Claude Universite

Bernard -Lyon

M François-Noël

Gilly M Le Professeur

Hamda Ben

Hadid M Le Professeur

Philippe Lalle

M Le Professeur

Germain Gillet

M Alain Helleu

Composantes Sante

J Etienne

La Mme

C Professeure

Burillon

D Bourgeois

Vinciguerra

Y Matillon

Mme La Professeure

A-M Schott

Stéphanie Périquet

Hervé Fritz

Marion Valeix

Eléonore Hellard

Nolwenn Drouet-Hoguet

Eloy Revilla

David W Macdonald

Andrew Loveridge

Julia Salnicki

Juliet Banda

Simeon Mudimba

Cynthia Mapendere

Jaelle Claypole

activités anthropogéniques sur le régime alimentaire et la réponse numérique de la hyène tachetée en savane arborée dystrophique dominée par l'éléphant

Being at the top of the food chain, apex predators have the potential to influence the whole community structure through food webs, even within their own guild. In Africa, lions (Panthera leo) and spotted hyaenas (Crocuta crocuta, hyaenas hereafter) are the largest and most numerous predators, with hyaenas often thought to be subordinate to the larger lion Never the less, our understanding of their interactions is limited, even more in wooded ecosystems. This work focuses on identifying the mechanisms allowing for hyaenas and lions to coexist, such as resource and habitat partitioning. The main hypothesis is that hyaenas should avoid lions both spatially and temporally.

A literature review shows that despite the high potential for exploitative and interference competition (high range and diet overlaps), hyaenas are present at nearly all sites occupied by lions and their densities are positively correlated. I collected data on hyaena and lion ecology, through direct observations and GPS collars, during 2.5 years of fieldwork in Hwange National Park (HNP), Zimbabwe. HNP is characteristic of a semi-arid dystrophic wooded savanna dominated by elephants (Loxodonta africana). In HNP, hyaena ecology is largely influenced by the location of artificial waterholes, elephant carcasses and lions. Hyaenas select for habitats where prey are abundant and locations close to artificial waterholes, as do lions. Hyaenas only spatially avoid lions in extreme conditions of vulnerability and risk.

Elephant carcasses are a major source of food for hyaenas and their used increased during a period of increased intraguild competition with lions, which lead to switch in hyaena foraging strategy from active hunting to scavenging. The presence of large carcasses is probably promoting coexistence between the two large carnivores. Encounters with lions at carcasses are common and can occur during several consecutives nights with the two predators staying in the vicinity of each other. However, when not related to food, encounters are very short with both predators often moving away after being in contact.

In stark contrast with the classical hypothesis, hyaenas in HNP do not show a general pattern of lion avoidance. Interactions between these two species are complex and hyaenas appear to respond to lion presence is reactive rather than predictive and very dynamic. Even though lions are their main competitors, in some circumstances hyaenas stay in their vicinity, as they can also be a source of food through scavenging and kleptoparatism. These results bring some light on the mechanisms of interaction and coexistence between large carnivores as well as the impact on management decisions on their ecology that could prove useful for planning their conservation.

COMPOSANTES ET DEPARTEMENTS DE SCIENCES ET TECHNOLOGIE

Les hyènes sélectionnent les habitats riches en proies et près des points d'eau, tout comme le font les lions qu'elles n'évitent que dans des conditions extrêmes de vulnérabilité et de risques.

Les carcasses d'éléphants représentent une ressource alimentaire majeure pour les hyènes qui en ont augmenté leur utilisation en réponse à une augmentation de la compétition avec les lions. La disponibilité de ces carcasses facilite probablement la coexistence entre les deux carnivores. Les rencontres avec les lions autour de carcasses sont communes et les deux espèces peuvent rester à proximité pendant plusieurs nuits consécutives. En revanche, les rencontres non liées aux carcasses sont de très courte durée et les deux prédateurs s'éloignent rapidement l'un de l'autre.

Contrairement à l'hypothèse classique, les hyènes n'évitent pas les lions de manière systématique. Les interactions entre les deux espèces sont complexes et les hyènes répondent aux lions de manière dynamique et réactive plutôt que prédictive. Bien que les lions soient leur plus grand compétiteur, les hyènes restent à proximité dans certaines circonstances, car ils représentent une source alimentaire grâce au charognage et au kleptoparasitisme. Ces résultats apportent de nouvelles connaissances sur les mécanismes de coexistence et d'interactions entre grands carnivores ainsi que sur l'impact potentiel des décisions de gestion sur leur écologie qui peuvent être utiles pour leur conservation.

Introduction

They are few animals, whose history has passed under the consideration of naturalists, that have given occasion to so much confusion and equivocation as the Hyena has done. It began very early among the ancients, and the moderns have fully contributed to their share.

James Bruce, 1970

Large carnivores and ecosystem functioning

Interactions between species have profound effects on natural population dynamics and shape community structure (Chase et al., 2002;Chesson & Kuang, 2008;Hopcraft, Olff & Sinclair, 2010;Johnson, 2010). Ecological theory has long predicted that abundance and distribution of apex predators can deeply influence ecosystem functioning (Hairston, Smith & Slobodkin, 1960;Fretwell, 1987). Nowadays, most of large carnivores species are endangered and their disappearance is bound to have major consequences on the ecosystems they live in.

There is now a growing literature on trophic cascades in which apex predators play a central role (Estes et al., 2011;Ripple et al., 2014). Being at the top of the food chain, they have the potential to influence all the other species downward through food webs in the ecosystem (Hairston et al., 1960;Ripple et al., 2001, see Figure 1). Indeed, predators have direct effects (i.e. lethal) on herbivore populations (Arrow 1 Figure 1) that can be regulated by predation, especially small and medium-size species [START_REF] Erlinge | Can vertebrate predators regulate their prey?[END_REF][START_REF] Sinclair | Does interspecific competition or predation shape the African ungulate community?[END_REF][START_REF] Sinclair | Population consequences of predation-sensitive foraging: the Serengeti wildebeest[END_REF][START_REF] Sinclair | Patterns of predation in a diverse predator-prey system[END_REF]. Carnivores also affect herbivore communities via indirect effects (i.e. non lethal) of predation risk. Prey respond to this "landscape of fear" by switching their habitat (Creel et al., 2005) to altering their movement patterns (Fortin et al., 2005) and adjusting their behaviour (Childress & Lung, 2003). For instance, African ungulates increased their levels of vigilance when lions (Panthera leo) were in the vicinity [START_REF] Périquet | Individual vigilance of African herbivores while drinking: the role of immediate predation risk and context[END_REF]Périquet et al., 2012). Such responses to predation risk can induce a decrease in fitness as prey face a trade-off between acquiring resources and safety. For example, by leaving preferred grassland for the protective cover of woodland when wolves (Canis lupus) are present, elk (Cervus elphus) move to a suboptimal habitat (Creel et al., 2005). By affecting individual fitness, indirect effects of predation risk might have even larger impacts on prey population dynamics than direct ones (Creel & Christianson, 2008). Apex predators affect not only prey, but also smaller mesopredators (Arrow 2 figure 1) whose populations sometimes increase after the removal of a larger species (mesopredator release, Soulé et al., 1988) which can lead to direct ecological and economical losses (Prugh et al., 2009;Ritchie & Johnson, 2009;[START_REF] Ripple | Widespread mesopredator effects after wolf extirpation[END_REF]. For instance, Courchamp et al (1999) showed that control of the cat population in Antarctic islands could lead to an increase of mortality in seabird due to increase predation by rats. Baker et al. (2008) reported that in Australia red foxes (Vulpes vulpes) were responsible for monetary losses more than three times higher that those due to dingoes (Canis lupus dingo), known to regulate fox populations (Glen et al., 2007). However, when it comes to predators, nothing is simple and mesopredators can also benefit from the presence of apex predators though scavenging opportunities (Arrow 3 Figure 1, Wilmers et al., 2003). Additionally, by controlling a given mesopredator species, a large predator can facilitate the existence of another mesopredator (Arrow 4 Figure 1). Large predators via their effects on prey also have the potential to affect vegetation structure and river channel (Beschta & Ripple, 2006;Ripple & Beschta, 2006;Beschta & Ripple, 2009, Figure 1). Wolves have recently been showed to affect grizzly bear (Ursus arctos) diet via a trophic cascade through elk [START_REF] Ripple | Trophic cascades from wolves to grizzly bears in Yellowstone[END_REF]. Knowing that vegetation structure influences predator hunting success (Funston, Mills & Biggs, 2001;Loarie, Tambling & Asner, 2013) and spatial distribution of prey, it can thus ultimately affect carnivore fitness and demography (Arrows 5 and 5' Figure 1). Large carnivores are highly charismatic species and probably the most revered and iconic ones [START_REF] Macdonald | Biology and Conservation of Wild Canids[END_REF]Macdonald & Loveridge, 2010). They also produce significant incomes from tourism across the world (Richardson & Loomis, 2009;[START_REF] Naidoo | Effect of Diversity of Large Wildlife Species on Financial Benefits to Local Communities in Northwest Namibia[END_REF]. Because of this, and their central role in ecosystem functioning, they have been the focus of extensive research [START_REF] Gittleman | Carnivore Conservation[END_REF]Brooke et al., 2014). Numerous endangered species now have dedicated specific conservation programs. Most of these programs used to target unique species such as lions, or cheetahs (Acinonyx jubatus).

However, taking management decisions focusing on one species without taking into account its effect on sympatric predators and the whole ecosystem can have unforeseen deleterious effects on all trophic levels [START_REF] Ripple | Widespread mesopredator effects after wolf extirpation[END_REF] see Figure 1). This is why there was a recent shift to ecosystem conservation, instead of species to species (Estes, 1996;[START_REF] Worm | Biodiversity, productivity and stability in real food webs[END_REF]. Large predators occur at low densities, they are wide ranging and elusive species, many of them active only at night (Carbone et al., 1999;Cardillo et al., 2004;Cardillo et al., 2005). As a consequence, they are difficult and expensive species to study [START_REF] Gittleman | Carnivore Conservation[END_REF]. In the mean time, the advance of telemetry technology during the last decades greatly helped in the understanding of their ecology and many large carnivore species are now followed thanks to GPS (Global Positioning System) collars (e.g. grizzly bear, Ciarniello et al., 2007;wolf, Latombe, Fortin & Parrott, 2013; Iberian lynx -Lynx pardinus-, Palomares, Delibes & Ferreras, 2000). Fine scale and long-term data provided by these collars are the source of a great increase of understanding of large carnivore ecology at an unprecedented level of details. For instance, Valeix et al. (2011) showed how the distribution of artificial waterhole influences movement patterns of lions. Squires at al (2013) used GPS data from Canadian lynx (Lynx canadensis) to predict corridors location necessary to maintain connection between populations.

However, there are still large gaps in our understanding of relationships between large carnivore species. We are just starting to understand how they affect each other space use [START_REF] Van Der Meer | Is the grass greener on the other side? Testing the ecological trap hypothesis for African wild dogs (Lyacon pictus) in and around Hwange National Park, Zimbabwe[END_REF]Broekhuis et al., 2013;Vanak et al., 2013) but have very little knowledge on how the influence each other diet or how they move in relation to each other.

Because such topic requires simultaneous data on several species at the same location and new statistical methods to analyses them (especially movement data), little work has been done in this field. A few studies recently provided new technics and framework to analyse dynamic interactions from GPS data (Long & Nelson, 2012;[START_REF] Benhamou | Movement-based analysis of interactions in African lions[END_REF]Long et al., 2014).

Large carnivores interactions

As for other species, interactions between large carnivores range from competition to facilitation. Competitive interactions are usually divided into exploitative and interference competition. Exploitative competition refers to indirect negative effects where one species uses resources that are then no longer available for others [START_REF] Vance | Interference competition and the coexistence of two competitors on a single limiting resource[END_REF]. It is likely to occur for food when diet overlap is high, which is often the case for carnivores and food is limiting [START_REF] Crooks | Resource utilization by two insular endemic mammalian carnivores, the island fox and island spotted skunk[END_REF][START_REF] Fedriani | Competition and intraguild predation among three sympatric carnivores[END_REF]Azevedo et al., 2006;Hayward & Kerley, 2008). Interference competition on the other hand, is the direct negative effects resulting from one species preventing the other to obtain resources [START_REF] Vance | Interference competition and the coexistence of two competitors on a single limiting resource[END_REF]. These negative interactions can lead to spatial segregation with subordinate species forced to use suboptimal habitat such as the case of red and Arctic foxes (Alopex lagopus), where the former exclude the later from the most productive areas (Hersteinsson & Macdonald, 1992) and best denning locations [START_REF] Linnell | Use of dens by red Vulpes vulpes and arctic Alopex lagopus foxes in alpine environments: Can inter-specific competition explain the non-recovery of Norwegian arctic fox populations?[END_REF][START_REF] Tannerfeldt | Exclusion by interference competition? The relationship between red and arctic foxes[END_REF].

Temporal segregation also has the potential to reduce competition between sympatric carnivores. For instance, black-backed jackals (Canis mesomelas) and side-striped jackals (C. adustus) in Zimbabwe share the same habitat but showed an almost complete avoidance in time (Loveridge & Macdonald, 2003). In addition, there are two types of interference competition that are specific to predators: kleptoparasitism and the extreme case of intraguild predation (Palomares & Caro, 1999;Caro & Stoner, 2003;[START_REF] Donadio | Diet, morphology, and interspecific killing in Carnivora[END_REF], see Figure 2: Diagram of interactions between two species of large carnivores. Both species indirectly affect each other though prey via exploitative competition but also when prey shift their habitat or adjust their behaviour to one predator. By killing prey, large predators also provide each other kleptoparasitism and scavenging opportunities. In addition, large carnivores directly influence each other via interference competition ranging from habitat shift and changes in movement patterns to intraguild predation.

Figure 2). Kleptoparasitism refers to the theft of food acquired by one species by another one, and thus results in one species being negatively impacted because it has to expand additional energy to compensate for its loss. Kleptoparasitism can be particularly detrimental to species in which hunting techniques are energetically costly such as the African wild dogs (Lycaon pictus, Gorman et al., 1998). Their populations are thought to be limited by this negative form of interaction with larger species such as lions and spotted hyaenas (Crocuta crocuta, Creel & Creel, 1996;Creel & Creel, 1998). Encounter between two carnivores with behavioral and morphological adaptations for killing are common and can lead to direct mortality that is referred to as intraguild predation (Palomares & Caro, 1999;[START_REF] Arim | Intraguild predation: a widespread interaction related to species biology[END_REF][START_REF] Donadio | Diet, morphology, and interspecific killing in Carnivora[END_REF]. The killer rarely benefit directly from the killing through consumption [START_REF] Kotler | Predation and competition: the interaction of two types of species interactions[END_REF] but rather indirectly by removing a competitor (Case & Gilpin, 1974).

In addition, a large carnivore species can also benefit form coexisting with another one providing scavenging opportunities (Pereira, Owen-Smith & Moleón, 2013). For example, coyotes (Canis latrans) scavenge from carcasses killed by wolves throughout the year [START_REF] Switalski | Coyote foraging ecology and vigilance in response to gray wolf reintroduction in Yellowstone National Park[END_REF]. Coexistence between large predators is thus a complex balance between direct and indirect competition and facilitation.

The African large carnivore guild

In Africa, species diversity is especially high and the large carnivore guild is composed of at least five species: lion, spotted hyaena, leopard (Panthera pardus), wild dog and cheetahs.

While wild dogs and cheetahs are almost exclusively predators (eating only what they kill), at least part of the meat consumed by the other three species comes from scavenging. They can thus benefit from kills made by any other species by using the carcass when the killer is gone (scavenging sensu stricto) or by chasing it (kleptoparatism). The outcome of interactions between them varies depending on the species involved, the group size of both parties [START_REF] Carbone | The Costs of Carnivory[END_REF] but also on the circumstances (Kruuk, 1972;Schaller, 1972;Cooper, 1991). Vanak et al. (2013) recently showed that wild dogs response to the risk of encountering lions depends on the season. While they avoid locations recently used by lions during the dry season, they were much more risk-prone during the wet season. A similar response has been found in cheetahs (Broekhuis et al., 2013). Disappearance or over abundance of one species can thus affect them all, and thus ultimately influence the whole ecosystem. In addition, where predators co-occur, their effects on prey population can by synergistic and not only additive (Schmitz, Hawlena & Trussell, 2010;Ripple et al., 2014).

For instance, while bears (Ursus sp.) usually prey on juvenile elk, wolves kill predominantly adults and the two predators thus have different impact on prey population dynamic (Barber-Meyer, Mech & White, 2008;Ripple & Beschta, 2012). As most large predator populations are now increasingly confined within protected areas, they are bound to interact with each other at higher rates. There is thus an urgent need in better understanding how they coexist with each other (Ripple et al., 2014). Many authors have studied the impact of lions on cheetahs and wild dogs, both endangered species (Creel & Creel, 1996;Creel & Creel, 1998;Durant, 1998;Durant, 2000;[START_REF] Durant | Factors affecting life and death in Serengeti cheetahs: environment, age, and sociality[END_REF]. However, we still lack a strong knowledge on lions and spotted hyaenas coexistence despite numerous studies hinting at the complexity of its mechanisms (Cooper, 1991;Honer et al., 2002;Trinkel & Kastberger, 2005).

