytes forsteri ) in the eastern Weddell Sea, Antarctica during late summer[END_REF][START_REF] Robertson | Diet composition of Emperor Penguin chicks Aptenodytes forsten' at two Mawson Coast colonies[END_REF][START_REF] Pütz | The post-moult diet of Emperor Penguins (Aptenodytes forsteri) in the eastern Weddell Sea, Antarctica[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Cherel | Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica[END_REF], Zimmer et al. 2007a[START_REF] Cherel | Isotopic niches of emperor and Adélie penguins in Adélie Land, Antarctica[END_REF]. As other penguin species [START_REF] Wilson | Diel dive depth in penguins in relation to diel vertical migration of prey: whose dinner by candlelight?[END_REF][START_REF] Pütz | Feeding behavior of free ranging king penguins[END_REF][START_REF] Ropert-Coudert | Foraging strategies and prey encounter rate of free-ranging Little Penguins[END_REF]), emperor penguins have been suggested to be visual hunters. Such hypothesis was based on the analysis of the diving patterns of birds during winter, a time of the year during which they dive primarily during the day (Kirkwood andRobertson 1997, Zimmer et al. 2008). The diving activity of those birds increased with the length of the day. Most foraging dives of emperor penguins occur between the surface and 150 m deep and lasts less than 10 minutes [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Zimmer et al. 2007b, 2008), even though deepest dives have been documented across different sites [START_REF] Kooyman | Diving Behavior of Emperor Penguins Nurturing Chicks at Coulman Island, Antarctica[END_REF][START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF][START_REF] Zimmer | Dive efficiency versus depth in foraging emperor penguins[END_REF]. Recent findings suggest that they access their foraging habitat by diving in small openings, including cracks, flaw leads and ephemeral short-term polynyas (Labrousse et al. 2019a). To date, only one study, performed in the Ross Sea region, monitored the diving behaviour of the same individuals (non-breeding birds only) right after the moult and through the winter, but with non-continuous and summarised dive profiles collected through ARGOS system [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]. Previous studies monitored the diving behaviour of adult emperor penguins for short periods, only a couple of months, either in winter or in summer [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Rodary et al. 2000a[START_REF] Wienecke | Extreme dives by free-ranging emperor penguins[END_REF][START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF], 2010). Consequently, the detailed diving behaviour of individuals over a full year and the consistency of their foraging strategies over a year are still unstudied, while improving our understanding of these strategies and their drivers is required, especially as changes in the spatio-temporal availability of prey can be expected to increase with global warming and its consequence on oceanic processes.

Our study had several objectives: (i) to identify the at-sea distribution of emperor penguins in the Atlantic sector of the Southern Ocean, where the implementation of a new MPA (the Weddell Sea MPA) is being discussed, but where no tracking data have been recorded so far; (ii) to investigate potential variability in habitat use according to different life-history stages throughout the season to encompassif possibleall breeding cycle stages and get a global picture of the emperor penguins' distribution in this area; (iii) to combine these novel information with datasets previously collected in Adélie Land, where the implementation of a new MPA (the East Antarctic MPA) is also being discussed, in order to assess emperor penguins' use of proposed MPAs so as to refine the scientific knowledge that can serve as an evaluation of the current and future proposed protected areas; (iv) to explore the environmental factors influencing the distribution at sea of emperor penguins in these two regions; (v) to examine the diving behaviour of adult emperor penguins in order to study changes in foraging strategies according to their breeding phases (pre-breeding/fall, incubation/winter and in chickrearing) and status (non-breeder, failed breeder, successful breeder) and their locations (Atka Bay, Dronning Maud Land versus Pointe Géologie, Adélie Land). This last part is still preliminary and requires further investigation to validate our hypotheses and draw valid conclusions. The first column indicates the five study groups, as an aggregation of the three following columns: Status refers to the lifehistory stage of birds (juv = juveniles, ad = adults), Colony to the colony of equipment (AB = Atka Bay colony, PG = Pointe Géologie colony), and Season to the period of tracking (y = year, f = fall, s = summer, w = winter). Thus, for instance, the group juvABy refers to juveniles equipped at Atka Bay colony and tracked during a whole year. * Platforms were programmed to stop emitting between April 25 th and May 20 th when birds were expected to be at their breeding site. All platforms restarted but they eventually stopped through the winter. By the time they stopped, only two birds were located outside the colony. The locations obtained after the April-May stop were considered as part of new trips.

V.3.1.2. Diving data

Juveniles were not equipped with Time-Depth Recorder (TDR) devices, while adults from Atka Bay were equipped with two different types of TDR (see Chapter III). We deployed Cefas g5+ TDR on chickrearing birds (the one equipped also with GPS) and Lotek Lat 1800 TDR on birds that were equipped with ARGOS platforms. Both types of loggers were programmed to record depth and temperature at 1 Hz frequency with a 30 cm resolution and 1% accuracy. Equipment procedures are described in Chapter III.

Amongst the birds monitored in November 2005, 4 birds were equipped with Splash Argos platforms that also recorded diving depth every 2 seconds with a 50-cm resolution. The dive data and deployment procedure were already published in Zimmer et al. (2007b[START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Zimmer | Dive efficiency versus depth in foraging emperor penguins[END_REF]. General information on TDRs are summarised in Table 15. For the study group column: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fa ll, s = summer, w = winter.

V.3.2. Spatial analysis

V.3.2.1.

Location filtering and separation of tracking datasets per individual into foraging trips

Given the heterogeneity of the trackers and years, locations were sampled at different and irregular time intervals and associated with different spatial errors. Specifically, ARGOS locations were associated with classes in increasing order for birds from PG (Z, B, A, 0, 1, 2, 3) and associated with error ellipses for birds from AB, spatial errors ranging from several kilometres to few hundred metres (Costa et al. 2010b, CLS 2016), while GPS trackers have an accuracy inferior to 100 metres.

Erroneous locations were filtered out using a speed filter from the R package 'argos filter' [START_REF] Freitas | A simple new algorithm to filter marine mammal Argos locations[END_REF] with the maximum travel speed fixed at 15 km.h -1 following [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 1997, Labrousse et al. 2019b). Periods spent at the colony (within a 5 km radius) were removed from analysis for all birds. Similarly, locations during the moulting periods of the three juveniles tracked throughout the year were removed prior to the analysis, as birds were not foraging. The moulting periods were identified by plotting the curve of the mean daily distance travelled as a function of time, and by checking the last inflexion point, indicating that the birds stopped travelling and started moulting.

Indeed, according to the literature, when moulting (between December and March for an average of 30 days, Groscolas 1978), emperor penguins remain out of water on ice floes or coastal fast ice (Kooyman et al. 2004). As such, their daily distance travelled switch from several tens of kilometres a day to almost none, an abrupt behavioural change easily detected on tracked birds. The device then falls off with the feathers to which it was attached and get lost.

V.3.2.2. Interpolation of locations at a regular time step

We used a state-space modelling approach [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF] to estimate hourly locations.

Specifically, a Kalman filter, which accounted for location error, was applied using the R package 'crawl' [START_REF] Johnson | Fit continuous-time correlated random walk models to animal movement data[END_REF], and Continuous-time Correlated Random Walk (CRW) models were used to predict locations at a regular time step interval of 1 h [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF]).

V.3.2.3. Identification of heavily used area

We analysed each study group according to the procedures developed by Lascelles and colleagues [START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF]. For each dataset, we estimated the 50% (i.e. core area) and 90% (i.e. home range) [START_REF] Börger | Effects of sampling regime on the mean and variance of home range size estimates[END_REF]) kernel utilisation distributions (UD ; Worton 1989), and we used a smoothing factor (in km) that corresponds to the scale of interaction of the birds with the environment. This smoothing factor is estimated from the peak of variance in first passage time (FPT), which assesses the time taken by an individual to cross the area of a circle of 5-150 km around each location [START_REF] Fauchald | Using First-Passage Time in the Analysis of Area-Restricted Search and Habitat Selection[END_REF][START_REF] Scheffer | Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia[END_REF][START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF][START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF][START_REF] Vacquie-Garcia | Hooded seal Cystophora cristata foraging areas in the Northeast Atlantic Ocean-Investigated using three complementary methods[END_REF]. Then, the value of FPT at each location was computed (with the relevant threshold for each study group) as a measure of residence since locations were interpolated on a regular time-step.

V.3.3. Dive analysis V.3.3.1. Dive identification

Dive extraction from pressure data collected by the TDRs was carried out with the MT-Dive software (Multi Trace-Dive, Jensen Software Systems, Laboe, Germany). By looking at the inflexion points along the surface, the software splits the record into dives. Dives are then analysed sequentially and various parameters either extracted or computed. Up to now, we specifically focused on the maximum dive depth, the dive duration, the time spent at the bottom of the dive (bottom duration), the number of undulations (wiggles) per dive, and the post-dive duration in order to assess diving and foraging activities and performances of equipped birds. This analysis considers for the moment only the dives deeper than 5 m.

V.3.3.2. Dive metric computation

The bottom phase of a penguin dive, in contrast to the descending and ascending phases, is the phase in which penguins are most likely to hunt [START_REF] Chappell | Diving Behavior During Foraging in Breeding Adelie Penguins[END_REF], Zimmer et al. 2007b). The start and end of bottom phases were defined as the first and last time the rate of change of depth became < 0.5 m/s during a dive. Such parameters allow maximising the detection of wiggles occurring during the part of dive slightly ascending. The current literature on penguins proposes that most of the predation events happening during the bottom phase are indicated by the wiggles (Rodary et al. 2000b[START_REF] Simeone | In-depth studies of Magellanic penguin (Spheniscus magellanicus) foraging: Can we estimate prey consumption by perturbations in the dive profile?[END_REF][START_REF] Ropert-Coudert | Foraging strategies and prey encounter rate of free-ranging Little Penguins[END_REF], Halsey et al. 2007, Zimmer et al. 2007b). Wiggles correspond to deviations of the depth at 3 points on which the vertical speed drops below 0m/s (inflexion points)

and with a change of depth above a threshold depending on the resolution of the TDR used. Adapting the method from [START_REF] Simeone | In-depth studies of Magellanic penguin (Spheniscus magellanicus) foraging: Can we estimate prey consumption by perturbations in the dive profile?[END_REF], we defined a wiggle as a change in 1 second of at least 0.75 m compared to the mean rate of the previous 3 seconds, unless an undulation had already occurred within this 3-second time window. The value of 0.75 m is more than twice the resolution of TDRs used on AB birds and 1.5 times the resolution of TDRs used on PG birds. The number of wiggles per dive depending on the dive duration, we computed a proxy of foraging effort called Attempts of Catch Per Unit Effort (ACPUE; [START_REF] Zimmer | Dive efficiency versus depth in foraging emperor penguins[END_REF][START_REF] Le Guen | Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins ( Pygoscelis adeliae )[END_REF], which is the ratio of the number of wiggles by the bottom time. We also computed a second proxy, the diving efficiency (DE), which is the ratio of the bottom duration by the sum of the dive time and the post-dive surface interval time [START_REF] Ydenberg | Aerobiosis and anaerobiosis during diving by western grebes: An optimal foraging approach[END_REF][START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Le Guen | Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins ( Pygoscelis adeliae )[END_REF]).

V.3.3.3. Foraging dive characterisation

Then, foraging dives were defined as dives to any depth showing a bottom phase with wiggles, or dives to depths > 20 m or duration > 60 s in the absence of such wiggles (Rodary et al. 2000b). To classify dives without any wiggle and of maximum depth < 20 m, we assumed that penguins foraging at shallow depth would not spend much time in transit from the surface to the foraging depth and consequently would have a faster descent phase than travelling dives (Rodary et al. 2000b). We looked at the distribution of the speed of descent and, unlike (Rodary et al. 2000b), we could not find a bimodality. As such, we kept dives with a speed superior to the third quartile (0.62 m/s). Other dives were considered as travelling dives and remove from subsequent analysis.

V.3.3.4. Benthic dive estimation

Emperor penguins have been shown to perform benthic dives (Rodary et al. 2000a[START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]. To assess if such behaviour was performed by our birds, dive locations were determined by linking dive time with time along the track line and linearly interpolated to the nearest minute [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF] with the function 'redisltraj' from the R package 'adehabitatLT' [START_REF] Calenge | Package ' adehabitatLT[END_REF]. Then, we extracted the bathymetric depth at each dive location and subtracted this value from the maximum dive depth. The resulting difference was then divided by the bathymetric depth. When the maximum dive depth was deeper than the bathymetric depth, the bathymetric depth was changed to the dive depth. Dives with value between 0.8 and 1 were classified as 'benthic' and all other dives as 'pelagic' [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF].

V.3.3.5. Diving effort characterisation

At the trip scale 15 , we focused on the diving effort per unit of time, i.e. the number of dives made per hour (in local time) of each group. The diving profiles of adABf birds (year-round TDR datasets) allowed to identify the period out of water. Switch between periods of diving or absence of diving gave us an indication on the sex of the birds and if they attempted to breed or not. We assessed their breeding success by direct observations at the colony at the end of the breeding season in November/December. For breeding birds, the extended periods without any dive are likely to correspond to period spent at the colony, while, for non-breeding birds, we can only affirm that they are not diving. The yearly data were divided into trips separated by an extended period (several days in a row) out of water (Fig. 49). However, one of the birds did not exhibit any extended period without diving between September and its recapture in November. We, therefore, manually split this period in two different trips at the date where we identified a switch in the diving effort, i.e. a change in the distribution of dives during the day. Each trip of each bird was then assigned one type of the two diving effort patterns.

V.3.4. Management and environmental feature analysis To account for spatial variability of sea ice, we additionally computed the sea ice concentration over a delineated area whose radius is the value of the smoothing factor that corresponded to the scale of interaction of the birds with the environment, as described previously in the location data processing (page 147). We also computed the percentage of sea ice > 90% over the area as a measure of full sea ice concentration and absence of cracks and daily polynyas used by emperor penguins to dive and forage (Labrousse et al. 2019a). The distance of the tracked penguins from the sea ice edge were calculated, using the R package 'geosphere' [START_REF] Hijmans | Package ' geosphere[END_REF], as the minimum distance between penguin positions and the sea ice edge contour defined by the 15% sea ice concentration isocline (Cavalieri 1991, Stammerjohn and[START_REF] Stammerjohn | Opposing Southern Ocean climate patterns as revealed by trends in regional sea ice coverage[END_REF]. This isocline defines the sea ice extent. Contours corresponding to outlying floes or polynyas were removed during extraction to prevent bias in the sea ice edge distance computation with QGIS 'r.contour.step' tool. Positive values indicated that the bird was inside the sea ice area.

(iii) Oceanographic conditions

The Southern Ocean fronts and the Antarctic Circumpolar Current boundaries (ACC; [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF] were downloaded from https://gis.ccamlr.org (CCAMLR 2019b). The shortest distance to the Southern Antarctic Circumpolar Current Front (SACCF) of the ACC [START_REF] Orsi | On the meridional extent and fronts of the Antarctic Circumpolar Current[END_REF] was computed for juveniles at each location.

(iv) Extraction process

To account for location error when extracting environmental variables, we used the fitted CRW model to create a dataset of 100 simulations of each location and individual bird [START_REF] Johnson | Continuous-time correlated random walk model for animal telemetry data[END_REF]. The 100 values for the bathymetry, slope, sea ice concentration covariates, and distances associated with each possible location were first extracted and then averaged, giving a mean value for each location along the mean track [START_REF] Heerah | Contrasting behavior between two populations of an ice-obligate predator in East Antarctica[END_REF]).

V.3.5. Statistical analysis

Except for the dive analysis, analyses were performed using the software R v. 3.5.0 (R Core Team 2018) and QGIS v. 2.18.18 (QGIS Development Team 2017) with the data package 'Quantarctica' [START_REF] Matsuoka | Quantarctica[END_REF]).

V.3.5.1. Residence time

We tested the statistical effect of the individuals and of the months on the residence time within the management features using Kruskal-Wallis rank sum tests. When a significant difference was measured among individuals or months, the Tukey's 'Honest Significant Difference' multiple comparison of means test was used to identify which individual(s) or month(s) differed from others [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF][START_REF] Thiebot | Adélie penguins' extensive seasonal migration supports dynamic Marine Protected Area planning in Antarctica[END_REF].

V.3.5.2. Dive analysis

To determine the relationship between the diving effort strategy of the adABf16 birds and their main diving metrics (e.g. bottom time, dive maximum depth, dive efficiency, number of wiggles, dive duration, and ACPUE), we fitted a Generalized Linear Mixed Model (GLMM) using the 'glmer' function from the R package 'lme4' [START_REF] Bates | Fitting Linear Mixed-Effects Models Using lme4[END_REF]. Exploratory variables were first normalised with a Cox

Box Power transform and their correlation assessed with the use of the variance inflation factor (VIF) and a threshold of 3, as well as with the Pearson correlation coefficient with a threshold of 0.6. [START_REF] Zuur | A protocol for data exploration to avoid common statistical problems[END_REF]). As a result, the dive duration and the number of wiggles were discarded from the analysis.

Models were fitted with Binomial distribution, and birds were included as random effects to account for inter-individual variability. The model selection was performed using the 'dredge' function from the R package 'MuMIn' (Kamil Barton 2020).

V.3.5.3. Assessing the influence of environmental factors on the distribution

We used Generalized Additive Mixed Models (GAMMs) to identify nonlinear functional relationships between species distribution and environmental conditions [START_REF] Zuur | Mixed effects models and extensions in ecology with R[END_REF]. We explored relationships between FPT and key physical variables (i.e. sea ice concentration, distance to the fronts and sea ice edge, day of year, bathymetry, slope, and habitat) using a Gaussian distribution with the identity link function. For each model, only the variables not highly correlated (< 0.8) were used and standardised after checking of outliers [START_REF] Vacquie-Garcia | Hooded seal Cystophora cristata foraging areas in the Northeast Atlantic Ocean-Investigated using three complementary methods[END_REF]). The response variable was log transformed prior to analysis to correct for non-Gaussian distribution and a correlation term was added to take into account the temporal correlation [START_REF] Zuur | Mixed effects models and extensions in ecology with R[END_REF]. Individual trips and colonies were included as random factors. GAMMs were computed separately for juveniles and for adults because of their highly different patterns of distribution that likely involved different variables that we did not want to confound. Model selection could not be conducted using Akaike's Information Criterion (AIC) due to the presence of the autocorrelation term [START_REF] Van Rijn | Package ' itsadug[END_REF]. We used adjusted R 2 and percent deviance explained to evaluate model performance [START_REF] Zuur | Mixed effects models and extensions in ecology with R[END_REF] with the help of the 'comparML' function from the R package 'itsadug'. Model assumptions pertaining to GAMMs, including normality and homogeneity of variance, were checked using plots of residuals against fitted values [START_REF] Zuur | Mixed effects models and extensions in ecology with R[END_REF][START_REF] Zuur | A protocol for data exploration to avoid common statistical problems[END_REF][START_REF] Wood | Generalized additive models: An introduction with R, second edition. Page Generalized Additive Models: An Introduction with R[END_REF]. GAMMs were computed with the R package 'mgcv' [START_REF] Wood | Generalized additive models: An introduction with R, second edition. Page Generalized Additive Models: An Introduction with R[END_REF]. For the study group 'adABf', only the time period spanning from January to April was considered since only two non-breeding birds were still transmitting afterwards and were therefore not representative of the group anymore.

V.4 Results

Detailed general information per birds, such as deployment and tracking durations or distance to colony are reported in Table 13 for juvenile emperor penguins from Atka Bay and in the Table 16 below, which also includes general information on diving metrics, for adult emperor penguins from Atka Bay (AB) and Pointe Géologie (PG).

-Chapter V - The distribution of the eight equipped juveniles in Atka Bay (juvABy; Fig. 39) covers a vast area (UD 50% = 0.6 million of km², Table 17), stretching over 3000 km from east to west and 2500 km from north to south. They travelled north when leaving the colony in mid-January 2019, reaching their northernmost latitude (maximum at 48.5°S) between the end of February and the beginning of April, being at 1500 to 2400 km from the colony (Table 13). Five of them went north of the maximal sea ice extent (Fig. 38) and spent several weeks above the bathymetric "plateau" structure located around Bouvet Island.

One of the birds expressed a very different behaviour than the seven others. This bird was the first to turn south. On March 16 th , this individual was located at the sea ice edge, only 30 km off the coast while the other juveniles were still within the ACC, 1400 km north of the coastline. The signal of its ARGOS platform was lost on March 24 th on the sea ice edge, 80 km north of Sanae emperor penguin colony. The seven other juveniles turned South in March/April and entered into the sea ice between mid-April and mid-May. From this time on, they split in two groups. Both groups remained in the pack ice, within 100-300 km of the sea ice edge (Fig. 40) over the abyssal plains (Fig. 41) for the rest of their tracking period. One group, made of four juveniles, went into the Weddell Gyre and their signal got lost one by one in June-July, while they were heading northward following the sea ice edge during its expansion.

The other group, made of the three other juveniles, remained for the whole winter around 1000 km north-northeast of Atka Bay. In December, they followed the sea ice edge during the sea ice retreat southward. They eventually moulted near the continent between mid-December and mid-January (Fig. 39). None of them returned to moult at their native colony. One moulted on the fast ice east of Troll Tunga and Sanae emperor penguin colony, at 360 km from Atka Bay, while the two others moulted at approximately 650 km southwest of Atka Bay in the vicinity of Stancomb and Drescher emperor penguin colonies. (ii) Adult emperor penguins from Atka Bay

In the Atlantic sector of the Southern Ocean, adults during fall (adABf) used a core area 15 times smaller than juveniles (juvABy) and 5 times bigger than adults in summer (adABs; Fig. 39). The latter mostly stayed in a radius of 200 km around the colony (median of maximum distance from the colony = 113 km, Table 17), over the shelf and the continental slope, while adABf birds also exploited the water column above the abyssal plains (21% of their time in average; Fig. 41).

Noteworthy, one of the non-breeding adABf birds went into the Weddell Gyre, following a similar pattern to the juveniles a year later, while the two others non-breeding adABf birds stayed along the Antarctic continent. Signals from ARGOS platforms of adABf birds were all lost during the winter.

(iii) Adult emperor penguins from Pointe Géologie

In the d'Urville Sea, adults in summer (adPGs) used an area 20 times bigger (Table 17) than adults in winter (adPGw; Fig. 39). The wintering foraging area of birds from PG (adPGw) was situated east of the colony, between their colony and the persistent Mertz polynya, with a median of maximum distance from the colony of 56 km. This area was exclusively over the shelf and consistent between years (Labrousse et al. 2019a). Part of the trips (16.3%) of breeding adults from adPGs group was situated over the continental slope (Fig. 41). None of the two groups from PG exploited areas above abyssal plains.

V.4.1.2. Residence time

Juveniles from Atka Bay (juvABy) spent the majority of their tracking time outside of the existing and proposed MPAs (86.1 ± 8.6%), being only present in the proposed WSMPA in January and in December (Fig. 37, see Chapter IV for details). Two birds were inside the SGSSI MPA in late June. They stayed there at least until July when their ARGOS platforms stopped transmitting. The three juveniles equipped with an ARGOS platform that transmitted the whole year moulted inside the WSMPA.

By contrast, from the date of their equipment in January until May, the eight post-moulting adult emperor penguins equipped from Atka Bay (adABf) spent in average 94 ± 5% of their tracking time inside the proposed WSMPA boundaries. Only two of the birds, both non-breeding birds, were still tracked in June. One of them was inside the proposed WSMPA, travelling along the continent, while the other one left the proposed WSMPA following the Weddell Sea Gyre. This last bird reached the SGSSI MPA in mid-July (Fig. 39 and Fig. 41). The signal of this bird was lost inside the SGSSI MPA in mid-August.

All the adults in chick-rearing from Atka Bay (adABs) and all the birds in a breeding stage at Pointe Géologie (adPGw and adPGs breeding, see Table 14) stayed within the boundaries of the relevant MPA, the proposed WSMPA and EAMPA, respectively (Fig. 39 and Fig. 41). In East Antarctica, only nonbreeders and pre-moulting birds crossed the boundaries of the proposed EAMPA. Seven adults from adPGs were tracked until their moult in January. Three of them moulted inside the western part of the adjacent Ross Sea Region MPA. The four others went west of the proposed EAMPA, with only one bird moulting inside its boundaries (and being inside for less than a kilometre, Fig. 39).

(i) Juvenile emperor penguins

We found a significant effect of the sea ice concentration, the day of the year, and the distance to the Southern Antarctic Circumpolar Current Front (SACCF) on the time spent by the juvenile emperor penguins from Atka Bay in an area (i.e. the first passage time, or FPT; see GAMM results in the Table of the Fig. 43). The bathymetry and the slope as well as the distance to the sea ice edge were not retained in the best model.

The time spent per area (FPT) increased linearly with the sea ice concentration. The season also influenced the FPT with higher values occurring during the winter, meaning that birds were moving less in winter. On the contrary, birds spent less time per area (lower FPT values) at the beginning and the end of the year. The effect of the distance to the SACCF on the FPT showed a more contrasting pattern. There was no clear tendency, except at the very extreme values of the range. Intermediate values of the FPT, from 400 to 1200 km south of the front (negative sign), included data from the heart of winter as well as from the trips at the beginning and end of the year.

(ii) Adult emperor penguins

We found that the time spent by adult emperor penguins from Atka Bay and Pointe Géologie in an area (FPT) was significantly influenced by the sea ice concentration, the day of the year, the bathymetry, and the distance to colony (see GAMM results in the Table of the Fig. 44). The gradient of bathymetry, the habitat as well as the distance to the sea ice edge and the proportion of ice > 90%

were not retained by the model selection.

Adult emperor penguins spent more time (higher FPT values) in area with high concentration of ice.