Spotted hyaenas and lions: coexistence between two "eternal enemies"

Spotted hyaenas (hyaenas hereafter) are the most numerous large predator in Africa, but have long been considered as scavengers, feeding from and stealing lion kills until Hans Kruuk (1972) shed some light on their ecology with his long-term study in the Serengeti and Ngorongoro Crater. He was the first to show that hyaenas are actually efficient hunters, playing an important role in the ecosystems, and that lions also scavenged from them, no only the other way around. Many studies on hyaenas followed, however most of them in open ecosystems. All of them stress the fact that relationships between hyaenas and lions are complex and dependent on their context. While in some ecosystems, hyaenas mostly scavenged from lions, the opposite happens in other ecosystems. In Etosha NP, hyaenas always lose their kills to lions (Trinkel & Kastberger, 2005), but they only lose about 5% in the Ngorongoro (Kruuk, 1972). Group sizes of both lions and hyaenas, as well as the presence of an adult male lion, have been shown to influence the outcome of competitive interactions between the two species (Cooper, 1991;Honer et al., 2002;Trinkel & Kastberger, 2005). One study also showed that competition with lions has a negative effect on hyaenas reproductive success (Watts & Holekamp, 2008).

Being the tow largest predators, hyaenas and lions have a strong potential to affect prey populations as well as smaller sympatric carnivores, and ultimately the whole food-web ecosystem functioning [START_REF] Fritz | A food web perspective on large herbivore community limitation[END_REF]. It is of crucial importance, both for our general knowledge of ecosystem functioning and for conservation purposes to better understand the mechanisms allowing hyaenas and lions to coexist.

Spotted hyaena biology

Hyaena (Figure 3) is the largest species to the smallest carnivore family, the Hyaenidea, containing only four members today (brown hyeana -Hyaena brunea-, striped hyaena -Hyaena hyaenaand aardworlf -Proteles cristata-, Figure 4).

Hyaenidae reached their peak of diversity and distribution during the early Pleistocene (0.5 millions years ago) when nine species were recorded and their closest relative family is the Viverridae (Civets and genets, Figure 4). Hyaenas are thus more closely related to Felids than Canids. Hyeana is a strongly dimorphic species with females bigger than males and weighting on average 55 kg (males 45kg) and reaching 70 kg (Mills, 1990) in some southern African populations. They form large groups called "clans" characterised by a strict matriarchal hierarchy, where females are dominant over males (Kruuk, 1972) and by a dynamic of fission-fusion. Hyaenas are extremely vocal, especially around carcasses and during interactions with other carnivores. Female genitalia are extensively masculinised, with a clitoris transformed into a fully erectile pseudo-penis (Frank, Glickman & Powch, 1990). One to three cubs per litter are born (with eyes open and teeth erected) in dens and are dependant on their mother milk on average for the first year of their lives (Kruuk, 1972). Hyaenas are opportunist and highly flexible, capable of taking down large prey such as zebras and elephant calves (Salnicki et al., 2001) and well adapted to scavenging thanks to very strong jaws and efficient digestive system (Kruuk, 1972). They also successfully kleptoparasite sympatric carnivores species (Kruuk, 1972;Honer et al., 2002;Watts & Holekamp, 2009) and take advantage of human refuse (Kolowski & Holekamp, 2008;Kolowski & Holekamp, 2009). When their main prey is not available, they can switch to another prey species or change their foraging behaviour (from hunting to kleptoparasitism, Honer et al., 2002).

Hyaena population is estimated between 27 000 and 47 000 individuals, with several populations exceeding 1 000 mostly in East and Southern Africa [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. They have a wide distribution south of the Sahara desert with the exception of tropical rain forests in West and Central Africa (Figure 5). Even though they are classified at "least concern" by the IUCN [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF], their population is decreasing across their range manly because of habitat loss, natural prey shortage and conflict over livestock depredation [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. However, they are still doing quite well compared to other carnivore species such as lions and wild dogs. Some life history traits of hyaenas are described in more details in the different chapters of this PhD.

Hyaenas and lions in wooded savannas

Most studies on hyaenas have been conducted in open areas where behavioural observations and following the animals for extended period of time is possible. However, hyaenas also inhabit wooded savannas. Out of the 68 scientific papers used for the literature review (Chapter 1), 25% present data from the open plains of East Africa (Serengeti/Ngorongoro and Masai Mara ecosystems) and an additional 23.5% from desert areas (Etosha National Park -NP-, Namib NP and Kalahari NP). The only wooded area with a substantial amount of data on hyaenas is Kruger NP, South Africa. [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF] The development of GPS radio-collars with relatively long lasting batteries now allows to develop long-term studies in ecosystems with low accessibility for researchers (e.g. Kruger NP, Owen- [START_REF] Goodall | Coping with savanna seasonality: comparative daily activity patterns of African ungulates as revealed by GPS telemetry[END_REF]Yellowstone NP, Winnie et al., 2006) and to follow animal movement and activity with unprecedented accuracy (Valeix et al., 2011;Loarie et al., 2013). However, publications based on such data from hyaenas are recent despite the early use of VHF (Very High Frequency) telemetry by Kruuk since 1972 andscarce (Cozzi et al., 2012;Broekhuis et al., 2013;Cozzi et al., 2013) with only one focusing on hyaenas (Stratford & Stratford, 2011).

With so few detailed GPS data on hyaenas, it is no surprise that we know very little on their fine scale interactions with lions. For example, when we know that they are both found in the richer patch in terms of prey (Durant, 1998;Durant, 2000), we do not know if use these patched at the same time or is there some extent of temporal partitioning. Hyaenas and lions have often been observed interacting around carcasses (e.g. Kruuk, 1972, Copper, 1991, Trinkel, 2005) but how do they come together at these carcasses? How these carcasses influence their movement patterns? And how do they move depending on each other? Do they follow each other? Many questions remain unanswered about the coexistence between these two apex predators in Africa.

PhD focus

The aim of my PhD is thus to contribute to a better understanding of the interactions between large predators and the mechanisms of their coexistence based on a case study of hyaenas and lions. I investigate the ecological and behaviour mechanisms of the response of hyaenas to the presence of lions. To reach my goal, I collected long-term and fine-scale observational and GPS data on hyaena ecology in a wooded savanna such as population estimation, home range and clan sizes, diet, habitat use and movement. Strong from this knowledge, I intend to determine how the presence of sympatric lions influences hyaena ecology in a wooded savanna.

dens. In addition, I tested whether hyaena tend to move away from lions or to follow them as they could provide kleptoparasitism and scavenging opportunities.

Hyaenas and lions in Hwange National Park, Zimbabwe

Data presented here were collected in the Main Camp area, located in the Northwestern part of Hwange National Park (HNP), Zimbabwe (Figure 6a). HNP vegetation is characteristic of a dystrophic savanna dominated by bushlands and bushed woodlands (Rogers, 1993 and Figure 6b, but also see Chapter 4) where observing and following animals is extremely difficult. Herbivore community in HNP is largely dominated by elephants (Loxondonta africana, making up for more the 25% of the prey community, Figure 6c, Chamaillé-Jammes et al., 2009). HNP is semi-arid with a wet season from November to April and a dry season from May to October. The long term mean annual precipitation averages 600 mm (CV= 25%). Natural depressions collect rainwater but most of them dry out during the dry season, when water is artificially supplied in about 50 waterholes spread throughout HNP (Figure 6c).

Hyaena research in HNP started in 1999 with the Hyaena Research Project [START_REF] Teichmann | Spotted hyaena research[END_REF], and was followed by a PhD study in 2004-200 (Drouet-Hoguet, 2007). These two studies were mainly based on direct observations and a few VHF radio-collars. A large amount of data on the general ecology of spotted hyaena in Hwange was then collected, including population size and diet. Since 2009, I deployed 12 GPS collars on adult females belonging to four clans in the Main Camp area. These allowed for a fine-scale remote monitoring of hyaena locations and movements across a study area of about 1 500 km 2 (Figure 6a). GPS data were used to estimate territories sizes, study habitat selection and movement pattern, as well as to identify dens and feeding sites based on GPS clusters. I also conducted direct observations of hyaenas on a daily basis to collect data on their social, foraging and feeding behaviour as well as their interactions with lions.

The Hwange Lion Research from Wildlife Conservation Research Unit (WildCRU, Oxford University, United Kingdom) has studied lions in HNP since 1999 (Loveridge et al., 2007;Loveridge et al., 2010) and now most of the female prides and male coalitions in the study area are followed thanks to GPS collars. This created a unique opportunity to study the dynamic of the interactions between hyaenas and lions using simultaneous fine-scale GPS data (hourly location at night for both species).

Thesis overview

I first review the literature looking for general patterns in hyaenas and lions competitive interactions across the African continent. I extracted all available data on hyaena clan and lion pride size, their home range size, diet, feeding and foraging group sizes, main cause of mortality for hyaenas and the issues of competitive interactions. Results of this meta-analysis are presented in Chapter 1.

To help filling the gaps in the literature, Chapter 2 describes the general ecology of spotted hyaena in a wooded savanna, and compares it to observations made in open areas.

This chapter uses data collected over 14 years in HNP and presents general results on density, clan size, ranging behaviour and territoriality. I use multiple types of data such as population estimates by calling exercise, direct observations, GPS data from collars and scats analysis. I discuss the importance of artificial waterholes and elephant in structuring hyaena ecology.

In Chapter 3, I study the long term potential for and consequences of exploitative competition between hyaenas and lions. Between 1999 and 2013, lion demography (density, pride size and adult sex ratio) changed drastically following a moratorium on lion trophy hunting around the protected area in 2005. This provided a near experimental context to study the influence on competition pressure from lion on hyaena diet. I compare hyaena diet composition and prey preferences between the 2 periods (before and after the moratorium) using scat data as well as carcasses detected thanks to GPS clusters from collared hyaenas. I then focus on interference competition between lions and hyaenas. Optimal foraging theory states that animals face a trade-off between acquiring resources while minimizing their predation risk. Hyaenas should then favour places rich in prey while avoiding encountering lions. But the picture is more complex, as lions also represent a potential source of food for hyaena through scavenging and kleptoparatism. Based on GPS data from hyaena and lion collars, I analyse how the risk of encountering lions influence fine scale hyaena habitat selection in Chapter 4 using Resource Selection Functions (RSFs).

At a finer scale, I analyse on the impact of predation risk (proxies and real risk) on den selection and attendance patterns in hyaenas. The results are presented in Chapter 5. I use data from GPS collars to identified den used by hyaenas. Each den was the characterised by its distance to the closest waterhole, its number of entrances and its visibility (i.e. vegetation density), all proxies of predation risk. Each den was also associated to a predation risk depending on its location within or outside a lion core home range (HR, 50% Kernel). I compare these characteristics of dens used by hyaena to those of control holes, selected randomly in the study area. I also use real-time GPS data from lion to study how their presence on the vicinity of a den affects its attendance by hyaenas.

In Chapter 6, I focus on the dynamics of the interactions between hyaenas and lions. I first describe hyaena movement characteristics in terms of distance travelled, speed and path sinuosity and compared them to those of lions. I also study how distance to a waterhole, predation risk by lions and moonlight influence these parameters. I provide measures of static and dynamic interactions between the two species as well. On a finer scale, I identify encounters between collared lions and hyaenas and analyse their characteristics and outcome depending on their location (habitat type, waterhole, carcass) and time (season, moon phase).

The last part of the manuscript is a synthesis and general discussion putting this work into perspective and drawing conclusions about large carnivore ecology and implication of their competitive interactions for species and ecosystem conservation. I also underline the effects of management decisions regarding artificial waterholes on large carnivore ecology and interactions.

Chapter 1

The Lion King and the Hyaena Queen: Large carnivore interactions and coexistence

INTRODUCTION

Large predator coexistence and conservation

Interactions between species have profound effects on natural population dynamics and community structure [START_REF] Estes | Sea otters: their role in structuring nearshore communities[END_REF][START_REF] Menge | Community regulation: variation in disturbance, competition, and predation in relation to environmental stress and recruitment[END_REF][START_REF] Paine | Direct and indirect effects of peregrine falcon predation on seabird abundance[END_REF][START_REF] Bengtsson | Competition and coexistence in plant communities[END_REF]. This is particularly true for large mammalian carnivores, many of which act a keystone species in the top-down control of terrestrial ecosystems (see review Estes et al., 2011). As such, their removal is thought to release other predator populations with consequences at other trophic levels (Terborgh, 1992;McLaren & Peterson, 1994;Palomares et al., 1998;Berger & Gese, 2007). Despite the increasing interest in trophic interactions, few studies have documented the interactions of top carnivores, partly because few systems host a diversity of them, and hence little is know about the consequences of a shift of dominance between top carnivore species.

These charismatic predator species are also flagships for conservation and produce significant tourism income, especially in Africa (Dalerum et al., 2008). The safekeeping of viable large carnivore populations is essential to ecosystem equilibrium, but this cannot be ensured without understanding how they affect each other.

Interactions between species range from facilitation to direct predation, through competition.

Facilitation occurs when interactions between organisms benefit at least one of them and cause harm to neither [START_REF] Bertness | Positive interactions in communities[END_REF]. For instance, [START_REF] Mcnaughton | Serengeti migratory wildebeest: facilitation of energy flow by grazing[END_REF] shown that Thomson's gazelles (Eudorcas thomsonii) prefer to feed in areas already grazed by wildebeests (Connochaetes taurinus) as these areas produce young green regrowth which is not found in ungrazed areas. Gazelles take advantage of this growth stimulated by the grazing, and so benefit from the wildebeest. Despite their importance in ecological processes, these positive interactions have been far less studied than negative ones.

On the other hand, competition can be defined in a stricter sense as interactions between individuals that lead to reduced fitness [START_REF] Wiens | The ecology of bird communities. Volume 2: processes and variations[END_REF]. However, this competition sensu stricto is very difficult to demonstrate in field studies. Competitive interactions are usually divided into exploitative and interference competition. Exploitative competition refers to indirect negative effects where one species uses resources that are then no longer available to others [START_REF] Vance | Interference competition and the coexistence of two competitors on a single limiting resource[END_REF]. It is likely to occur when food is limiting and diet overlap is high, which is often the case for carnivores [START_REF] Crooks | Resource utilization by two insular endemic mammalian carnivores, the island fox and island spotted skunk[END_REF][START_REF] Fedriani | Competition and intraguild predation among three sympatric carnivores[END_REF]Azevedo et al., 2006;Hayward & Kerley, 2008). Interference competition on the other hand, is the direct negative effect resulting from one species preventing the other from obtaining resources [START_REF] Vance | Interference competition and the coexistence of two competitors on a single limiting resource[END_REF]. These range from interspecific territoriality (Durant, 1998(Durant, , 2000a, b), b), kleptoparasitism (Cooper, 1991;Creel & Creel, 1996) and ultimately intraguild predation which constitutes an extreme case of interference competition and affects many species (Palomares & Caro, 1999;[START_REF] Donadio | Diet, morphology, and interspecific killing in Carnivora[END_REF]. Most theoretical and empirical studies have focused on exploitative competition, which contrast with the omnipresence of interference competition. Competition can have profound effects on populations, resulting in behavioural responses, changes in space and habitat use, reductions in population size and even local extinction (Creel & Creel, 1996;Durant, 1998;[START_REF] Vucetich | Ecological interactions, social organization, and extinction risk in African wild dogs[END_REF]Durant, 2000a, b;[START_REF] Creel | Four factors modifying the effect of competition on carnivore population dynamics as illustrated by African wild dogs[END_REF][START_REF] Kamler | Impacts of coyotes on swift foxes in northwestern Texas[END_REF][START_REF] Durant | Factors affecting life and death in Serengeti cheetahs: environment, age, and sociality[END_REF][START_REF] Ripple | Wolves and the Ecology of Fear: Can Predation Risk Structure Ecosystems?[END_REF]Fortin et al., 2005;Hayward & Kerley, 2008).

However, competing species can live sympatrically, and it has been suggested that resource partitioning can promote coexistence. In such cases, the realized ecological niche of the competitors differs from each other. A competitively inferior species can escape competition by using different areas, finding empty patches (spatial avoidance, e.g. Durant, 2000a) or using the same patch but at different times (temporal avoidance, e.g. Hayward & Slotow, 2009). This leads to a reduction in interspecific competition and thus facilitates coexistence (Durant, 2000a;Broekhuis et al., 2013). In most cases, the situation is complex as the coexistence simultaneously generates costs and benefits for both species. For example, spotted hyaenas (Crocuta crocuta) and lions (Panthera leo) in Africa. They both prey on medium to large size herbivores, kleptoparasitise from each other and scavenge from each other's kills (Kruuk, 1972;Schaller, 1972;[START_REF] Switalski | Coyote foraging ecology and vigilance in response to gray wolf reintroduction in Yellowstone National Park[END_REF]Hayward & Kerley, 2005;Hayward, 2006;Atwood & Gese, 2008).

The African savanna presents a unique opportunity to study the coexistence between large carnivores as it is one of the few remaining ecosystems with complete guilds of both predators and prey. As the largest and most abundant large carnivores, spotted hyaenas (hereafter hyaenas) and lions have profound effects on smaller carnivores such as African wild dogs (Lycan pictus) and cheetahs (Acinonyx jubatus, (Creel & Creel, 1996;Durant, 2000a;Durant, 2000b) and prey population dynamics [START_REF] Erlinge | Can vertebrate predators regulate their prey?[END_REF][START_REF] Sinclair | Does interspecific competition or predation shape the African ungulate community?[END_REF]Sinclair et al., 1985;[START_REF] Sinclair | Population consequences of predation-sensitive foraging: the Serengeti wildebeest[END_REF]. Even though their potential for competition is high (Hayward, 2006), hyaena and lion distributions overlap extensively with lions sharing nearly 95% of their range with hyaenas (Fig. 1). This overlap is likely to rise, as they are both increasingly restricted to protected areas (PA) due to human encroachment, and the subsequent habitat and prey losses (Packer, 1990;[START_REF] Castley | Estimation of the lion (Panthera leo) population in the southwestern Kgalagadi Transfrontier Park using a capture-recapture survey[END_REF][START_REF] Kissui | Top-down population regulation of a top predator: lions in the Ngorongoro Crater[END_REF]. Within some of these PAs, predator densities are increasing locally (especially in small fenced reserves, Hayward et al., 2007a), as is competition for food and space thus increasing the impact of potential competition on their long-term viability [START_REF] Riggio | The size of savannah Africa: a lion's (Panthera leo) view[END_REF].