Higher values of FPT were observed at the beginning of the year with a decreasing trend between January and April. Then, the residence time increased through the beginning of the winter with a peak in mid-July. Finally, the time the adults spent per area during the chick-rearing period was lower than in winter. We found higher FPT values over the shelf area (i.e. bathymetry between 0 and 1000 m).

Finally, the time spent by the adult emperor penguins per area increased with the distance to their colony. Nevertheless, the incertitude is high and the confidence interval increasing after 600 km.

Values above this threshold should not be considered since 89% of the data collected are within 600 km from the colony, amongst which all the data from breeding or post-moulting birds. For instance, no difference was found in the median of the mean maximal distance from the colony between the chickrearing birds of Atka Bay and Pointe Géologie (Mood's median test, p-value = 0.5; Table 17), the birds being located within ca. 200-km radius around the colony. V.4.2. Foraging analysis

V.4.2

.1. Diving effort estimation

The results presented in this section are preliminary and require further investigation and validation.

General statistics (mean ± SD) of the main diving metrics, i.e. the maximum dive depth, the dive duration, the time spent at the bottom of a dive, the dive efficiency (ratio of the bottom duration by the sum of the dive time and the post-dive surface interval time), the number of wiggles and the ACPUE (ratio of the number of wiggles per dive per the bottom time) per study groups are presented in Table 18. Remarkably, we collected the first year-round diving data at high-resolution frequency (1 Hz) on the same adult emperor penguins (N = 4, adABf group17 , Table 15) resulting in the detection of 106 980 dives (100 263 foraging dives). Therefore, for this study group adABf, TDR datasets have been divided in four subgroups to take the seasonality into account (see details in Table 18). 122.0 ± 73.1 4.9 ± 2.1 1.9 ± 1.1 29.9 ± 16.0 1.2 ± 1.8 0.5 ± 0.7 ACPUE = Attempt of Catch Per Unit Effort (ratio of the number of wiggles by the bottom time). For the study group classes: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter. * = sub-groups from the adABf study group made to correspond with the season of monitoring. adABf1 = monitored from January to April (fall; also corresponding to the post-moult/pre-breeding period). adABf2 = monitored from May to August (deep winter). adABf3 = monitored from September to mid-October (spring). adABf4 = monitored from mid-October to their recapture in November (summer). UA = under analyses. Artefacts in the data from the TDRs still have to be cleaned.

Foraging dives occurred throughout the trips of adult emperor penguins at each study site and for every season (Fig. 45). The study of the mean maximum dive depth per hour of each study group reveals a contrasting pattern between Atka Bay birds (adAB groups) and Pointe Géologie birds (adPGs group; see Fig. 46 and Table 18). The mean depth of foraging dives is significantly lower for the birds from Atka Bay colony than for the birds from Pointe Géologie colony (Wilcoxon test, p < 0.001). Additionally, chick-rearing birds from Pointe Géologie (adPGs) dove deeper during the day-time hours than at night-time hours, while the pattern is reversed for chick-rearing birds from Atka Bay (adABf4 and adABs). Birds from Atka Bay present a consistent pattern through the day for the rest of the year.

V.4.2.2. Behavioural patterns identification

We identified two daily diving patterns. In the first one, referred herein as 'day-time diving effort' strategy, the majority of the dives occurred during day-time hours, while a lower diving effort (fewer dives per hour) took place during night-time18 hours. The second one, referred herein as 'night-time diving effort' strategy, is characterised by two peaks of diving effort, one in the middle of the day and the other one during night hours with a decrease in intensity between the two peaks of activity.

The 'day-time diving effort' strategy was displayed by adABf birds from January to October as well as by adPGs birds in November (Fig. 47 for adABf and Fig. 48 for adPGs). The 'night-time diving effort' strategy was displayed by adABf birds in November as well as by adABs birds in November/December (Fig. 47 for adABf and Fig. 48 for adABs). In a preliminary analysis, we aimed to explore if the diving strategies we previously observed ('nighttime diving effort' and 'day-time diving effort') could be explained by particular diving metrics. The best GLMM model retained all the diving parameters (i.e. the bottom time, the dive maximum depth, the dive efficiency, and the ACPUE) as descriptor of the daily diving patterns.

V.4.2.3. Benthic vs pelagic dives

Adult emperor penguins from Atka Bay performed less benthic dives than those from Pointe Géologie (z-test, p < 0.001; Table 17). For the periods during which the TDR datasets and the concurrent ARGOS tracking data were available (i.e. January to April) to extract the bathymetry, the adults from Atka Bay (adABf) performed only 0.5 ± 0.7% of benthic dives in average (Table 17). Similarly, during the chickrearing period, the adABs birds made in average 3.9 ± 5.4% of benthic dives. On the contrary, 34.6 ± 21.5% of the dives from the chick-rearing adults equipped with TDRs at Pointe Géologie (adPGs) were benthic.

Fig. 49. Diving profiles of the four adult emperor penguins from Atka Bay equipped year-round with a TDR. For each profile, the x-axis represents the time and the y-axis the depth reached. The first profile on top belongs to a successful breeding male (long fasting period in winter and several absences of diving period in October and November). The second profile belongs to a male that was in breeding failure (no absence of diving period in October and November). The third profile belongs to a female that was in breeding failure (confirmed in the field). The last one is a non-breeding bird (no fasting period in winter) of unidentified sex. Trips are indicated by blue arrows and numbers.

V.5 Discussion V.5.1. Distribution at sea, habitat and Marine Protected Areas use

Our study shows that juvenile and adult emperor penguins from the Atlantic sector of the Southern Ocean were segregated in space through the year. Juveniles dispersed and spent their first year at sea, several hundred kilometres away from the colony of origin. On the contrary, breeding adults remained in the close vicinity of the colony, even before the breeding season started (Table 17). Similar at-sea spatial segregation between juveniles and adults has been observed at the four other emperor penguin colonies where tracking of adults and juveniles has been performed (see Zimmer et al. (2007b), [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. (2019bLabrousse et al. ( , 2019a) ) for Pointe Géologie colony; [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], [START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF] and [START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF] for Auster and Taylor colonies, and [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF], [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF] for Cape Washington colony).

Such habitat-use segregation between different life-history stages is common in seabirds as revealed by studies in penguins, albatrosses and a few other large procellariforms [START_REF] Clarke | Post-fledging and winter migration of Adélie penguins Pygoscelis adeliae in the Mawson region of East Antarctica[END_REF][START_REF] Péron | Tracking through Life Stages: Adult, Immature and Juvenile Autumn Migration in a Long-Lived Seabird[END_REF], Weimerskirch et al. 2014[START_REF] Fayet | Lower foraging efficiency in immatures drives spatial segregation with breeding adults in a long-lived pelagic seabird[END_REF][START_REF] Campioni | Niche segregation between immature and adult seabirds: does progressive maturation play a role?[END_REF], Orgeret et al. 2019).

Additionally, our results suggest that adult emperor penguins from Atka Bay express a comparable seasonal movement behaviour than adults from other colonies [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Zimmer et al. 2007b, Labrousse et al. 2019a). For instance, the breeding adults from Atka Bay are foraging within ca. 200-km radius around the colony during the chick-rearing season, similar to what we also found for Pointe Géologie birds. Post-moult trips of adults from Atka Bay are also analogous to what Kooyman and colleagues (2004) reported in the Ross Sea between January and June.

Atka Bay and Pointe Géologie colonies are both situated within proposed MPAs that run alongside the continent, the WSMPA and the EAMPA, respectively (Fig. 39; CCAMLR 2018a, 2019b). We found that the life-history stage, the breeding status, and the season highly influenced the residence time of emperor penguins inside these MPAs. Juveniles spent the vast majority of their time outside the WSMPA, while breeding birds from both breeding colonies remained inside the relevant MPA boundaries. Breeding adults are indeed constrained spatially and temporally as they must return to the colony to provision their offspring [START_REF] Ropert-Coudert | Patterns of energy acquisition by a central place forager: Benefits of alternating short and long foraging trips[END_REF]). The situation is more contrasted for non-breeding birds. Only one of the three adults from Atka Bay, which did not try to breed, left the WSMPA during the winter, while 86% of the adults from Pointe Géologie tracked until their moult crossed the EAMPA boundaries to moult. Three of them eventually moulted in the adjacent Ross Sea region MPA. Such findings reveal that emperor penguins (and not only juveniles, as already highlighted and discussed in Chapter IV) commonly range outside existing and proposed MPAs. If the Ross Sea region MPA and the WSMPA would procure shelter for moulting birds of these regions [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF], our results from Pointe Géologie reveal that important moulting areas (some were also identified in [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF] would still be lacking protection if the proposed EAMPA was to be accepted. During their moult, emperor penguins must remain out of the water for approximately a month [START_REF] Groscolas | Study of molt pasting followed by an experimental forced fasting in the emperor penguin Aptenodytes forsteri: Relationship between feather growth, body weight loss, body temperature and plasma fuel levels[END_REF][START_REF] Williams | The Penguins: Spheniscidae. Page The penguins. Bird families of the world[END_REF]. Thus, they are highly dependent of stable platforms of ice that are still accessible between January and March. We, thus, recommend that MPA boundaries also include ice shelves, adjacent fast ice, and pack ice to secure potential moulting areas by preventing additional anthropogenic pressures to the physiological stress induced by the moult (Trathan et al. 2020). Juveniles, non-breeding immatures and adults that skip breeding also represent a nonnegligible segment of emperor penguin populations [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF][START_REF] Abadi | Integrated population modeling reveals the impact of climate on the survival of juvenile emperor penguins[END_REF], Trathan et al. 2020) and of seabird populations in general [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]). However, they are often not considered in MPA planning that focuses mainly on breeding colonies, like for the proposed WSMPA (Teschke et al. 2016a, CCAMLR 2018a). In that context, our analysis reveals the importance of building a connected network 19 of MPAs (e.g. WCPA/IUCN 2007, Hannah 2010) for such highly dispersive components of the populations, to ensure continuity in the protection process throughout the life cycle of the individuals [START_REF] Grüss | Consequences of adult and juvenile movement for marine protected areas[END_REF][START_REF] D'aloia | A multiple-species framework for integrating movement processes across life stages into the design of marine protected areas[END_REF]).

In addition to the need of protected corridors between MPAs of the EAMPA, and between the EAMPA and the Ross Sea region MPAs to, at least, access suitable moulting areas, our results from Atka Bay colony also highlight the importance of a global management of connected network of MPAs in the Atlantic sector of the Southern Ocean. Indeed, some of our juveniles and non-breeding (and probable immature of 1.5 year-old, see page 182) birds reached the South Georgia and South Sandwich Islands MPA distant of 1150 kilometres from Atka Bay.

Noteworthy, we lost the signal of the five birds from Atka Bay that went into the Weddell Gyre, four juveniles and the probable immature mentioned above. Contrastingly, the three juveniles that stayed in the pack ice north of Atka Bay kept their device for a full year. As such, the technique of attachment on juveniles seems robust and does not appear to be the most plausible cause of signal loss, unlike for adults (see page 109). There is no clear environmental explanation either, the two groups were both foraging into the pack ice and resting on ice floes. Yet, leopard seals are known to prey on emperor 19 IUCN defines an MPA network as: 'a collection of individual MPAs or reserves operating cooperatively and synergistically, at various spatial scales and with a range of protection levels that are designed to meet objectives that a single reserve ca not achieve' (WCPA/IUCN 2007).

penguins [START_REF] Hiruki | Hunting and social behaviour of leopard seals (Hydrurga leptonyx) at Seal Island, South Shetland Islands, Antarctica[END_REF]) 20 but sightings never happened at sea during the winter. However, studies on leopard seal movement and activities over the winter in the Weddell Sea region (Nordøy andBlix 2009, Staniland et al. 2018) reveal the presence of leopard seals in the Gyre region at the same time of the year than the birds for which we lost the signal. On the contrary, there is no recorded presence of leopard seals in the area where the signals of the equipped birds were not lost. As such, we suggest that the birds present in the Weddell Gyre may have been subject to predation events. Predation events by killer whales (Orcinus orca) could also be a possibility [START_REF] Andrews | Satellite tracking reveals distinct movement patterns for Type B and Type C killer whales in the southern Ross Sea, Antarctica[END_REF]) although killer whales have been spotted only once during the winter in the vicinity of emperor penguins in East Antarctica [START_REF] Gill | A winter sighting of killer whales ( Orcinus orca ) in Antarctic sea ice[END_REF].

V.5.2. Environmental drivers of the time spent in an area

We showed that both juveniles and adults spent more time in areas (FPT) with high sea ice concentration (Fig. 43 and Fig. 44). Such finding is in coherence with their resting behaviour on ice floes especially at night in winter [START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Zimmer et al. 2007b[START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Labrousse et al. 2019b, 2019a), as illustrated by the high values of FPT for both groups in winter. Then, juveniles and adults present dissimilar patterns for the rest of the year, which might reveal the influence of different environmental parameters encountered by these two lifehistory stages during these periods.

For the juveniles, low values of FPT were observed i) at the beginning of the year, which corresponds to the round trip between the Antarctic continent and the Southern Antarctic Circumpolar Current Front (SACCF), and ii) at the end of the year, when the juveniles were following the sea ice retreat.

These results suggest that, during those periods, juveniles were moving around a lot and mostly travelling, being located between 1400 km (i.e. the distance between Atka Bay and the SACCF) and 200 km south of the front. Conversely, high FPT values were observed i) in March, which coincides with the relatively high values of FPT recorded between 200 km south and 200 km north of the SACCF, and points to a high effort of foraging activities in this area, and ii) during the winter period, when the birds spend most of the day resting on the sea ice, as highlighted above. Between June and October, the birds were situated at distances between 1400 km and 200 km south of the SACCF. Due to the confounding effect of the travelling periods and of the winter period, FPT values for those intermediate distances do not show any specific trend. In contrast, in May, the birds were at the southernmost part of their trip, the only period during which they were distant to more than 1400 km 20 See also https://www.youtube.com/watch?v=skoWevMUemc&list=RDEhsTCvLI5O4&index=19

to the SACCF. This is when and where they were encountering the sea ice habitat and starting to exhibit high FPT values, which could be interpreted as resting behaviour on ice floes. Note that the values of FPT corresponding to the birds being located more than 200 km north of the SACCF cannot be interpreted due to the high dispersion of the confidence interval (CI). Such CI dispersion might be explained by the fact that three of the five juveniles that went north of the SACCF, exhibited high FPT values for few days, suggesting high effort of foraging activities in this area, while the rest of their trips in this zone consisted of travelling period with low FPT values.

High FPT values of adults at the beginning of the year (January to April) concerned only the adults from Atka Bay after the moult and before the breeding season (adABf), when they need to replenish their reserves, thus accessing and remaining in very productive zones to forage. A more detailed analysis will help us to explain the decreasing trend observed over the season, by investigating if the birds adjusted their spatial and/or diving behaviour during this period (e.g. increased diving effort, increased distance travelled per day). The winter's high values of FPT, marked with a peak in July and August, concerned only one bird from Atka Bay (adABf group) and the females from Pointe Géologie during the winter (adPGw). As we have already shown, birds from Pointe Géologie had a small distribution area (Table 17) and foraged only few hours a day [START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF], resting on the pack-ice for most of the time, limiting the daily travelled distance to a minimum. During the chick-rearing period in summer, the birds used a wider area than in winter (Table 17) while diving day and night (Fig. 47 and Fig. 48). This mobility on short-time periods resulted in the lower FPT values recorded for this time of the year. The higher FPT values over the shelf (i.e. bathymetry between 0 and 1000 m) were heavily influenced by the high winter FPT values exhibited by the birds from Pointe Géologie (adPGw) and from Atka Bay right after the moult (adABf).

V.5.3. Foraging behaviour

Our unique datasets on depth use and diving behaviour of adult emperor penguins in the Atlantic sector of the Southern Ocean suggest a change in the diving effort of the birds at the beginning of the summer (late October -early November). Adult birds from Atka Bay switched from a 'day-time diving effort' strategy expressed from January until the last week of October, to a 'night-time diving effort' strategy at the end of October and beginning of November 21 .

All but one of the chick-rearing adults from Atka Bay equipped in November and December expressed only the 'night-time diving effort' strategy, in 2017 as well as in 2018. Recording the same type of diving effort at the same period of the year, two years in a row, hints towards a common behavioural pattern for this period at this colony. Logistical constraints of fieldwork in Antarctica make it unlikely that we will soon be able to deploy TDRs on breeding adult emperor penguins in October to confirm the switch observed on the year-round monitored birds. Interestingly, the only chick-rearing individual that expressed a 'day-time diving effort' strategy also displayed different movement behaviours: the bird was the only chick-rearing bird to move inside a pair of inlets, ~100 km west of Atka Bay, and dove and rested in this specific area for 10 days, i.e. half of its trip. The other birds stayed off the coast to forage, only coming back towards the continent when they returned to their colony.

Our preliminary analyses on the year-round-monitored adults from Atka Bay (adABf) suggest that these daily diving patterns performed at the trip scale can be described by diving parameters such as the maximum dive depth, the time spent at the bottom of the dive, the number of catching attempt (ACPUE), and a measure of the diving efficiency. The next step will be to perform the analysis with the diving data from chick-rearing birds from Atka Bay to assess if their diving parameters are similar to those of the 'night-time effort' strategy of the post-moult/pre-breeding birds.

Previous study performed on the diving behaviour of emperor penguins in winter at Pointe Géologie [START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF]) showed a 'day-time diving effort' strategy similar to the birds from Atka Bay in winter, with most of the dives occurring between 6 am and 6 pm (Fig. 47). The birds from Pointe

Géologie studied in early summer also presented a 'day-time diving effort' strategy, even though dives are more scattered during the day (Fig. 48; [START_REF] Zimmer | Seeing the light: Depth and time restrictions in the foraging capacity of emperor penguins at pointe géologie, Antarctica[END_REF]. The birds monitored in winter and in summer at Pointe Géologie were not the same birds, but they were equipped the same year. Yet, we do not detect a change in the diving effort, the majority of the dives occurring in the middle of the day for both seasons. Birds from Pointe Géologie dove deeper in average than Atka Bay birds (Fig. 46 and Table 18). Foraging chick-rearing birds from Pointe Géologie exploited the water column only over the continental shelf, at depth where they can and do perform benthic dives. In contrast, the shelf around Atka Bay is narrow (~20 km wide off the coast of Atka Bay vs 100 km wide off the coast of Pointe Géologie, Fig. 23) and steep. The seabed being quickly out of reach of the diving emperor penguins from Atka Bay, the opportunities to perform benthic foraging strategy is therefore very limited in this sector, as suggested by the low amount of benthic dives performed by all the birds from Atka Bay in summer and fall.

Overall, our results suggest that different prey items are targeted between the birds from Pointe Géologie and those from Atka Bay. Given the behaviour of the birds from Pointe Géologie presented in this study and given the previous studies that described birds from Pointe Géologie as ichthyophagous in summer [START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF]Ridoux 1986, Cherel 2008), Zimmer and colleagues (2008) proposed that the birds fed primarily on Antarctic silverfish. Results from Atka Bay will require further investigations and analyses to confirm our hypotheses. Debate is still ongoing about krill diel migration and depth to which they can be found [START_REF] Flores | The association of Antarctic krill Euphausia superba with the under-ice habitat[END_REF][START_REF] Siegel | Biology and Ecology of Antarctic Krill[END_REF], and it is likely that there is considerable variability depending on the environment and time of year [START_REF] Cresswell | Diel vertical migration of Antarctic krill (Euphausia superba) is flexible during advection across the Scotia Sea[END_REF]. However, several studies found that swarms in the Atlantic sector of the Southern Ocean had mean depths between 30 and 80 m [START_REF] Godlewska | Vertical migrations of krill [Euphausia superba Dana[END_REF][START_REF] Lascara | Seasonal variability in the distribution of Antarctic krill, Euphausia superba, west of the Antarctic Peninsula[END_REF][START_REF] Siegel | Biology and Ecology of Antarctic Krill[END_REF], and they agreed that 95% of the krill range below 200 m [START_REF] Siegel | Biology and Ecology of Antarctic Krill[END_REF]. Given the mean low depth of the foraging dives performed by emperor penguins from Atka Bay in winter, we propose that birds primarily fed on krill during this period. The switch of diving effort in late October, and the second peak of foraging activity at night in summer remains unclear. Some studies in the Scotia Sea and offshore of South Georgia found a reverse diel pattern of krill migration, with patches being at greater depth at night than during the day (see [START_REF] Tarling | Varying depth and swarm dimensions of open-ocean Antarctic krill Euphausia superba Dana, 1850 (Euphausiacea) over diel cycles[END_REF] and references therein). However, why would penguins increase their diving effort by diving more and deeper to target the same prey species? Studies in the Weddell Sea [START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF][START_REF] Pütz | The post-moult diet of Emperor Penguins (Aptenodytes forsteri) in the eastern Weddell Sea, Antarctica[END_REF] and in the Ross Sea [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]) regions suggested two different pelagic feeding strategies in emperor penguins. They hypothesised that the diving birds target krill during shallow dives, while they prey on mesopelagic fish (especially the Antarctic silverfish) and squid during deeper dives. Increasing the dive depth requires longer recovery periods and decreases the diving efficiency of the birds [START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF]Ponganis 1998, Zimmer et al. 2010). However, fish is more energetically valuable than krill [START_REF] Ainley | Spatial and Temporal Variation of Diet Within a Presumed Metapopulation Of Adélie Penguins[END_REF][START_REF] Ruck | Regional differences in quality of krill and fish as prey along the Western Antarctic Peninsula[END_REF]), especially at depth since biggest Antarctic silverfish are found above the seabed [START_REF] Mintenbeck | Impact of Climate Change on the Antarctic Silverfish and Its Consequences for the Antarctic Ecosystem[END_REF]. In the Ross and Weddell Sea regions, Antarctic silverfish represent as much as 90% of the ichtyofauna (La Mesa and Eastman 2012, [START_REF] Vacchi | Advances in Polar Ecology The Antarctic Silverfish: a Keystone Species in a Changing Ecosystem[END_REF], and they are generally found over the continental slope and innershelf depressions at water depths below 200 m [START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF][START_REF] Plötz | Foraging behaviour of Weddell seals, and its ecological implications[END_REF][START_REF] Lancraft | A krill-dominated micronekton and macrozooplankton community in Croker Passage, Antarctica with an estimate of fish predation[END_REF][START_REF] Mintenbeck | Impact of Climate Change on the Antarctic Silverfish and Its Consequences for the Antarctic Ecosystem[END_REF]. As such, we hypothesise that chick-rearing birds from Atka Bay exhibited both strategies over the course of the day, foraging on krill at shallow depths during the day and on fish at greater depth at night-time hours.

Although preliminary, these analyses suggest a change in diet during the austral summer for emperor penguins breeding in Atka Bay. Environmental seasonality (e.g. decrease in sea ice thickness, retreat of the sea ice, increase of day length) is likely influencing the abundance, the diel distribution and the type of prey available in an area, leading to a switch in the foraging strategies performed by the birds during the course of the year. Emperor penguins from Atka Bay appear to be mostly pelagic feeders along the year, but during the chick-rearing period, they may adapt their foraging behaviours to different prey items (i.e. shallow, medium, and, to some extent, benthic dives).

In a review about the conservation status of the Emperor penguin, Trathan and colleagues (2020), advocated for an "Action Plan (that) should also include priorities for telemetry work to help determine where and when, and which demographic categories of emperors are at greatest risk in relation to threats at sea".

Although initiated prior to this publication, the studies that compose my PhD project are part of that stream of thought. The aim of my PhD thesis was, through the use of telemetry, to enhance our knowledge and understanding about the at-sea ecology, i.e. distribution as well as activities, of the Emperor penguin, and this specifically in an area where such questions had not been studied before and where conservation stakes are high. My PhD project is part of a larger programme with the main objectives to (i) ensure a fundamental knowledge of the species by collecting unprecedented data that can answer unresolved questions, and to (ii) start long-term monitoring at sea and on land through systematic data collection observatories set up all around the Antarctic continent to monitor changes resulting from anthropogenic pressures. In this Chapter, I will summarise the main results obtained during my PhD work and consider them in a more general perspective. First, I will focus on the new knowledge gathered on the distribution and behaviour at sea of emperor penguins. Then, I will discuss the importance to collect such data within an ethical, standardised and reliable framework. Finally, I will consider the use of tracking data for conservation purposes in the Southern Ocean. I will conclude by investigating future research perspectives raised by the results obtained during my PhD project.

VI.1 Global overview on the at-sea distribution and activities of the Emperor penguin VI.1.1. A partially filled distribution

Up to now, 61 known colonies of emperor penguins have been identified around the Antarctic continent (Fig. 16; see review in [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]), Trathan et al. (2020) and in [START_REF] Fretwell | Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins[END_REF]). During my PhD, we collected tracking data on adult and juvenile birds from one colony settled at Atka Bay in the Atlantic sector of the East Antarctica, and we used previous data on juveniles and adults collected on four others colonies: at Cape Washington in the Ross sea sector, and at Taylor Glacier, Auster, and Pointe Géologie in the Indian sector of the East Antarctica (Fig. 36; Zimmer et al. 2007b[START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], Labrousse et al. 2019b).

In a recent review about tracking studies in the Southern Ocean, Hindell and colleagues compiled several datasets that they managed to obtain on emperor penguins [START_REF] Hindell | Tracking of marine predators to protect Southern Ocean ecosystems[END_REF], Ropert-Coudert et al. 2020). Noteworthy, they mostly considered adult datasets except for Auster and Taylor colonies were they also used juvenile tracking information. Adult datasets were from three other colonies (Amanda Bay in the Indian sector of the East Antarctica, and Ross and Coulman Islands in the Ross sea sector) and from few birds equipped directly on the sea ice in the Ross Sea. To our knowledge, Fig. 50 shows the maximum extent of all the tracking data available on emperor penguins (but not every single emperor penguin's track). The comparison between the two maps highlights the contribution of the data gathered during my PhD project to the general knowledge on the emperor penguins' distribution at sea. We provide the first tracking data (adults and juveniles) in the Atlantic sector of the Southern Ocean (including the Weddell Sea region), which is home to more than a third of the breeding population of emperor penguins [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF], Teschke et al. 2016b).