However, there is a paucity of literature on the mechanisms by which lion and hyaena coexist. Many detailed studies have been conducted on each species separately, while to our knowledge there has been only one comprehensive study of lions and cheetahs across their range (Watts & Holekamp, 2008) .

In order to further our understanding of the mechanisms by which predators coexist, we reviewed the available literature on lions and hyaenas searching for critical parameters relating to their cohabitation. We used a meta-analysis to identify the parameters affecting the extent of competition and/or facilitation between these two species.

We start with a short description of hyaena and lion life histories based on available data for their densities and different population parameters (group size, adult sex ratio, foraging group size). We then evaluate their diets and overlap across their range to measure the potential of exploitation competition. We review the evidence for potential direct competition such as kleptoparasitism and predation. We also investigate mechanisms (prey age selection, scavenging opportunities) that could facilitate their coexistence. Finally, we stress the fact that there are still many gaps in our knowledge and that more research is necessary to better understand coexistence between lions and hyaenas in particular, and large predators in general.

Life history of two large predators

Spotted hyaenas and lions are the biggest and most abundant large predators in Africa (Cardillo et al., 2004). Being at the top of the food chain, they share some of their characteristics but are different in many ways. Spotted hyaenas are the largest member (45-60kg) of the Hyaenidae family. Their estimated total population is between 27 000 and 47 000 with several populations exceeding 1 000 mostly in East and Southern Africa [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. They have a wide distribution south of the Sahara desert with the exception of tropical rain forests in West and Central Africa (Fig. 1). They live in matriarchal societies with a strict hierarchy (among each sexes, with females dominant over males) unique among carnivores. Groups, or clans, are characterised by of fission-fusion dynamic, forming foraging groups (hunting or looking for food to scavenge) which are variable in composition and size (Kruuk, 1972). Clans are highly territorial when prey resources are stable but boundaries between clan territories can fade when prey are nomadic or migrant (Kruuk, 1972;Mills, 1990;Hofer & East, 1993a, b). Hyaenas are predominantly crepuscular and nocturnal, but can also be active during the day during the cold winter months (Kruuk, 1972;Mills, 1990;Hayward & Slotow, 2009;Cozzi et al., 2012).

Hyaenas are efficient hunters, killing up to 95% of their prey (Cooper et al., 1999). Their hunting success averages 33% (Holekamp et al., 1997) and can reach 92% depending on prey species (Kruuk, 1972;Mills, 1990). Hyaenas are cursorial predators, relying on their endurance to take down their prey after chases up to several kilometres (Kruuk, 1972;Mills, 1990). Their preferred prey body mass range is 56-182 kg (Hayward, 2006). They are highly flexible in their foraging strategies and will readily scavenge of carcasses left by other predators (Kruuk, 1972;Cooper, 1991;Creel & Creel, 1996;Honer et al., 2002;Watts & Holekamp, 2009). Moreover, large groups are capable of stealing carcasses from other predators including lions while they are still present (e.g. Kruuk, 1972;Cooper, 1991;Creel & Creel, 1996;Honer et al., 2002). Long-term changes in prey populations have been shown

to trigger functional responses and changes in foraging behaviour (e.g. Honer et al., 2002). In the Ngorongoro Crater, hyaenas respond to changes in prey guild composition by switching to species easier to hunt and increasing kleptoparasitism from lions (Honer et al., 2002). When anthropogenic food resources are available, hyaenas may change their foraging behaviour to use those additional resources (Kolowski & Holekamp, 2008). Hyaenas may influence sympatric carnivores and prey species, whose populations are suspected to be affected, and sometimes limited, by hyaena predation (Kruuk, 1972;[START_REF] Vucetich | Ecological interactions, social organization, and extinction risk in African wild dogs[END_REF]Durant, 2000a;[START_REF] Creel | Four factors modifying the effect of competition on carnivore population dynamics as illustrated by African wild dogs[END_REF]. Hyaenas are therefore a key species in most of the African ecosystems.

Lions are the second biggest member of the Felidae family. Their population is currently estimated at between 32 000 and 35 000 individuals [START_REF] Riggio | The size of savannah Africa: a lion's (Panthera leo) view[END_REF]. Bauer et al (2008) with the IUCN SSC Cat Specialist Group estimated that 42% of major lion populations are declining, particularly those outside PAs. Lions are a dimorphic species, with males weighting 150 -225 kg and females 122 -192 kg (Sunquist & Sunquist, 2009). They have a wide habitat tolerance but are not found in dense lowland forests, and are now largely constrained to PAs (Riggio et al., 2012, Fig. 1). Lions are the most social of all the felids and live in fission-fusion groups, the foundation of which is a group of related females and their offspring (Packer et al., 1990). Male lions are transient to the pride and often form single sex coalitions of related males during sub-adulthood and adulthood (Schaller, 1972). Lions display male-biased dispersal, but some females (around one third) do disperse [START_REF] Pusey | The evolution of sex-biased dispersal in lions[END_REF] Lions are mostly sedentary but some populations follow migratory movements of their prey (Schaller, 1972). Each pride defends its own territory from neighbouring prides.

Lions usually hunt at night, resting during the day (Schaller, 1972;Sunquist & Sunquist, 2009). Lions hunt predominantly medium to large size ungulates (Hayward & Kerley, 2005).

They ambush their prey from cover and manage to run them down over short distances (a few to a hundred meters, Loarie et al., 2013). In the Serengeti, 30% of stalks are successful when several individuals hunt together, but this drops to 17-19% when hunting alone (Schaller, 1972). Their preferred prey body mass range is 190-550 kg (Hayward & Kerley, 2005). Lions readily scavenge and it is relatively easy for them to chase cheetahs or wild dogs from their kill, but fights with spotted hyaenas at carcasses can be lethal for both species. Because of the rapidly growing human population, lions are in closer proximity with humans and are renowned livestock killers, fostering intense conflicts with populations leaving along side them. Retaliatory killing is one of the main cause of death in some areas and can cause population decline [START_REF] Frank | People and predators in Laikipia District, Kenya. In People and wildlfie: conflict or coexistence[END_REF]Woodroffe & Frank, 2005;Kissui, 2008;[START_REF] Chardonnet | Managing the conflicts between people and lion[END_REF][START_REF] Funston | Population characteristics of lions (Panthera leo) in the Kgalagadi Transfrontier Park[END_REF]. On the other hand, lions have a high economic value for game viewing and trophy hunting [START_REF] Loveridge | People and wild felids: conservation of cats and management of conflicts[END_REF][START_REF] Lindsey | The significance of African lions for the financial viability of trophy hunting and the maintenance of wild land[END_REF].

Coexistence between lions and hyaenas is thus a complex balance of competition and facilitations (Figure 2 summarizes our current understanding of their interactions). The goal of this review is to provide detailed information on the extents of these two mechanisms and their impact in shaping both carnivores life histories.

MATERIAL AND METHODS

Data collection

We gathered data on hyaenas, lions and their prey across Africa from a total of 148 publications (see Appendix 1 for a full list of all references used). These studies were From the point of view of the spotted hyaenas, lions have a negative impact on live prey and both a positive (predation) and negative (scavenging) on the availability of carrion. Lions also have a direct negative effect on hyaenas through intra guild predation. Live prey and carrion availability both have a positive effect on hyaenas through predation and scavenging. Lions thus have a positive effect on hyaenas providing scavenging and kleptoparasitism opportunities. The situation is symmetrical from the point of view of lions except that there is barely any mortality directly due to hyaenas.

(average 681.3 ± 48.6 mm). For two locations (Ngorongoro NP and Katavi GR), we found detailed information for two different time periods, thus both were included in building a final dataset of 44 studies.

Diet estimation

We pooled raw data (number of prey eaten per species for each location based on direct observations and scat analyses) to assess the diet composition of each predator for each site.

Prey were also assigned to size classes based on their 75% of their female adult weight [START_REF] Jooste | Effect of prey mass and selection on predator carrying capacity estimates[END_REF], see Appendix 2) and diet based on the prey classes were also computed for each site. These diets were used to calculate diet overlap and breadth for each study site.

Overall diet composition was calculated as the average of the proportion of each species in the diet across all sites (sum of all proportions can thus be above 1). We then polled all the raw data together without any distinction by location to estimate proportion of each prey items in each predator diet and used this to calculate the overall diet breadth and overlap for hyaenas and lions. Species occurring in very low proportions in the diets such as porcupine, ostrich, rodents or birds, as well as predator species were all regrouped in a class named "other" for both analyses.

We used the Levin's index [START_REF] Smith | Niche breadth, resource availability, and inference[END_REF] to define niche breadth for lions and hyaenas. We then used Pianka's niche overlap indexes (Pianka, 1973) and the percentage overlap (Krebs, 1989) to estimate diet overlap between the two species.

Statistical analysis

We estimated range overlap between the two species using spatial data from IUCN database [START_REF] Bauer | Panthera leo. IUCN Red List of Threatened Species[END_REF][START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. We first calculated the total area of overlap and the proportion of overlapping area for each species. We used Pearson and Spearman correlation tests and linear models to look for any statistical relationships between the variables of our dataset.

All statistical analyses were performed in R 3. 0.2 (R development Core Team, 2013).

Results are presented with standard errors (SE) unless otherwise specified.

PREDATOR POPULATION CHARACTERISTICS AND DIET

Predator populations

Hyaena density ranges from 0.005 to 1.8 individuals/km 2 (average 0.39 ± 0.10, number of studies n = 27). Total clan size and adult clan size respectively ranged from 3.8 to 60.1 (30.84 ± 7.39, n = 10) and from 1.2 to 34.7 (14.97 ± 4.27, n = 8). Lion density ranged from 0.0015 to [START_REF] Van Orsdol | Ecological correlates of lion social organization (Panthera leo)[END_REF]Hayward et al., 2007c). For any given ecosystem, hyaenas are more numerous than lions. Hyaena clans are bigger in areas with higher prey biomass (ρ = 0.80, p = 0.005, n = 9) but interestingly lion pride size is not to be correlated to any prey abundance parameter. Clan size increases with hyaena density (ρ = 0.83, p = 0.031, n = 9) indicating that at higher density hyaenas form larger groups rather than more groups.

The average foraging group size for hyaenas is 2.6 ± 0.28 (1.3-4.8, n = 13). Indeed, hyaenas are reported to usually forage alone (75% of the time) for small prey items, but also to form large groups to take down big prey (Holekamp et al., 1997). However, they feed in groups averaging 7. 73 ± 1.48 individuals (3.4-16.7, n = 9). These group sizes are neither correlated with clan size nor with prey abundance. Lions forage in groups ranging from 1.5 to 5.23 individuals (3.54 ± 0.28, n = 20). Similar hyaenas, foraging group size in lions is not correlated with pride size or prey abundance. Adult sex ratio of lions average 0.43 ± 0.04 male per female (0.18-0.90, n = 15).

Lion home range (HR) size obtained by minimum convex polygons (MCPs) and Kernels isopleths average 209.33 ± 113.19 km 2 and range from 29.5 to 1 112.5 km 2 (n = 10). Hyaena

HRs average 178 ± 79.19 km 2 (n = 15) ranging from 24.5 to 1 095 km 2 . For both carnivores, HR size is inversely correlated to prey abundance (lion-total prey density ρ = -0.79, p = 0.007, n = 9; hyaena-total prey biomass ρ = -.83, p < 0.001, n = 13). This result is in accordance with those from [START_REF] Loveridge | Changes in home range size of African lions in relation to pride size and prey biomass in a semi-arid savanna[END_REF] showing that lion HR size decreased as prey biomass increased. Hayward et al. (2009) also showed that lion territory sizes were correlated with preferred prey availability. In addition, hyaena HR size is inversely correlated with their density (ρ = -0.86, p < 0.001, n = 14) and clan size (ρ = -0.77, p = 0.01, n = 10) and lion HR size is negatively correlated with lion density (ρ = -0.71, p = 0.017, n = 10) but was not link to pried size (ρ = -0.47, p = 0.35, n = 6).

Hyaena:lion ratio, calculated for 26 locations as the ratio between hyaena and lion densities, averages 5.68 ± 1.59 hyaena per lion (ranges: 0.28 -36.36). This ratio was not correlated with any of the studied parameters.

Predator diets

Hyaena diet is composed by 33 food items and their main prey are gemsbok (41.3% ± 19.5), springbok (29.8% ± 23.5), wildebeest (28.3% ± 8.0), impala (22.7% ± 7.1) and zebra (17.5% ± 5.1) where they occur. Lion feed on 35 food items and their main prey are wildebeest (24.6% ± 3.8), buffalo (21.9% ± 3.5), kob (20.2% ± 5.0), roan (15.4% ± 4.5) and hartebeest (15.0% ± 5.1) where they occur (see Table 1).

Both predators prey mostly on medium size ungulates (45.1% of lions diet and 41.5% of hyaena diet, Table 2) but hyaenas seem to rely more on smaller prey (31.8%) than do lions, which eat more large prey (20.1%). Proportions of very large prey and other types of prey are also higher in hyaena diet (14% and 13.2% respectively against 7.6% and 6.2% in lions).

Overall, there appears to be no significant differences between lion and hyaena diets in term of prey size classes eaten (Freidman ℵ 2 = 9.1429, df = 5, p = 0.104), which is in accordance with findings of Hayward (2006).

The proportion of medium sized prey consumed by both predators increases with the ratio of this prey type within the prey population (hyaenas: ρ = 0.62, p = 0.023, lions: ρ = 0.62, p = 0.004). Lions consume less large and very large size prey as the ratio of medium size prey increases (large prey ρ = -0.62, p = 0.004; very large prey ρ = -0.74, p = 0.004) showing a tendency to prefer medium size prey. This is in accordance with Hayward et al. (2006) Predator effects on each other

Hyaena and lion densities are positively correlated (ρ = 0.56, p = 0.003, n = 26, Fig. 3b) suggesting that competition does not lead to mutual exclusion at the population level. Lion and hyaena densities are therefore mainly driven by abundance of their prey rather their main competitor. Hyaena HR size decreases as the lion density increases (ρ = -0.77, p = 0.01, n = 10). Hyaena foraging group size decreases with increasing adult pride size (ρ = -0.95, p = 0.004, n = 6).

Prey abundance appears to be key to understand the mechanisms of coexistence between hyaenas and lions, although not in a simple way. The more prey, the more these predators are able to coexist with each other, i.e. the competition pressure decreases with increasing prey abundance. However, increasing prey abundance leads to an increase in both predators' densities, thus possibly increasing interference competition, as they are more likely to encounter each other. Further, as prey abundance increases so does hyaena clan and foraging group sizes while their HR decreases. All these combine to enable hyaenas to better sustain competition with lions: as they form bigger groups, more clan members share a smaller territory and are thus quickly recruited in case of conflict. Therefore, as prey abundance increases, hyaenas are more able to protect their kills or to aggressively take over lion kills.

We expected a positive correlation between lion pride size and hyaena foraging group size, since both predators would be better able to defend their kills or chase the other off theirs.

However, in spite of the low sample size (n = 6), we found a negative correlation between these two variables which is somewhat surprising It is interesting to note, that pride size does not seem to be related to prey abundance. However, pride size might be more related to local prey availability rather than the global one (Hanby & Bygott, 1995;Mosser et al., 2009). In addition, pride members do not spend all their time together and the sometimes split in different groups that can hunt independently (Schaller, 1972). Increasing prey abundance could lead to the formation of larger foraging groups in hyaena thereby increasing the risk of lions losing their kills and decreasing their chance of stealing hyaena prey. In this case, it would be beneficial to lions to form smaller prides being less conspicuous when on the move, and tackling smaller prey which can be quickly consumed, hence reducing the time spent at carcasses. If this holds true, it would demonstrate that competition with hyenas actually has an impact on lion group forming patterns as suggested by Cooper (1991).

Overall, it appears that if prey abundance is reduced, despite predator densities decreasing and hence their encounter rate, competition pressure is likely to increase and local competitive exclusion may occur. We tested these hypotheses using published data on the intensity of competition between the two species. We expected diet overlap, kleptoparasitism and direct killing to increase with decreasing prey abundance.

THE POTENTIAL FOR COMPETITION BETWEEN HYAENAS AND LIONS

Dietary breadth and overlap

Dietary breadth (Levin's index) is higher for hyaenas (Table 3). This is in accordance with their eclectic diet and opportunistic feeding behaviour. Pianka's index is also higher for hyaenas indicating that they proportionally share more of their prey with lions than vice versa (Table 3). The overall percentage of diet overlap between these two predators is high (over 68%) and matches the value of 68.8% for the preferred prey species overlap obtained by Hayward (2006). This suggests that there is a strong potential for exploitation competition between lions and hyaenas.

Kleptoparasitism

From 13 studies conducted in ten locations in Southern Africa, it is clear that kleptoparasitism occurs both ways. It is however impossible to know to what extent this activity contributes to the predator diets. Hyaenas appear to lose more of their kills to lions than vice versa (Wilcoxon test, W=27, p=0.015, Table 4). Despite this, hyaenas do not lose more food to lions in term of food biomass than they gain from them (W=14, p>0.05, Table 4), neither do lions to hyaenas (W=5, p>0.05, Table 5). Somewhat surprisingly, both predators obtain an identical amount of food from the other (W=5.5, p>0.05, Table 4).

Hyaenas most probably compensate for the loss of their kill by obtaining more food from lions by scavenging their leftovers. Hyaenas are well equipped to acquire nutrients from carcasses due to their very efficient digestive system and strong jaws, allowing them to make use of skin, bones and dry meat where lions cannot (Kruuk, 1972). Kleptoparasitism success has been suggested to depend on the ratio of hyaenas to lionesses and large cubs at a kill and/or the presence of adult male lions. This suggests that lion foraging group size can have an impact on hyaenas. Only two studies (Cooper, 1991 in Savuti, Botswana;Honer et al., 2002 in Ngorongoro Crater, Tanzania) looked in detail at the ratio lionesses:hyaenas at kills and both conclude that the more hyaenas, the higher the chance they displace lions from kills or keep their own. Cooper (1991) showed that to take over a kill, hyaenas had to outnumber lions by a factor 4. This ratio is linked to clan and pride sizes, and hyaena foraging group sizes, as well as territory sizes. Indeed, the larger the clan and the smaller the territory, the easier and quicker it is for hyaenas to recruit clan members and therefore to access/defend a kill. In Etosha NP, where hyaenas failed to recruit enough clan members scattered over large territories, they were unable to steal kills from lions and to defend their own kills (Trinkel & Kastberger, 2005).

Three studies report the effect of the presence of an adult male lion on the outcome of encounters at carcasses. They all conclude that if at least one male is present, hyaenas will almost always lose their kill and never access a lion kill. In the Ngorongoro Crater, [START_REF] Honer | The effect of prey abundance and foraging tactics on the population dynamics of a social, territorial carnivore, the spotted hyena[END_REF] reported that when a male lion was present at a carcass, hyaenas never attempted to acquire it before the male left. Cooper (1991) showed that in the Savuti region, Botswana, when hyaenas were chased away by a male lion they usually left the scene, whereas if only lionesses and cubs were present, they remained in the vicinity of the carcass. McTaggart Cowan (1978) report that male lions never abandoned their kills to hyaenas whereas lionesses sometimes do. Furthermore, prides with males obtain between 10% to 40% of their food from hyaenas instead of 7% for a pride of females. Hyaenas seem to fear male lions much more than lionesses and this might be due to the fact that male lions are a higher cause of mortality than lionesses (see section 4.3).

However, we were not able to detect any pattern suggesting an effect of lion group size (clan, pride, foraging group) or adult sex ratio in lions on kleptoparasitism intensity. This might be due to a very limited number of locations where figures for these parameters are available (n < 6). Based on the previous results, it appears that no species is permanently dominant when it comes to food related interactions, but the issue of such interactions rather depends on the ecosystem in which they occur. If at least an adult male lion is present, then hyaenas are subordinate. However, if the lion group is composed only of lionesses and subadults, then the numerically dominant species wins the encounter In some areas, one species may benefit more from the other (Kruuk, 1972;Schaller, 1972;Cooper, 1991;Honer et al., 2002), while in others, neither of them has a clear advantage (Mills, 1990) .

Intra guild predation

Lions were to kill hyaenas in 16 studies (six locations, Table 5). Ten of them report lions, particularly adult males, as being a primary cause of mortality for both adult and juvenile hyaenas (Kruuk, 1972;Watts & Holekamp, 2008, 2009). Most of predation events on adults hyaenas occur at kills during fights with lions. There is little information on hyaenas killing lions, although a cub was reported being killed in the Serengeti (Schaller, 1972) and an old lioness in Hwange NP (Loveridge et al., 2010a). Lionesses are also sometimes severely injured in fights with hyaenas. Although, we could not find any correlation between the intensity of direct killing of hyaenas by lions and prey abundance (prey total density: ρ = -0.31, p = 0.56, prey total biomass: ρ = 0, p = 1), this could be due to our very limited sample size (six locations).

Spatial and temporal overlap

Both species overlap in there distribution to a wide extent. Lions share 94.9% of their overall distribution range with hyaenas, while only share 33.6% of their distribution with lions (Fig 1).

Hyaenas are generalists in their habitat requirements, as they do not need vegetation to hide themselves while hunting. We can therefore suppose that they will use whichever habitat where prey are most abundant. On the contrary, the hunting tactic of lions requires some degree of concealment: hunting success increases in taller grass (Funston et al., 2001) and when the terrain provides concealment in a general way (Schaller, 1972;[START_REF] Elliott | Prey capture by the African lion[END_REF]Van Orsdol, 1984;Davidson et al., 2012). In addition, lion appear to favour habitat were prey are more easily caught rather than were the are more abundant (Hopcraft et al., 2005). Lion optimal habitat seems to be open woodland with thick bush and grass complexes that provide shade to rest and cover to ambush prey (Sunquist & Sunquist, 2009). Davidson et al., (2012) showed that within their HR, lions select for bushed grassland and open areas around waterholes, both characterised by high prey density. However, in their study on cheetah, Broekhuis et al. (2013) showed that lions and hyaenas select for mixed woodland and grassland while avoiding swamps in Moremi GR, Botswana. Mills and Biggs (1993) also noted that in Kruger NP (South Africa) both hyaena and lions favour thickets with high concentrations of impalas. A more recent study [START_REF] Schuette | Occupancy patterns and niche partitioning within a diverse carnivore community exposed to anthropogenic pressures[END_REF] showed that patterns of occupancy of mixed-used landscapes in Kenya were very similar between lions and hyaenas.

For instance, they both favoured habitat close to water and highest occupancies were found in the protected area. This suggests that both species can prefer the same habitat, most probably where prey are more abundant, thus increasing their probability of encounter.

Both predators are reported to be mainly nocturnal and crepuscular (Kruuk, 1972;Schaller, 1972;Mills, 1990;Kolowski et al., 2007). Both can also be active during cool winter days. In the Okavango Delta, Botswana, Cozzi et al. (2012) showed that respectively 60% and 68% of lions and hyaenas activity budget was at night, thus leaving little room for temporal partitioning. These results are comparable to those of Hayward & Slotow (2009) showing an overlap in activity period of more than 80% between hyaenas and lions. However, [START_REF] Schuette | Occupancy patterns and niche partitioning within a diverse carnivore community exposed to anthropogenic pressures[END_REF] showed that even though both were predominantly nocturnal, their activity peaks were slightly different. Hyaenas seem to be active a couple of hours after sunset and before sunrise, while lions are more active during the middle of the night.

To date, there is no study using telemetry data on both species simultaneously to evaluate any form of spatio-temporal avoidance. It is possible that depending on prey and predators population parameters such as density, group size or lion adult sex ratio, hyaenas would avoid (risk of kleptoparasitism and predation) or follow lions (kleptoparasitism and scavenging opportunities). 1987-1992[START_REF] Lamprey | Estimation of the large mammal densities, biomass and energy exchange in the Tarangire Game Reserve and the Masai Steppe in Tanganyika[END_REF]-19691966-1969Hofer & East (1995) Kruuk ( 1972) Schaller (1972) CONDITIONS FOR FACILITATION

Resource partitioning in prey size

Hyaenas are much smaller than lions, and although they do hunt in groups, we expected that both predators would select for prey of different body size, at least to some extent [START_REF] Kissui | Top-down population regulation of a top predator: lions in the Ngorongoro Crater[END_REF]Hayward & Kerley, 2005;[START_REF] Donadio | Diet, morphology, and interspecific killing in Carnivora[END_REF]Hayward, 2006). Main prey for lions and hyaenas are medium-size herbivores (Tables 1 &2) and when their ratio in the prey population (number of medium-size prey/number of total prey) increases, hyaenas

and lions both increase the proportion of medium-size ungulates in their diet. Hoverer, hyaenas seem to make more use of small and very large prey than do lions (Table 2).

A priori, we expected dietary breadth to decrease with increasing prey abundance as the availability of preferred prey would increase. Niches should also increasingly differ with increasing prey abundance. In addition, we expected diet overlap to be lower in areas rich in prey, as there should be more of a resource partitioning with hyaenas switching to small and very small prey, leaving the rarer medium prey to lions.

Hyaena dietary breadth seems to be independent of prey richness. However, lion dietary breadth significantly decreases with increasing total prey biomass (ρ = -0.51, p = 017, n = 22) and with total prey density. In addition, we found that Pianka's index for hyaenas significantly decreases with increasing small prey biomass (Spearman correlation, ρ = -0.76, p = 0.025, n = 10) and small prey biomass ratio in the prey community (ρ = -0.67, p = 0.039, n = 10).

Percentage overlap also decreased with increasing small prey density ratio in the ecosystem (ρ = -0.68, p = 0.035, n = 10) as does the overall Pianka's index (ρ = -0.61, p = 0.037, n = 10).

All these results suggest that the increasing availability of small prey in an ecosystem allow hyaenas to make more use of them, tending to reduce their niche overlap with lions.

In medium, large and very large size prey, juveniles are much smaller than adults and easier to kill, providing yet another opportunity for niche partitioning between hyaenas and lions. We found that the proportion of juveniles in hyaena diet was significantly higher than in the lion diet (ℵ 2 = 98.75, df = 1, p < 0.0001, Table 6). This result is in accordance with these of Mills (1984b) in the Kalahari desert, Kruuk (1972) in the much richer Serengeti ecosystem and Mills and Biggs (1993) in Kruger NP. By preying on different age classes within the same prey species, lions and hyaenas reduce their niche overlap.

Scavenging opportunities and food gains from the other species

Here, we define scavenging in the strict sense as a species consuming food left by another species with no actual fight or confrontation. This food is thus cost free for the finder. It is very difficult to quantify scavenging benefits from another species as it would require knowing all kills made by the two species over a certain period of time, the amount of food left and also all the carcasses at which they fed. In any case, both hyaenas and lions are efficient scavengers so they can potentially benefit from what the other leaves behind.

However, hyaenas would probably gain more from scavenging from lions left overs as they can use remains that lions cannot, like bones and skin; whereas lions would need more meat to be left in the carcass for it to be profitable.

Scavenging appears to be more beneficial to hyaenas, making up 5% of their diet in the Ngorongoro Crater (Kruuk, 1972;Palomares et al., 1999), 36.3% in the Kalahari (Mills, 1984b) and as much as 80% in the Timbavati GR (Bearder, 1977). As for lions, between 1% and 42% of their food is scavenged, most of it coming from hyaenas (Schaller, 1972;Elliott & McTaggart-Cowan, 1978;Hanby et al., 1995). Once again, there is a difference between sexes as in lionesses appear to scavenge less (~7% of their food) than do males (up to 40%, Elliott & McTaggart-Cowan, 1978;Sunquist & Sunquist, 2009) Overall, hyaenas obtain (from scavenging and kleptoparasitism) between 0% and 20% (Kruuk, 1972;Henschel & Skinner, 1990;Gasaway et al., 1991;Honer et al., 2002) of their food from lions and loose between 0.6 and 22% of their own to lions (Kruuk, 1972;Cooper, 1991;Cooper et al., 1999;Watts & Holekamp, 2008, Table 4). In Amboseli NP, Watts and Holekamp (2008) reported that hyaenas lose 0.2 kg/day of meat to lions, but gain a bit less than 0.3 kg/day, leading to a net benefit of 0.05 kg/day of meat. Thus, by coexisting with lions hyaenas gain only 1.5% of the 3.5 kg they have to ingest daily (Kruuk, 1972). However, in the Masai Mara, the same study reported that hyaenas were not able to benefit in such a way from lions and they actually lose 0.16 kg/day of meat to lions. This shows that dominance between competing species depends on the ecosystem, but that overall the loss and gain are minimal compared to their overall daily requirements.

CONCLUSION

(1) Both hyaena and lion population densities are linked to that of their prey and thus positively correlated with each other (Hayward et al., 2007c). Their diets are very similar (see Hayward, 2006) but there are some ways by which they minimise their niche overlap, most probably by preying on different prey size (species or age classes). Figure 5 summarizes our findings in a schematic. Our results show here that when prey abundance is high, large foraging groups of hyaenas could have a negative impact on lion pride size. This would mean that at low prey density, hyaena pressure on lion group size would be released allowing lions to form bigger groups and to outcompete hyaenas at carcasses, potentially leading to a reduced abundance of hyaenas. This situation is unlikely to happen in PAs where prey densities are usually stable, but it could be the case for areas outside these PAs. However, in unprotected areas, lion densities are low due to their conflict with humans (retaliatory killing) and trophy hunting [START_REF] Chardonnet | Managing the conflicts between people and lion[END_REF].

(2) While exploitation competition most likely plays an important role in shaping large carnivore communities [START_REF] Loveridge | The impact of sport-hunting on the population dynamics of an African lion population in a protected area[END_REF], the impact of interference competition should not be neglected and more research is needed to better understand large carnivore guild functioning. For instance, there is little data published on the spatio-temporal use of their habitat so it is impossible to conclude on the role of this competition. In addition, most of the studies were conducted in open areas, but interactions are likely to be different in closed savannas. For instance, it is much more difficult for predators to detect carcasses in dense habitat, thus the extent of kleptoparasitism may be reduced in such areas [START_REF] Balme | Feeding habitat selection by hunting leopards Panthera pardus in a woodland savanna: prey catchability versus abundance[END_REF]. Habitat heterogeneity in space and time has a crucial role in facilitating coexistence of hyaenas and lions, as it does for cheetahs (Mills et al., 2004;[START_REF] Balme | Feeding habitat selection by hunting leopards Panthera pardus in a woodland savanna: prey catchability versus abundance[END_REF]Broekhuis et al., 2013). Further research is needed on their simultaneous resource use (food, space and time) to be able to identify the mechanisms behind their coexistence, and thus increasing our understanding of how best both species could be maintained within small PAs.

(3) It is important to note that with populations within PAs averaging 936 ± 232 hyaenas (10-5148) and 519 ± 136 lions (15-4095), any tip in the competition balance can have dramatic effects. For instance, if prey base is reduced, prey guild composition is modified or habitat is changed, this could lead to one species outcompeting the other resulting in local extinction. For instance, an increase in the small prey community should favour hyaenas more than lions. In addition, hyaenas and lions can have strong effects on sympatric carnivore species. Indeed, increasing competition pressure with lions and hyaenas is thought to be responsible for decrease of wild dog populations inside PAs (Durant, 1998) and could be responsible for their local extinction (Creel & Creel, 1996;[START_REF] Van Der Meer | Is the grass greener on the other side? Testing the ecological trap hypothesis for African wild dogs (Lyacon pictus) in and around Hwange National Park, Zimbabwe[END_REF]. A recent series of papers (Packer et al., 2013a;Packer et al., 2013b) argue that fencing is a solution for lion conservation. However, within small fenced areas, lion population need to be actively managed as their populations are rapidly increasing, raising concern bout the impact of predation on prey communities [START_REF] Miller | Management of reintroduced lions in small, fenced reserves in South Africa: an assessment and guidelines[END_REF]. In these small fenced areas, it would thus be possible that if lion populations are not artificially reduced, they would outcompete hyaenas and lead to their local decline and possibly extinction. Large PAs, where both predators and prey are free to roam over large distances seem to be highly relevant for the conservation of these carnivores, particularly for lions, and for the maintenance of their role in the food chain and ecosystem processes. (1967( ) 1968[START_REF] Peters | Scent-marking in wolves[END_REF][START_REF] Rudnai | Reproductive biology of lions (Panthera leo massaica Neumann) in Nairobi National Park[END_REF]( , 1979) ) Rudnai (1974,1979) East Africa (continued) (1989,1991) Gasaway et al.

(1991) [START_REF] Berry | Abnormal levels of disease and predation as limiting factors for wildebeest in the Etosha National Park[END_REF]; Gasaway et al. (1989, 1991) 1985-198917,680 Standers (1991, 1992) Gasaway et al. (1991) 10,000 Mills (1984aMills ( , 1984bMills ( , 1990)); [START_REF] Broomhall | Home range and habitat use by cheetahs (Acinonyx jubatus) in the Kruger National Park[END_REF][START_REF] Eloff | Lion preation in the kalahari gemsbok national park[END_REF]; [START_REF] Mills | Some population characteristics of the lion Panthera leo in the Kalahari Gemsbok National Park[END_REF]; [START_REF] Eloff | Food ecology of the Kalahari lion Panthera leo vernayi[END_REF]; Mills (1984bMills ( , 1990) Mills (1990) 1979-1984Mills & Gorman (1987) Katavi (1987,1990,1991); Mills & Biggs (1993); Mills et al. (2001) Mills & Biggs (1993); Mills et al. (1995[START_REF] Frank | Social organization of the spotted hyaena (Crocuta crocuta): I. Demography[END_REF]-1993235 Mills & Shenk (1992); Mills et al. (1995) Mills & Shenk (1992); Mills & Biggs (1993); Mills et al. (1995) 1933-194619,485 Pienaar (1969) Pienaar (1969( ) 1954( -1966( 19,485 Pienaar (1969) ) Pienaar ( 1969) [START_REF] Pienaar | Predator-prey relationships amongst the larger mammals of the Kruger National Park[END_REF]) 1974-197819,485 Smuts (1976, 1979) Madikwe

2001

Predator population data

We extracted all available data on hyaena and lion densities (27 study sites for hyaenas, 40

for lions), adult and total hyaena clan/lion pride size (adult clan size n = 10, total clan size n = 8, adult pride size n = 12 and total pride size n = 15), foraging size (hyaena n = 13 and lion n = 20) and home range (HR) size (hyaena n = 15, lions n = 10). For lions total pride size included all individuals while adult pride size includes only adult females and large cubs. For hyaenas, adult clan size includes only adult and sub-adults.

Prey density and biomass

We also extracted data on ungulates i.e. prey densities in each sites. We use total prey densities as the sum of densities of all species (hippopotamus, ostriches and apes were never accounted for, see Appendix 2). We also calculated densities of different prey size classes when publications provided densities by prey species. We calculated prey biomass (75% of adult female weight) based on unit weights from Coe et al. (1976) and [START_REF] Wilson | Handbook of the Mammals of the World[END_REF]. Missing data from some publications were obtained from other works conducted in the same location and during the same time frame.