These maps also emphatically reveal the geographical gap of knowledge in the distribution at sea of the Emperor penguin. Tracking data are particularly missing in the Bellingshausen and Amundsen seas of the West Antarctica sector, around the Peninsula, and in the deepest part of the Weddell Sea since no tracking has ever occurred in these sectors of the Southern Ocean, for any life-history stage.

VI.1.2. A 2-D differential use of the Southern Ocean between adults and juveniles, but consistent across breeding sites

Many studies on seabirds focus on the distribution and habitat use of adult animals and neglect that immatures and juveniles can inhabit vastly different areas [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]. The studies (Chapter IV and Chapter V) on emperor penguins performed during my PhD project confirm the results of previous studies, and reveal different use of the Southern Ocean between juvenile and adult emperor penguins.

The seasonal travel pattern we found in the post-fledging juvenile emperor penguins from Atka Bay, Queen Maud Land, resembles those of the other colonies [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b). At the end of the summer (i.e. February), after leaving for the first time their colony of origin, juveniles migrate northward towards and into the Antarctic Circumpolar Current (ACC, Fig. 37). This northward exploration can be observed even for the juveniles from Atka Bay and Cape Washington despite the remoteness of the ACC from the continent/colonies in these regions (Fig. 37). Remarkably, none of the birds ventured far north of the Polar Front (PF) that most likely acts as an ecological boundary. In late fall (i.e. April), juvenile emperor penguins migrate southward towards the Antarctic continent and reach the pack ice where they spend the winter and spring, moving northward as the sea ice extends (Fig. 38). The following summer (i.e.

November), juveniles follow the southward contraction of the pack ice. According to our tracking data of juveniles up to their annual moult, the first data of this kind reported so far, one-and-a-half-year-old juveniles moult in late December-January near the Antarctic continent, hundreds of kilometres from their colony of origin 22 (Chapter V, Fig. 39). Only a few juveniles (i.e. birds with white chin and white/yellow auricular patches) have been observed moulting at Atka Bay or at Pointe Géologie colonies during our fieldwork sessions, but it was, of course, not possible to determine if they belonged to these colonies as they were not marked. Similarly to adults, > 1-year-old juvenile emperor penguins appear to engage their moult on consolidated part of the sea ice, fast ice or even ice shelf (Houstin, Le Bohec, unpublished observations). Juveniles and adults have also been spotted to moult together in the pack ice deep inside the Weddell and Ross Seas [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF].

Overall, adult emperor penguins from Atka Bay reveal similar behaviour in their seasonal 2-D movements than adults from other colonies [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF], Zimmer et al. 2007b, Labrousse et al. 2019b). We showed that their distribution at sea is mostly constrained by the breeding status of the birds and the distance between the breeding colony and the limit of the continental slope over which they forage presumably in ephemeral polynya, cracks and leads where the productivity is high (Chapter V). Right after their moult, adults range further to reach foraging grounds (probably more productive) to build up their reserve for the next breeding season. They explore areas, which they cannot reach during the breeding season, near other colonies or at the margin of the continental slope (up to 486 km, Fig. 39). The ARGOS deployed on the post-moult adults from Atka Bay stopped transmitting between May and July for breeding birds. Thus, we could not collect data on breeding birds after their return to the colony for the courtship and incubation phase. Nevertheless, as for adults breeding at Pointe Géologie (median of maximum distances to the colony = 56 km, Table 17), between May and September, breeders from Atka Bay are also likely constrained around the colony.

The tracks we collected at Atka Bay during the chick-rearing period reach the limits of the maximum extent determined by the model of probability of occurrence of breeding emperor penguins 23 developed by Teschke andcolleagues (2016b, 2019), with some parts of the tracks at the very edges of the boundaries (Fig. 51). Given the few (but only available for the region) data we collected, we suggest that this model underestimates the probability of occurrence of breeding birds, at least over the chick-rearing period. In the deep winter, if breeding emperor penguins from the Atlantic sector of the Southern Ocean exhibit the same habitat use behaviour than the ones in the d'Urville Sea (Chapter V), then the tracks of breeding birds would fall within the model boundaries.

In the case of non-breeding birds, either individuals in post-moult period (i.e. January to April before breeding) or birds that chose not to breed during the winter, the model is not trustworthy: emperor penguins from Atka Bay range commonly outside the predicted area of presence (Fig. 51). In our study, like in the study carried out in the Ross Sea [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], non-breeding adults express two different habitat-use strategies: either they spend the winter foraging along the Antarctic continent (N =2), or travel clock-wise in the Weddell Sea Gyre (N = 1). Consequently, such model shall not be used to infer the probability of occurrence of emperor penguins in the area. 23 The model of probability of occurrence that used to estimate the distribution at sea of breeding emperor penguins in the Weddell Sea region assumes that "the probability of an emperor penguin being present at a certain geographical locality depends on three major factors, the overall density of penguins in the wider area (e.g. colony size), the distance from the colony, and the sea ice conditions, i.e. to which extent entry into the water is possible" (Fig. 51; Teschke et al. 2016b[START_REF] Teschke | An integrated data compilation for the development of a marine protected area in the Weddell Sea[END_REF]. In the absence of tracking data on emperor penguins from the Weddell Sea region, the distance parameter is based on the winter distribution of male emperor penguins from the Pointe Géologie colony (Zimmer et al. 2007b). A distance model weighted by the penguin density (estimates from [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF]) was combined with a sea ice concentration model considering the mean sea ice concentration between June and January from 2002 to 2011. (2016b, 2019). Red tracks are from chick-rearing adults (GPS datasets obtained in November/December) and black lines are from non-breeding birds (ARGOS datasets obtained between January and August). The purple track belongs to the nonbreeding adult that exhibited a Gyre habitat-use strategy

24

.

VI.1.3. Inferring the reasons for the dispersion of juveniles

Interestingly, juvenile emperor penguins from Atka Bay are heading northward, on the open sea, at a time when adults are spreading along the continent, over the continental shelf and slope, to replenish their reserves after the annual moult and before breeding (Chapter V, Fig. 39). Then, in April, while 24 The mass and the morphological characteristics (flippers, beak and feet lengths) of this bird were not extreme. However, its auricular yellow patches appeared to us slightly smaller and lighter than the ones from the other post-moulting birds that we were able to find and capture on the colony. The coloration of auricular patches has been shown to be indicative of birds' age for the sister king penguin species [START_REF] Nicolaus | Ornamental colors reveal age in the king penguin[END_REF]. Additionally, the habitat-use strategy displayed by this bird is strikingly similar to the one displayed by our equipped fledglings and dissimilar from the two other non-breeding birds. As such, we suggest that this bird might actually be an immature of 1.5 year old.

juveniles are back in the vicinity of the Antarctic continent, adult emperor penguins are at the colony to mate and breed. This finding suggests that these two life-history stages might not overlap in their distribution over the year and until the annual moult period (December to February) during which they gather in the same habitat (Houstin, Le Bohec, unpublished observations; [START_REF] Kooyman | Moult of the emperor penguin: Travel, location, and habitat selection[END_REF]. At-sea spatial segregation of conspecifics according to age-class is not uncommon in other southern oceanic bird and mammal species [START_REF] Field | Resource partitioning through oceanic segregation of foraging juvenile southern elephant seals (Mirounga leonina)[END_REF][START_REF] Weimerskirch | Postnatal dispersal of wandering albatrosses Diomedea exulans : implications for the conservation of the species[END_REF][START_REF] Trebilco | At sea movement of Macquarie Island giant petrels: Relationships with marine protected areas and Regional Fisheries Management Organisations[END_REF].

Noteworthy, ranging so far north (up to 48.5°S for one juvenile of Atka Bay) during their dispersion in fall, our results reveal that juvenile emperor penguins overlap in space and time with juvenile and possibly non-breeding adult king penguins (Fig. 52). The two species of the Aptenodytes genus split up 3 million years ago [START_REF] Cole | Mitogenomes Uncover Extinct Penguin Taxa and Reveal Island Formation as a Key Driver of Speciation[END_REF]. However, in contrast to emperor penguins, king penguins have not been tracked within the pack ice area during winter, but only up to its edge [START_REF] Orgeret | Exploration during early life: distribution, habitat and orientation preferences in juvenile king penguins[END_REF].

Given the similarities in size and diving ability between juvenile emperor penguins and king penguins (Kooyman et al. 1992a[START_REF] Ponganis | Development of diving capacity in emperor penguins[END_REF], it is likely that juvenile emperor penguins forage on the same prey species, i.e. lantern fish (myctophids) and squids than king penguins when they forage at their northern range [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 2002, Wienecke et al. 2010); a diet drastically different to the one they were being fed with (i.e. krill and Antarctic silverfish) by their parent [START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF][START_REF] Robertson | Diet composition of Emperor Penguin chicks Aptenodytes forsten' at two Mawson Coast colonies[END_REF][START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF][START_REF] Cherel | Isotopic niches of emperor and Adélie penguins in Adélie Land, Antarctica[END_REF]. Post-natal dispersal has been shown to be partially pre-determined in various species, for instance, in flying seabirds [START_REF] De Grissac | Contrasting movement strategies among juvenile albatrosses and petrels[END_REF][START_REF] Yoda | Compass orientation drives naïve pelagic seabirds to cross mountain ranges[END_REF], sea turtles [START_REF] Scott | Ontogeny of long distance migration[END_REF], seals [START_REF] Bornemann | Southern elephant seal movements and Antarctic sea ice[END_REF][START_REF] Tosh | The importance of seasonal sea surface height anomalies for foraging juvenile southern elephant seals[END_REF], or some penguin species like the King penguin [START_REF] Pütz | Post-Fledging Dispersal of King Penguins (Aptenodytes patagonicus) from Two Breeding Sites in the South Atlantic[END_REF], Orgeret et al. 2019). As suggested by [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], the northward-directed movement into the ACC of all tracked juvenile emperor penguins might be driven by innate mechanisms. What triggers the southward return of juvenile emperor penguins remains also unclear. Several nonexclusive hypotheses can be at stakes including physiological maturation (e.g. increase in body insulation as shown in king penguins [START_REF] Enstipp | Apparent changes in body insulation of juvenile king penguins suggest an energetic challenge during their early life at sea[END_REF] or in O 2 storage capacity as suggested by [START_REF] Ponganis | Development of diving capacity in emperor penguins[END_REF] and shown in seals [START_REF] Thorson | Developmental Aspects of Diving in Northern Elephant Seal Pups[END_REF]), development of foraging skills (e.g. [START_REF] Ponganis | Development of diving capacity in emperor penguins[END_REF][START_REF] Orgeret | Early diving behaviour in juvenile penguins: improvement or selection processes[END_REF][START_REF] Grecian | Understanding the ontogeny of foraging behaviour: insights from combining marine predator bio-logging with satellite-derived oceanography in hidden Markov models[END_REF], a switch in diet or of the prey distribution over the seasons [START_REF] Charrassin | Seasonal changes in the diving parameters of king penguins (Aptenodytes patagonicus)[END_REF][START_REF] Matthysen | Multicausality of dispersal: a review[END_REF], intra-and inter-specific competition for food resources [START_REF] Burns | Habitat Use by Weddell Seals and Emperor Penguins Foraging in the Ross Sea, Antarctica[END_REF][START_REF] Ballance | An energetic correlate between colony size and foraging effort in seabirds, an example of the adelie penguin[END_REF], Ainley et al. 2010a), as well as predation avoidance regarding, for instance, the leopard seals or killer whales [START_REF] Ainley | Non-consumptive factors affecting foraging patterns in Antarctic penguins: a review and synthesis[END_REF]. The survival rate of emperor penguins over their first year at sea is relatively low (40%, [START_REF] Abadi | Integrated population modeling reveals the impact of climate on the survival of juvenile emperor penguins[END_REF]. In comparison, the return (and thus survival) rate of juvenile king penguin is between 68-87% (Saraux et al. 2011b). Yet, juveniles are more sensitive to environmental factors than adults, and juvenile survival can have a critical influence on the population dynamics especially in longlived species [START_REF] Stearns | The Evolution of Life Histories[END_REF]. Given the ecological upheavals that are expected in a near future as a result of global change (see page 38), an improved understanding of the factors that influence juvenile emperor penguins' survival during their dispersion should, therefore, become a research priority in order to predict as accurately as possible the future demographic trends of the species.

VI.1.4. Adaptive capacity through behavioural flexibility in foraging to cope with a changing environment

Adult emperor penguins are associated with the pack ice both during the breeding [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 1997, Zimmer et al. 2007b) and post-breeding seasons [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], Rodary et al. 2000a, Kooyman et al. 2004[START_REF] Wienecke | Premoult foraging trips and moult locations of Emperor penguins at the Mawson Coast[END_REF]). They access their foraging grounds from small openings, including holes, cracks, flaw leads, and ephemeral short-term polynyas; the sea ice restricting their access to the water [START_REF] Zimmer | Constraints on Foraging and their Consequences for Emperor Penguins PhD[END_REF], Labrousse et al. 2019a). Once immerged, they search for food items that is patchily distributed, both horizontally and vertically [START_REF] Wienecke | Review of historical population information of emperor penguins[END_REF]Robertson 1997, Zimmer 2007). The diving data we collected on adult emperor penguins in the Weddell Sea region and the Atlantic sector of the Southern Ocean (Chapter V) are the first of their kind, since the activities at sea of the species had never been studied in this area, home of a third of the global population. Indeed, to date, studies on the diving behaviour of emperor penguins occurred essentially in the Ross Sea [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF][START_REF] Kooyman | Diving Behavior of Emperor Penguins Nurturing Chicks at Coulman Island, Antarctica[END_REF][START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF], in the d'Urville Sea [START_REF] Ancel | Foraging behaviour of emperor penguins as a resource detector in winter and summer[END_REF], Zimmer et al. 2007b, 2008, 2010), and along the Mawson coast (Kirkwood and[START_REF] Wienecke | Foraging space of emperor penguins Aptenodytes forsteri in Antarctic shelf waters in winter[END_REF]Robertson 1997). Emperor penguins exhibit dive capacities, both in terms of dive duration and maximum dive depth, similar to those of marine mammals such as Weddell seals [START_REF] Burns | Habitat Use by Weddell Seals and Emperor Penguins Foraging in the Ross Sea, Antarctica[END_REF].

The exploration of the foraging behaviour of diving birds using proxies of the daily diving effort (i.e. the distribution of dives throughout the day and the depth of dives) allowed us to investigate the diet of the emperor penguins from the Atlantic sector of the Southern Ocean. Indeed, our unprecedented year-round high-resolution complete datasets (N = 4) suggests a switch in the diving effort strategy of the birds in late October (from a 'day-time diving effort' strategy before the summer to a 'night-time diving effort' strategy in summer). The prevalence of this second strategy in summer was confirmed by the equipment of chick-rearing birds in summer (except one bird, all (N = 22) exhibited this pattern).

We interpreted this switch as a change in the diet of the birds, and we suggest that they forage on krill during the day, while the dives occurring at night hours in the 'night-time diving effort' strategy indicate a higher predation effort on fish exhibiting a diel vertical migration (Mintenbeck and Torres 2017) and of a higher energetic value for the birds [START_REF] Ainley | Spatial and Temporal Variation of Diet Within a Presumed Metapopulation Of Adélie Penguins[END_REF].

Our study in that sector of the Southern Ocean supports the hypothesis of an existing flexibility in the foraging behaviour of the Emperor penguin giving birds the ability to adapt their diet according to season, year and location. For instance, it has been shown that emperor penguins from Auster colony switched from a fish diet in 1988 to a krill diet in 1993 [START_REF] Kirkwood | The foraging ecology of female Emperor Penguins in winter[END_REF], while birds from Pointe Géologie presented a fish diet in two studies 20 years apart [START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF]Ridoux 1986, Cherel 2008). The prey availability may vary with seasons and years due to environmental factors like sea ice extent and thickness, water salinity, or light quantity. However, the physical environment of each locality also influences the prey composition of an area and may offer different perspectives for emperor penguins according to their breeding sites. For instance, the shelf around Atka Bay is narrow and steep (Zimmer et al. 2007b, Jerosch et al. 2016, Labrousse et al. 2019a), while the shelf in the Ross Sea and the d'Urville Sea is wide [START_REF] Anderson | Antarctic Marine Geology[END_REF][START_REF] Beaman | A new high-resolution bathymetry model for the Terre Adélie and George V continental margin, East Antarctica[END_REF]) and presents particular bathymetric features (called 'banks') between 200 and 500 m of depth aggregating bentho-pelagic fish within reach of emperor penguins. As [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF] in the Ross Sea, we showed that birds from Pointe Géologie perform benthic dives, a strategy not expressed by the large majority of our birds in the Atlantic sector of the Southern Ocean. As a result, both physical and geographical environmental differences in localities may lead to various foraging strategies expressed by the individuals within the species. Consequently, foraging but also general behavioural strategies observed at a given breeding site might not be generalised to colonies form other regions. Additionally, multi-year data on a same breeding site are required to investigate the consistency of the strategies with regards to environmental stochasticity and more persistent changes.

Although unique, the year-round diving datasets we obtained are from a small sample size (N = 4), which does not allow to draw strong conclusions regarding differences in sex and breeding status. In addition, the absence of tracking data over the winter prevents us from getting a fully comprehensive understanding of the foraging behaviour of emperor penguins from Atka Bay. Therefore, we could not investigate the effect of sea ice and the presence of ephemeral short-term polynyas on the spatial and diving behaviour of the birds from this region.

Noteworthy, in all the emperor penguins foraging related studies listed here, including ours, the subice foraging behaviour was not considered. Shallow dives are very common in emperor penguins [START_REF] Cherel | Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica[END_REF], and they are mostly considered as non-foraging dives, travelling dives, or part of the recovery from an oxygen debt [START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF]Kooyman 1995, Kirkwood andRobertson 1997). They are, therefore, classically removed from the foraging analyses based on the wiggles' detection at depth. However, such sub-ice foraging behaviour has been documented on emperors [START_REF] Ponganis | Sub-ice foraging behavior of emperor penguins[END_REF] as well as on Adélie penguins (Watanabe and Takahashi 2013) and is highly suspected on Weddell seals [START_REF] Watanabe | Seal-mounted cameras detect invertebrate fauna on the underside of an Antarctic ice shelf[END_REF]. Moreover, the occurrence of cryopelagic fish and krill species as well as scavenger amphipods in the diet of emperor penguins has also been reported [START_REF] Offredo | The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land[END_REF][START_REF] Klages | Food and feeding ecology of emperor penguins in the eastern Weddell Sea[END_REF][START_REF] Pütz | The post-moult diet of Emperor Penguins (Aptenodytes forsteri) in the eastern Weddell Sea, Antarctica[END_REF][START_REF] Cherel | Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica[END_REF]. Surface or shallowdepth foraging seabirds in the Ross Sea are known to feed on a similar diet and on Antarctic silverfish [START_REF] Ainley | The Marine Ecology of Birds in the Ross Sea, Antarctica[END_REF][START_REF] Mund | Diet of the south polar skua Catharacta maccormicki at Cape Bird, Ross Island, Antarctica[END_REF][START_REF] Cherel | Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica[END_REF]. In conclusion, as Cherel and Kooyman (1998), we consider that there is no reason to believe that emperor penguins would not forage on sub-ice prey and at shallow depths as well, and this behaviour will need to be investigated

. Global change and emperor penguins

There is growing evidence that ongoing climate change is adversely affecting penguin populations on a global scale (Ainley et al. 2010a). Recent studies on the two major Antarctic species -the Adélie penguin [START_REF] Jenouvrier | Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models[END_REF][START_REF] Cimino | Projected asymmetric response of Adélie penguins to Antarctic climate change -supplemental figures[END_REF], Ropert-Coudert et al. 2018) and the Emperor penguin (Jenouvrier et al. 2009b[START_REF] Matthysen | Multicausality of dispersal: a review[END_REF], 2014[START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF], Trathan et al. 2011) -have highlighted their exposure to environmental changes, and the vulnerability of the Emperor penguin to changes in sea ice extent, formation, and persistence.

Sea ice monitoring by satellites is on-going since 1978 [START_REF] Stammerjohn | Regions of rapid sea ice change: An inter-hemispheric seasonal comparison[END_REF][START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF]).

Contrasting trends have been observed depending on the Antarctic sector considered [START_REF] Stammerjohn | Regions of rapid sea ice change: An inter-hemispheric seasonal comparison[END_REF][START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF]. Sea ice extent and persistence have been decreasing in the West Antarctic Peninsula sector since records started (Massom andStammerjohn 2010, Stammerjohn et al. 2012) 25 , while a reverse trend has been observed in the Ross and the Weddell Seas [START_REF] Stammerjohn | Regions of rapid sea ice change: An inter-hemispheric seasonal comparison[END_REF][START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF]. Moreover, despite some uncertainties, models project sea ice loss over the 21 st century in all scenarios [START_REF] Roach | Antarctic Sea Ice Area in CMIP6[END_REF].

Top predator species have already been negatively impacted by environmental changes. For instance, declines in populations of Chinstrap and Adélie penguins in Western Antarctic peninsula, as well as of Antarctic fur seals (Arctocephalus gazella) around South Georgia, has been associated to a decrease in krill biomass, their main prey species [START_REF] Forcada | Contrasting population changes in sympatric penguin species in association with climate warming[END_REF][START_REF] Trathan | Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability[END_REF][START_REF] Trivelpiece | Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica[END_REF][START_REF] Lynch | Sensitivity analysis identifies high influence sites for estimates of penguin krill consumption on the Antarctic Peninsula[END_REF]). Sightings of Weddell seals have also been reported to have declined In the western Antarctic Peninsula [START_REF] Siniff | Opinion: Projecting the effects of environmental change on Antarctic seals[END_REF]. Moreover, direct environmental impacts have already been monitored on emperor penguins' colonies with the loss of two breeding colonies associated with sea ice decline and fast ice alteration [START_REF] Trathan | First Recorded Loss of an Emperor Penguin Colony in the Recent Period of Antarctic Regional Warming: Implications for Other Colonies[END_REF]Trathan 2019). Birds may have relocated to other colonies or sites, as it has been shown for the Mertz colony after the Glacier Tongue calving in 2010 [START_REF] Ancel | Emperors in hiding: When ice-breakers and satellites complement each other in Antarctic exploration[END_REF]) and for the Ruppert Coast colony that relocated from sea ice to an ice shelf in 2012 [START_REF] Fretwell | Emperor Penguins Breeding on Iceshelves[END_REF]). Yet, if sea ice, and specifically fast ice, around Antarctica tends to disappear in the near future due to global warming, suitable areas for relocation for breeding might shrink (Trathan et al. 2020). Indeed, to access ice shelves that can be up to several tens of meters above the sea ice level, emperor penguins require the presence of snow bridges connecting the shelf and the sea ice [START_REF] Zitterbart | Are environmental factors responsible for changed breeding behaviour in emperor penguins?[END_REF]). In the absence of sea ice, such bridges are unlikely to be present.

Emperor penguins are tied to sea ice not only for their breeding ground, but also for feeding. Their main prey species (krill and Antarctic silverfish) have both larval stages dependent on sea ice (Mintenbeck andTorres 2017, Atkinson et al. 2019). The disturbance of the sea ice cycle is thus likely to negatively affect these prey populations in terms of abundance, structure, size, quality, and distribution [START_REF] Piñones | Projected changes of Antarctic krill habitat by the end of the 21st century[END_REF]Fedorov 2016, Mintenbeck and[START_REF] Mintenbeck | Impact of Climate Change on the Antarctic Silverfish and Its Consequences for the Antarctic Ecosystem[END_REF], and/or to lead to temporal mismatch between their availability and the critical phase of the breeding cycle of these predators (e.g. the very demanding chick-rearing period). If food resources were to be limited, then emperor penguin populations would indubitably decrease. However, myctophids or demersal notothenioids might progressively replace krill and Antarctic silverfish in areas where sea ice disappears and water temperature rises [START_REF] Mintenbeck | Impact of Climate Change on the Antarctic Silverfish and Its Consequences for the Antarctic Ecosystem[END_REF]. Given their opportunistic behaviour and diving capacities (Chapter V), it is worth considering that emperor penguins will probably be able to adapt, to some extent, their diet accordingly.

The ongoing global change has already started to affect Southern Ocean ecosystems [START_REF] Constable | Climate change and Southern Ocean ecosystems I: How changes in physical habitats directly affect marine biota[END_REF], Gutt et al. 2014) and emperor penguins [START_REF] Trathan | First Recorded Loss of an Emperor Penguin Colony in the Recent Period of Antarctic Regional Warming: Implications for Other Colonies[END_REF]Trathan 2019).

However, each emperor penguin colony presents specific environmental conditions (e.g. distance to oceanic fronts, persistence of sea ice in time and space, seaward extent of Antarctic continental shelf, presence of specific oceanic currents, like gyres, that may lead to contrasting population trajectories [START_REF] Jenouvrier | Projected continent-wide declines of the emperor penguin under climate change[END_REF][START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF][START_REF] Kooyman | Rise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012[END_REF].