Kleptoparasitism and scavenging intensity

Fourteen studies provided details on the kleptoparasitism and scavenging intensity between hyaenas and lions. We thus extracted the percentage of kills from one species at which the other one was present, the percentage of kills lost to the other species and the percentage of food (in terms of biomass) obtained from and lost to the other species. Kills were attributed to a given species either when the hunt and/or kill was directly observed or when predation marks on the carcasses allowed to identify the killer. We also extracted the percentage of carcasses (killed or scavenged) at which the two species were seen feeding irrespectively of the killer species.

Diet estimation

For sites where diet was recorded for several lion prides, hyaena clans or at different periods, we pooled all the data together to obtain diet composition for each site. The complete data set provided 59 diet compositions in 13 different sites for hyaenas and 78 diet compositions in 31 different sites for lions. Diet estimation for hyaenas was balanced between scats (n=26) and feeding observations (n=33) but was skewed toward direct observations for lions (74 versus 4 estimations based on scat data). Diet based on the prey classes were also computed for each site.

We used the Levin's index [START_REF] Smith | Niche breadth, resource availability, and inference[END_REF] where pi is the proportion of prey item i in the carnivore diet to define niche breadth for lions and hyaenas. We then used Pianka's niche overlap indexes (Pianka, 1973) for species j and species k where and are the proportion of food item i in species j and k diets, respectively. We also used Pianka's index symmetrical for both species (i.e. niche breadth are considered the same) and the percentage overlap defined as (Krebs, 1989) to estimate diet overlap between the two species. We calculated Levin's index for 14 sites for hyaenas and 33 sites for lions, and were able to calculated niche overlap for 11 sites (i.e. where diet composition was known for both species and prey availability was know as well). We did not investigate prey preferences.

Hyaena and lion range overlap

We estimated range overlap between the two species using spatial data from IUCN database [START_REF] Bauer | Panthera leo. IUCN Red List of Threatened Species[END_REF][START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. We calculated the total area of overlap and the proportion of overlapping area for each species.

1 ( p i ) 2 i ∑ α jk = p ij p ik i ∑ p ij 2 i ∑ α kj = p ij p ik i ∑ p ik 2 i ∑ p ij ik p α jk = α kj = p ij p ik i ∑ p ij 2 × p ik 2 i ∑ i ∑ ( min( p ij , p ik ) i ∑ ) ×100 Appendix 1.3
Proportion of each prey species in lion and hyaena diets.

n gives the number of studies reporting a given prey to be eaten by the predator. Bold italic numbers represent main prey species.

INTRODUCTION

Apex predators act as keystone species in the top-down control of prey populations (Sinclair, Dublin & Borner, 1985;Borner et al., 1987;[START_REF] Sinclair | Patterns of predation in a diverse predator-prey system[END_REF], but also of other predator populations with mesopredator release documented on several occasions (McLaren & Peterson, 1994;Palomares et al., 1998;Berger & Gese, 2007).

Ultimately, they can initiate trophic cascades in terrestrial and aquatic systems [START_REF] Menge | Indirect effects in marine rocky intertidal interactions webs: patterns and importance[END_REF]Ripple et al., 2013), and can have profound consequences for ecosystem functioning (see review Estes et al., 2011). Large predators can also be the source of significant income (tourism, trophy hunting), and they are charismatic species, being some of the most admired animals (Dalerum et al., 2008).

Spotted hyaenas (Crocuta crocuta, hyaenas hereafter) are the most abundant large predators in Africa (Cardillo et al., 2004). Their estimated population worldwide is between 27 000 and 47 000 individuals with several populations still exceeding 1 000 mostly in East and Southern Africa [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]. Despite the fact that hyaenas are classified as "least concern" by the IUCN [START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF], their number is decreasing especially outside protected areas and they nowadays occupy 73% of their historical range (Ripple et al., 2014). They have a wide distribution south of the Sahara desert with the exception of tropical rain forests in West and Central Africa. They live in matriarchal societies unique among carnivores. Groups, or clans, are characterised by a dynamic of fission-fusion (Kruuk, 1972) forming foraging groups highly variable in composition and size. Clans are highly territorial when prey resources are stable but boundaries between clan territories can fade when prey are nomadic or migrant (Kruuk, 1972;Mills, 1990;Hofer & East, 1993a;Hofer & East, 1993c). Hyaenas are predominantly crepuscular and nocturnal (Kruuk, 1972;Mills, 1990). Contrary to popular beliefs, they are efficient hunters, killing up to 95% of their prey (Cooper, Holekamp & Smale, 1999). Their hunting success averages 33% (Holekamp et al., 1997) and can reach 92% depending on prey species (Kruuk, 1972;Mills, 1990). They are highly flexible in their foraging strategies and carcasses left by other predators also represent a source of food (Kruuk, 1972;Cooper, 1991;Creel & Creel, 1996;Honer et al., 2002;Watts & Holekamp, 2009). Moreover, large groups are capable of stealing carcasses (kleptoparasitisme) from other predators, including lions, while they are still present (Kruuk, 1972;Cooper, 1991;Creel & Creel, 1996;Honer et al., 2002). Hyaenas strongly influence both sympatric carnivores and prey species, whose populations are suspected to be affected, and sometimes limited, by hyaena predation (e.g. wildebeest; Kruuk 1972) and are therefore a key species in most African ecosystems.

Most of the current knowledge of hyaena ecology comes from studies in open ecosystems, the plains of East Africa (Kruuk, 1972;Hofer & East, 1993a;Hofer & East, 1993c;Hofer & East, 1993b;Honer et al., 2002) or deserted areas in Southern Africa such as the Kalahari (Mills, 1990) and Etosha National Parks (NP, Gasaway, Mossestad & Standers, 1989;Gasaway, Mossestad & Standers, 1991;[START_REF] Trinkel | Spotted hyenas (Crocuta crocuta) follow migratory prey. Seasonal expansion of a clan territory in Etosha, Namibia[END_REF][START_REF] Trinkel | A keystone predator at risk? Density and distribution of the spotted hyena (Crocuta crocuta) in the Etosha National Park, Namibia[END_REF][START_REF] Trinkel | Prey selection and prey preferences of spotted hyenas Crocuta crocuta in the Etosha National Park, Namibia[END_REF]. A few detailed studies have been conducted in wooded ecosystems, such as Moremi (Cooper, 1989;Cooper, 1990;Cooper, 1993) and Kruger NP (Henschel & Skinner, 1987;Henschel & Tilson, 1988;Henschel & Skinner, 1990a;Henschel & Skinner, 1990b;Mills & Biggs, 1993) mainly on group size and diet. Behavioural observations are difficult in such woodland savannas but the recent development of GPS (Global Positioning System) telemetry, combined with various more standard survey methods, now allows for collection of fine scale and long-term data on hyaena ecology (ranging behaviour, habitat use, feeding ecology).

Here, we present results from the 14-year monitoring of a hyaena population in the wooded

DATA COLLECTION

Study area

HNP is located in north-western Zimbabwe (19°00'S, 26°30'E), covering an area of approximately 14,600 km 2 (Figure 1). The study area (≈ 1 500 km 2 ) is located in Main Camp area in the northern part of HNP characterized by Kalahari sand soils. The vegetation is primarily bushland and woodland savanna, interspersed with small patches of grassland (Rogers 1993). HNP is semi-arid with three seasons commonly defined as wet (November to April but most rain from December to March), early dry (May to June) and late dry (August to October). The long-term mean annual precipitation is 600 mm (CV = 25%). Availability of surface water to animals is primarily from rainwater collected in natural depressions.

However, most of these do not hold water during the late dry season, when water is artificially supplied in about 50 waterholes spread throughout HNP (Figure 1). The most abundant herbivores are elephant, buffalo (Syncerus caffer), giraffe (Giraffa camelopardalis), plains

Hyaena density estimation

We conducted annual callings (i.e. sound playback surveys) between 1999 and 2012 (total of 10 surveys). Calling surveys were conductedn the late dry season (between August and October) and were 12 months apart to avoid habituation. All calling stations were located in open areas surrounding waterholes (Figure 2). To allow for comparability, we used the method developed by Mills, Juritz and Zucchini (2001) in Kruger National Park, South Africa whose ecosystem is very similar to HNP in terms of vegetation structure. Mills et al. (2001) assumes that hyaenas would respond to a call when they are within 3.2 km of the station and we used this value to estimate hyaena density in Hwange. To minimize the chances that an individual could hear and answer to two different calling stations, they were at least 10 km apart. Broadcasts were conducted in the absence of rain and in weak or still winds. We used a MP3 player and a speaker (MegaVox 6000 Anchor, 2 watts / 126 dB at 1 m) to broadcast a 5 minutes long tape 3 times with 5 minutes silent intervals from the roof of a vehicle. We used recordings of bleating wildebeest (Connochaetes taurinus), hyaenas competing on a kill and social interactions between hyaenas to lure hyaenas to the station. During the broadcast, the speaker was turned by 90° every 75 secondes to ensure the sound was broadcasted equally in all directions. At the end of the calling, we remained at the station for an additional 20 min.

All individuals approaching the vehicle were counted, and their sex and age were recorded when possible. Hyaenas are notoriously difficult to sex in the field, thus we do not present any data on sex ratio. From 2010 to 2012, we conducted callings at all stations within a given clan home range on the same night, therefore we could estimate the clan size as the total number of hyaenas responding to the calls that night. However, only adults and sub adults independent from the dens respond to the calls, thus our estimates do not include small cubs.

Hyaena feeding and foraging group sizes

We collected opportunistic data of foraging and feeding group sizes whenever we saw hyaenas. We drove within the study area at least five nights per week to monitor hyaena location and behavior. We recorded any hyaena encounter by GPS location and time, their activity, group size and composition. We observed hyaenas feeding on 96 carcasses (killed or scavenged).

Data on foraging group size were collected each time hyaenas were seen moving about but neither on a carcass nor resting. We observed a total of 800 foraging groups and classified them into the following sizes: alone, small (2-4), medium (5-7) and large (>7). From 2009 to 2013, we also recorded the exact numbers of hyaenas in each foraging group (n=97).

Hyaena spatial data

From July 2009 to October 2013, nine adult females belonging to four different clans were equipped with GPS radio-collars (African Wildlife Tracking, UHF 407, GPS collar with UHF download and VHF transmitter). Collars were programmed to take one GPS fix every hour from 16:00 to 06:00 and one fix at 10:00 and 14:00 making a total of 17 fixes per 24 h. Collar accuracy was about 16 m and 7 m in wooded and open areas respectively. Collars recorded GPS locations of individuals from 7 to 22 successive months. We collected a total of 57 672 locations (an average 6 400 locations x individual, ranging from 1 259 to 8 478 locations).

Collar success rate at acquiring GPS location was 98%.

Hyaenas were immobilized by a professional team either with a standard mix of 500 mg We tracked collared hyaenas from a vehicle using a four-element yagi antenna and VHF (Very High Frequency) receiver (Icom IC-R20). We followed them as long as the vegetation permitted. Data from GPS collars were downloaded using a downloading console and a USB UHF modem on a monthly basis whenever possible, either directly by the observer or retrieved from automatic downloading stations (African Wildlife Tracking, range of download: ~300 m) located at waterholes.

DATA ANALYSIS

Hyaena abundance, clan size and foraging group size

Hyaena annual population densities were calculated using the following equation:

where . We assumed a probability of response of 100% meaning that all hyaenas hearing the broadcast within the 3.2 km radius respond to it and approach the vehicle. We tested for correlation between foraging group size and clan size, as well as feeding group size and clan size, using Spearman correlation test.

Home range analysis

We defined total HRs and HR core areas for each individual using 95% and 50% kernel isopleths calculated using location-based kernel density estimation (LKDE, [START_REF] Worton | Kernel methods for estimating the utilization distribution in homerange studies[END_REF].

We used fixed kernel density estimator using the reference smoothing factor h ref as recommended by Hemson et al (2005). We chose this method to provide HR sizes comparable with those of other studies. For each individual, we also calculated HR and core overlaps with individuals belonging to the same clan or to neighboring clans (there was no overlap between non neighboring clans).

We first tested if LKDE HR and core sizes were correlated with clan size using a Spearman correlation test. We used Wilcoxon tests to assess seasonal variation in LKDE HR and core size. We counted the number of artificial waterholes and total number including natural ones within each individual LKDE HR. We calculated the distance between each pair of artificial waterholes within clan LKDE HR. For each clan HR, we tested if the average distance between artificial waterholes was correlated with clan LKDE HR and core size using a Spearman correlation test.

Habitat selection

We assessed the third order habitat selection (Johnson, 1980) where habitat use of each animal is compared to habitat availability within its home range. We used a vegetation map with a 30 m resolution divided into six classes of vegetation structure varying in their cover:

open grassland, sparsely bushed grassland, bushed grassland, bushland, bushed woodland and woodland (Chamaillé-Jammes, unpublished work). For each individual, we defined total HRs and HR core areas using 95% and 50% kernel isopleths estimated from movement-based kernel density estimation (MKDE, Benhamou & Cornélis, 2010;Benhamou, 2011). The MKDE method was developed by Benhamou et al. (2010;2011) and improves the spatial resolution of utilization distributions (UDs) by taking advantage of movement information provided by the serial correlation between successive locations. We defined the available habitat as the non-weighted proportion of each habitat type within the 95% MKDE. The habitat used was defined as the UD-weighted proportion of each habitat type. UD-weighted habitat use has previously been use to assess habitat selection [START_REF] Millspaugh | Analysis of resource selection using utilization distributions[END_REF][START_REF] Vanak | Multi-scale resource selection and spatial ecology of the Indian fox in a human-dominated dry grassland ecosystem[END_REF][START_REF] Monsarrat | How Predictability of Feeding Patches Affects Home Range and Foraging Habitat Selection in Avian Social Scavengers?[END_REF]. For each vegetation class and individual, we computed the Manly's selection ratio defined by the used proportion of vegetation type divided by its availability proportion (Manly, McDonald & Thomas, 2002). We tested individual and overall habitat selection using Chi-square tests with Bonferroni corrections and the function widesII (package adehabitaHS) in R software.

Use of waterholes

Artificial waterholes are a key resource during the dry season, as they are the only ones containing water. However, all waterhole areas, including around natural waterholes, are important during the wet season as they constitute open grasslands intensively used by numerous grazers and mixed feeders species. We first tested if hyaenas selected for areas close to waterholes (artificial or natural) using the same method as for habitat selection. Each cell of the UD was assigned a distance class to the closest waterhole: 0-1 km, 1-2 km, 2-4 km, 4-6 km, 6-8 km and >8 km. We then calculated the MKDE UD-weighted distance to water and used the function widesII to compare it to the availability within individual MKDE UDs.

From GPS data, we selected hyaena fixes within 250 m of a waterhole (i.e. within open areas surrounding waterholes) and calculated the duration of each visit as the time span between the first and the last point within 250 m, each successive fix being not separated by more than 2 h. We also calculated the monthly frequency of visits per waterhole for each season.

Data extraction and statistical analyses were performed in R 3.0.2 (R development Core

Team, 2013) and averages are given ± standard deviation (SD).

RESULTS

Hyaena population abundance and group sizes

Hyaena density was stable between 1999 and 2012 (Table 1) and average density was 0.09 ± 0.02 individuals/km 2 (range 0.07-0.14). Based on callings from 2010 to 2012, average clan size was 13.9 ± 5.7 individuals (not including dens dependant cubs) ranging from 7 to 27.

Foraging group sizes ranged from 1 to 8 individuals (average 2.1 ± 1.7). Hyaena foraged most of the time alone (58.4%) and in small groups of 2 to 4 individuals (23.4%), followed by medium sized groups (12.6%) and large groups only 5.6% of the time. Foraging group size was not linked to clan size (Spearman correlation test: S=12, df=2, p=0.9). We observed hyaenas feeding on 96 occasions in groups ranging from 1 to 19 individuals (average 5.0 ± 3.9). We observed hyaenas feeding on 40 elephant carcasses and their group size was not significantly different from when they fed on other species (t=-1.33, df=92.7 2,p=0.19).

Mean feeding group size did not correlate with clan size (Spearman correlation test: S=12, df=2, p=0.9).

Home ranges

Average global LKDE HR size was 239.3 ± 71.2 km 2 (range: 134.1-359.9) and core HR was 45 ± 19 km 2 (range: 18.8-74.3, see Table 2 for individual HR sizes and Figure 3a for HR locations).

Both HR and core size were positively correlated with clan size (one side Spearman correlation test for both 95% HR and core: S=0, df=2, p=0.04, ρ=1). Neither HR nor core size were correlated with the average distance between waterholes when all were included (oneside Spearman correlation test core: S=4, df=2, p=0.21 and HR: S=2, df=2, p=0.17).

However, clan HR but not core size significantly increased with increasing distance between artificial waterholes (one side Spearman correlation test core: S=7.4, df=2, p=0.4 and HR: S=0, df=2, p=0.04, ρ = 0.8). There was no effect of season on individual HR size (Wilcoxon test: wet-late dry: W=45, p=0.73; wet-early dry: W=19, p=0.70 and early-late dry: W=16, p=0.44) nor HR core (wet-late dry: W=43, p=0.86; wet-early dry: W=20, p=0.80 and earlylate dry: W=14, p=0.30).

HR overlap was high between individuals belonging to the same clan (80.5 ± 13.9 %, range: 50.9-100) but low for individuals from different clans (6 ± 7 %, range: 0-20.7). Cores together data from all individual from the same clan (Figure 3b). Clan HR size averaged 239.8 ± 72.9 km 2 (range: 177.7-320.6) and core averaged 43.1 ± 19.6 km 2 (range: 24.3-62.5).

There was no overlap between clan HR cores but 95% HRs overlap of 5.1 ± 5.5 % (ranging from 0 to 16). 95% LKDE overlap between clans can be mainly explained by an atypical ranging behaviour of two individuals: one from the Airstrip clan and the other form the Guvalala clan (see Figure 3). The first one remained in her clan HR for the first year after but took a long trip going about 70 km to the south, then returning to the clan territory. Later in the year, she took a second trip before disappearing. Even though we removed all data from her GPS collar after the start of the first trip from the analysis, she was already exploring quite a lot before, which results in an extension of the clan HR calculated. The other individual collared from the same clan followed for three years and never showed such a ranging behaviour. The second hyaena (from the Guvalala clan) was followed for more than a year before she greatly extended her territory towards the West and visited less often her clan core HR after this. She finally disappeared from the clan, never to be seen again.

Hyaena habitat selection

Analyses based on Manly's selection ratio showed that hyaenas did not exhibit a significant habitat selection (ℵ 2 =53.49, df=45, p=0.18). There was only a slight tendency to prefer open grassland (Figure 4a andb).

Clan HR included 7.3 ± 2.2 (range: 5-10) waterholes, of which 3 ± 0.5 (range: 3-4) were artificial and cores contained 2.2 ± 1 (range: 2-4) waterholes including 1.3 ± 1.2 (range: 0-3) which were pumped. Hyaenas showed a significant pattern of habitat selection depending on distance to closest waterhole (ℵ 2 =159.17, df=37, p<0.0001). They significantly preferred locations less than 2 km from a waterhole while avoiding those further away than 4 km (Figure 4c andd).

The frequency of visits to artificial waterholes was clearly higher during the late dry season (17.1 ± 17.1 visits per month ranging from 2-44.7) compared to other seasons (5.8 ± 6.2 visit per month in the early dry season, range: 1-17.3, and 5.8 ± 5.3 visits per month in the wet season, range: 0.4-14.6). However, the frequency of visits did not vary much through the year for natural waterholes (early dry season 2.5 ± 3.2, range 0-8.8; wet season 3.5 ± 3.6, range: 0.4-11.6 and late dry 2.4 ± 2.9, range: 0-8.3, Figure 5a). Hyaenas spent more time around artificial waterholes than natural ones during the late dry (3.2 ± 1.1 h; range: 1.4-4.3; versus 1.6 ± 0.3 h; range: 1.3-2; for natural waterholes) and wet season (2.9 ± 1.1 h; range: 1-4.1 versus 2.1 ± 0.6 h; range: 1-3; for natural waterholes, Figure 5b).

Chapter 4 presents hyaena habitat selection in relation to waterhole, season and lions in more details.

DISCUSSION

Hyaena population and group sizes

The use of broadcast calls is particularly suitable to estimate density of vocal and territorial species. Since Kruuk (1972) first used this method in his long-term study of hyaenas in the Serengeti, it has been applied in many other ecosystems to estimate hyaena and lion densities and distributions in heterogeneous habitat [START_REF] Ogutu | The response of lions and spotted hyaenas to sound playbacks as a technique for estimating population size[END_REF]Mills et al., 2001;Kiffner, Waltert & Meyer, 2007;Cozzi et al., 2013). We believe that the response radius of 3.2 km is reasonable as the vegetation in HNP is very similar to the one in Kruger NP, where this radius was obtained by Mills et al. (2001). If the actual radius of response was smaller than 3.2 km, our method would underestimate hyaena density. For instance, an actual radius of 3 km the average density would be 11 instead of 9 hyaenas/100 km 2 . Due to logistic and time constraints, we did no conduct any calibration experiment to determine the true response radius and probability of response of hyaenas in HNP. We thus assumed a probability of response of 100%, with all hyaenas hearing the call responding to it. Indeed, Mills et al. (2001) show that within the 3.2 km radius the probability of response was constant no matter the distance to the calling station. However, Mills et al. (2001) estimated the probability of response to 61% and the 100% used here most probably overestimated the actual density, as hyaenas feeding on a carcass at the time of a calling are less likely to respond than others.

Moreover, only adults and sub-adults respond to callings (cubs younger than a year remain at the den). Thus, hyaena density provided here are probably underestimated, and part of the variation between years may also be due to variations in their motivation to respond. Hyaena density has been stable for the past 10 years. The very high density observed in 2010 might be due to a particularly high probability of response. The 2010 callings were conducted early in the dry season at a time when hyaenas did not yet have access to many elephant carcasses.

These density estimates are valid for the Main Camp area only which probably harbours a higher hyaena density than the rest park as most artificial waterholes are concentrated in this area.

Hyaena density and clan size in the northern part of HNP are similar to those observed in the Kalahari and Etosha NPs (see Table 4). This is surprising as prey density and biomass are quite high in HNP and close to values of richer ecosystems such as the Masai Mara for density and Kruger NP for biomass. We would have thus expected density and clan size to be closer to those in these locations. However, the high prey density and biomass in HNP are mainly due to the large elephant population. Hyaenas do not hunt adults nor sub-adult but occasionally kill young calves (Salnicki et al., 2001). Thus, the vast majority of the elephant biomass is only accessible to hyaenas when animals die (lion predation, old age…). Medium and small sized prey density is relatively low in HNP (7.7 indiv./km 2 and biomass of 515.7 kg/km 2 during the dry season, Chamaillé-James at al., 2009) which might explain why hyaenas defend larger territories with smaller clans compared to richer ecosystems. Hyaenas in HNP spend most of their time foraging alone or in small groups. This is a common characteristic of hyaenas as it was reported by several other studies in various ecosystems (Kruuk, 1972;Bearder, 1977;Whateley & Brooks, 1978;Mills, 1985;Henschel & Skinner, 1991). However, many members of a clan usually feed together, especially on large carcasses (Kruuk, 1972;Sillero-Zuberi & Gottelli, 1992;Smith et al., 2008). The absence of relationship between clan size and foraging and feeding group sizes is probably a result of the fission-fusion dynamics in the hyaena society (Kruuk, 1972). It has been showed that foraging group size appears to be linked to the prey species available for hyaenas to hunt (Kruuk, 1972;Whateley & Brooks, 1978;Mills, 1990). Several studies showed that relatedness and social rank influence the patterns of group formation (Mills, 1985;Smith et al., 2008). While we did not have access to this kind of data in HNP, we believe that further research is needed to understand foraging group formation and the dynamics of interactions between clan members. Gasaway et al. 1989[START_REF] Trinkel | Spotted hyenas (Crocuta crocuta) follow migratory prey. Seasonal expansion of a clan territory in Etosha, Namibia[END_REF], Trinkel and Kastberger 2005[START_REF] Trinkel | A keystone predator at risk? Density and distribution of the spotted hyena (Crocuta crocuta) in the Etosha National Park, Namibia[END_REF]; 2010

Hyaena territoriality

With an average clan LKDE HR of 239.8 km 2 , HNP hyaenas have territories smaller than in desert ecosystems but considerably larger than in rich ecosystems such as the Serengeti and Ngorongoro (see Table 4). This is another fact in favour of the hypothesis that despite quite high prey density in HNP, prey themselves are not easily accessible. HR overlap is high only for individuals belonging to the same clan showing that hyaenas in HNP are territorial. Our values of 95% LKDE overlap between individuals from the same clan are very similar to those obtained by Boydston et al. (2003) in the Masai Mara. We did not have enough individuals collared to test for an effect of social rank on HR size or overlap. Clans were also well defined with the same groups of animals seen together most of the time. Prey in HNP are resident [START_REF] Trinkel | Comparison of land-use strategies of spotted hyenas(Crocuta crocuta, Erxleben) in different ecosystems[END_REF] showed that in such ecosystems hyaenas tend to be territorial. However, 95% HR showed some degree of overlap between clans, indicating that boundaries between clan territories might not be well defined. We found only one latrine that could be used to mark a territory boundary and it was located at the edge of the core LKDE of the Guvalala clan. This is quite typical for species with large territories and living at low densities [START_REF] Revilla | Spatial organization, group living and ecological correlates in low-density populations of Eurasian badgers, Meles meles[END_REF]. Mills (1990) showed that brown (Hyaena brunnea)

and spotted hyaenas in the Kalahari do the same. Other latrines were found along roads often travelled by hyaenas well within their territory, a behaviour also observed in other species (e.g. wolf, [START_REF] Peters | Scent-marking in wolves[END_REF]. Additionally, large territories in Hwange might prevent hyaenas from intensively patrolling and defending their boundaries as suggested by Mills & Gorman (1987) in the Kalahari. [START_REF] Tilson | Spatial arrangement of spotted hyaena groups in a desert environment, Namibia[END_REF] also found latrines only within HR cores in the Namib desert.

In our study area, 95% LKDE overlap between clans can be mainly explained by an atypical ranging behaviour of two individuals. The first one was clearly dominant in the hierarchy of their clan (pers. obs.), thus had good access to food resources within her territory (Kruuk, 1972;[START_REF] Tilson | Social dominance and feeding patterns of spotted hyaenas[END_REF][START_REF] Honer | The effect of prey abundance and foraging tactics on the population dynamics of a social, territorial carnivore, the spotted hyena[END_REF]Smith et al., 2008). Low ranking females also range more widely than high ranking females (Boydston et al., 2003) and sometimes emigrate when prey availability is low in their territory [START_REF] Honer | The effect of prey abundance and foraging tactics on the population dynamics of a social, territorial carnivore, the spotted hyena[END_REF].

Prey availability does not seem to be linked to these behaviour as both hyaena left their territory during the dry season, when prey are easy to find around waterholes. Thus, its unconventional ranging behaviour might be explained by a change in the hierarchy. She might have lost her prime position in the clan and been excluded from it. We did not know the hierarchical status of the second hyaena but it is possible that she was excluded from the clan.

In the Kalahari, Mills (1990) observed that adult females sometimes leave their clan but they usually do so in groups. However, one female did leave her clan and join a neighbouring one.

Space use

In HNP, prey distribution varies widely throughout the year. While they are dispersed over the entire NP during the wet season, they congregate around artificial waterholes (20 in the study area) as the dry season progresses. Prey concentrations around these waterholes at the end of the dry season are particularly high but drop very quickly after the first rains. In Etosha NP, where prey show the same patterns (even though they tend to be more migratory than in HNP), [START_REF] Trinkel | Spotted hyenas (Crocuta crocuta) follow migratory prey. Seasonal expansion of a clan territory in Etosha, Namibia[END_REF] showed that hyaena territories contracted around waterholes during the dry season. We did not find any effect of season on LKDE size in HNP. Territories were stable in size and location throughout the year. However, artificial waterholes played a key role in hyaena ecology in HNP as distance between them influences HR sizes even with our small sample size (n=4). Hyaenas spent about 50% of their time within 2 km of a waterhole. Throughout the year, they make more use of artificial waterholes than natural ones, both in terms of frequency of visits and their duration. Interestingly, hyaenas still visit waterholes often and for long periods during the wet season, while they spend little time there during the early dry season. This is explained by the fact that prey and water are found at these waterholes during the late dry season and grazers are attracted to open areas surrounding them during the wet season. It is then not surprising that all but one core HRs contain at least one artificial waterhole. The only clan not having an artificial waterhole within its core HR is the Airstrip clan but its territory is centred on the park staff village at the entrance of the park.

There, hyaenas can find both water and food at rubbish pits and do not rely as much on waterholes.

Hyaenas tend to select for open grasslands. These areas are characterised by a high visibility and most are often found around waterholes, which is in accordance with previous results on the importance of waterholes in HNP. There is very little literature on habitat selection by hyaenas. Mills and Biggs (1993) noted that in Kruger NP hyaenas favour thickets with high concentrations of impalas. Broekhuis et al. (2013) showed that hyaenas select for mixed woodland and grassland while avoiding swamps in Moremi Game Reserve. Due to their cursorial hunting technique hyaenas do not have specific habitat requirements, as vegetation is not needed for cover. As prey in HNP also favour open and sparsely bushed grassland (see Chapter 4), hyaenas do select for habitats where prey are most abundant, easy to spot and to pursue.

CONCLUSIONS AND FURTHER RESEARCH

Because of their position at the top of the food chain, hyaenas play a crucial role in ecosystem functioning through their impact on both prey and sympatric predator populations and their importance in disposing of carcasses. They have been extensively studied in open ecosystems such as the Serengeti plains and the Ngorongoro Crater. However, far less literature is available on their ecology in more densely wooded ecosystems.

Thanks to GPS collars, this study is one of the first to provide extensive data on hyaena ecology in wooded savannas. We showed that the social organisation of hyaena in this type of ecosystem is quite similar to that observed in more open areas. In HNP, hyaenas form territorial clans and their density has been stable for the past 14 years. Artificial waterholes, which are the only place where water is available during the dry season are key components shaping hyaena space-use in terms of territory size and location, as well as habitat selection, as prey concentrate around them.

Due to its large elephant population, HNP is a unique ecosystem and hyaenas take great advantage of this availability of "free" food as reflected by their diet. Indeed, 57% of the carcasses were hyaenas fed were elephants (see Chapter 3 for more details), therefore making this single species the most important source of food for hyaenas. Even though we did not estimate diet in terms of biomass, it safe to say that elephant also contribute to most of the biomass ingested by hyaenas as they often feed on these very large carcasses for several consecutive nights (pers. obs.). Previous studies in HNP (Drouet-Hoguet, 2007) suggested that elephant carcasses from culling operations (taking place in the 80s) and ration hunts to provide meat for park staff (one elephant shot per month in the study area) did not overly benefit the hyaena population as they prefer to prey on medium herbivores. However, we do believe that the abundance of elephant carcasses helps to maintain a stable hyaena population even though the availability of medium-sized prey appears to be declining [START_REF] Valeix | Vegetation structure and ungulate abundance over a period of increasing elephant abundance in Hwange National Park, Zimbabwe[END_REF]. It is therefore possible that hyaena predation played a role in medium-sized prey decline. Elephant populations in semi-raid savannas are thought to be regulated by surface water availability (Chamaillé-Jammes, Valeix & Fritz, 2007) and calf mortality during the dry season (Young & Van Aarde, 2010). The abundance of elephant carcasses might promote coexistence between large carnivores, especially between hyaenas and lions and maintain large populations. However, interactions between the two species, and thus intraguild killing, are also more likely to occur at these large carcasses where they both spend much time (see Chapter 6 for details). In addition, the availability of elephant carcasses might also increase their predation levels on other prey species, playing a role in their decline. Artificial water management decisions should thus be taken bearing these cascading effects in mind to also preserved rarer and less iconic species. In addition, one of the big gap left in our hyaena knowledge that would help understanding their impact on prey populations, is which proportion of their food actually is provided by their own hunt and which part is scavenged.

In areas surrounding protected land, hyaenas are responsible for livestock depredation [START_REF] Patterson | Livestock predation by lions (Panthera leo) and other carnivores on ranches neighboring Tsavo National Parks, Kenya[END_REF][START_REF] Holmern | Livestock loss caused by predators outside the Serengeti National Park, Tanzania[END_REF], taking part in fostering intense human-wildlife conflicts. As other carnivore species, they are killed in retaliation (Kissui, 2008). Protected areas are important to maintain large viable hyaena populations. More research is thus needed in a variety of ecosystems to better understand their ecology and population dynamics, as well as their interactions with other species including humans, in order to promote their conservation.

The following chapters of this PhD manuscript focus on the interactions between lions and hyaenas in HNP to try to decipher the mechanisms of their coexistence.

AKNOWLEDGMENTS

The

INTRODUCTION

Diet is a fundamental aspect of a species ecological niche. In a community, the assemblage of diets has the potential to affect competition between species [START_REF] Pianka | Competition and niche theory[END_REF][START_REF] Karanth | Prey selection by tiger, leopard and dhole in tropical forests[END_REF], predator-prey interactions [START_REF] Sih | Predation, competition, and prey communities: a review of field experiments[END_REF], prey populations (Owen-Smith [START_REF] Mills | Shifting prey selection generates contrasting herbivore dynamics within a large-mammal predator-prey web[END_REF] and the whole ecosystem functioning (Ripple & Beschta, 2006). An understanding of diets and prey selection is thus key to ultimately reaching a capacity to predict diet shifts in responses to environmental and community changes. In large ranging terrestrial carnivores, predator diet is not only affected by the energetic benefits and costs involved [START_REF] Carbone | The Costs of Carnivory[END_REF], but also prey vulnerability (Hopcraft, Sinclair & Packer, 2005) and habitat characteristics related to hunting or escape success (Funston, Mills & Biggs, 2001;Loarie, Tambling & Asner, 2013). Prey selection is further influenced by predator hunting strategies. For instance, [START_REF] Husseman | Assessing differential prey selection patterns between two sympatric large carnivores[END_REF] reported that cursorial wolves (Canis lupus) select more for old and weak individuals than ambushed cougars (Puma concolor). For some social predators, group-hunting allows larger prey to be killed [START_REF] Lamprecht | The function of social hunting in larger terrestrial carnivores[END_REF][START_REF] Gittleman | Carnivore group-living: comparative trends in carnivore behaviour, ecology, and evolution[END_REF][START_REF] Carbone | Feeding success in African wild dogs: Does kleptoparasitism by spotted hyenas influence hunting group size?[END_REF]. For instance, lion (Panthera leo) hunting success doubles for impala (see Table 1 for prey Latin names) and nearly doubles for wildebeest and zebra when lions hunt in pairs rather than alone (Schaller, 1972). By hunting in groups, African wild dogs (Lycaon pictus) have access to prey much larger than they could kill on their own and at a lower energetic cost [START_REF] Creel | Communal hunting and pack size in African wild dogs, Lycaon pictus[END_REF]. In addition, large groups are capable of defending their kills from competitors, and kleptoparasitism success is linked to group sizes (Kruuk, 1972;Cooper, 1991).