VI.2.2. A limited knowledge and amount of data on the most iconic species of Antarctica

Our understanding of climate change impacts on emperor penguins is fragmented (Ainley et al. 2010b[START_REF] Larsen | Polar Regions[END_REF]. Most of our current knowledge about the breeding behaviour, life-history and demographic parameters of emperor penguins (e.g. breeding date, breeding cycle duration, survival and reproductive rates) is based on the monitoring of a single colony at Pointe Géologie, Terre Adélie, monitored continuously since 1952 [START_REF] Prévost | Ecologie du manchot empereur[END_REF][START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF][START_REF] Barbraud | Comparison of emperor penguin declines between Pointe Géologie and Haswell Island over the past 50 years[END_REF].

However, heavy flipper banding scheme was carried out in the 70's and 80's [START_REF] Jenouvrier | Longterm contrasted responses to climate of two antarctic seabird species[END_REF],

while it has been later shown to negatively affect survival and breeding success [START_REF] Gauthier-Clerc | Long-term effects of flipper bands on penguins[END_REF][START_REF] Dugger | Effects of flipper bands on foraging behavior and survival of adélie penguins (pygoscelis adeliae)[END_REF], Saraux et al. 2011a, Le Maho et al. 2011). Thus, biodemographic parameters, trends and conclusions from flipper-banded dataset gathered in this colony until the 2000's are questionable and should be interpreted with caution [START_REF] Cristofari | Full circumpolar migration ensures evolutionary unity in the Emperor penguin[END_REF]). Yet, to evaluate the overall trend of a species and the amplitude of its adaptive capacities, it is crucial to monitor over the long-term more than one population breeding in different ecosystems; a trend from a single colony may not be a good environmental sentinel [START_REF] Kooyman | Rise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012[END_REF]. However, to date, only a few other long-term time series of colony size exists for other colonies than Pointe Géologie (Trathan et al. 2020), and [START_REF] Kooyman | Rise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012[END_REF] demonstrated that colonies should be counted every year at a regional scale, given the high yearly fluctuations of colony size they recorded in a 12-years census over 7 colonies in the Ross Sea.

In addition to these time series, other studies have been conducted on the species (see Table 20), including satellite censuses [START_REF] Fretwell | An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space[END_REF][START_REF] Larue | A method for estimating colony sizes of Adelie penguins using remote sensing imagery[END_REF], population genetics [START_REF] Cristofari | Structure and dynamics of the penguin synnomes -Understanding seabird life history and response to climate change through population genomics -PhD[END_REF][START_REF] Younger | The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins[END_REF], investigations on the colony functioning [START_REF] Zitterbart | Coordinated movements prevent jamming in an emperor penguin huddle[END_REF], 2014[START_REF] Gerum | The origin of traveling waves in an emperor penguin huddle[END_REF], Richter et al. 2018a), the huddling behaviour and its associated thermoregulation physiology (Le [START_REF] Maho | The Emperor Penguin: A Strategy to Live and Breed in the Cold: Morphology, physiology, ecology, and behavior distinguish the polar emperor penguin from other penguin species, particularly from its close relative, the king penguin[END_REF][START_REF] Gilbert | Huddling behavior in emperor penguins: Dynamics of huddling[END_REF], 2007[START_REF] Mccafferty | Emperor penguin body surfaces cool below air temperature[END_REF], Richter et al. 2018b) as well as some diving physiology experimentations (Kooyman et al. 1992b[START_REF] Ponganis | O2 store management in diving emperor penguins[END_REF][START_REF] Sato | Stroke rates and diving air volumes of emperor penguins: implications for dive performance[END_REF][START_REF] Williams | What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins[END_REF], Wright et al. 2014). Finally, the spatial distribution at sea and the foraging-related studies resulting in the global overview presented in this thesis, concern about 10 colonies for adults and 5 colonies for juveniles. This inventory highlights the cruel lack of available data on general ecology and life-history processes in emperor penguins, not mentioning physiological insights. In other words, the bottom of the pyramidal structure to set up adequate conservation measures (Fig. 2) is very narrow and fragmented.

Given the rapid on-going global changes, without baseline data in space and time on demographic trends, distribution and general ecology of emperor penguins, it will be soon impossible to disentangle changes owing to natural environmental stochasticity from those due climate upheavals or more direct anthropogenic disturbances (e.g. fisheries, tourism, pollution, or geopolitical pressures for scientific station multiplication; see [START_REF] Maxwell | Cumulative human impacts on marine predators[END_REF][START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], Trathan et al. 2018). Such an initial state of knowledge is also a prerequisite to frame conservation objectives and to their efficiency [START_REF] Mihoub | Setting temporal baselines for biodiversity: the limits of available monitoring data for capturing the full impact of anthropogenic pressures[END_REF], Ropert-Coudert et al. 2020 2017). Tracking behavioural changes (variation of e.g. the foraging ranges, diving strategies, diet) of individuals and populations over successive years within a monitoring framework, which also gives us access to life-history and genetic data, has the potential to vastly improve our knowledge and understanding of occurring changes (Le [START_REF] Bohec | Polar Monitoring: Seabirds as Sentinels of Marine Ecosystems, in "Adaptation and Evolution in Marine Environments[END_REF]. However, data from animal-borne sensors must be collected in such a way that animal behaviour is still representative and unbiased so that conclusions drawn are valuable.

VI.2.3.2. An old and fragmented at-sea ecology literature

Despite the fact that emperor penguins have been equipped with biologgers for half a century [START_REF] Kooyman | Diving Behavior of the Emperor Penguin, Aptenodytes forsteri[END_REF], there were no specific publication dedicated on the capture and equipment protocols of non-anaesthetised emperor penguins in the field. This information is most of the time not mentioned in the scientific literature, or with very limited details (see Chapter III for review). During my PhD project, techniques of captures and logger attachments, seen on the field during my overwintering and discussed beforehand with experts working on emperor penguins and/or with biologging, have been initially used. However, we discovered that some of these techniques were unsuccessful, inefficient or even damageable for the animals, and, for most of them, their potential impacts have not been fully assessed. Typically, potential adverse effects of the commonly-used technique of gluing the logger to the back feathers of emperor penguins for long-term deployment were not evaluated, given that until our study, such equipped bird had never been resighted. Some of the techniques presented in this very limited and fragmented literature are, therefore, out of date and should not be considered as reference anymore. For instance, the rugby-like catch technique mentioned to capture adult emperor penguin ( and ethical point of view, the potential deleterious effects of the deployment procedures and the devices must be assessed and mitigated.

Thus, in the context of fragmented knowledge on emperor penguin tagging, in Chapter III, we presented three techniques to capture and/or recapture emperor penguins with minimal disturbance:

adult-chick pair capture with a corral, fledging juveniles capture with a corral, and capture of an adult with a crook. Two of those are new to the literature (the coral captures), while the last one is for the first time exposed in a movie. Additionally, we shared two deployment methods that are novel procedures and have ensure the longest deployment duration ever performed for this species (382 days). Above all, being the first to resight long-term equipped birds on which devices had been glued on the back feathers, we showed that the loggers and the feathers to which it was attached were missing. We thus revealed that the classical technique used for long-term deployment on emperor penguins is detrimental to the bird and answer the question of Kooyman and colleagues (2015) who provided only few months of data: "Why ARGOS devices stopped transmitting over the winter?". We illustrated our work with an exhaustive documentation made of slideshows and movies to make our work transparent and easily reproducible. We also encourage regular updates of this material.

Chapter III was not initially planned at the beginning of my PhD project. As mentioned earlier, the Chapter was born from discovering the damage to the animals and gaps in literature. Therefore, it was obviously not design with predefined protocols to answer methodological questions about welfare impacts or ethical questions in wildlife experiments. For instance, the timing of each handling step together with an ethogram should be developed and used to monitor birds' behaviour and stress level throughout the manipulation. Moreover, although we were able to highlight the loss of feathers and its unambiguously detrimental effect for the birds' insulation, it was not possible to properly assess the degree of disturbance caused to the birds due to the lack of control birds. "Does the loss of feathers alter the capacities of the birds to cope with winter fasting period? Do the birds increase their diving efforts to compensate the heat loss? Ultimately, does feathers' damage impact their breeding success or their survival?" are still pending questions without this control group. Another methodological difficulty was linked to the deployment of several instruments on the same bird, which prevents us from disentangling with certainty the impacts of each logger. Those are well known issues relevant to biologging studies [START_REF] Beaulieu | Ecophysiological response of Adelie penguins facing an experimental increase in breeding constraints[END_REF][START_REF] Vandenabeele | Tags on seabirds; how seriously are we considering instrumentinduced behaviors?[END_REF][START_REF] Forin-Wiart | Why implantation of bio-loggers may improve our understanding of how animals cope within their natural environment[END_REF].

Unfortunately, there are still no device on the market designed to collect simultaneously all the data (location, pressure, and acceleration), at the frequency and for the duration we needed to use, to address our research questions. By deploying several devices on the same bird, we minimised the number of birds disturbed (the "Reduction" principle from the Three Rs -Replacement, Reduction, Refinement -framework; [START_REF] Russel | Page The principles of humane experimental technique[END_REF]) even though we possibly increased the amount of disturbance per bird.

VI.2.3.4. Calling for future methodological improvement and standardisation

The alternative techniques we developed during my PhD project (leg-band attached TDR and backtaped-epoxied GPS) have given encouraging results (Chapter III). For the first time on emperor penguins, these methods allowed to successfully collect year-round data leading to unprecedented insights into the species' behaviours (Chapter IV and Chapter V). Yet, logistical constraints prevented us from testing the most updated version of the leg-band attached TDR that incorporated latest improvements to reduce bird disturbance26 . However, we will be able to test these updates within the next years and deployment sessions planned through the long-term monitoring programme (see page 192). Given the promising results and the detrimental impacts of the classical deployment techniques, we opted for the principle of precaution and shared our techniques and results (Chapter III submitted to Animal Biotelemetry) to prevent avoidable animal disturbance and/or suffering in future projects [START_REF] Hawkins | Bio-logging and animal welfare : practical refinements[END_REF].

While biologger characteristics have undergone rapid progress (e.g. size, shape, weight, power consumption; see [START_REF] Wilson | Diel dive depth in penguins in relation to diel vertical migration of prey: whose dinner by candlelight?[END_REF]Vandenabeele 2012, Portugal and[START_REF] Portugal | Miniaturization of biologgers is not alleviating the 5% rule[END_REF], deployment techniques have stagnated (at least in emperor penguins), leading to incomplete datasets owing to technical and logistical constraints. We demonstrated that continuous improvement and refinement are fundamental and achievable. Our work does not pretend to be a collection of best practices, but intends to provide a baseline (resource) for the development of a standardised, reproducible, efficient and ethical framework for future deployments on the species, as well as to provide comprehensive data while ensuring minimal disturbance to equipped individuals. The continuous enhancement of equipment protocols, ensuring the expression of genuine natural behaviours and their recording over meaningful duration, will greatly improve our understanding of wildlife ecology and allow the design of adequate conservation and management measures. For instance, thanks to our new leg-band attachment technique of TDR on adult emperor penguins, we have been able to identify the change in diving effort that occurred in late October, suggesting a concomitant switch in diet (Chapter V). With the classical gluing technique, the device would have been lost too early to detect this behavioural flexibility in emperor penguins. Similarly, thanks to the long-term attachment technique we developed for juveniles, we identified the importance of the South Georgia and South Sandwich Islands MPA for juvenile emperor penguins as well as the moulting sites and the complete annual pattern of the ocean use of this life-history stage. Such finding would have not been possible with the use of previous techniques.

Finally, during my PhD project, my involvement in the development of equipment techniques resulted in the perception that various methods have been elaborated and tested (not necessarily in-situ on wildlife) and then abandoned because they revealed unsuccessful. We deplore the fact that these developments are (hardly) ever reported, resulting in the investment of a lot of resources and time to develop similar techniques that will prove to be equally unsuccessful. We are convinced that it would be beneficial to give more exposure to fieldwork developments and methodology in scientific publications to improve and facilitate experimental designs and their results -a practice that would benefit both, animals and scientists. This should not only be the burden of researchers but also a change of paradigm of editors and journals. Tests, errors and failures are inherent of research and thus should be, to some extent, valued as significant results. Their highlighting would also contribute to

VI.3.2. Only breeding sites matters in current MPA planning

The monitoring of emperor penguin juveniles has been called since years to become a priority [START_REF] Trathan | First Recorded Loss of an Emperor Penguin Colony in the Recent Period of Antarctic Regional Warming: Implications for Other Colonies[END_REF]; however, tracking studies of juveniles are relatively rare (to date, five studies on five colonies, including ours [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF][START_REF] Wienecke | Maiden journey of fledgling emperor penguins from the Mawson Coast, East Antarctica[END_REF][START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019a; see Chapter IV). This shortcoming holds not only for penguins but also for other seabirds, sea turtles, and marine mammals. The main reasons are that biologgers' recovery is more difficult and biologgers' size is often less suitable for juveniles [START_REF] Hays | Key Questions in Marine Megafauna Movement Ecology[END_REF]. Juvenile distributions are therefore usually not considered, while they are of primary importance for conservation plans and species viability [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF].

For penguins, the common approach for designating boundaries of MPAs focuses on protecting breeding birds and colonies [START_REF] Sherley | The initial journey of an Endangered penguin: implications for seabird conservation[END_REF], Boersma et al. 2019). As a result, 32 of the 61 emperor penguin colonies (52%) are situated within planned or existing MPAs. In the Weddell Sea Marine Protected Area (WSMPA) proposal, only models of probability of occurrence of breeding adults (see footnote page 182) were considered to assess emperor penguin's distribution (Teschke et al. 2016b, CCAMLR 2018a). As a consequence, important pelagic areas for juvenile and non-breeding adult emperor penguins are lacking consideration. For instance, in the southern Atlantic region of the Southern Ocean, the Antarctic Circumpolar Current (ACC) region is not included in the proposed 199 WSMPA (CCAMLR 2018a), while we showed that the area was critical for the juveniles (Chapter IV).

We already stressed the importance of juvenile survival for the species viability (see also [START_REF] Abadi | Integrated population modeling reveals the impact of climate on the survival of juvenile emperor penguins[END_REF]). On the other hand, the proportion of non-breeding adults and how often emperor penguin adults skip breeding still remains unknown [START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]. [START_REF] Barbraud | Emperor penguins and climate change[END_REF] stated that, at Pointe-Géologie colony, 'the number of breeding pairs represents 80% of the overall population size'. However, this assessment might stand for Pointe Géologie colony only. Additionally, it is unclear if this statement reflects the proportion of birds at the colony site (breeding birds and birds that failed to find a partner), or also include birds at sea that did not return at the colony site for breeding at the beginning of the season. In the first case, there is no estimation of the number of nonbreeding birds that remained at sea to skip breeding. With climate change impacts, the proportion of non-breeding emperor penguins is likely to increase. Indeed, as long-lived species, we expect that adults in poor conditions may favour their own survival by skipping breeding opportunities (i.e. if they did not succeed to accumulate enough body reserves before breeding), as it has been shown in albatross species [START_REF] Jouventin | Why breed every other year? The case of albatrosses[END_REF]. As such, the number of birds commonly out of existing and planned marine protected areas is likely to increase with future global upheaval, while they would be in need of more protection. Another level of protection afforded by the Annex V of the Protocol on Environmental Protection to the Antarctic Treaty System (ATS 1991) is the designation of an area as an Antarctic Specially Protected Area (ASPA). To date, eight ASPAs including emperor penguins colony have been designated (Trathan et al. 2020). However, they provide only very limited protection at sea, the designation of MPAs having been historically left to the CCAMLR27 [START_REF] Chown | Antarctica and the strategic plan for biodiversity[END_REF], Trathan et al. 2020).

VI.3.3. The challenging position of the Convention on the Conservation of Antarctic Marine Living Resources

With only two operational MPAs since 2009 and three under consideration (Table 1), the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) is falling short on its initial ambition (Cordonnery and Kriwoken 2015, Cordonnery et al. 2015, Nicoll and Day 2017, Trathan and Grant 2020) to establish a harmonised regime for the protection of the Antarctic marine environment.

The three proposals (CCAMLR 2018a(CCAMLR , 2018b(CCAMLR , 2019a) ) for the establishment of the new MPAs have been under intense international negotiations for years and the size of the potential protected areas substantially reduced (Sylvester andBrooks 2020, Brooks et al. 2020b), while it took five years of negotiations to delimit the Ross Sea region MPA status and its size was reduced of 40% to satisfy some Member countries with high economic interest in fisheries (Brooks et al. 2020b). With a limited duration of 35 years, the Ross Sea MPA shall not even be considered as an MPA in regards to IUCN status, some of the species having longer life span [START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], 2020b[START_REF] Nicoll | Correct application of the IUCN protected area management categories to the CCAMLR Convention Area[END_REF].

Indeed, this duration violates the "long-term conservation" objective fixed in the definition of an MPA 28 . Not to mention the fact that areas of primary importance to safeguard predators were left unprotected to accommodate fishing [START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF].

Noteworthy, 60% of the protected areas within CCAMLR boundaries are inside nationally managed MPAs (Table 1). This observation highlights the difficulty to manage areas beyond national jurisdiction (ABNJ) 29 due to the very different views between members on how marine ecosystems should be managed [START_REF] Rogers | A Biophysical and Economic Profile of South Georgia and the South Sandwich Islands as Potential Large-Scale Antarctic Protected Areas[END_REF], Cordonnery et al. 2015, Brooks et al. 2020b). Initially created with the purpose of long-term conservation, CCAMLR appears on the brink of becoming only a fisheries management entity (Nicoll andDay 2017, Trathan et al. 2020). As an illustration, the investigation of the CCAMLR's Conservation Measures of the 2016-2017 season reveals that 76% of the measures focused on fisheries management, while 14% concerned species/habitat protection and 10% both categories [START_REF] Nicoll | Correct application of the IUCN protected area management categories to the CCAMLR Convention Area[END_REF]. Some Members are pressing for increased quotas, and for permitting fishing within closed management areas [START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], Trathan et al. 2020). Those Members are reversing the initial CCAMLR approach: to prevent fishing, they are now demanding that sufficient data should be available to show that fishing is damaging the ecosystem [START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], Trathan et al. 2020). Against the advice from the CCAMLR's Scientific Committee, Russia also initiated research fishing for toothfish in the Weddell Sea in 2013 and 2014 [START_REF] Brooks | Competing values on the Antarctic high seas: CCAMLR and the challenge of marine-protected areas[END_REF], Teschke et al. 2016a).

Additionally, a recent study in Antarctic Peninsula [START_REF] Watters | Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution[END_REF] suggests that the precautionary approach 30 to the management of the fisheries (i.e. reaching sustainability of fisheries without jeopardizing the structure and functioning of the ecosystem) does not yield the expected protection.

Even if catches are sustainable, the presence and activities of fisheries are suggested to disrupt the 28 IUCN defines an MPA as : "A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values.", while long-term conservation is defined as : "managed in perpetuity rather than a short term or a temporary management strategy." (WCPA/ICUN 2019).

29 Areas of the oceans for which no one nation has sole responsibility for management (referred also as 'high seas'). They represent ~2/3 of the oceans (IUCN website).

30 "CCAMLR's precautionary approach requires that management decisions should have a low risk of long-term adverse effects" [START_REF] Nicol | The Fishery for Antarctic Krill: Its Current Status and Management Regime[END_REF].

structure of krill swarms or their distribution in the water column, which, in turn, affect the performance of krill-dependent penguins that forage in the area [START_REF] Watters | Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution[END_REF]). Together with our findings in emperor penguins, such studies highlight the current limitations of the protection measures in place in the Southern Ocean. Clearly, current CCAMLR measures and intents are not sufficient to ensure the protection of highly dispersive species that cross distinct ecoregions. Even though the acceptance of proposed MPAs would greatly improve the representativeness of Antarctic biodiversity (Brooks et al. 2020a), the broad-scale region zoning used in the designation process of MPAs by the CCAMLR (Brooks et al. 2020a) is too coarse to fully encompass the heterogeneity of southern ecosystems. For instance, the ACC system, critical habitat for many species [START_REF] Tynan | Ecological importance of the Southern Boundary of the Antarctic Circumpolar Current[END_REF], Bost et al. 2009a) Increasingly recognised as a major ecological criterion in the design of effective conservation plans [START_REF] Carr | The central importance of ecological spatial connectivity to effective coastal marine protected areas and to meeting the challenges of climate change in the marine environment[END_REF][START_REF] Laffoley | Marine Protected Areas[END_REF][START_REF] Balbar | The current application of ecological connectivity in the design of marine protected areas[END_REF], this network of connected MPAs in the Southern Ocean would ensure a continuity of protection to individuals and species that move through the seascape. With such a complementary approach, the CCAMLR could design MPAs including critical habitats that are still unprotected like the ACC area.

VI.3.4. Management alternatives VI.3.4.1. Hot-spot areas

To make the best use of tracking data and translate them into management policy, a wide spread approach is to combine tracking data from different top predator taxa and to estimate the areas where they concentrate (see review in [START_REF] Hays | Translating Marine Animal Tracking Data into Conservation Policy and Management[END_REF]and Hindell et al. 2002[START_REF] Block | Tracking apex marine predator movements in a dynamic ocean[END_REF], Raymond et al. 2015[START_REF] Dias | Using globally threatened pelagic birds to identify priority sites for marine conservation in the South Atlantic Ocean[END_REF][START_REF] Reisinger | Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean[END_REF][START_REF] Harrison | The political biogeography of migratory marine predators[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF]).

Those regions, called "hotspot of biodiversity", can be designated under different names in the literature, but all referring to the "hotspot" concept. Here, is a non-exhaustive list of the nomenclatures used in marine studies: Ecologically or Biologically Significant Marine Areas (EBSAs;[START_REF] Cbd | Updated Assessment of Progress Towards Selected Aichi Biodiversity Targets and Options To Accelerate Progress[END_REF][START_REF] Clark | Identifying Ecologically or Biologically Significant Areas (EBSA): A systematic method and its application to seamounts in the South Pacific Ocean[END_REF][START_REF] Dunstan | Using ecologically or biologically significant marine areas (EBSAs) to implement marine spatial planning[END_REF], marine Important Bird Areas (mIBAs ; BirdLife International 2010, [START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF][START_REF] Dias | Using globally threatened pelagic birds to identify priority sites for marine conservation in the South Atlantic Ocean[END_REF][START_REF] Heerah | Important areas and conservation sites for a community of globally threatened marine predators of the Southern Indian Ocean[END_REF], or Area of Ecological Significance (AES; [START_REF] Hindell | Tracking of marine predators to protect Southern Ocean ecosystems[END_REF]. Such areas of top predator concentrations are indicative of predictable abundance and/or diversity of lower trophic organisms, and, therefore, require specific management consideration [START_REF] Block | Tracking apex marine predator movements in a dynamic ocean[END_REF], Raymond et al. 2015, Ropert-Coudert et al. 2020).

Presence data can also be implemented into predicting models of suitable habitats in order to estimate probability of presence in non-sampled areas [START_REF] Raymond | Important marine habitat off east Antarctica revealed by two decades of multi-species predator tracking[END_REF], Ropert-Coudert et al. 2020). The main drawback of this latter approach is that the bias in data sampling is not easily corrected, and predictions are not always reliable. Moreover, data encompassing the full life-history stage [START_REF] Carneiro | A framework for mapping the distribution of seabirds by integrating tracking, demography and phenology[END_REF]) and the entire life cycle of individuals are required to properly assess the species' distribution in time and space. For instance, the critical importance of the ACC region for the Emperor penguin would have not been discovered if only adult data were considered (Chapter IV). We also confirmed the importance of the continental slopes and shelf areas for foraging adult emperor penguins replenishing their reserves in summer (Chapter V). However, these areas where the sea ice may retreat in the near future could be stormed by fishing vessels (Teschke et al. 2016a), although those habitats are critical for emperor penguins' feeding, but also breeding and moulting (Chapter V).

Protecting biodiversity is likely to require the development of ground-breaking and creative concepts in environmental management. New approaches have emerged in the last two decades, but their diffusion and practical implementation in the field are still limited.

VI.3.4.2. Dynamic management

Currently, most of the marine management approaches (e.g. quota setting, MPAs) are relatively static, while the Southern Ocean is a highly dynamic system in time and space. A shift towards the need of a more dynamic ocean management 31 emerged during the last two decades [START_REF] Hyrenbach | Viewpoint: Marine protected areas and ocean basin management[END_REF][START_REF] Maxwell | Dynamic ocean management: Defining and conceptualizing real-time management of the ocean[END_REF], concurrently with the quality of biologging data and the remote sensing of environmental data by satellite. A good example of this flexible management is TurtleWatch, launched in 2008 [START_REF] Howell | TurtleWatch: a tool to aid in the bycatch reduction of loggerhead turtles Caretta caretta in the Hawaii-based pelagic longline fishery[END_REF]. A daily map of the preferred habitat of Loggerhead sea turtles (Caretta caretta), defined by water temperature, is transmitted to fishing vessels so that they can avoid these areas preventing by-catch of the endangered turtles. The model was developed by integrating tracking data from 1997 to 2006. Similarly, the WhaleWatch management tool [START_REF] Hazen | WhaleWatch: a dynamic management tool for predicting blue whale density in the California Current[END_REF]) combines 14 years of tracking data to build a habitat model and to predict current estimates of abundance of blue whales (Balaenoptera musculus) using remotely sensed variables. An application shares the data with vessels in order to avoid strikes. Such examples are not readily to the Southern Ocean context, but might serve as inspiration for the CCAMLR and the researchers involved in tracking studies, especially in the context of fisheries development [START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF], Trathan et al. 2020). Management measures may only be necessary at particular period (e.g. during a species' breeding season, during a moulting period) and in certain areas. Additionally, dynamic MPAs could be used to protect dynamic 31 Management that changes rapidly in space and time in response to the shifting nature of the ocean and its users, based on the integration of new biological, oceanographic, social and/or economic data in near real-time [START_REF] Maxwell | Dynamic ocean management: Defining and conceptualizing real-time management of the ocean[END_REF].

oceanographic habitats critical for ecosystem functioning (such as fronts, currents, or eddies), or to protect individual species or groups of species [START_REF] Hyrenbach | Viewpoint: Marine protected areas and ocean basin management[END_REF][START_REF] Maxwell | Dynamic ocean management: Defining and conceptualizing real-time management of the ocean[END_REF].

Global change will lead to environmental disruption [START_REF] Collins | Climate Change 2013 the Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change[END_REF], IPCC 2019[START_REF] Rogers | Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean[END_REF] that will, in turn, alter the distribution and abundance of interacting species [START_REF] Reed | Phenotypic plasticity and population viability: the importance of environmental predictability[END_REF], Constable et al. 2014, Dunn et al. 2019). For instance, the ACC system is expected to shift southward in response to ocean warming [START_REF] Collins | Climate Change 2013 the Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change[END_REF]). Thus, it is crucial that future conservation measures are adaptive and not tied to coordinate boundaries, but associated with environmental parameters.

Our study on juvenile emperor penguins showed that they are wandering within the ACC limits during two months at the end of the summer right after fledging. The protection and management policies could, therefore, be limited in time but also in space, with specific measures implemented for critical colonies. Critical colonies could be either colonies experiencing a decrease in population size or colonies expected to act as refugia for the species in the context of global changes (i.e. colonies from the Weddell Sea and Ross Sea regions; Ainley et al. 2010b[START_REF] Jenouvrier | Influence of dispersal processes on the global dynamics of Emperor penguin, a species threatened by climate change[END_REF][START_REF] Parkinson | A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic[END_REF]), or colonies from which individuals are or will be in the near future competing with fisheries.

VI.3.4.3. A need of a governance for the common good

While calls are increasing for a more aggressive protection of ABNJ [START_REF] Warner | Protecting the Oceans Beyond National Jurisdiction. Page Protecting the Oceans Beyond National Jurisdiction[END_REF][START_REF] O'leary | Effective Coverage Targets for Ocean Protection[END_REF][START_REF] Dias | Using globally threatened pelagic birds to identify priority sites for marine conservation in the South Atlantic Ocean[END_REF], the Southern Ocean appears to be a perfect place for ambitious conservation action due to the international framework and agreements linked to the Antarctic Treaty, and to the relatively small amount of anthropogenic activities in this area, up to now. In an international context burdened by the tensions generated by the threat of climate change, CCAMLR members have the opportunity to send an ambitious message by banning all industrial activities from the Southern Ocean, like the Antarctic Treaty (ATS 1959) did for the continent. Such a measure would be the second best action to ensure the protection of these polar and subpolar regions, the first being the diminution of greenhouse gases emissions (Trathan et al. 2020). This is unlikely to happen given that CCAMLR Members fishing states outnumber the non-fishing States by a ratio of 5:3 (Brooks 2013, Smith and[START_REF] Smith | MPAs in ABNJ: lessons from two high seas regimes[END_REF], leading to intense negotiations each year regarding new MPA proposals [START_REF] Sylvester | Protecting Antarctica through Co-production of actionable science: Lessons from the CCAMLR marine protected area process[END_REF].

Noteworthy, the existing and planned CCAMLR MPAs are mostly out of the ACC region, while the ecological importance and productivity of the frontal system of the ACC is well established [START_REF] Tynan | Ecological importance of the Southern Boundary of the Antarctic Circumpolar Current[END_REF], Bost et al. 2009a[START_REF] Trathan | The South Orkney Islands Southern Shelf Marine Protected Area[END_REF]. On the contrary, the countries owning islands situated within the ACC have established MPAs and conservation measures, with the exception of Norway around Bouvetoya Island (Fig. 10). These countries are also most of the ones leading the proposals for new MPAs around Antarctica (Table 1). This highlights the difficulties for an international organisation based on consensus to act in the interest of all when national interests are given priorities by some Member states (Cordonnery et al. 2015[START_REF] Brooks | Science-based management in decline in the Southern Ocean[END_REF]. Despite a relative shortness of the Antarctic science-policy communication pathways [START_REF] Hughes | Antarctic environmental protection: Strengthening the links between science and governance[END_REF], like in the rest of the oceans where only 1.2% of the high seas have been designated in MPAs [START_REF] Visalli | Data-driven approach for highlighting priority areas for protection in marine areas beyond national jurisdiction[END_REF], the management of ABNJ collides with political and economic barriers and interests [START_REF] Smith | MPAs in ABNJ: lessons from two high seas regimes[END_REF]. In definitive, much remains to be done to make the Southern Ocean an area of peace and science like the continent it encircles.

VI.4 Future research perspectives

The studies carried out during my PhD project have improved the knowledge and understanding about the at-sea ecology of the Emperor penguin. To start the long-term monitoring of a new colony in a region where emperor penguins' at-sea distribution was unknown, we made an intense use of biologging and improved capture and tagging techniques on different life-history stages of the species.

Our findings reveal a much larger extent of the species distribution than previously assessed and highlight the current lack of protection of the species. Our preliminary analyses on the foraging activities of the species suggest various strategies between sites, seasons, and birds. Nevertheless, the methods we developed can (and should) still be improved while numerous ecological questions are still pending. studies in Antarctica and the promising results of the leg-band techniques on other penguin species (Bost et al. 2009b, Thiebot et al. 2011[START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF]Houstin, Le Bohec, unpublished observations), we recommend that the development of such long-term attachment system should be considered with emperor penguins.

The RFID systems that will be deploy in Atka Bay the next coming season, have been very successful at detecting emperor penguins at Pointe Géologie colony and are expected to give similar results in Atka Bay. These systems are communicating with field workers when a micro-tagged bird is detected. Thus, in addition to the collection of micro-tagged cohorts' detection data for population dynamic analyses, they will be precious tools for the recapture of equipped birds (which are also systematically microtagged) and, thus, for the device recovery over the years.

Tracking technology is also likely to continue its on-going enhancement. For instance, the new generation of ARGOS satellites is being developed and should be fully operational by ~2023 with 20 dedicated nanosatellites32 . The main benefits of this network of nanosatellites will be an increased bandwidth, an enhanced capacity, new modulations of the signals and high data rate transmissions for wildlife tracking 33 . In other words, it will be possible to send more efficiently a bigger amount of data.

The Fastloc® technology, similar to a low-power-consumption and fast-acquisition-time GPS, is also expected to reach a size ethically compatible with a deployment on emperor penguins, enabling longer-term deployments with higher acquisition rate. Together with less disruptive long-term attachment techniques, this new technology will greatly improve our understanding of the foraging activities in space and time, with a more accurate correspondence between locations and dives and, thus, with environmental variables.

VI.4.1.2. Capture

Our easy-removable and light corral allows the simultaneous capture of several individuals in the field.

This might be especially useful for research requiring simultaneous equipment and/or marking of individuals, whether breeding pairs or adult-chicks pairs with chicks of any age. For instance, by equipping with GPS-TDR-Acc biologgers both partners of breeding pairs simultaneously, it will be possible to study the different foraging tactics exhibited within breeding pairs and, more precisely, if

(and how) compensation mechanisms exist between partners during the chick-rearing period, if one of the partners is less performant at sea. The simultaneous equipment with GPS or acoustic recorders of an adult and its chick will, for instance, help us to investigate how their spatial interactions (e.g. how an adult is able to find its chick in a colony of several thousand individuals, at which distance) change over the winter, especially if coupled with a camera observation system like SPOT (for Single Penguin We highlighted that, to date, no tracking of emperor penguins ever occurred in the western part of Antarctica, from the eastern Ross Sea to the Peninsula (via the Amundsen and Bellinghausen seas) and deep inside the Weddell Sea (Fig. 50). The first priority should, thus, be to track birds from colonies in these areas. Moreover, until now, immature emperor penguins (i.e. 1.5 to ~2.5 years old) have never been equipped with biologgers. We, therefore, do not know the at-sea distribution and diving behaviours and strategies of this life-history stage. However, due to its at-sea behaviour similar to our juveniles and the doubt we had regarding the coloration of ornaments, we suggest that one of the post-moult birds we tracked from Atka Bay could be an immature emperor penguin of 1.5 year old, even though it is currently impossible to validate this hypothesis (Fig. 51). As such, the tracking of birds of this age would require marking them at the beginning of their moult and managing to monitor them (if they stay in the study area) until the end of their moult when devices could be deployed. Telemetric data on all life-history stages are essential to assess and monitor, in time and space, the risks these different categories are facing. This baseline knowledge is fundamental for discussing future conservation measures for the species as well as monitoring future changes. If considered by the policy bodies and broadcasted, this information should also be of great importance in the discussion of current -and hopefully future -proposals on spatial and ecosystem-based management, such as MPA design and systematic conservation planning, in the Southern Ocean.

VI.4.2.2. The connectivity between colonies

Due to discordance on minimal sample size and analytical methods to use, population genetic studies led to an intense debate on the existence of one global population or several metapopulations (at least four) of emperor penguins, and on the connectivity between breeding colonies [START_REF] Cristofari | Full circumpolar migration ensures evolutionary unity in the Emperor penguin[END_REF][START_REF] Younger | The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins[END_REF]. Tracking data obtained to date on juvenile emperor penguins suggest that birds from the Ross Sea region might not travel as far as George V and Adélie Lands (and vice versa [START_REF] Thiebot | Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri during postnatal dispersal[END_REF], Labrousse et al. 2019b)), but would remain in the Ross Gyre (Fig. 50; [START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF] ; whereas juveniles from the Weddell Sea region might not be able to cross Drake Passage in an anticlockwise direction and to reach the West Peninsula due to the strength of the ACC and the presence of the Weddell Gyre (Chapter IV; Fig. 4). The same applies to breeding and nonbreeding adults tracked so far for these sectors (Fig. 50). On the contrary, the distribution at sea of birds born or breeding in the East Antarctica, from Dronning Maud Land to Adélie Land, overlaps (Fig. 36) enabling the existence of mixing populations in this area. Tracking studies on colonies at the edge of the gyres might help answering such primordial questions for risk assessment and conservation measures design. For instance, if no dispersive event between sectors is observed and if the existence of several populations is demonstrated, then a priority will be to avoid local extinction of specific colonies to preserve every single population as a genetic unit, even small ones [START_REF] Moritz | Defining "Evolutionarily Significant Units" for conservation[END_REF][START_REF] Palsbøll | Identification of management units using population genetic data[END_REF]). On the contrary, if there is only one global population spanning around the continent, the focus might be to preserve the main colonies or the ones situated in the more favourable habitats, i.e.

future potential refugia, in the context of global change.

VI.4.3. Foraging behaviour and strategies VI.4.3.1. Further analyses of the data collected during my PhD project Some of the data collected over the course of my PhD project have been only partially analysed, while others were collected for future use. Their future analysis will improve our knowledge on the foraging strategies of adult emperor penguins.

The diving dataset from chick-rearing birds equipped with back-taped GPS-TDR in Atka Bay will be reanalysed and compared with the unique diving dataset from adults equipped leg-band attached TDR over the full year. Given the similar diving effort strategy that we identified between these two groups at the beginning of summer, we expect their diving parameters (dive depth and duration, diving efficiency, Attempts of Catch Per Unit Effort or ACPUE) to be similar (Chapter V). Additionally, by resampling the diving datasets from Atka Bay birds at the frequency of those used at Pointe Géologie,

we will be able to compare at-sea activities and foraging strategies observed at Pointe Géologie and Atka Bay during the chick-rearing period. We expect to confirm our preliminary results of different diving behaviours (pelagic vs benthic) and to emphasise the difference of diet between the two regions, notably through a detailed comparative analysis of the ACPUE index [START_REF] Le Guen | Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins ( Pygoscelis adeliae )[END_REF][START_REF] Zimmer | Dive efficiency versus depth in foraging emperor penguins[END_REF], a proxy of foraging effort.

Additionally, the analyses of the blood samples at capture and recapture of the equipped adults and their chicks (e.g. stable isotope analyses), together with stomach samples from dead chicks (e.g. direct prey species identification), will provide information on the trophic level and diet of emperor penguins from Atka Bay colony at least during the chick-rearing period. The diet determination will also help us to refine our understanding of the diving profiles and diving parameters.

The GPS of the chick-rearing birds from Atka Bay was also paired with a 3-axis accelerometer. Such data can deliver great insights on how animals change behaviour as a function of space and, therefore, on the influence of the environmental conditions they encounter during their foraging trips. They can easily be used to estimate general activity time-budget (e.g. walking, resting, diving, porpoising ; see [START_REF] Watanabe | Activity Time Budget during Foraging Trips of Emperor Penguins[END_REF]. We are convinced that such data can be used to detect catching events with more accuracy (due to the frequency of recording) than the methods using depth and wiggles data from TDR, as it has been shown in other diving top predators [START_REF] Viviant | Prey capture attempts can be detected in Steller sea lions and other marine predators using accelerometers[END_REF][START_REF] Carroll | Supervised accelerometry analysis can identify prey capture by penguins at sea[END_REF][START_REF] Watanabe | Testing optimal foraging theory in a penguin-krill system[END_REF][START_REF] Vacquié-Garcia | Predicting prey capture rates of southern elephant seals from track and dive parameters[END_REF][START_REF] Jeantet | Combined use of two supervised learning algorithms to model sea turtle behaviours from tri-axial acceleration data[END_REF]). However, before using proxies from acceleration, prior analyses are required to correlate signals identified in the datasets with proven behaviours. Without such validation, we consider that the interpretation of the results might be biased [START_REF] Jeantet | Behavioural inference from signal processing using animal-borne multi-sensor loggers: a novel solution to extend the knowledge of sea turtle ecology[END_REF]. To perform such validation, the method consists of synchronising a video recording with the corresponding signals from the accelerometer. This can be realised either in captivity [START_REF] Yoda | A new technique for monitoring the behaviour of freeranging Adélie penguins[END_REF] or in the wild with the concomitant deployment of an accelerometer and externally attached camera [START_REF] Van Dam | Stroke frequencies of emperor penguins diving under sea ice[END_REF][START_REF] Watanabe | Linking animalborne video to accelerometers reveals prey capture variability[END_REF][START_REF] Thiebot | On the significance of Antarctic jellyfish as food for Adélie penguins, as revealed by video loggers[END_REF]).

However, behaviours display in captivity are not representative of all the behaviours expressed in the wild [START_REF] Jeantet | Combined use of two supervised learning algorithms to model sea turtle behaviours from tri-axial acceleration data[END_REF], while the video recordings are limited to short-term studies. Indeed, in order to record prey capture attempts and investigate foraging activities, the video-recorder needs to be placed on the head of the animal-borne individual, which induces significant disturbance (Culik and Wilson 1991, Culik et al. 1994, Kay et al. 2019) incompatible with long-term deployment. Additionally, memory and power consumption are still technological limits preventing the long-term deployment of such devices [START_REF] Heylen | Bio-telemetry as an Essential Tool in Movement Ecology and Marine Conservation[END_REF]. The combination of supervised learning algorithms and multi-signal analysis tools are being developed [START_REF] Jeantet | Behavioural inference from signal processing using animal-borne multi-sensor loggers: a novel solution to extend the knowledge of sea turtle ecology[END_REF]) and should provide automated and reliable identification of the various behaviours exhibited by diving animals. However, calibration data are still required and not available on emperor penguins. Future analyses of such datasets should allow a better assessment of predation attempts, and we expect the detection of such events outside of the bottom phase. Indeed, the investigation of sub-ice foraging behaviour should receive specific attention, since it has been shown to occur for emperor [START_REF] Ponganis | Sub-ice foraging behavior of emperor penguins[END_REF] and Adélie (Watanabe and Takahashi 2013) penguins, while the frequency and the importance of such behaviour has not yet been estimated and is currently neglected as already highlighted ~25 years ago [START_REF] Cherel | Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica[END_REF].

One of the main interests of decoding behaviours and space usage is ultimately to get enough information to build conservation management decision. A current useful tool is the environmental (or ecological) niche modelling [START_REF] Aarts | Estimating space-use and habitat preference from wildlife telemetry data[END_REF][START_REF] Kearney | Mechanistic niche modelling: combining physiological and spatial data to predict species' ranges[END_REF][START_REF] Scales | Identifying predictable foraging habitats for a wide-ranging marine predator using ensemble ecological niche models[END_REF]). The niche modelling aims at making inferences over space and time on the favourable habitats available for a species (Aarts et al. 2008, Kearney and[START_REF] Kearney | Mechanistic niche modelling: combining physiological and spatial data to predict species' ranges[END_REF]. Prior to the modelling, the analysis of habitat selection (i.e. an estimation of the magnitude from which the distribution of the habitat use (i.e. where the species is present) differs from the distribution of the habitat available (i.e. where the species could be present); see [START_REF] Aarts | Estimating space-use and habitat preference from wildlife telemetry data[END_REF], Labrousse et al. 2019a) is performed. This step reveals insights about the studied population (e.g. preference of diving towards specific depth, preference of area with a high concentration of ice for resting) that are used to make prediction at other sites or at larger scale (Aarts et al. 2008, Kearney and[START_REF] Kearney | Mechanistic niche modelling: combining physiological and spatial data to predict species' ranges[END_REF]. Such knowledge does not only improve our understanding of animal behaviour [START_REF] Scales | Identifying predictable foraging habitats for a wide-ranging marine predator using ensemble ecological niche models[END_REF], Labrousse et al. 2019a) and ecology, but also provides valuable planning tools for conservation measures. Labrousse et al. (2019a) performed such a study on emperor penguins from Pointe Géologie and Auster over several winter. Their analyses revealed that, despite differences in the habitat availability between the two sites, they consistently targeted the same type of features in a dynamic environment: the ephemeral polynyas while avoiding icebergs areas. The analysis of our data under such a framework, in a new environment and seasons, and with various life-history and breeding stages, would greatly enhance the understanding of the ecological niche of the species around the Antarctic continent. This will provide conservation and management bodies with relevant information to ensure the species protection.

VI.4.3.2. Cutting-edge technologies

In a recent study, video cameras with built-in microphones were deployed on king, gentoo (Pygoscelis papua) and macaroni (Eudyptes chrysolophus) penguins [START_REF] Thiebault | First evidence of underwater vocalisations in hunting penguins[END_REF]. All the recorded vocalisations were emitted during feeding dives, and half of them were directly associated with hunting behaviour. The exact function of these vocalisations (e.g. by-product of physiological need, group coordination, role in the capture process) still needs to be assessed and requires further investigation. This behaviour (at-sea vocalisations) still needs to be proven for emperor penguins. It would be valuable to know, as noise pollution at sea is a rapidly increasing threats for many marine species globally.

It would also be interesting to investigate social interactions of emperor penguins at sea. African penguins (Spheniscus demersus) have been recently shown to hunt in groups thanks to video recordings [START_REF] Mcinnes | Group foraging increases foraging efficiency in a piscivorous diver, the African penguin[END_REF], while Adélie penguins have been recorded exhibiting underwater group behaviour [START_REF] Takahashi | Penguin-mounted cameras glimpse underwater group behaviour[END_REF]) and emperor penguins are also often seen in groups when spotted at sea [START_REF] Kooyman | Diving Behavior of the Emperor Penguin, Aptenodytes forsteri[END_REF]. The use of acoustic loggers can also serve this purpose.

For instance, the use of microphone-camera loggers on gentoo penguins suggests that off-shore vocalisations resulted in group association of birds that subsequently foraged at the same patch of prey [START_REF] Choi | Group association and vocal behaviour during foraging trips in Gentoo penguins[END_REF]). In our study, two juvenile emperor penguins tagged together entered the water at the same time, however, due to the ARGOS locations uncertainty, we could not confirm that they entered in the water at the exact same location.

Finally, ongoing research and technological development lead to the emergence of new biologgers that may refine or even revolutionise our understanding of marine ecosystems. For instance, a new prototype of biologger has been recently tested on Weddell seals (Heerah pers. com.). Using sonar-like technology, the logger is designed to measure sea ice sickness as well as to detect prey and their shape for subsequent identification. Improvements in sea ice data remote detection (e.g. resolution, thickness, temporality) and of bathymetry resolution (Hindell et al. 2002b), matching the fine-scale resolution of dataloggers, would also greatly contribute to refine our perception of the spatial Iconic species used to raise public awareness, the Emperor penguin is first and foremost a top predator and umbrella species playing a pivotal role in Antarctic ecosystems. Standing at the forefront of climate upheavals, much remains to be learned about the ecology, distribution, and activities at sea of the species.

Biologging allows to refine our understanding of the interactions between a species and the different components (biotic and abiotic) of its environment, in particular with a view of management, conservation, and assessment of the adaptive capacity of populations to face global change.

In this study, we develop and share new equipment methods that increase equipment and data collection duration, while reducing the disturbance of the equipped individuals.

By carrying out a spatio-temporal analysis of the data collected on individuals of different life-history stages, reproductive status, and from different colonies spanning around Antarctica, we investigate the species' foraging behaviours and strategies and assess the influence of environmental conditions and habitat on these parameters. Such knowledge acquisition allows us to assess the degree of protection of the species at the scale of the Southern Ocean and to discuss strategic plans for conservation and management, such as the establishment of networks of Marine Protected Areas around the Antarctic continent.

Key-words: biologgingconservationdistributionat-sea ecology -Emperor penguin -MPA -Southern Oceanrefinementforaging strategies!

  Résumé en français ...................................................................................................................... 9

Fig. 1 .

 1 Fig. 1. Illustration of the multidisciplinary of conservation biology. ....................................................... Fig. 2. Schematic view of the hierarchical organisation of conservation biology. ..................................

Fig. 3 .

 3 Fig. 3. Major physical features of the Southern Ocean: bathymetry, major fronts, currents, and subpolar gyres. .............................................................................................................................. Fig. 4. Schematic meridional section in the Southern Ocean showing the water masses, meridional circulation, fronts, and most zones. ............................................................................................... Fig. 5.Trophic network of the Southern Ocean. ..................................................................................... Fig. 6. Schematic of the changes facing the sub-Antarctic (left), Southern Ocean (centre) and Antarctic (right) environments. .....................................................................................................................Fig. 7. Map of Antarctica showing territorial claims. .............................................................................. Fig. 8. Map showing CCAMLR members and Acceding States. ............................................................... Fig. 9. Total catch composition (top) and commercial value (bottom) of landed toothfish (blue), icefish (red), and krill (green) in the CCAMLR area between 1982 and 2012 for all Member States combined. ...................................................................................................................................... Fig. 10. Map of proposed and existing MPA within the CCAMLR area and distribution of emperor penguin breeding sites. ................................................................................................................. Fig. 11. Number of biologging studies. ................................................................................................... Fig. 12. Hotspots of biodiversity in the Southern Ocean. ....................................................................... Fig. 13. Example of visualisation of various biologging data................................................................... Fig. 14. Illustration of the Marginal Value Theorem from the Optimal Foraging Theory........................ Fig. 15. Illustration of Area Restricted Search (ARS) behaviour in the horizontal and vertical dimensions. ....................................................................................................................................................... Fig. 16. Distribution and population size of emperor penguin colonies. ................................................ Fig. 17. Different phases of the annual breeding cycle of the Emperor penguin in relation to sea ice dynamic (dashed line). ................................................................................................................... Fig. 18. Depth profile (on top) of an emperor penguin and zoom on a dive (bottom). .......................... Fig. 19. Main prey of emperor penguins. ............................................................................................... Fig. 20. Tourism pressures at Atka Bay colony. ...................................................................................... Fig. 21. IUCN categories .........................................................................................................................

Fig. 22 .

 22 Fig. 22. Atka Bay study site. .................................................................................................................... Fig. 23. Study sites bathymetry. ............................................................................................................. Fig. 24. Pointe Géologie study site. ........................................................................................................ Fig. 25. Comparison of sea ice concentration depending on the resolution used. ................................. Fig. 26. Principle of the smoothing of a group of points by the kernel method. ....................................Fig. 27. Distribution over the first year at sea of the 8 juvenile emperor penguins tagged at Atka Bay in 2019. .............................................................................................................................................. Fig. 28. Raw hourly proportion of immersion collected by the ARGOS platforms deployed on the 8 adult emperor penguins at Atka Bay in January 2018............................................................................. Fig. 29. Interpolation and simulation of locations. ................................................................................. Fig. 30. Wiggle definition. ....................................................................................................................... Fig. 31. Required tools to capture emperor penguins. ...........................................................................Fig. 32. Painted number on emperor penguin...................................................................................... 102 Fig. 33. Pictures of the different instrumentations performed. ........................................................... 103 Fig. 34. Adult emperor penguin at the end of its moult. ...................................................................... 104 Fig. 35. Back of the 4 penguins having lost their back-glued loggers during the winter. ...................... 109 Fig. 36. Overlap between existing and planned conservation zones and the distribution of juvenile emperor penguins tracked to date in the Southern Ocean. ........................................................ 129 Fig. 37. Proportion of time that the eight tagged juvenile emperor penguins from the Atka Bay colony spent either inside or outside the main conservation and management bodies of the Atlantic sector of the Southern Ocean. ..................................................................................................... 130 Fig. 38. Monthly tracks of the 8 juvenile emperor penguins tagged at Atka Bay in 2019. .................... 132 Fig. 39. Distribution (Kernel UD) of study groups equipped at Atka Bay (up) and Pointe Géologie (bottom). ..................................................................................................................................... 159 Fig. 40. Distance from the sea ice edge over the course of the year for juvenile emperor penguins equipped in AB in January 2019................................................................................................... 160 Fig. 41. Proportion of time spent in the different classes of habitat per study groups. ....................... 160 Fig. 42. Monthly proportion of time spent, over the year, by each study group in the relevant proposed Marine Protected Areas ............................................................................................................... 162 Fig. 43. Results of the best model of the GAMM analysis illustrating the functional relationship between the FPT value at each location and the significant variables for juveniles .................... 163

Fig. 1 .