Several studies have now shown that intraguild interactions among large carnivores play a significant role in carnivore ecology (Durant, 2000;Caro & Stoner, 2003;Broekhuis et al., 2013). In species capable of killing each other, interference competition can reach the extreme level of intra-guild predation, a phenomenon widespread in carnivores worldwide (Palomares & Caro, 1999). Interference competition has been shown to influence space use and behaviour of carnivores. For example, coyotes (Canis latrans) spatially and temporally avoid wolves [START_REF] Arjo | Behavioral responses of coyotes to wolf recolonization in northwestern Montana[END_REF] and are more vigilant when wolves are more likely to be present [START_REF] Switalski | Coyote foraging ecology and vigilance in response to gray wolf reintroduction in Yellowstone National Park[END_REF]. However, carnivore diet is also likely to be dynamic and influenced by the level of these intraguild pressures, but this is extremely difficult to measure in the field and the impact of intraguild interactions between large carnivores on their diets has been largely understudied.

Chapter 3: Large carnivore menus 123

In African savannas, lions and spotted hyaenas (Crocuta crocuta, hyaenas hereafter) are the largest and most numerous predators. Their diets overlap extensively as they both predominantly prey and scavenge on large and medium sized herbivores (Hayward, 2006).

Hyaenas have been shown to spend a lot of time foraging on their own, but they join into large groups to hunt large prey with strong anti-predator defence such as zebras (Kruuk, 1972;Holekamp et al., 1997) and clan members often join together to feed on large carcasses (Cooper, 1990). Larger hunting groups also benefit from a higher hunting success that increases by 19% when hyaenas hunt in pairs rather than alone (Holekamp et al., 1997). Lion hunting group size also influences the prey species kill (Bauer et al., 2008) and their hunting success (Funston et al., 2001). Both lions and hyaenas are capable of stealing kills from each other (Kruuk, 1972;Cooper, 1991;Trinkel & Kastberger, 2005) and lions are often the main cause of mortality for hyaenas (Palomares & Caro, 1999;Watts & Holekamp, 2008;Watts & Holekamp, 2009). Adult male lions are of particular importance when it comes to kleptoparasitism success on or by hyaenas, with the presence of at least one adult male providing a substantial advantage to lions (Kruuk, 1972;Cooper, 1991;Trinkel & Kastberger, 2005). Hoverer, very little is known about the extent of interference competition between these two species and even less how they affect each other's diet.

In

METHODS

Study area and prey and predator populations

Hwange National Park (HNP) is located in north-western Zimbabwe (19°00'S, 26°30'E)

and covers an area of approximately 14,600 km 2 . The study area (≈ 1 500 km 2 ) comprised the Main Camp area, located in the northern part of HNP characterized by Kalahari sand soils.

The vegetation is primarily woodland and bushland savanna, interspersed with small patches of grassland (Rogers 1993). HNP is semi-arid with a wet season from November to April and

Hyaena group size

As part of the baseline monitoring of the hyaena population in the study area, we drove at least five nights per week (from sunset to midnight and 4 am to 8 am), and spent full nights at waterholes during the dry season to find and observe hyaenas. Group size was systematically recorded during this monitoring. Additionally, we collected opportunistic data on group sizes whenever we saw hyaenas. We distinguished foraging groups (groups of hyaenas moving around the landscape, either hunting or looking for a carcass to scavenge) from feeding groups (groups of hyaenas seen feeding on a carcass, see Chapter 2 for more details). We classified foraging groups into the following size classes: alone, small (2-4), medium (5-7)

and large (>7). We observed 678 foraging groups during period 1 and 122 during period 2.

We recorded 54 hyaena feeding group sizes during period 1 and 42 during period 2.

Scat data

Hyaena scats are easily recognisable thanks to their white colour due to the high amount of calcium hyenas ingest through eating bones. We collected 226 scats during period 1 and 300 scats during period 2. Each scat was soaked for 30 min in water and bleach in a nylon stocking to extract only the hair content. Hairs were then sundried and analysed to identify the prey species they belonged to. Most of the time, it was possible to identify prey species simply by looking at the bulk of hairs with the naked eye. When this was not feasible, a sample of hair (five on average) were analysed under the microscope (scale patterns and cross section) and compared to a reference collection [START_REF] Koegh | A photographic reference system of the microstructure of the hair of southern African bovids[END_REF][START_REF] Buys | Notes on the microstructure of hair of the Orycteropodidae, Elephantidae, Equidae, Suidae and Giraffidae[END_REF]. Forty four and two scats for period 1 and 2 respectively contained either hairs we could not identify or no hair at all. These scats were discarded in the following analyses. Twelve and seven scats for period 1 and 2 respectively contained hairs from two different species and each was thus counted as two samples, one with each prey species. To avoid any pseudo-replication, only one scat was taken from those collected the same day at a given latrine or carcass. We eventually obtained a final sample size of 180 scats for period 1 and 206 for period 2.

Carcass data

Hyaenas were opportunistically observed feeding on 58 different carcasses during period 1 and on 22 carcasses during period 2. Prey species was recorded at each carcass. Additionally, during period 2, nine hyaenas (from four clans) were equipped with GPS radio-collars (African Wildlife Tracking, UHF 407, GPS collar with UHF download and VHF transmitter) that recorded hourly positions at night (from 18:00 to 6:00). Hyaenas were immobilized by a professional team either with a standard mix of 500 mg Ketamine (Kyron laboratories Pvt.

Ltd, Ben-rose, RSA) and 200 mg Xylazine (Rompun; Bayer, Leverkusen, Germany) or of 80 mg Zoletil (Virbac RSA, Halfway house, RSA) and 4 mg Medetomidine (Zalopine, Wildlife Pharmaceuticals, Karino, RSA). Drugs were then reversed with 16 mg of Yohimbine (Rx drug, Kyron Labs, Benrose, RSA). Full recovery was ensured by staying with the animal until it awoke and walked away normally. We used these GPS data to search for potential feeding sites by identifying clusters of GPS fixes that included at least 3 h of successive locations within a 50 m radius. We identified 281 clusters and visited 263 on foot. Clusters were visited as soon as possible after hyaenas had left the site and maximum two months after. We searched for feeding sites, identified by the presence of a carcass, bones, horns or large amount of hairs, within a 100 m radius of the first GPS point of the cluster. If other GPS points identified as part of the cluster did not fall within this 100 m search radius, new 100 m search radii were investigated around those GPS positions. No cluster investigation took place during the rainy season. It was not possible to assess if the prey animal had been killed or scavenged by hyaenas, thus these clusters represent feeding sites rather than kill sites. At 90 sites, we found a carcass or identifiable prey remains and recorded the prey species for each.

In total, we thus identified 112 carcasses on which hyaenas fed during period 2.

Diet composition

Each prey species was assigned to a prey size class (Table 1) based on the adult female body weight (Coe, Cumming & Phillipson, 1976). Common duiker and steenbok were regrouped in a class "small antelopes". Because of their low abundance, but also their similarities in size and ecology, sable and roan were regrouped in a class "rare ungulates". We also regrouped birds, small mammals (mongoose, rodents…), springhare (Pedetes capensis), porcupine (Hystricomorph hystricidae) and other carnivores into a class "other" of unknown availability, thus not taken into account in the prey preference analyses. For each period, we calculated the proportion of each prey species and prey size class in the diet by dividing the number of scats containing hairs or carcasses of the given species by the total number of scats containing identifiable hairs or carcasses. Elephant is a species that is not reliably identified from scat data as hyaenas may avoid feeding on the skin with very few hairs from an entire elephant carcass and the proportion of flesh (hence meat with no hair) in an elephant is large.

Additionally, a bias may exist in our study for period 1 when most scats were collected from a clan living in close proximity to a National Park camp where hyaenas could access elephant meat and skin left-overs from a butchery processing staff rations. Consequently, comparison of diet composition (and prey preferences) based on scat analysis between the two periods were conducted excluding scats containing elephant hairs (20 scats for period 1 and five for period 2).

Prey availability data and prey preference analyses

Prey densities were estimated in the Main Camp area by using line transect surveys carried out in September/October (end of the dry season) and in May/June (beginning of the dry season). We used most oh the available roads as transects. Data were analysed using Distance Sampling software [START_REF] Thomas | Distance 6.0. Research Unit for Wildlife Population Assessment[END_REF]. Details of the methodology used to analyse the data are provided in Chamaillé-Jammes et al. ( 2009), from which we extracted estimated densities of prey populations for period 1. We calculated the more recent densities for period 2 based on road counts from 2008 to 2013. Overall prey abundance was estimated by averaging values for the late and early dry seasons. As selection, or preference indices, may vary according to the specific bias associated with their calculations, we used two different metrics for more robust conclusions. For each prey species and prey size class we computed the Jacobs' index D [START_REF] Jacobs | Quantitative measurement of food selection[END_REF] which standardizes the relationship between the proportion of each species (or prey class) in the diet r and its proportion in the prey community p. D ranges from -1 maximum avoidance to +1 maximum preference. The Jacobs'

index was chosen as it minimizes bias in preference estimation, especially with proportion below 10% (see Hayward & Kerley, 2005 for details). We also calculated Manly's selection ratio (proportion of food item used/proportion of food item available, Manly et al., 2002) using both scat and carcass data. We used the function widesI from the package adehabitatHS to perform ℵ 2 tests to estimate prey preferences for each period in R software v. 3.0.2 (R development Core Team, 2013). We compared prey preferences between periods graphically.

The class "other" for prey species was not included in prey preference analyses as their availability was not known. As results were similar using Manly selection ratios and Jacobs' indices, we chose to graphically represent prey preference using Jacobs' index only (but see Appendix 3.1 for Manly's selection ratios). Averages are presented with their standard deviation (± SD), unless stated otherwise.

RESULTS

Changes in prey community composition

The composition of the prey community significantly differed between the 2 periods (ℵ 2 =946.9, df=9, p<0.0001). The proportion of giraffe and wildebeest in the prey community decreased from period 1 to period 2, whereas the proportion of buffalo and kudu increased (Figure 1). All other species were equally abundant in the prey community with elephant being the dominant species.

Changes in hyaena group sizes

Foraging group size differed between the two periods (ℵ 2 =10.15, df=1, p=0.02) with hyaenas foraging more on their own and less in groups during period 1 (Figure 2). However, they fed in significantly larger groups during period 1 (6.3 ± 4.3 individuals) than during period 2 (3.5 ± 2.4 individuals, W=1608.5, p<0.0001, Figure 2).

Changes in hyaena diet composition

Hyaenas fed on at least eight different species based on carcass data (one rhinoceros, Ceratotherium simum, carcass is not mentioned here) and 17 species based on scat data (Table 1). Diet composition was different between the two periods based on both carcasses (Fisher exact test p<0.0001) and scats (ℵ 2 =35, df=9, p<0.0001). Based on scat data (and excluding elephant), from period 1 to period 2, hyaenas fed 5 times more on warthog, 2.1 times more on giraffe, 7.5 times more on rare antelopes, 7.5 times less on other, 2.8 times less on wildebeest and 2.3 times less on buffalo (Table 1, Figure 3a). Based on carcass data, from period 1 to period 2, hyaenas fed 3.7 times more on giraffe, 1.8 times more on elephant, 13.4 times less on wildebeest, 4.5 times less on impala, 3.8 times less on buffalo, more than 2.5 times less on zebras, and 1.6 times less on kudu (Table 1; Figure 3b). In terms of prey size classes, diets were significantly different between the two periods based on scats when including the class other (ℵ 2 =17.15, df=5, p<0.0001) but this did not hold true when excluding that class other from the analyses (ℵ 2 =7.0, df=4, p=0.36). However, from scat data, from period 1 to period 2, hyaenas fed 2.1 times more on very large prey.

Diet composition was significantly different between the two periods based on carcasses (Fisher exact test p<0.0001) and hyaenas fed 1.9 times more on very large herbivore carcasses whereas they fed 3.8 times less on large prey, 2.4 times less on medium prey, and 3.4 times less on small prey carcasses from period 1 to period 2. 1: Hyaena diet composition from scats and feeding sites. Percentage in the diet from scats was not calculated for elephant as it is not reliable. Numbers in parentheses give the sample size and those in bold give the percentages of each prey size class in hyaena diet.

Changes in hyaena prey preference

We found that hyaenas did not take prey in proportion to their availability in the Hwange ecosystem. Based on scat data, prey preference changed from period 1 to period 2 (Figure 3c and 3d). Whereas hyaenas avoided giraffe and warthog in period 1, they selected for these 2 species in period 2. Contrarily, while they selected for buffalo and zebra in period 1, this was not the case in period 2, when they avoided buffalo and took zebra in proportion to their availability. Sable and roan were taken in proportion to their availability in period 1, but there was a definite preference shown in period 2. Based on carcass data, we detected similar changes for giraffe and buffalo. Elephants were taken in proportion to their availability in period 1 whereas they were selected in period 2. Additionally, there was a selection for wildebeest and kudu in period 1, whereas these species were avoided in period 2. Zebra and impala were always avoided, but far more in period 2.

In terms of preference for prey size classes, based on scat data, very large prey were avoided in period 1 while they were selected for in period 2. This was the reverse for large prey which were avoided during period 2 instead of being selected in period 1 (Figure 4a).

Based on carcass data, very large prey were selected for in period 2. All other classes were avoided during period 2 while large and medium prey were selected for during period 1 and small prey were taken in proportion to their availability (Figure 4b).

DISCUSSION

We showed that hyaenas feed on virtually all prey available to them ranging from very large species such as elephants, to very small prey such as steenboks, but also including birds and other small mammals. This is in accordance with previous studies concluding that hyaenas have very eclectic tastes (Kruuk, 1972;Mills, 1990;Hayward, 2006). While most of the large prey (elephant, giraffe, and buffalo) were most probably scavenged, the others have a greater chance to have been actively hunted and killed by hyaenas. Indeed, several studies have shown that hyaenas are efficient hunters and capable of taking down large prey (Kruuk, 1972;Mills, 1990). similar to other sites such as Ngorongoro Crater (Honer et al., 2002) and Moremi Game Reserve (Cooper, 1990), we found that hyaenas showed a significant prey preference pattern in HNP. This goes against the conclusion of Hayward ( 2006) that across different study sites, hyaenas eat prey according to their availability. However, this adds more weight to his remark that there are site-specific prey preferences that might negate each other creating a generalist diet pattern for hyaenas.

Methodological considerations

Following individuals for long periods is one of the best ways to estimate their diet.

Unfortunately, due to the very dense vegetation in HNP, this method could not be applied.

Even though it was difficult to detect small and very small prey which hyaenas take less than 3 h to process, we trust that our GPS cluster method provides a reasonable approximation of the carcasses used by hyaenas, and this method has been successfully used in wolves [START_REF] Webb | Statistical methods for identifying wolf kill sites using Global Positioning System locations[END_REF], cougars [START_REF] Bacon | Do GPS clusters really work? Carnivore diet from scat analysis and GPS telemetry methods[END_REF] and lions (Tambling et al., 2010;[START_REF] Tambling | Estimating carnivoran diets using a combination of carcass observations and scats from GPS clusters[END_REF]Davidson et al., 2012;[START_REF] Davidson | Seasonal Diet and Prey Preference of the African Lion in a Waterhole-Driven Semi-Arid Savanna[END_REF]. Scat data are known to overestimate small prey [START_REF] Klare | A comparison and critique of different scat analysis methods for determining carnivore diet[END_REF], and they should also largely underestimate elephants. However, because we removed elephants when studying diet composition and prey preferences from scat data, we believe these limitations are not a problem for the comparison of frequency of occurrence in the diet between species and periods as the methodological bias is the same. The fact that we did not analyse all the hairs contained in each scat but rather did so on a small sample of them should not affect the results [START_REF] Ciucci | Assessment of the point-frame method to quantify wolf Canis lupus diet by scat analysis[END_REF]. In addition, because frequency of occurrence based on scat data is the most often used method to asses diet in carnivores [START_REF] Klare | A comparison and critique of different scat analysis methods for determining carnivore diet[END_REF], our results can be compared with previous studies. We do not believe that the amount of hairs remaining in a scat is a good indicator of the quantity of meat ingested, as it depends on the prey species, the body part consumed and the state of the carcass (Kruuk, 1972;Bearder, 1977). Indeed, hyaenas ingest more skin and hairs from small and medium prey than they do from larger ones (Henschel & Skinner, 1990). Feeding trials would have allowed us to link the total biomass consumed to the amount of hairs left in a scat, however such trials are impractical in the field. For this reason, we did not estimate the diet composition in terms of biomass. Even though frequency of occurrence has been argued to have less ecological significance than quantity methods, [START_REF] Klare | A comparison and critique of different scat analysis methods for determining carnivore diet[END_REF] showed that when trace items were removed, as we did in this study, this method gives results close to quantity methods.