 1 Fig. 1. Illustration of the multidisciplinary of conservation biology. Adapted from Jacobson (1990).

Fig. 2 .

 2 Fig. 2. Schematic view of the hierarchical organisation of conservation biology. Adapted from Mazaris (2017). This framework has been formalised at the international level with the signature of the Convention on Biological Diversity (CBD, CBD (2010)) at Rio in 1992 by 195 states and the European Union with the objective to develop national strategies for the conservation and sustainable use of biological diversity. This strategic plan was subdivided in 2010 in 20 objectives called the Aichi Biodiversity Targets (CBD 2010) establishing a biodiversity policy framework. In particular, the Target 11 states: "By 2020, at

Fig. 3 .

 3 Fig. 3. Major physical features of the Southern Ocean: bathymetry, major fronts, currents, and subpolar gyres. SACCF is Southern Antarctic Circumpolar Front and ASF is Antarctic Slope Front. Arrows indicate direction of current flow. Adapted from Stark et al. (2019).

Fig. 4 .

 4 Fig. 4. Schematic meridional section in the Southern Ocean showing the water masses, meridional circulation, fronts, and most zones. CSW = Continental Shelf Water, AASW = Antarctic Surface Water, SAMW = Sub-Antarctic Mode Water, SASW = Sub-Antarctic Surface Water, STSW = Subtropical Surface Water, ASF = Antarctic Slope Front, SB = Southern Boundary, SACCF = Southern ACC Front, PF = Polar Front, SAF = Sub-Antarctic Front, STF=Subtropical Front. Adapted from Talley et al. (2011).

Fig. 5 .

 5 Fig. 5. Trophic network of the Southern Ocean. Adapted from the British Antarctic Survey.

Fig. 6 .

 6 Fig. 6. Schematic of the changes facing the sub-Antarctic (left), Southern Ocean (centre) and Antarctic (right) environments. Adapted from Chown and Brooks (2019).

Fig. 7 .

 7 Fig. 7. Map of Antarctica showing territorial claims. Adapted from Natural Earth http://www.naturalearthdata.com.

Fig. 8 .

 8 Fig. 8. Map showing CCAMLR members and Acceding States (in green). Adapted from http://www.geo-ref.net CCAMLR's Article 2 states that any harvesting and associated activities shall not have long-term or irreversible adverse effects on either the harvested species or dependent and ecologically associated species and populations (Nicoll and Day 2017). The CCAMLR can then be considered as the ocean

Fig. 9 .

 9 Fig. 9. Total catch composition (top) and commercial value (bottom) of landed toothfish (blue), icefish (red), and krill (green) in the CCAMLR area between 1982 and 2012 for all Member States combined. Adapted from Brooks (2013).

Fig. 10 .

 10 Fig. 10. Map of proposed and existing MPA within the CCAMLR area and distribution of emperor penguin breeding sites. Adapted from Trathan et al. (2020) and Brooks et al. (2020b).

Fig. 11 .

 11 Fig. 11. Number of biologging studies. Adapted from (Forin-Wiart et al. 2019).

Fig. 12 .

 12 Fig. 12. Hotspots of biodiversity in the Southern Ocean. Adapted from Hindell et al. (2020) on top and Raymond et al. (2015) at the bottom.

Fig. 13 .

 13 Fig. 13. Example of visualisation of various biologging data. a) Space use in 3D (Tracey et al. 2014), b) Benthic dive of a southern elephant seal on seamounts (Maxwell et al. 2012), c) Spherical plot of data from an accelerometer (Wilson et al. 2016).

Fig. 14 .

 14 Fig. 14. Illustration of the Marginal Value Theorem from the Optimal Foraging Theory.Adapted from[START_REF] Charnov | Optimal foraging, the marginal value theorem[END_REF]). The optimal time spent in a patch is given by the tangent to the cumulative food intake curve. The predator needs to spend enough time in the patch to cover the energy expenditure of moving from one patch to another but also to leave the patch before the resource is too depleted as resource intake within a patch diminishes with time.

Fig. 15 .

 15 Fig. 15. Illustration of Area Restricted Search (ARS) behaviour in the horizontal and vertical dimensions. Adapted from Heerah (2014).

Fig. 16 .

 16 Fig. 16. Distribution and population size of emperor penguin colonies. Study sites are indicated by the black arrow. Adapted from Trathan et al. (2020) and counts from[START_REF] Fretwell | Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins[END_REF]. Recent movement between Halley Bay and Dawson-Lambton colonies are not accounted for[START_REF] Fretwell | Emperors on thin ice: three years of breeding failure at Halley Bay[END_REF]. Colonies where tracking occurred are underlined in violet.

Fig. 17 .

 17 Fig. 17. Different phases of the annual breeding cycle of the Emperor penguin in relation to sea ice dynamic (dashed line). Note that phenology can vary by several weeks depending on the latitude of the colonies. Adapted from Trathan et al. (2020).

  155°W and 170°E) and around Dumont d'Urville (66°40'S, 140°01'E) and Mawson (67°36'S, 62°52ʹE)

Fig. 18 .

 18 Fig. 18. Depth profile (on top) of an emperor penguin and zoom on a dive (bottom). The duration of the dive is indicated by the green arrow, the bottom phase by the purple arrow and the post-dive duration by the blue arrow. Wiggles are indicated only at their maximum by black triangles.

Fig. 19 .

 19 Fig. 19. Main prey of emperor penguins. a) Krill (Euphausia superba). b) Antarctic silverfish (Pleuragramma antarcticum). c) squid (unknow sp.). © Stephen Brookes, Antarctic Australian Division, Dale Maschette, respectively.

Fig. 20 .

 20 Fig. 20. Tourism pressures at Atka Bay colony. a) A tourist plane flying over the colony. b) Tourists around the colony.

Fig. 21 .

 21 Fig. 21. IUCN categories. Adapted from www.iucnredlist.org.

Fig. 22 .

 22 Fig. 22. Atka Bay study site. a) Location of Atka Bay in Antarctica. b) Satellite image of Atka Bay with the classical location (in green) of the emperor penguin colony. c) Research station of Neumayer III. d) Panorama of Atka Bay emperor penguin colony.Atka Bay (AB) emperor penguin colony is located deep inside the west side of the Atka Bay along the ice-shelf. The ice is very stable during the year and the bay is only ice free in January-February (König-Langlo et al. 1998) providing a safe ground for the emperor penguins colony over their breeding season. The colony (or subgroups) can and do climb on the ice-shelf through natural snow ridges during the year[START_REF] Zitterbart | Are environmental factors responsible for changed breeding behaviour in emperor penguins?[END_REF]). The on-land behaviour of the colony is being investigated since the summer season 2012/2013(Richter et al. 2018a), and in 2017, we set-up the 2 nd Life Observatory of the species. The colony is estimated to host currently 13 to 14 000 breeding pairs (Le Bohec & Zitterbart pers. com.). AB is situated in the Atlantic sector of the Southern Ocean, at the Eastern boundary of the Weddell Sea. In this region, the shelf is relatively narrow (~20 km), and the continental slope consists of a complex pattern of troughs, flat ridges, steep slopes, seamounts, outcrops, and narrow ridges (Fig.23;[START_REF] Jerosch | A geomorphological seabed classification for the Weddell Sea, Antarctica[END_REF]) that stretch over a hundred kilometre wide.

Fig. 23 .

 23 Fig. 23. Study sites bathymetry. a) Bathymetry around the Atka Bay and Ekström shelf ice. b) Bathymetry around the Pointe Géologie archipelago.

Fig. 24 .

 24 Fig. 24. Pointe Géologie study site. a) Location of Pointe Géologie archipelago in Antarctica. b) Satellite image of Pointe Géologie archipelago with the classical location (in yellow) of the emperor penguin colony. c) Research station of Dumont d'Urville. d) Panorama of Pointe Géologie emperor penguin colony.

  The Advanced Research and Global Observation Satellite (ARGOS) technology: ARGOS is a system for locating and collecting georeferenced data by satellite. A specific beacon (referred as ARGOS platform or Platform Transmitters Terminals, PTT) sends messages to compatible satellites (ARGOS class). The location of the ARGOS platform can be estimated by comparing the time difference between the transmission of the signals by the ARGOS platform and their reception by the satellite (Doppler Effect). Each location is accompanied by an estimate of precision (error classes or ellipses), depending in particular on the number of messages that have reached the satellite before it 13 I also carried out a first field work session during the austral summer 2016-2017 in Adélie Land to initiate a similar monitoring program at sea on Adélie penguins (Pygoscelis adeliae). The preliminary results of this project are presented in Annex C of the thesis.

Table 4 .

 4 General information on the loggers deployed including the logger type, name, dimensions, and weight, as well as the manufacturer names and location. *Loggers combined together by TechnoSmArt.

Fig. 25 .

 25 Fig. 25. Comparison of sea ice concentration depending on the resolution used. The colour code gives the ice concentration between 0 and 100%. Missing data is marked grey, and land is shown in brown. The red ellipse marks a region of open water visible at high resolution (3.125 km) but not visible at the 12.5km resolution. Adapted from Spreen et al. (2008).

Following

  the procedures developed by[START_REF] Lascelles | Applying global criteria to tracking data to define important areas for marine conservation[END_REF], we computed the kernel utilisation distributions, i.e. a measure of probability of occurrence[START_REF] Worton | Kernel Methods for Estimating the Utlization Distribution in Home-Range Studies[END_REF], for each group. In this method, each location is assigned a probability density function. The spatial sum of these probability density functions gives the Utilisation Distribution (UD; Fig.26), which is the relative frequency of use for a given spatial unit.

Fig. 26 .

 26 Fig. 26. Principle of the smoothing of a group of points by the kernel method. The probability density function of the presence of an event is calculated from the sum of the kernel functions placed above each observed location. Adapted from Calenge (2005).

Fig. 27 .

 27 Fig. 27. Distribution over the first year at sea of the 8 juvenile emperor penguins tagged at Atka Bay in 2019. Main environmental, conservation and management features of this sector of the Southern Ocean are specified in the legend. MPAs: Marine Protected Areas; CCAMLR: Commission for the Conservation of Antarctic Marine Living Resources; IUCN: International Union for Conservation of Nature; WSMPA: Weddell Sea Marine Protected Area.

Fig. 28 .

 28 Fig. 28. Raw hourly proportion of immersion collected by the ARGOS platforms deployed on the 8 adult emperor penguins at Atka Bay in January 2018. Each panel corresponds to one bird; the x-axis represents the date and the y-axis the daily hours. Period of diving are in blue and period out of water are in yellow.

Fig. 29 .

 29 Fig. 29. Interpolation and simulation of locations. White dots are true ARGOS location of the bird (a juvenile leaving Atka Bay colony). Red dots are the hourly interpolated locations. Blue, green and pink features represent 3 different crawl simulations. Dark to grey gradient in the background represents the bathymetry with the 1000 m isobaths in brown, and the Antarctic continent in light blue. Atka Bay colony location is indicated with an orange dot.

Fig. 30 .

 30 Fig. 30. Wiggle definition. Adapted from Mt-Dive manual.

Fig. 31 .

 31 Fig. 31. Required tools to capture emperor penguins. a An adult-chick pair inside the corral. b A 3 m long bamboo stick at the top, one of the panels of the corral (a 50 cm ruler is placed just above it to facilitate scaling) in the middle, and the crook at the bottom.

Fig. 32 .

 32 Fig. 32. Painted number on emperor penguin. a Fresh painted number on "bird 22". b The same marked bird after a 10 months deployment period. Notice the marks on its right leg. The other bird is a non-painted random emperor penguin.

Fig. 33 .

 33 Fig. 33. Pictures of the different instrumentations performed. a. Adult emperor penguin equipped with back-taped loggers (a TDR in the middle of the back and a GPS underneath). The green line on the bird's belly is non-permanent marking. b. Adult emperor penguin equipped with back-glued loggers (an accelerometer in the middle of the back and ARGOS satellite transmitter underneath) and a leg-banded logger on its right foot. c. Two juvenile emperor penguins both equipped with a back-taped-epoxied logger.

Fig. 34 .

 34 Fig. 34. Adult emperor penguin at the end of its moult.

  and their unfinished growth, prevent the use of other types of externally attached devices.III.3.4.4. Long-term deployment: leg-banded loggersTo reduce drag and behaviour disturbance induced by devices on the back of penguins, we developed a leg-band (bracelet) for mounting TDR-loggers on emperor penguins. This development was guided by the Refinement principle from the Three Rs framework[START_REF] Russel | Page The principles of humane experimental technique[END_REF] and inspired by 105[START_REF] Ratcliffe | A leg-band for mounting geolocator tags on penguins[END_REF] and our experience on Global Location Sensors (GLS) deployments on Adélie penguins.

Fig. 35 .

 35 Fig. 35. Back of the 4 penguins having lost their back-glued loggers during the winter.

  , Le[START_REF] Bohec | Population dynamics in a long-lived seabird: I. Impact of breeding activity on survival and breeding probability in unbanded king penguins[END_REF]) and without long-term deleterious effects of flipper-banding for life[START_REF] Gauthier-Clerc | Long-term effects of flipper bands on penguins[END_REF][START_REF] Dugger | Effects of flipper bands on foraging behavior and survival of adélie penguins (pygoscelis adeliae)[END_REF], Le Maho et al. 2011). Such automatic detection systems have been successful at detecting emperor, Adélie and king (Aptenodytes patagonicus) penguins over the last years at the Pointe Géologie archipelago and Crozet and Kerguelen archipelagos (Le Bohec, Houstin, Chatelain, Courtecuisse, unpublished observations;[START_REF] Cristofari | Climate-driven range shifts of the king penguin in a fragmented ecosystem[END_REF]

  years, CCAMLR members have been discussing the implementation of the three new MPAs adjacent to the Antarctic continent, without reaching agreement. If these new MPAs are eventually established, this would increase the percentage of the protected waters of the Southern Ocean to only 22%, which is insufficient compared to the 30% protection target as recommended by the IUCN to ensure an ecologically representative and well-connected systems of MPAs. Even then, assessments and recommendations are based on limited and partially flawed data. For instance, in the Atlantic sector of the Southern Ocean, which is home to one-third of the global emperor penguin population, very little is known about their at-sea distribution since no tracking studies have been conducted in this region.

(

  ~ 10 km) to the German Antarctic research base "Neumayer Station III". In January 2019, we equipped eight 6-month-old chick emperor penguins with satellite communicating SPOT-367 ARGOS platforms (Wildlife Computers, Redmond, WA 98052, USA). The ARGOS platforms were programmed to transmit their identification every day at 4, 6, 10, 16, 19 and 21:00 GMT, corresponding to time points with optimum ARGOS satellite coverage over the Weddell Sea area (ARGOS CLS, Toulouse, France).

Fig. 36 .

 36 Fig. 36. Overlap between existing and planned conservation zones and the distribution of juvenile emperor penguins tracked to date in the Southern Ocean. Distribution areas of juveniles are indicated by coloured polygons. MPAs: Marine Protected Areas; CCAMLR: Commission for the Conservation of Antarctic Marine Living Resources; IUCN: International Union for Conservation of Nature.

Fig. 37 .

 37 Fig. 37. Proportion of time that the eight tagged juvenile emperor penguins from the Atka Bay colony spent either inside or outside the main conservation and management bodies of the Atlantic sector of the Southern Ocean. Daily average across all individuals computed over hourly data points. WSMPA: Weddell Sea Marine Protected Area; IUCN: International Union for Conservation of Nature; SO: Southern Ocean (i.e. at the parallel of 60°S as defined in the Antarctic Treaty); ACC: Antarctic Circumpolar Current.

Fig. 38 .

 38 Fig. 38. Monthly tracks of the 8 juvenile emperor penguins tagged at Atka Bay in 2019. Sea ice concentration is shown for the last day of each month. Sea ice extent is indicated by the green lines for the 4 th , 11 th , 18 th , 25 th of each month as indicated by the gradient colour scale from dark green (4 th ) to light green (25 th ).

Fig. 39 .

 39 Fig. 39. Distribution (Kernel UD) of study groups equipped at Atka Bay (up) and Pointe Géologie (bottom). 'h' corresponds to the scaling factor used in the kernel estimation for each group. The black part of the background corresponds to the shelf area (1000 m isopleth). For the Kernel UD nomenclature: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter.

Fig. 40 .

 40 Fig. 40. Distance from the sea ice edge over the course of the year for juvenile emperor penguins equipped in AB in January 2019. Each coloured line represents one bird.

Fig. 41 .

 41 Fig. 41. Proportion of time spent in the different classes of habitat per study groups. * = only breeding birds were considered. For the study group classes: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter.

Fig. 42 .

 42 Fig. 42. Monthly proportion of time spent, over the year, by each study group in the relevant proposed Marine Protected Areas: the Weddell Sea MPA (WSMPA) for Atka Bay (AB) birds and East Antarctic MAP (EAMPA) for Pointe Géologie (PG) birds. For the study group classes: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter.

Fig. 43 .

 43 Fig. 43. Results of the best model of the GAMM analysis illustrating the functional relationship between the FPT value at each location and the significant variables for juveniles (i.e. sea ice concentration, day of the year, and distance to the Southern Antarctic Circumpolar Current Front). Negative value of the variable 'Distance to front' indicates that the birds are located south of the front. Thin grey line indicates 95% confidence intervals. The table is the model output of the best GAMM model (R²-adj = 0.294 ; deviance explained = 29.5%). Significance is indicated by stars with *** < 0.001 ; edf = estimated degrees of freedom.

Fig. 44 .

 44 Fig. 44. Results of the best model of the GAMM analysis illustrating the functional relationship between the FPT value at each location and the significant variables for adults (i.e. sea ice concentration, day of the year, bathymetry, and distance to the colony). Thin grey line indicates 95% confidence intervals. The table is the model output of the best GAMM model (R²-adj = 0.455 ; deviance explained = 45.5%). Significance is indicated by stars with *** < 0.001 and ** < 0.01 ; edf = estimated degrees of freedom.

Fig. 45 .

 45 Fig. 45. Interpolated locations of the foraging dives (small red dots) along the two trips of the bird "7740093" equipped with GPS and TDR devices at Atka Bay in November 2018. Large green dots are hourly locations. The blue line is the 1000 m isopleth delineating the shelf break, and the bathymetry is in the background in grey scale. The first trip to the north extends beyond the shelf area and counts only 2% of benthic dives, while the second trip east of the colony remains over the shelf habitat and count 20% of benthic dives.

Fig. 46 .

 46 Fig. 46. Mean maximum dive depth per hour per study group equipped with TDRs. For the study group classes: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter. adABf1 = monitored from January to April (fall; also corresponding to the post-moult/pre-breeding period). adABf2 = monitored from May to August (deep winter). adABf3 = monitored from September to mid-October (spring). adABf4 = monitored from mid-October to their recapture in November (summer).

Fig. 47 .

 47 Fig. 47. Averaged hourly diving effort per month of the adult emperor penguins from Atka Bay equipped just after their moult for the whole year (adABf).

Fig. 48 .

 48 Fig. 48. Averaged hourly diving effort of the adult emperor penguins from Atka Bay equipped in November/December (adABs) and from Pointe Géologie equipped in November (adPGs).

Fig. 50 .

 50 Fig. 50. Emperor penguin tracking data overview. (a) Data used in Ropert-Coudert and Hindell studies (Hindell et al. 2020, Ropert-Coudert et al. 2020). Adapted from Ropert-Coudert et al. (2020). (b) Data used in my PhD thesis. Tracks are in black, except tracks obtained during my PhD project on juveniles equipped in Atka Bay: thin red lines correspond to their tracks and the red outlined polygon to their distribution area. Yellow outlined polygons represent the distribution areas of juveniles equipped and tracked at other colonies. The green dashed outlined polygon represents the distribution areas of non-breeding birds from Goetz et al. (2018) and was obtained thanks to the method described page 126. Study sites where equipment has been performed, are indicated with red dots, while pink dots correspond to other emperor penguin colonies. The International Union for Conservation of Nature (IUCN) range is represented by the thin blue line.

Fig. 51 .

 51 Fig. 51. Probability of occurrence of breeding emperor penguins in the Weddell Sea region overlaid on adult tracks obtained during my PhD project. The probability of occurrence and their colour scale were obtained from Teschke et al.(2016b, 2019). Red tracks are from chick-rearing adults (GPS datasets obtained in November/December) and black lines are from non-breeding birds (ARGOS datasets obtained between January and August). The purple track belongs to the nonbreeding adult that exhibited a Gyre habitat-use strategy

Fig. 52 .

 52 Fig. 52. At-sea distribution of juvenile emperor and king penguins and of non-breeder king penguins tagged with ARGOS platforms in the Atlantic and Indian sectors of the Southern Ocean. Tracks from March and April of juvenile emperor penguins equipped at Atka Bay in 2019 are in red (N = 8). The at-sea distribution area, during the fall season (March/April/May), of juvenile (N = 17) and non-breeding (N = 6) king penguins equipped at Crozet archipelago in 2013/14 and 2014/15 is represented by a yellow and blue polygons, respectively (Orgeret et al. 2019). The at-sea distribution area of juvenile emperor penguins (N = 17) equipped at Auster and Taylor colonies is represented by a green polygon (Wienecke et al. 2010). Brown dots are emperor penguin breeding colonies. Dashed lines are from top to bottom the Polar Front and the Southern Boundary of the Antarctic Circumpolar Current. The white line is the median maximum sea ice extent between 1981 and 2010 and the greyscale background represents the bathymetry.

(

  see Perspectives page 208). VI.2 Acquisition of baseline data and set up of a global monitoring in the context of global change VI.2.1

  2018a) monitors on land the emperor penguins' colony of Atka Bay, providing already population census and phenological data. Finally, Atka Bay colony is situated nearby a research station that enables logistic supports, an elementary asset to ensure continuous monitoring over time.Similar to what we set up at the Pointe Géologie emperor penguins' colony, a close monitoring of the phenology and demography of the colony has been initiated in 2017 and is now carried out through and over years in order to establish long-term time series. Annual cohort of 300 fledging chicks is electronically marked every year with subcutaneous passive integrated transponder (PIT, page 95) that allows life-long identification by automatic detection systems (page 95). Classical vital rates can then be estimated to perform population dynamic analyses and assess population trends, and to predict population trajectories under the projection of different environmental scenarii. Additionally, every 3 years and over 2 years, the distribution and activities at sea of ca. 70 adults and juveniles are investigated in order to track and interpret fluctuations of their distribution and activities at sea over time in regards to environmental drivers. Such programme is a novelty much needed on emperor penguins while similar projects have been running for years on Adélie and king penguins[START_REF] Péron | Projected poleward shift of king penguins' ( Aptenodytes patagonicus ) foraging range at the Crozet Islands, southern Indian Ocean[END_REF][START_REF] Le Guen | Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins ( Pygoscelis adeliae )[END_REF] or on other predators of the Southern Ocean. For instance, Weimerskirch and colleagues (2012) linked the southward shift of wandering albatrosses over 20 years to the poleward shift of the westerly winds. Southern elephant seals are also the focus of several long-term monitoring programmes. An eleven-years time series described the effect of the inter-annual variability in sea ice advance and concentration on seals' foraging behaviour[START_REF] Labrousse | Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator[END_REF] while a seven-years time series revealed the long-term fidelity of individuals to the same foraging areas, suggesting limited behavioural adaptations to rapid environmental changes(McIntyre et al.

Fig. 53 ;

 53 Fig. 53; Robertson 1991, Zimmer 2007) should not be used, as stressed by ethic committees like the one of the CRBPO (Centre de Recherches sur la Biologie des Populations d'Oiseaux) in France (Fournier pers. com.) due to the level of risk and stress induced for the birds.

Fig. 53 .

 53 Fig. 53. Catch of an adult emperor penguin by rugby-like tackling at the edge of the penguin colony of Pointe Géologie, Adélie Land. Adapted from Zimmer (2007). See also https://www.youtube.com/watch?v=RxgScMyZDXI.

  make research more transparent to people in those time of mistrust towards science, the clarity of information being the focus of conservation researchers[START_REF] Mcmahon | Animal welfare and decision making in wildlife research[END_REF].VI.3 Biotelemetry on emperor penguins and conservationmeasures in the Southern Ocean VI.3.1. Emperor penguins commonly range outside marine protected areasThe tracking data gathered during my PhD project together with the previous ones extracted from the literature reveals that emperor penguins are marginally present in specific protection zones of the Southern Ocean (Chapter IV and Chapter V). We showed that juveniles spent the vast majority of their time outside of the extents of proposed or existing marine protected areas (MPAs), and their distribution extends up to 1500 km north of the species range used by the IUCN to evaluate the global conservation status of the species. We also showed that non-breeding and post-breeding adults (e.g. moulting birds of Pointe Géologie) commonly range outside those areas. Similar observations can be made in the Ross Sea area, except that the MPA has already been implemented. One third (3 on 9) of the non-breeding adults tracked over the winter in this region[START_REF] Goetz | Habitat preference and dive behavior of non-breeding emperor penguins in the eastern Ross Sea, Antarctica[END_REF]) spent the majority of their time outside the Ross Sea region MPA, like the juveniles tracked from Cape Washington (Fig.54;[START_REF] Kooyman | The initial journey of juvenile emperor penguins[END_REF].

Fig. 54 .

 54 Fig. 54. Distribution areas of juvenile and non-breeding adult emperor penguins in the Ross Sea Region Marine Protected Area.

  As outlined in Chapter III, the improvement or development of new equipment techniques are still needed for emperor penguins. The success of the back-taped-epoxied technique on juvenile emperor penguins advocates for the use of this technique on adults before any other. Similarly, the testing of the updated version of the leg-band should also be a priority. Given the logistic constraints of field

  Observation and Tracking ; Richter et al. 2018a) or the micrObs (for mobile micro-observatory ;Richter et al. 2018b[START_REF] Gerum | CameraTransform: A Python package for perspective corrections and image mapping[END_REF]; Annex A and Annex B) observatories. Using acoustic tags, it would be possible to investigate the ontogeny of chick calls and the recognition process between adult-chick pairs. Yet, the main disadvantage of our corral lies in the number of people needed to handle it (i.e. 3 persons). Knowing that two persons are sufficient to handle and equip an emperor penguin, it would be advantageous to develop a technique requiring only two people.VI.4.2. Spatial distribution and conservation implicationsVI.4.2.1. General distribution

(

  horizontal and vertical) interactions of sub-ice diving animals with their environment. Accelerometer, acoustic and video recording tags have a huge potential -and have already started -to open up a new window on our understanding of the foraging behaviour of diving species. Their use on emperor penguins is still limited mainly due to logistical constraints, but is likely to spread with their technological improvement in miniaturisation, design optimisation, storage capacity, and power consumption.

  Espèce emblématique régulièrement utilisée pour sensibiliser le public, le manchot empereur est avant tout un prédateur supérieur ainsi qu'une espèce parapluie qui joue un rôle clé au sein des écosystèmes antarctiques. En première ligne face au changement climatique et ses conséquences, il reste cependant beaucoup à apprendre sur la répartition et les activités en mer de cette espèce.L'utilisation du biologging permet d'affiner la compréhension des interactions existant entre une espèce et les différentes composantes (biotiques et abiotiques) de son environnement dans un souci notamment de gestion, de conservation et d'estimation des potentialités d'adaptation future aux changements globaux.Dans cette étude, nous développons et partageons de nouvelles méthodes d'équipement qui permettent une durée de suivi accrue et un dérangement réduit des individus équipés.Grâce à l'analyse spatio-temporelle des données récoltées par le suivi d'individus de différents âges, statuts reproducteurs et issus de différentes colonies autour de l'Antarctique, nous explorons les comportements et stratégies de prospection et de recherche alimentaire présents chez cette espèce, et examinons l'influence des conditions environnementales et de l'habitat sur ces paramètres. Ces informations nous permettent de plus d'évaluer le degré de protection de l'espèce à l'échelle de l'océan Austral et de discuter de plans stratégiques de conservation et gestion globale, telle que la mise en place de réseaux d'Aires Marines Protégées autour du continent Antarctique.Mots-clés : biologgingconservationdistributionécologie en mer -Manchot empereur -MPA -océan Australraffinementstratégies d'approvisionnement ! Résumé!en!anglais!

Table 1 .

 1 List of current and proposed MPAs within the CCAMLR area. ..................................................

Table 2 .

 2 Information on Emperor penguin diet obtained from stomach content collected at different locations and years/seasons. .........................................................................................................

Table 3 .

 3 Summary of deployments performed at Atka Bay. ...................................................................

Table 4 .

 4 General information on the loggers deployed including the logger type, name, dimensions, and weight, as well as the manufacturer names and location. ......................................................

Table 5 .

 5 Summary of deployments performed at Pointe Géologie. .......................................................

Table 6 .

 6 List of features related to conservation management in the Southern Ocean. ........................

Table 7 .

 7 Summary of the study groups according to the study site and the period of deployment. ......

Table 8 .

 8 General information on deployments and captures. ................................................................

Table 9. Comparison between at-sea-ecological studies that equipped emperor penguins over the last 30 years. ...................................................................................................................................... Table 10. Comparison of the mean mass of PIT-tagged chicks from the annual cohort and chicks of equipped adults. .......................................................................................................................... Table 11. Number of dead and alive emperor penguin chicks over the two summer seasons. ........... Table 12. Tracking studies of juvenile emperor penguins at sea. ......................................................... Table 13. At-sea distribution metrics for the 8 juvenile emperor penguins equipped with ARGOS platforms at Atka Bay in January 2019. ....................................................................................... Table 14. General information on tracking device deployments. ......................................................... Table 15. General information on TDR deployments. ..........................................................................

Table 16 .

 16 General information and at-sea metrics of adult emperor penguins from Atka Bay (AB) and Pointe Géologie (PG). ..................................................................................................................

Table 17 .

 17 Distribution metrics of study groups. ...................................................................................

Table 18 .

 18 General statistics (mean ± SD) of the main diving metrics per study group equipped with TDRs. ............................................................................................................................................

Table 19 .

 19 Results of the best model of the GLMM analysis illustrating the functional relationship

between the diving effort strategy (i.e. 'night-time diving effort', 'day-time diving effort') and the diving metrics. ............................................................................................................................. Table 20. Summary of the main research topics on emperor penguins and their level of knowledge achieved in the literature. ........................................................................................................... Chapter I. Introduction -Chapter I -

  In 2018, only 15% of the land surface and inland waters and 7% of the ocean were protected, but only 1% of the Areas Beyond National Jurisdiction (UNEP

least 17% of terrestrial and inland water, and 10% of coastal and marine areas, especially areas of particular importance for biodiversity and ecosystem services, are conserved through effectively and equitably managed, ecologically representative and well connected systems of protected areas and other effective area-based conservation measures, and integrated into the wider landscapes and seascapes".

  according toIUCN criteria, despite what the CCAMLR states (CCAMLR 2011). The CCAMLR area is a management zone in which protected areas are nested.Since 2002, the concept of a representative network of MPAs has emerged to be able to preserve marine biodiversity as whole and not only as small disconnected hot spots of biodiversity(UN 2002). A

	MPA network consists of a networked-system of individual MPAs designed to ensure interconnectivity
	and representativeness of ecosystems (WCPA/IUCN 2007), i.e. it represents all the habitats and species
	present in a region. Several studies (O'Leary et al. 2016, Dinerstein et al. 2019) suggest reaching a
	global level of protection of at least 30% of each marine habitat to ensure an effective protection of
	the high seas (IUCN 2014).
	In this context, the CCAMLR has agreed to develop a representative system of MPAs based on the best
	scientific evidence available and an ecosystem-based management approach (Teschke et al. 2016a,
	Brooks et al. 2020a)

10

. As a result, in 2009, the South Orkney Islands Southern Shelf MPA became the first MPA established in the Southern Ocean, followed by the implementation of the Ross Sea region MPA in 2017 (Fig.

10

). MPAs have also been established under national jurisdiction within the CCAMLR boundaries around several sub-Antarctic Islands (Kerguelen Island, Crozet Island, Prince Edward Islands, Heard Island and McDonald Islands, South Georgia and South Sandwich Islands) owned by states members of the CCAMLR (Australia, France, South Africa and the United Kingdom) (Table

1

Table 1 . List of current and proposed MPAs within the CCAMLR area.

 1

	MPA	Size (km²)	Status	Proposed by	Designated	Region
	South Orkneys Islands	94 000	Designated	United Kingdom	2009	Antarctica
	Ross Sea region	1 525 000	Designated	New Zealand, United States	2016	Antarctica
	East Antarctica	969 000	Proposal	Australia, France, European Union	N/A	Antarctica
	Weddell Sea	1 968 000	Proposal	Germany, European Union	N/A	Antarctica
	Antarctic Peninsula	466 000	Proposal	Argentina, Chile	N/A	Antarctica
	Heard Island and	71 000	Designated	Australia	2002	sub-Antarctic
	McDonald Island
	Kerguelen	568 000	Designated	France	2006	sub-Antarctic
	Crozet	410 000	Designated	France	2006	sub-Antarctic
	South Georgia and South	1 241 000	Designated	United Kingdom	2012	sub-Antarctic
	Sandwich Islands
	Prince Edward Islands	161 000	Designated	South Africa	2013	sub-Antarctic
	Adapted from Brooks et al. (2020a).

  [START_REF] Vacchi | Advances in Polar Ecology The Antarctic Silverfish: a Keystone Species in a Changing Ecosystem[END_REF]), crustaceans (mainly Antarctic krill (Euphausia superba), see detailed description in Siegel (2016)), and squids (particularly the arrow squid (Psychroteuthis glacialis) and the Antarctic neosquid (Alluroteuthis antarcticus), see detailed description in[START_REF] Rodhouse | Biogeographic Atlas of the Southern Ocean[END_REF]; Fig.19).

Table 2 . Information on Emperor penguin diet obtained from stomach content collected at different locations and years/seasons.

 2 Adapted from[START_REF] Kooyman | Evolutionary and ecological aspects of some Antarctic and sub-Antarctic penguin distributions[END_REF].

	Colony	Area	Diet (% mass)	Period	Year	Location	Reference
	Drescher Inlet	Weddell Sea	52 K, 38 F, 10 S Oct-Nov	1986	72.9°S, 19.4°W	Klages 1989
	Drescher Inlet	Weddell Sea	25 K, 75 F, 0 S	Feb	1990 & 1992 72.9°S, 19.4°W	Pütz 1995
	Taylor	East Antarctica	0 K, 31 F, 69 S	Nov	1988	67.5°S, 60.9°E	Robertson et al. 1994
	Auster	East Antarctica	0 K, 55 F, 45 S	July-Nov	1988	67.4°S, 64.1°E	Robertson et al. 1994
	Auster	East Antarctica	68 K, 26 F, 5 S	Aug	1993	67.4°S, 64.1°E	Kirkwood and Robertson 1997
	Auster	East Antarctica	10 K, 20 F, 65 S	Nov	1993	67.4°S, 64.1°E	Kirkwood and Robertson 1997
	Cape Washington	Ross Sea	8 K, 92 F, 0 S	Nov	1992	74.7°S, 165.4°E	Cherel and Kooyman 1998
	Coulman Island	Ross Sea	0.5 K, 96 F, 3 S	Nov	1993	73.3°S, 169.6°E	Cherel and Kooyman 1998
	Pointe Géologie	d'Urville Sea	2 K, 95 F, 3 S	Oct-Nov	1982	66.67°S, 140.01°E	Offredo et al. 1986
	Pointe Géologie	d'Urville Sea	by far dominated by fish*	Oct-Nov	2002	66.67°S, 140.01°E	Cherel et al. 2008

K = krill, F = Fish, S = squid. * stable isotope analysis, no mass available.

Table 3 . Summary of deployments performed at Atka Bay.

 3

	Deployment duration	Short-term	Long-term	Long-term

Life-history stage ADULT ADULT JUVENILE Number of individuals 36 (16 in 2017/18, 20 in 2018/19) 8 8 Logger type GPS-VHF-acc*+ TDR ARGOS + TDR + acc* ARGOS Period of equipment Late chick-rearing Post-moult Post-moult chick at fledging

Table 5 . Summary of deployments performed at Pointe Géologie. Year Period of equipment Monitored period Number of birds Logger type, Manufacturer

 5

	Device
	dimensions
	(mm) and
	weight in air(g)

*Sirtrack, Havelock North, New Zealand; NB: it is now Lotek NZ.

Table 7 . Summary of the study groups according to the study site and the period of deployment. Study group Life-history stage Colony Tracking period Tracking device Number of individuals Multiple foraging trips

 7

	juvABy	Juvenile	Atka Bay	year	ARGOS	8	n
	adABf	Adult	Atka Bay	fall	ARGOS	8	y
	adABs	Adult	Atka Bay	summer	GPS	22	y
	adPGs	Adult	Pointe Géologie	summer	ARGOS	18	y
	adPGw	Adult	Pointe Géologie	winter	ARGOS	15	n

  [START_REF] Small | Analysis of albatross and petrel distribution within the CCAMLR Convention Area: Results from the global Procellariiform tracking database[END_REF][START_REF] Cooke | Biotelemetry and biologging in endangered species research and animal conservation: relevance to regional, national, and IUCN Red List threat assessments[END_REF], Costa et al. 2012) as demonstrated by the establishment of the Ross Sea Marine Protected Area (MPA) in 2017. This first MPA adjacent to Antarctica was partly justified by the range of Adélie penguins (Pygoscelis adeliae)

during their energy-intensive premoult period

(CCAMLR 2009[START_REF] Hays | Key Questions in Marine Megafauna Movement Ecology[END_REF]

).

Emperor penguins have not yet been tracked in the Weddell Sea and in the Atlantic sector of the Southern Ocean, thus not much is known about their distribution in the area. To improve the scientific knowledge about this species and to provide data in support of the development of a MPA in the Weddell Sea area, we have equipped several adult and juvenile emperor penguins. Data logger types

Table 8 . General information on deployments and captures.

 8

	Category of attachment	Back-taped	Leg-banded & back glued	Back-taped-epoxied
	Deployment duration	Short-term	Long-term	Long-term
	Life-history stage	ADULT	ADULT	JUVENILE
	Logger type	GPS -VHF -TDR	TDR -ARGOS	ARGOS
	Monitored period	summer	winter	winter
	Number of individuals equipped	36	8	8
	Capture setup	with its chick at the colony edge	alone at the edge of groups	groups on their way to the sea
	Capture technique	corral + crook	crook or corral	corral
	Minimum of persons required	3	2 to 3	3
	Recapture technique	crook	crook	not possible,
				not returning to
	Minimum of persons required	2	2	breeding site
	III.3.1.1. Short-term deployment: back-taped loggers
	We equipped 16 adults in 2017/2018 and 20 adults in 2018/2019 with a GPS-Acc-VHF logger (a
	combination of a Global Positioning System (GPS), a 3-axis Accelerometer (Acc) and a Very High
	Frequency (VHF) locator beacon) and a separate Time-Depth Recorder (TDR, see Table 4 for technical
	details on the loggers). Both are archival devices and, therefore, need to be retrieved to access the
	data. The VHF locator beacon sends a device-specific signal that allows us to locate the equipped birds
	in the colony and facilitate device recovery. To minimise deleterious effects such as extra drag on
	diving animals

  and numerous subsequent short-term studies on other penguin species[START_REF] Ropert-Coudert | Individual Diving Strategies in the Little Penguin[END_REF][START_REF] Chiaradia | Diving behaviour of Little Penguins from four colonies across their whole distribution range: bathymetry affecting diving effort and fledging success[END_REF][START_REF] Pichegru | Diving patterns of female macaroni penguins breeding on Marion Island, South Africa[END_REF][START_REF] Vaillant | How age and sex drive the foraging behaviour in the king penguin[END_REF][START_REF] Poupart | Variability in the foraging range of Eudyptula minor across breeding sites in central New Zealand[END_REF], we used a rounded knife to lift a few feathers from the back of the penguin and insert pre-cut strips of waterproof adhesive tape (e.g. Tesa® tape 4651, Beiersdorf AG, Hamburg, Germany). The number of strips depends on the logger's length. To strengthen the bond between strips, it is ideal if the strips overlap each other by 50%. To further reinforce the attachment, we added glue (e.g. cyanoacrylate glue, Loctite 401, Loctite, Henkel AG., Düsseldorf, Germany) between the adhesive part of the tape strips and the logger. Cable ties (e.g. Panduit, Panduit Corp, Illinois, USA) should be tightened with a cable tie gun. The size and number of cable ties used depend

Table 9

 9

). The recovery rate from December 2018 (30%), despite being higher, is statistically similar to what

[START_REF] Robertson | Some field techniques for ecological research on emperor penguins[END_REF]

recorded for deployments performed in December on the opposite side of Antarctica (near Australia's Mawson Station) with a loss rate of 89%. The probability to recover a device deployed in December is significantly lower (z-test, p-value < 0.05) than in November.

Table 9 . Comparison between at-sea-ecological studies that equipped emperor penguins over the last 30 years.

 9

	Category of deployment	Season	Age class	Type of device	Device dimension (mm)	Device weight (g)	Recovery	Mean duration (days)	Sd (days)	Range # deploy # recup % recup	Publication	Study site and year
	long-term	W-Jan/Feb	ad	Argos	140x55x16	195	no	66	52	15-133	7	0	0	Kooyman et al. 2004	Ross Sea 2000
														Goetz &
	long-term	W-Mar	ad	Argos	109x32x26	100	no	114	98	12-323	20	0	0	Kooyman 2018,	Ross Sea 2013
														2015
	long-term	W-Jan	ad	Argos Acc tdr	107x18x21 70x16x16 36x13x10	45 10 9	yes	150	30	118-201	8	4	50	This study	Atka Bay 2018
	long-term	W-Dec	juv	Argos	NA	120	no	64	12	43-81	8*	0	0	Kooyman et al. 1996 and 2007	Cape Washington 1994, 1995, 1996
	long-term	W-Dec	juv	Argos	NA	NA	no	113	49	41-160	7*	0	0	Wienecke et al. 2010	Taylor glacier 1996
	long-term	W-Dec	juv	Argos	NA	NA	no	121	55	38-189	10	0	0	Wienecke et al. 2010	Auster 2007
	long-term	W-Dec	juv	Argos	NA	62	no	112	77	38-255	5*	0	0	Thiebot et al. 2013	Pointe Géologie 2010
	long-term	W-Dec	juv	Argos	NA	62	no	193	93	30-344	13*	0	0	Labrousse et al. 2019b	Pointe Géologie 2014
	long-term	W-Jan	juv	Argos	107x18x21	45	no	233	108	73-382	8	0	0	This study	Atka Bay 2019
	short-term	S-Nov	ad	Argos tdr	78x50x23 67x17x17	105 30	yes	7	1	2-19	15	10	67	Zimmer et al. 2010	Pointe Géologie 2005
	short-term	S-Nov	ad	Acc	128x27 or 122x22	101 or 73	yes	14	4	8-20	12	11	92	Watanabe et al. 2012	Cape Washington 2005
	short-term	S-Nov	ad	GPS tdr	105x38x18 35x12	60 7	yes	16	6	9-25	21	18	90	This study	Atka Bay 2017 & 2018
	short-term	S-Dec	ad	tdr	NA	NA	yes	NA	NA	NA	19	2	11	Robertson, 1991	Auster & Taylor glacier 1988
	short-term	S-Dec	ad	GPS tdr	105x38x18 35x12	60 7	yes	14	6	9-18	15	4	30	This study	Atka Bay 2018 & 2019

Table 10 . Comparison of the mean mass of PIT-tagged chicks from the annual cohort and chicks of equipped adults.

 10

	Summer season	PIT-tagged chicks from annual cohort (mean ± sd in kg)	Chicks of equipped adult (mean ± sd in kg)
	End of Nov. 2017	11.8 ± 2.4 (N=300)	11.7 ± 2.6 (N=16)
	End of Nov. 2018	10.2 ± 1.9 (N=300)	10.2 ± 2.3 (N=20)

Table 11 . Number of dead and alive emperor penguin chicks over the two summer seasons. Summer season Dead chicks Alive chicks

 11

		CEB	PIT	Total	Total
	2017/2018	1 (16)	7 (300)	350	6352
	2018/2019	4 (20)	14 (300)	731	7606

  Table9) is the longest documented deployment duration for the genus Aptenodytes and presumably for any penguin species since the deployments lasted from one moult to the next. None of the 5 remaining birds were spotted on colony despite visual search in summer 2019/2020. One device stopped transmitting after 73 days while the four others lasted between 142 and 185 days resulting in an average deployment duration of 233 ± 108 days. This average deployment duration is longer than any previously reported (p-value > 0.05, ANOVA, see Table9for mean ± sd values) but not significantly compared toLabrousse et al. (2019b),

(p-value < 0.05, ANOVA).

  have been deployed during the late chick-rearing period, presumably due to a combination of technical and logistical constraints. The increased temporal and spatial resolution of GPS loggers in comparison to ARGOS devices, combined with their lower cost that allows to sample a greater number of birds, can facilitate a better understanding of foraging activities and behaviour at a finer scale, thus improving fundamental knowledge about this iconic species.The methods presented herein allow the deployment of high-resolution data acquisition loggers with a high probability of recovery once the phenology of the colony has been assessed, for instance by the size and moulting stage of chicks. At Atka Bay, the best deployment period is in November with a logger recovery rate of 90%. The low recovery rate (38%) during the 2017-2018 season can be explained by logistical issues we encountered and not the deployment technique. An unexpected late on-site arrival led to late deployment of 11 loggers in December 2017, compared to 4 in December 2018, and consequently to a substantial loss of devices. The higher mortality rate (Table11) and the lower body condition of the chicks in 2018/2019 compared to 2017/2018 (Table

Table 12 . Tracking studies of juvenile emperor penguins at sea.

 12

	Colony	Colony coordinates	Colony population	estimate*	Number of birds	Mean tracking	duration (days)	Maximal distance	from colony (km)	Northernmost	latitude reached	Distribution area	(millions km²)	% in ACC	% in SO -Treaty	limit	% in IUCN	% in CCAMLR	% in MPAs	Publication
	Cape Washington	74.58 S, 165.48 E	11808	10	64	2845	56.9°S 1.7 54.6 73.5 14.6 73.5 4.4	Kooyman et al. 2007
																				Labrousse
	Pointe Géologie	66.66°S, 140.00°E	2456	21	171	3503 53.76°S 3.6 75.9 62.7 35.8 98.0 13.5	et al. 2019b Thiebot et
																				al. 2013
	Auster	67.38°S, 64.03°E	7855	10	121	2343 56.25°S 3.3 60.7 79.1 61.4 100	6.7	Wienecke et
	Taylor Glacier	67.47°S, 60.88°E	519	7	113	1570 54.23°S 1.7 87.3 67.7 43.4 100	9.3	al. 2010
	Atka Bay	70.62°S, 08.15°W	9657	8	221	2474 48.37°S 5.1 19.3 60.7 51.4 99.2 16.3	This study
	Mean sd	/	6459 4798.3 5.6 11.2 138	2547	/		3.1 59.6 68.7 41.3 94.1 10.0	/

Table 13 . At-sea distribution metrics for the 8 juvenile emperor penguins equipped with ARGOS platforms at Atka Bay in January 2019.

 13 % of time spent during the trip duration, 3 in days. ACC: Antarctic Circumpolar Current; SO: Southern Ocean (i.e. at the parallel of 60°S as defined in the Antarctic Treaty); IUCN: International Union for Conservation of Nature; MPA: Marine Protected Area; WSMPA: Weddell Sea MPA.

	ID	Start trip	End trip		Trip duration (days)	Max distance from colony (km)	Date of max distance from colony	Yearly travelled distance 1 (km)	Mean daily distance 1 (km)	% 2 in ACC	% 2 in SO -Treaty limit	% 2 in IUCN	% 2 in WSMPA	% 2 in SGSSI MPA
	65787	11/01/19 29/12/19	352	2287	21/03/19	15593	44.3 14.4 59.3 40.1 16.9	0
	65788	13/01/19 03/07/19	171	2390	10/04/19	NA	NA	28.8 44.4 36.6 10.7 5.6
	65789	12/01/19 24/03/19	71	1484	26/02/19	NA	NA	0	18.1 81.6 29.8	0
	65790	12/01/19 12/12/19	334	2176	05/04/19	13452	40.3 16.8 54.2 42.8	5.3	0
	65791	12/01/19 01/06/19	140	1518	20/03/19	NA	NA	11.1 17.5 72.0 11.0	0
	65792	11/01/19 13/07/19	183	1519	20/03/19	NA	NA	6.5	28.8 49.8 12.7 7.5
	65793	12/01/19 18/06/19	157	2149	04/03/19	NA	NA	41.3 47.7 49.4	6.3	0
	65794	10/01/19 01/01/20	356	2474	07/03/19	18326	51.5 19.3 48.5 50.6	5.3	0
	Median
	(date) or	12/01/19 08/07/19 220.5 1999.6 20/03/19 15790.3 45.4 18.0 55.3 48.9 10.6 1.4
	Mean values
	sd	0.9	3	109.8	3	110.4	421.3	15.1	3	2443.0	5.7	11.3 15.1 13.3	7.5	3.8

1 Yearly travelled distance was computed using one location every 6 hours (in km), 2

  1 in the framework of the priority program "Antarctic research with comparative investigations in Arctic ice areas". Logistics and field efforts were supported by the AWI within the framework of the program "Monitor the health of the Antarctic maRine ecosystems using the Emperor

	Foraging tactics of emperor penguins differ between sites
	and seasons
	Chapter V. Foraging tactics of emperor
	Aymeric Houstin 1,2 , Daniel P. Zitterbart 3,4 , Karine Heerah 5 , Olaf Eisen 6,7 , Alexander Winterl 3,4 , Sebastian
	penguins differ between sites and seasons Richter 3,4 , André Ancel 2 , Víctor Planas-Bielsa 1 , Benoit Vallas 2 , Damien Chevallier 2 , Ben Fabry 3 , Céline Le
	Bohec 1,2
	1 Centre Scientifique de Monaco, Département de Biologie Polaire, Principality of Monaco

penguin as a sentinel" (MARE). The long-term project MARE, to which this study belongs, and all procedures were approved by the German Environment Agency (Umweltbundesamt-UBA permit no.: II 2.8 -94033/100 delivered on the 04/10/2017 and 04/10/2018), and conducted in accordance with the Committee for Environmental Protection (CEP) guidelines. 2 Université de Strasbourg, CNRS, IPHC UMR 7178, F-Strasbourg, France 3 Department of Physics, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany 4 Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, USA 5 Zoophysiology, Department of Biology, Aarhus University, C.F. Møllers Allé 3, 8000 Aarhus C, Denmark 6 Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar-und Meeresforschung, Bremerhaven, Germany 7 Fachbereich Geowissenschaften, Universität Bremen, Bremen, Germany

Table 14 . General information on tracking device deployments.

 14

	Study group	Life-history stage	Colony	Season	Tracking period	# inds	# trips	Tracker type
	juvABy	juv	AB	year	Jan 2019-Jan 2020	8	8	ARGOS -SPOT-367
	adABf	ad	AB	fall	Jan-Aug (May)* 2018	8	10 (8)*	Wildlife Computers
	adABs	ad ad	AB AB	summer summer	Nov-Dec 2018 Nov-Dec 2017	16 6	32 7	GPS -Axy-Trek TechnoSmArt
	adPGs	ad	PG	summer	Nov 2005 Jan-2006	18	28	ARGOS -Splash & SPOT-5 Wildlife computers
		ad	PG	winter	May-Sep 2005	3	4
	adPGw	ad	PG	winter	May-Jul 2001	3	3	ARGOS -ST-10 Sirtrack
		ad	PG	winter	Jul-Oct 1998	9	19

Table 15 . General information on TDR deployments.

 15

	Study group	Life-history stage	Colony Season Tracking period # inds # trips	Tracker type	TDR Frequency, resolution
	adABf	ad	AB	year	Jan-Nov 2018	4	4	ARGOS	Cefas g5+ 1 HZ, 30 cm
	adABs	ad	AB	summer	Nov-Dec 2017 & 2018	22	32	GPS	Lotek Lat 1800 1 HZ, 30 cm
	adPGs	ad	PG	summer	Nov 2005	4	4	ARGOS	Wildlife Computer Splash 0.5 Hz, 50 cm

Table 16 . General information and at-sea metrics of adult emperor penguins from Atka Bay (AB) and Pointe Géologie (PG).

 16

	Study group	Bird and trip ID*	Status	# locations	Start trip	End trip	Trip duration (days)	Max distance from colony (km)	Date of max distance from the colony	% in MPA	# dive kept	Max dive depth (m)	Max dive duration (min)	Proportion of benthic dives
		44837	nb	2173	25/01/2018 11:00	25/04/2018 23:00	90.5	1025	23/04/2018	100
		44839_1	nb	2197	24/01/2018 11:00	25/04/2018 23:00	91.5	1348	25/04/2018	81.7
		44839_2	nb	2009	20/05/2018 05:00	13/08/2018 21:32	83.7	1547	21/07/2018	11.5			NA
		44842	b	1658	26/01/2018 17:00	05/04/2018 18:00	69.0	351	22/03/2018	98.9
	adABf	44843	b	1760	24/01/2018 11:00	07/04/2018 18:00	73. 3	486	31/03/2018	94.5
		44836	b	2027	25/01/2018 05:00	19/04/2018 15:00	84.4	308	20/03/2018	100	21670		13.3	0.3**
		44840	b	1907	27/01/2018 05:00	16/04/2018 15:00	79.4	257	27/02/2018	100	24448		19.5	1.5**
		44841	b	1991	26/01/2018 17:00	19/04/2018 15:00	82.9	275	22/03/2018	86.6	18282		29.7	0**
		44844_1 44844_2	nb nb	2107 905	27/01/2018 05:00 20/05/2018 05:00	24/04/2018 23:00 26/06/2018 21:00	87.8 37.7	410 550	29/03/2018 26/06/2018	100 100	35863		21.7	0.3**
		0602949	b	140	28/11/2017 17:00	04/12/2017 12:00	5.8	97	02/12/2017	100	777		13.2	0.4
		7740383	b	150	30/11/2017 13:00	06/12/2017 18:00	6.2	360	06/12/2017	100	1157		9.2	0
		7740387	b	172	01/12/2017 16:00	08/12/2017 19:00	7.1	143	05/12/2017	100	820		12.1	0
		7740392_1	b	89	01/12/2017 19:00	05/12/2017 11:00	3.7	86	02/12/2017	100	653		9.9	0.2
		7740392_2	b	63	05/12/2017 19:00	08/12/2017 09:00	2.6	103	08/12/2017	100	490		9.8	0.8
		7740427	b	147	02/12/2017 16:00	08/12/2017 18:00	6.1	80	08/12/2017	100	794		17.7	1.5
		7740429	b	175	02/12/2017 23:00	10/12/2017 05:00	7.2	122	03/12/2017	100	956		16.0	11.2
		7740091_1	b	118	06/11/2018 10:00	11/11/2018 07:00	4.9	78	07/11/2018	100	729		10.0	0
		7740091_2	b	126	12/11/2018 02:00	17/11/2018 07:00	5.2	97	15/11/2018	100	783		15.3	0.1
		7740093_1	b	125	06/11/2018 05:00	11/11/2018 09:00	5.2	96	08/11/2018	100	771		11.3	1.9
		7740093_2	b	164	12/11/2018 02:00	18/11/2018 21:00	6.8	133	15/11/2018	100	779		13.1	20.2
		7740101_1	b	161	08/11/2018 17:00	15/11/2018 09:00	6.7	59	11/11/2018	100	883		10.2	5.4
		7740101_2	b	160	16/11/2018 04:00	22/11/2018 19:00	6.6	94	16/11/2018	100	896		12.5	4.1
		7740097_1	b	160	07/11/2018 15:00	14/11/2018 06:00	6.6	101	11/11/2018	100	1139		15.0	0.2
		7740097_2	b	262	15/11/2018 08:00	26/11/2018 05:00	10.9	190	19/11/2018	100	2044		11.3	0
		7740115_1	b	213	08/11/2018 20:00	17/11/2018 16:00	8.8	192	14/11/2018	100	1651		14.4	0.2
		7740115_2	b	182	18/11/2018 22:00	26/11/2018 11:00	7.5	133	24/11/2018	100	1418		11.2	1.2
		7740099_1	b	174	07/11/2018 11:00	14/11/2018 16:00	7.2	102	11/11/2018	100	1176		17.1	3.2
		7740099_2	b	168	15/11/2018 13:00	22/11/2018 12:00	7.0	143	16/11/2018	100	1015		11.6	17.4
	adABs	7740099_3	b	148	23/11/2018 13:00	29/11/2018 16:00	6.1	82	24/11/2018	100	785		9.9	35.9
		7740095_1	b	133	07/11/2018 03:00	12/11/2018 15:00	5.5	150	09/11/2018	100	1303		18.6	0.1
		7740095_2	b	211	13/11/2018 18:00	22/11/2018 12:00	8.8	146	16/11/2018	100	1670		12.2	0

Table 17 . Distribution metrics of study groups.

 17 only breeding birds are taken into account, ^ only non-breeding trips are taken into account. For the study group: juv = juveniles, ad = adults, AB = Atka Bay colony, PG = Pointe Géologie colony, y = year, f = fall, s = summer, w = winter.

	Study group	juvABy	adABf	adABs	adPGs	adPGw
	Home range size (UD 90% in km²)	2 619 470	258 268	26 552	199 371	11 309
	Core area size (UD 50% in km²)	624 868	40 661	8 270	37 118	1 788
	Maximum distance from the colony (km)	2474	486* / 1547^	360	316* / 924^	223
	Median of mean max distance from the colony (km)	1834	304* / 1026^	113	101* / 569^	56

*

Table 18 . General statistics (mean ± SD) of the main diving metrics per study group equipped with TDRs.

 18

	Study group	Max depth (m)	Dive duration (min)	Bottom time (min)	Dive efficiency (%)	Number of wiggles	ACPUE
	adABf1* (N=4)	42.1 ± 43.1	2.8 ± 1.4	1.4 ± 0.9	37.6 ± 17.8	2.3 ± 2.2	1.5 ± 1.3
	adABf2*(N=4)	43.7 ± 49.9	3.1 ± 1.9	1.5 ± 1.3	37.5 ± 20.3	2.3 ± 2.5	1.4 ± 1.3
	adABf3* (N=4)	52.6 ± 54.7	3.6 ± 2.2	1.8 ± 1.4	37.7 ± 19.3	3.1 ± 3.1	1.6 ± 1.4
	adABf4*(N=4)	53.3 ± 55.4	3.4 ± 1.8	1.6 ± 1.1	35.4 ± 18.6	2.7 ± 2.9	1.6 ± 1.3
	adABs (N=22)	UA	UA	UA	UA	UA	UA
	adPGs (N=4)

Table 19 . Results of the best model of the GLMM analysis illustrating the functional relationship between the diving effort strategy (i.e. 'night-time diving effort', 'day-time diving effort') and the diving metrics.

 19 Variables were first normalised with a Cox Box Power transform. Significance is indicated by stars with ***< 0.001.

	Variable	Estimate	Std. Error	z value	Pr(>|z|)	Signif
	Bottom time	0.44871	0.01495	30.008	< 2e-16	***
	Max depth	-0.15733	0.02058	-7.645	2.09e-14	***
	Diving efficiency	-2.95857	0.13953	-21.204	< 2e-16	***
	ACPUE	0.29125	0.02121	13.729	< 2e-16	***

Table 20 . Summary of the main research topics on emperor penguins and their level of knowledge achieved in the literature.

 20

	Research topics

a : a few colonies have been monitored on the long-term (through aerial images or direct counts). Global population of the species is estimated mainly through satellite images, therefore, time series are very short. b : one colony initially monitored with flipper-banded birds over the 61 colonies. Electronic long-term monitoring (microtagged birds detected by automatic identification systems) started in 2009/2010 in Pointe Géologie (Adélie Land) and in 2017/2018 in Atka Bay (Queen Maud Land). c : investigations initiated by our research team.

  ).Concerned by these shortcomings from the very beginning of this thesis, one of our first and main objectives was to set up a second worldwide long-term monitoring programme of micro-tagged emperor penguins; the first one having been implemented in 2009/2010 by the team at the Pointe Géologie colony based on the RFID methodology we developed in the King penguin from Crozet archipelago. Atka Bay colony has been chosen for several reasons. First, as highlighted in Chapter 2 (page 70), Atka Bay and Pointe Géologie colonies present contrasting population size, a slightly shifted phenology as well as contrasted environmental characteristics (e.g. winds regime, shelf configuration, and oceanographic conditions), and are, therefore, optimal for comparisons. Second, since 2013, a remote-controlled camera observatory (developed by Zitterbart and colleagues, seeRichter et al.

	VI.2.3. Building up a new framework
	VI.2.3.1. Setting up long-term monitoring programmes

  VI.2.3.3. The development of new methodologies Noteworthy, several studies have been published recently on best tagging practices in different taxa (see, for instance, Horning et al. (2019) on pinnipeds, or Andrews et al. (2019) for cetaceans). As stated by Andrews and colleagues (2019) "As tag designs and tagging methods develop, information about the most successful refinements and innovations should be shared to facilitate the use of techniques that are most appropriate for a project and that minimise any potential adverse effects on tagged animals". In other words, to ensure that the data collected are of exemplary quality from a scientific

  , including juvenile emperor penguins (Chapter IV), is not considered in planned CCAMLR MPAs. Additionally, the ecological spatial connectivity between MPAs (UN 2002, WCPA/IUCN 2007, Carr et al. 2017) is a component currently absent from CCAMLR framework (CCAMLR 2011).

En plus d'avoir déjà pris part à des études sur la colonie de manchots empereurs de Pointe Géologie (étude présentée en annexe de cette thèse), j'ai réalisé une période de terrain en début de thèse sur ce site afin d'initier un programme de suivi en mer similaire sur des manchots Adélie (Pygoscelis adeliae), et dont les résultats préliminaires sont présentés en annexe. Cette période de terrain impliquait la supervision quotidienne de deux Volontaires de Service Civique.

d'outils et de techniques les moins perturbants pour les animaux équipés. La mise en place et le partage de nouvelles méthodologies de capture et d'équipement au cours de cette thèse, afin de servir de ressource de base pour faciliter les futures recherches sur cette espèce sensible, répond à ce besoin.Ces précieuses informations élémentaires sont indispensables pour la mise en place de mesures adéquates de conservation comme nous l'illustrons pour les juvéniles. L'application d'une vision d'ensemble a permis de mettre en évidence la non-adéquation entre leur utilisation de l'océan et les systèmes de protection (AMP notamment) existants ou prévus. Elle a également confirmé l'hypothèse de l'importance des structures océaniques particulières (fronts et courant circumpolaire) pour cette classe d'âge à l'échelle du continent bien que les raisons n'en soient pas encore déterminées. Enfin, nous apportons de nouvelles connaissances sur la répartition spatio-temporelle en mer des manchots empereurs et leur comportement de recherche alimentaire. Ces données sont de premières importances afin d'éviter ou limiter la compétition spatio-temporelle avec les pêcheries si celles-ci continuaient à se développer dans l'océan Austral.En définitive, nous soulignons la nécessité de conduire des études similaires sur d'autres colonies afin de disposer d'une vision la plus holistique qu'il soit de la niche écologique de l'espèce à l'échelle de l'océan Austral. Ces informations sont d'ailleurs un prérequis pour appuyer la révision du statut de l'espèce sur la Liste Rouge de l'Union Internationale pour la Conservation de la Nature (UICN) à un niveau plus adapté aux menaces multiples qui pèsent sur cette espèce.

See https://www.antarctica.gov.au/antarctic-operations/travel-and-logistics/aviation/davis-aerodrome/

See https://theconversation.com/australia-wants-to-build-a-huge-concrete-runway-in-antarctica-heres-whythats-a-bad-idea-139596

4 I have been involved during my PhD project, through fieldwork and preliminary analyses, in a study focusing on the contaminant accumulation on Adélie penguins from Pointe Géologie. The ready to submit version of the resulting manuscript is presented in Annex D.

https://www.ats.aq/e/key-documents.html

https://www.ats.aq

An umbrella species is a species whose conservation is expected to confer protection to a large number of naturally co-occurring species.

Chapter II. Material and Methods

Since my overwinter in Dumont d'Urville, from November 2013 to March 2015, I'm involved in numerous studies on the emperor but also Adélie penguins breeding at PG. Resulting publications and preliminary results from these studies are presented in Annexes of the thesis (see page 236).

The two latest requirements are not met by Global Locating System (GLS;[START_REF] Phillips | Accuracy of geolocation estimates for flying seabirds[END_REF].

Our preliminary analysis focused only on one group (the adults from Atka Bay during the fall ; adABf) for the moment.

For birds from the adABf group, the ARGOS platforms transmitted until the winter, while we collected yearround data with the TDRs for four of the birds (Table14 and Table 15).

In November and December, the night is no more present at these latitudes. Night-time hours referred therefore to hours between 8 pm and 4 am.

Chapter VI. General discussion-Chapter VI -

See also https://www.climate.gov/news-features/understanding-climate/understanding-climate-antarctic-seaice-extent

Detailed descriptions of the systems have been deposited in PANGAEA repository and are available at https://doi.pangaea.de/10.1594/PANGAEA.913447.

Over 72 existing ASPAs, only nine, all of them less than 1,000 km 2 , have a marine component[START_REF] Chown | Antarctica and the strategic plan for biodiversity[END_REF] . Entry to an ASPA is prohibited without a permit, and activities must be conducted in accordance with the Management Plan of the area (ATS 1991).

See https://www.cls-telemetry.com/argos-solutions/the-future-of-argos-argos4ng/ and https://www.clstelemetry.com/production-underway-on-kineis/

Acknowledgements

To all the penguins that I handled…. I apologize for the disturbance and the discomfort and hope their contribution to this work will be of help for their species.

Acknowledgements

We thank the Alfred Wegener Institut Helmholtz-Zentrum für Polar-und Meeresforschung, Logistics Department, the winterers and campaigners at Neumayer Station III for their invaluable support in 2017-2018 and 2018-2019 seasons.

We are very grateful to Prof. Patrick Rampal for support in initiating the project, to Dr. Laurent Godet (CNRS) for lending his VHF antennas and receivers, and to Dr. Olaf Eisen (AWI) for his invaluable help with fieldwork and related activities.

We warmly thank 'Galileo' and 'ProSiebenSat.1 TV Deutschland GmbH' for their shooting in the field and providing Additional files 3 and 5.

Acknowledgements

We thank the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI), Logistics Department, the winterers and campaigners at Neumayer Station III for their invaluable support. We are very grateful to Prof. Patrick Rampal for support in initiating the project. This study was funded by the Centre Scientifique de Monaco with additional support from the LIA-647 and RTPI-NUTRESS (CSM/CNRS-University of Strasbourg), by The Penzance Endowed Fund and The Grayce B. Kerr Fund in Support of Assistant Scientists, and by the Deutsche Forschungsgemeinschaft (DFG) grants

Availability of data and material

All data generated or analysed during this study are included in this published article and its supplementary information files available in the "Publishing Network for Geoscientific & Environmental Data" (PANGAEA) via https://doi.pangaea.de/10.1594/PANGAEA.913447.

Additional files list

ü Additional file 1 (.pdf): Table S1. General information on the loggers deployed including the logger type, name, dimensions and weight, as well as the manufacturers name and location (Table 4 of this manuscript) ü Additional file 2 (.mp4): Movie S1. PIT-tagging of an adult emperor penguin ü Additional file 3 (.mp4): Movie S2. Capture of an adult-chick pair ü Additional file 4 (.mp4): Movie S3. Weddell seal disturbance on the emperor penguin colony ü Additional file 5 (.mp4): Movie S4. Release of an adult-chick pair ü Additional file 6 (.mp4): Movie S5. Capture of a single adult with the crook ü Additional file 7 (.mp4): Movie S6. Adult emperor penguin handling ü Additional file 8 (.mp4): Movie S7. Back-taped GPS deployment ü Additional file 9 (.pdf): Fig. S1. Marking of an emperor penguin with a painted number (Fig. 32 of this manuscript) ü Additional file 10 (.mp4): Movie S8. Back-taped TDR deployment ü Additional file 11 (.pdf): Fig. S2. Adult emperor penguin at the end of its moult (Fig. 34 of this manuscript) ü Additional file 12 (.mp4): Movie S9. Back-taped-epoxied logger deployment -epoxy spreading ü Additional file 13 (.pdf): Slideshow S1. Leg-banded TDR mounting manual ü Additional file 14 (.pdf): Slideshow S2. Leg-banded TDR deployment and recovery

Union for Conservation of Nature (IUCN) in raising awareness and as a political and financial lobby for conservation purposes, we included the range of the Emperor penguin species defined by the IUCN as a boundary delineating potential implementation of conservation efforts for the species.

All the boundaries were obtained online as shapefiles, except for the proposed Domain 1 MPA since no shapefile was available (Table 6).

II.2.3.2. Environmental variables

To characterise the marine environment used by the emperor penguins, we extracted and used remote-sensing datasets collected by satellites and available online.

(i) Sea ice

The Emperor penguin is a sea ice obligate species [START_REF] Ainley | Decadal-scale changes in the climate and biota of the Pacific sector of the Southern Ocean, 1950s to the 1990s[END_REF]. Sea ice information is therefore a major feature to consider. Sea ice concentration values (ranging from 0 to 100%) were obtained from Advanced Microwave Scanning Radiometer (AMSR-2) satellite estimates of daily sea ice concentration at 3.125 km resolution from the University of Bremen (https://seaice.uni-bremen.de/data/amsr2/ ; [START_REF] Spreen | Sea ice remote sensing using AMSR-E 89-GHz channels[END_REF]. This sea ice concentration (SIC) product has been widely used in recent studies (SCAR 2014[START_REF] Shi | Retrieval and Validation of Sea Ice Concentration from AMSR-E/AMSR2 in Polar Regions[END_REF], Labrousse et al. 2019b[START_REF] Herr | Aerial surveys for Antarctic minke whales ( Balaenoptera bonaerensis ) reveal sea ice dependent distribution patterns[END_REF].

ASMR-2 estimates were not available before 2006. Consequently, for Pointe Géologie data analysis, we used daily sea ice concentration at 12.5 km resolution from the Institut Français de la Recherche pour l'Exploitation de la Mer (IFREMER, ftp://ftp.ifremer.fr/ifremer/cersat/products/gridded/psiconcentration/data/ ; [START_REF] Ezraty | Arctic and Antarctic sea-ice concentration and {A}rctic sea ice drift estimated from Special Sensor Microwave Imager data[END_REF]), also used in previous studies [START_REF] Widmann | Habitat use and sex-specific foraging behaviour of Adélie penguins throughout the breeding season in Adélie Land, East Antarctica[END_REF], Ropert-Coudert et al. 2018).

127 edge contour was defined by the 15% sea ice concentration isocline (Fig. 38; Cavalieri 1991, Stammerjohn and[START_REF] Stammerjohn | Opposing Southern Ocean climate patterns as revealed by trends in regional sea ice coverage[END_REF].

The maximum and minimum median sea ice extent between 1981-2010 presented in Fig. 36 were obtained from the National Snow and Ice Data Center NSDIC [START_REF] Fetterer | Sea Ice Index, Version 2, updated daily[END_REF]) implemented in the 'Quantarctica3' package [START_REF] Matsuoka | Quantarctica[END_REF] of the QGIS software.

IV.3.4. Management features

The

IV.3.5. Assessing the overlap between bird distribution and management zones

The average residence time that each of the birds equipped in our study spent inside existing or proposed management zones of the Southern Ocean was computed on a daily, weekly and monthly basis, and averaged over the total tracking period.

We tested if the observed monthly-averaged residence time changed significantly over the course of a year using the Kruskal-Wallis rank sum tests. For all tests, the significance threshold was set at p=0.05.

Statistical analyses were performed using the software R v. 3.5.0 (R Core Team 2018) and QGIS v.

2.18.18 (QGIS Development Team 2017) with the data package 'Quantarctica3' [START_REF] Matsuoka | Quantarctica[END_REF]).

V.1 Abstract

Despite being one of the most iconic seabird species of Antarctica, knowledge of the distribution at sea and of the fine-scale foraging behaviour of the Emperor penguin is fragmented and limited.

The species is however threatened by the ongoing climate change and the resulting projected sea-ice loss in a very near future around Antarctica. How the species will respond to global change is still uncertain. Acquisition of baseline data on the distribution and activities at sea of the species through the entirety of the life cycle, across all life-history stages, and at different breeding locations around the continent, are required to refine our understanding and the predictive models.

Here, we assessed and revealed the distribution of juvenile and adult emperor penguins in the Atlantic sector of the Southern Ocean throughout the year. We also investigated the fine-scale vertical foraging behaviour of adults from this area. The seasonal distribution and the foraging strategies identified were then compared to data previously collected in an antagonistic environment in the d'Urville Sea region in East Antarctica.

We showed that juvenile and adult emperor penguins from the Atka Bay colony in the Atlantic sector of the Southern Ocean were segregated in time and space throughout the year. We found that chickrearing adults from Atka Bay colony used a core area 20 times smaller than juveniles and 5 times smaller than post-moult pre-breeding adults from this region. Adults from Atka Bay colony performed shallower dives in average than adults from Pointe Géologie. We also identified a switch in the diving effort of the adults from Atka Bay at the beginning of the summer: they appeared to perform 'daytime diving effort' strategy until end of October, and switch to a 'night-time diving effort' strategy for the rest of the season; a strategy that was not expressed by the adults from Pointe Géologie. These results suggest that different prey items are targeted between the birds from the two localities. 3 and Table 5 for details). Tracking data from 2005 were previously published in Zimmer et al. (2007b).

Birds from AB were instrumented either with ARGOS platforms or GPS systems as exposed in Chapter III and birds from PG were instrumented with ARGOS platforms as explained in Zimmer et al. (2007b) (Table 14). Birds were instrumented across different life-history stages (i.e. fledging chicks/juveniles, adults), breeding status (i.e. breeding, non-breeding) and phases (i.e. pre-breeding, incubating, chickrearing, moult) corresponding to different seasons (fall, winter, summer), resulting in five study groups (Table 14).

Deployments on adults were carried out over the summer during the late chick-rearing stage (adABs and adPGs groups), over the fall (after the moult) when birds were mostly not breeding (adABf group), and also in winter during the breeding season at Pointe Géologie colony (adPGw group).

-Chapter V -150 (SGSSIMPA) and the sub-Antarctic MPAs boundaries were downloaded from www.protectedplanet.net (UNEP-WCMC 2020).

The International Union for Conservation of Nature (IUCN)'s range of the Emperor penguin was obtained from www.iucnredlist.org (Birdlife International 2018).

V.3.4.2. Residence time

To assess the intensity of use of features related to conservation management in the Southern Ocean by the tracked birds, we averaged the proportion of time they spent monthly inside each feature, referred hereafter as 'residence time'. We also computed the residence time per individual over the total tracking duration for each bird. Additionally, for each study site and each management feature, we computed the proportion of the distribution area falling inside the boundaries of a particular feature with the R package 'raster' (Hijmans and van Etten 2020).

V.3.4.3. Environmental features (i) Habitat features

To examine the importance of bathymetric depth, the bathymetry covariate at one-minute horizontal spatial resolution was obtained from the ETOPO1 Global Relief Model provided by the NOAA National Geophysical Data Center [START_REF] Amante | ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis[END_REF]. We calculated the slope covariate in degree for each grid cell from the bathymetry values of the eight neighbouring cells using the 'terrain' function from the R package 'raster' (Hijmans and van Etten 2020).

We divided the Southern Ocean in three habitat types to take into account the effect of bathymetry and water movements: 1) The continental shelf break was considered as the area along the continent below the 1000 m isobaths [START_REF] Knox | Biology of the Southern Ocean[END_REF][START_REF] Nicholls | Ice-ocean processes over the continental shelf of the southern Weddell Sea, Antarctica: A review[END_REF]). We then used the classification of Douglass and colleagues (2014) to segregate 2) the Antarctic continental slope area (roughly areas around the continent ranging between 1000 and 4000 m) from 3) the deep ocean (abyssal plain) characterised by a smooth bathymetric slope and depth > 4000 m. Each penguin location was attributed to one of the classes, and the proportions by study group were computed.

(ii) Sea ice

Sea ice concentration values (ranging from 0 to 100%) at particular locations for AB were extracted from Advanced Microwave Scanning Radio meter (AMSR-2) satellite estimates of daily sea ice concentration at 3.125 km resolution from the University of Bremen (https://seaice.unibremen.de/data/amsr2, [START_REF] Spreen | Sea ice remote sensing using AMSR-E 89-GHz channels[END_REF]. Sea ice concentration values for PG were extracted from