Avoidance of large and medium sized prey following increase of intraguild competition

Our results show that there was a significant change in hyaena diet composition and prey preference in terms of size class between the two periods. Whereas in period 1, hyaena diet composition was dominated by large and medium sized prey and hyaenas selected for such prey, this was not the case anymore in period 2. Regarding hyaena diet composition, the contribution of buffalo, zebra, wildebeest and kudu has declined between period 1 and period 2, and quite drastically for some species (e.g. buffalo and wildebeest in carcass data). These trends were consistent based on both scat and carcass analyses (except for kudu based on scats). Regarding prey preference, whereas hyaenas selected for buffalo (based on scats and carcasses), zebra (based on scats), wildebeest (based on carcasses) and kudu (based on scats and carcasses) in period 1, they tended to avoid these prey species in period 2. There was no strong difference in annual rainfall between the two periods (634 ± 261 mm for period 1 and 789 ± 196 mm for period 2) and no recognisable disease outbreak, hence the numbers of animals dying from natural causes unrelated to predation was unlikely to have changed (pers.

obs.). The reported changes in hyaena diet and prey preferences do not support the hypothesis that these parameters are driven by hyaena foraging (i.e. hunting) group size. Indeed, since hyaenas foraged in larger groups in period 2, we would have expected the proportion of large prey hunted by hyaenas (excluding elephant and giraffe which are almost exclusively scavenged) to have increased in their diet. The observed changes are however compatible with a scenario of increased intraguild competition with lions that affected hyaena foraging ecology. In period 1, due to the lower abundance of lions in the ecosystem and the lower probability of encountering adult male lions, hyaenas were more likely to retain the mediumsize prey they killed even in the presence of lions. During this period, lions were also likely to be sensitive to kleptoparasitism from hyaenas due to the low numbers of adult males in the lion population (Cooper, 1991;Trinkel & Kastberger, 2005). As a consequence, hyaenas might have been able to steal numerous buffalo carcasses, which is lion main prey species in HNP [START_REF] Davidson | Seasonal Diet and Prey Preference of the African Lion in a Waterhole-Driven Semi-Arid Savanna[END_REF]. However, as the intraguild competition increased in period 2, the risk of hyaenas losing their carcasses to lions increased while their ability to steal lion kills dropped. The cost of kleptoparasitism from lions was likely to be higher for large and medium-sized prey that are hunted as hyaenas expend energy for the hunt and have a high risk of attracting lions in the process because of the noise and commotion (Kruuk, 1972). Our results suggest that in response to the increased competition from lions, hyaenas switched from hunting the large and medium size prey species they previously hunted when lion competition was low.

Increase of very large herbivore scavenging resulting from intraguild facilitation

A striking result of our study is the strong increase of elephant and giraffe contribution to hyaena diet between period 1 and period 2 and the new preference shown for these two species in period 2. HNP harbours one of the largest elephant populations in the world. In the study area, elephant density is particularly high during the dry season (Chamaillé-Jammes et al., 2009) when surface water is provided at artificial waterholes. It thus comes as no surprise that both lions [START_REF] Davidson | Seasonal Diet and Prey Preference of the African Lion in a Waterhole-Driven Semi-Arid Savanna[END_REF] and hyaenas (this study) incorporate this species in their diets. In HNP, some lion prides are now specialised in killing elephants including large sub-adults and weak adults (pers. obs.), a likely result from the increase in the number of male lions in the population (Loveridge et al. 2010). However, even if hyaenas sometimes kill newborn (Salnicki et al., 2001), the large majority of the elephant biomass they consumed was scavenged (only 11 elephants out of 75 that hyaenas consumed were calves). In addition, elephant carcass availability increases during the late dry season as old and new-born calves die of exhaustion or are killed by lions (pers. obs.). As elephant carcasses provide large quantities of meat, hyaenas might thus be actively looking for this rewarding "free" food source. In addition, they are better equipped for scavenging than any other carnivore (Kruuk, 1972), thus elephant carcasses are probably more profitable to hyaenas than to lions.

Giraffe is a common prey for lions but is not usually killed by hyaenas. Their very large carcass provides a lot of meat and scavenging opportunities at relatively low cost for hyaenas.

Because of their size, more meat is probably left by the time lions leave a giraffe carcass compared to a buffalo. This might be why the preference for giraffe increased, while a large pride with adult males would completely finish a buffalo and leave nothing to scavenge from.

Data on lion diet during the period 2 is unfortunately not available, but we can assume that larger groups of lions have a better chance of success in hunting giraffe and they thus might have increased their predation of this species, providing more giraffe carcasses for hyaenas to scavenge. These results are in accordance with those from Honer et al. (2002) showing that in the Ngorongoro, hyaenas switch from hunting to scavenging as the availability of buffalo carcasses killed by lion increased. Our study provides another example of the capacity of hyaenas to adjust their foraging strategies to changing food availability conditions. Not only do they take advantage of food provided by sympatric carnivores, but they include anthropogenic resources in their diet when they are available, thus modifying their space use (Kolowski & Holekamp, 2008;Kolowski & Holekamp, 2009;[START_REF] Yirga | Adaptability of large carnivores to changing anthropogenic food sources: diet change of spotted hyena (Crocuta crocuta) during Christian fasting period in northern Ethiopia[END_REF]. Hyaenas therefore changed their foraging strategies in response to an increased intraguild competition with lions, switching from large and medium-sized prey probably mostly hunted to very large prey mainly scavenged. These results also support Vanak et al. (2013) conclusion that diet, hence dietary overlap, might be a result from competition rather than a mechanism promoting coexistence between large carnivores.

Changes in hyaena foraging and feeding group size

The observed changes in hyaena foraging and feeding group sizes might also be a response to the increased competition with lions. While larger foraging groups are more likely to retain a carcass (killed or scavenged) and to steal one from lions, the decrease in feeding group size between the two periods could result from a lower recruitment of clan members at feeding sites. Less noisy hunting (mainly of medium-sized prey) and interactions at carcasses most likely decreased the probability of lions discovering feeding hyaenas. Therefore, changes in lion population composition and pride size might thus have induced changes in the fissionfusion dynamics of hyaena clans.

Even though, hyaena diet overlapped extensively with that of lions during the low competition period (67%, see Appendix 3.2), their diets differed significantly. Resource diversity and heterogeneity has been shown to promote species coexistence (Durant, 1998 in large carnvores;Cromsigt, Prins & Olff, 2009 in ungulates). [START_REF] Karanth | Prey selection by tiger, leopard and dhole in tropical forests[END_REF] also showed that the availability of large prey for tigers (Panthera tigris) greatly reduces their competition with leopards. The abundance of elephant carcasses, especially during the dry season, might act as an alternative food resource for hyaenas and help release the competition pressure from lions. The use of these carcasses might be a compensatory mechanism for the decrease of hunting of medium and large size prey in response to increasing competition with lions. This might also be why the hyaena density remained stable through the period of increasing competition from lions. While intraguild competition is known to influence large carnivore habitat use and behaviour, this study shows that changes in its intensity also have the potential to affect their diets as well as their foraging strategies (hunting versus scavenging). The associated change in predation pressure on the various prey body sizes could ultimately impact the dynamics of their populations and the functioning of the ungulate community [START_REF] Fritz | A food web perspective on large herbivore community limitation[END_REF] and possibly the whole ecosystem functioning through trophic cascades or shifts in food web structures (Estes et al., 2011;Ripple et al., 2014). for species j and species k where and are the proportion of food item i in species j and k diets, respectively, and Pianka's index symmetrical for both species (i.e. niche breadth are considered the same) .

During a period of low intraguild competition from lions, the percentage of diet overlap between lion and hyaenas was 66.7%. Pianka's indexes are 0.81 for lions and 0.80 for hyaenas with a symmetrical index of 0.80 based on carcasses. Estimates of overlap using scats data are lower, 57.2% for the total overlap, and 0.6 for the three other indexes. The very close values for the Pianka indexes indicate that both species use a similar prey niche and share the same proportion of their diet with the other one.

( min( p ij , p ik ) i ∑ ) ×100 p ij ik p α jk = p ij p ik i ∑ p ij 2 i ∑ α kj = p ij p ik i ∑ p ik 2 i ∑ p ij ik p α jk = α kj = p ij p ik i ∑ p ij 2 × p ik 2 i ∑ i ∑
Hyaenas and lions have significantly different diets based both on scats (ℵ 2 =103.7, df=7, p<<0.0001) and kills (ℵ 2 =50.8, df=7, p<<0.0001). Overall, lions eat more buffalo (19.1-40.1% against 7.7-13.8%) and suidae (5.3-17.8% against 0-1.8%) than hyaenas, but consistently less elephant (3.9-8.6% against 11.9-37.9%) and small antelopes (2.4-2.6% against 12.1-31%, Figure 1). Based on carcasses data only, lions also eat more giraffe (9.4% against 3.4%) and zebra (8.6% against 5.2%) than hyaenas (Figure 1a). From scats data, this pattern was reverse for zebra and hyaenas eat more kudu than lions (25.7% against 13.1%, Figure 1b) Overall prey preferences are very similar the two species (Figure 1c,d). They both prefer buffalo and medium bovidae, with a tendency to avoid elephant and giraffe. The major difference is for suidae that are preferred by lions and avoided by hyaenas.

There was a high potential for competition between hyaenas and lions judging by their diet overlap. We found very similar figures to the ones already published (Hayward, 2006).

Pianka's indexes indicate that both species share the same extents of their diet with each other.

This suggests that no species is suffering from exploitative competition more that the other.

Even though these two predators use the same prey niche, their diets in term of prey species were significantly different. The general pattern is that prey actively selected or avoided by lions were taken accordingly to their abundance by hyaenas. This shows that hyaenas do not rely mainly on scavenging from lions to acquire food, otherwise prey preferences would be the same for the two species. Both species take zebra in proportion to their availability. This is might be due to the active anti-predatory behaviour of zebra stallions that make the species a difficult target for hunting. Kruuk (1972) noted that when hunting for zebra, hyaena tend to do so in groups to counter the defence of the stallion. However, during the foaling season, hyaenas have been reported to heavily prey on juvenile zebra (Cooper, 1990), which might be responsible for the non-avoidance of the species as a prey.

Hyaenas have been shown to prey more on juveniles and sub adults than lions in several ecosystems (Kruuk, 1972;Mills, 1990;Mills & Biggs, 1993). Scats cannot differentiate between adults and juveniles prey, and we did not have enough data on species other than elephant to test if hyaenas and lions select prey from different age classes. Such a selection would certainly release the exploitative competition between the two species.

INTRODUCTION

Understanding how animals select their habitat is of crucial importance for both theoretical and applied ecology. They are thought to select habitats maximising their fitness. They are thus facing a trade-off between selecting for habitats where food is easily acquired but also where there is less intra-and inter-specific competition and/or where the risk of predation is lower [START_REF] Lima | Stress and decision-making under the risk of predation: recent developments from behavioral, reproductive, and ecological perspectives[END_REF][START_REF] Sih | Predator-prey space use as an emergent outcome of a behavioral response race[END_REF]. For example, leopards (Panthera pardus) prefer habitats with intermediate cover level where prey are easier to kill [START_REF] Balme | Feeding habitat selection by hunting leopards Panthera pardus in a woodland savanna: prey catchability versus abundance[END_REF]. Elk (Cervus elaphus) have been shown to move to wooded areas when wolf (Canis lupus)

predation was high, while they prefer grassland when predation risk is low (Creel et al., 2005). Animals are therefore facing a trade-off between feeding and safety. Habitat selection occurs at different spatial scales (Johnson, 1980) and the availability of long term and fine scale telemetry data from GPS collars has recently greatly improved our understanding of its processes. For instance, white tailed deer (Odocoileus virginianus) and roe deer (Capreolus capreolus) forage mainly in open habitat but use conifer cover to rest [START_REF] Schmitz | Thermal constraints and optimization of winter feeding and habitat choice in white-tailed deer[END_REF][START_REF] Mysterud | Bed-site selection by European roe deer (Capreolus capreolus) in southern Norway during winter[END_REF].

Most studies on predators have focused on how prey availability and catchability influences their habitat selection (e.g. Hopcraft, Sinclair & Packer 2005) . For instance, while within their territories lions (Panthera leo) prefer bushed grassland areas where prey are abundant, they preferentially kill in thickets where prey are easier to ambush (Davidson et al., 2012). In areas where several predators are sympatric, competition and intraguild predation can also affect their habitat selection [START_REF] Mills | Factors affecting the density and distribution of wild dogs in the Kruger National Park[END_REF][START_REF] Creel | Interspecific competition and the population biology of extinction-prone carnivores[END_REF]. [START_REF] Fedriani | Niche relations among three sympatric Mediterranean carnivores[END_REF] showed that subordinate species such as European mongoose (Herpestes ichneumon) avoided habitat favoured by Iberian lynx (Felis pardina) because of the high risk of predation, even though these are richer in prey. Therefore, just as prey, predators select their habitat based on the trade-off between finding food and being safe [START_REF] Mukherjee | Patch use in time and space for a mesopredator in a risky world[END_REF]. Despite the fact that African savannas have one of the most complex guilds of predators, few studies have been conducted on how they impact each other habitat use. Most of the literature available focused on endangered species such as cheetahs (Acinonyx jubatus)

and wild dogs (Lycaon pictus) because of conservation issues (Durant, 2000). All these studies concluded that the two subordinate species avoid areas preferred by the two larger predator species, lions and/or spotted hyaenas (Crocuta crocuta). To our knowledge, there has not been any work done to understand how these two top predators affect each other in terms of habitat selection. Their diets are often very similar (Hayward, 2006), they are also capable of stealing carcasses from each other and lions are known to kill spotted hyaenas (hyaenas hereafter) mainly during fights around carcasses (Kruuk, 1972;Mills, 1990;Watts & Holekamp, 2008;Watts & Holekamp, 2009). For hyaenas, the risk that lions represent is a combination of several factors (see Figure 1). A first one is the probability of encountering them at a given location, which is determined by lion space use. A second factor is the availability of cover providing ambush opportunities for lions and increasing their hunting success (Funston, Mills & Biggs, 2001a;Loarie, Tambling & Asner, 2013). A third factor is the visibility at a given location influencing the ability of both predators to detect each other.

For nocturnal predators (and not taking into account the vegetation density i.e. the presence of bushes), visibility is enhanced by the moonlight intensity and the absence of canopy obscuring its light. Night brightness has long been thought to increase predation risk [START_REF] Lockard | Moon-related surface activity of bannertail (Dipodomys spectabilis) and fresno (D. Nitratoides) kangaroo rats[END_REF] because predators are more likely to detect prey in bright conditions.

However, the contrary is also true as prey can detect approaching predators more easily during full moon nights. Dark nights are likely to be riskier for hyaenas as it would be more difficult to detect lions, which in addition have a higher hunting success during moonless nights [START_REF] Packer | Fear of Darkness, the Full Moon and the Nocturnal Ecology of African Lions[END_REF]. On the other hand, it would be easier for them to hide from lions than during full moon nights. Hyaenas thus face a trade-off between detecting approaching lions and not being seen by them. Which option minimizes their risk of predation most probably depends on the habitat type and vegetation density. Last factor, group size will also affect detectability and predation risk. Large groups of hyaenas are more conspicuous to lions, but also more able to defend themselves. Lion group size also has an influence as larger groups are greater threat to hyaenas, especially if at least one adult male lion is present (Kruuk, 1972;Trinkel & Kastberger, 2005;Watts & Holekamp, 2009).

We used Resource Selection Functions (RSFs, Manly, McDonald & Thomas, 2002) to understand how predation risk by lions influenced hyaena 3 rd order habitat selection in the semi-arid savanna of Hwange National Park (HNP), Zimbabwe. Our study is based on simultaneous fine scale GPS data from radio-collars deployed on both predator species. In semi-arid savannas, waterholes, especially artificial ones, are key features where prey congregate in large numbers during the dry season. This in turn attracts numerous predators, and lions have been shown to intensively use areas close to these waterholes in HNP (Valeix et al., 2009). Open areas are equally important in the wet season, as grazer species such as zebras (Equus quagga) and wildebeests (Connochaetes taurinus) and mixed feeders such as impalas (Aepyceros melampus) intensively use these grasslands.

Following the optimal foraging strategy [START_REF] Charnov | Optimal forgaing, the Marginal Value Theorem[END_REF][START_REF] Brown | Patch use as an indicator of habitat preference, predation risk, and competition[END_REF], hyaenas should select for habitats balancing a trade-off between habitats as profitable as possible in terms of prey and with the lower possible predation risk. We thus expected that hyaenas should (1) select for areas rich in prey, i.e. waterhole and open areas during the dry and wet season respectively as well as habitats favoured by prey and that they should (2) avoid areas recently used by lions, even more in areas poor in prey. This avoidance should be higher during the wet season when prey are dispersed and harder to find and catch in dense vegetation. We also expected that lion avoidance should be mediated by the interaction between habitat type and night brightness due to moonlight. Indeed, the effect of moonlight can be mediated by canopy cover. Moonlight can increase hunting success in some habitats that could outweigh the risk of using them in risky areas. We tested two hypotheses regarding hyaenas strategy to avoid lions depending on habitat type and night brightness. (3.1) If hyaenas prefer avoiding being detected by lions, then lion avoidance should be higher in habitats where the ground visibility distance is high (i.e. grassland and woodland) and lower in bushy areas. Furthermore, lion avoidance should increase in habitats with no canopy cover when the moon is full.

Conversely, (3.2) if hyaenas prefer seeing approaching lions, then they should select for habitats with high visibility and few bushes when the risk is high and for habitats with no canopy cover when the night is bright. In any case, they should favour areas with few bushes when the risk of encountering lions increases. As hyaena foraging group formation is very dynamic (Kruuk, 1972;Mills, 1985), it was not possible to estimate their group size for most foraging trips used in the habitat selection analyses. We thus did not test the effect of this factor on habitat selection in response to lion encounter risk.

METHODS

Study area

Hwange National Park (HNP) is located in north-western Zimbabwe (19°00'S, 26°30'E)

and covers an area of approximately 14,600 km 2 . The study area (≈ 1 500 km 2 ) is located in the northern part of HNP, in the Main Camp area, characterized by Kalahari sandy soils. The vegetation is primarily bushed woodland and bushland savanna, interspersed with small patches of grassland (See Figure 2 and Appendix 4.2). HNP is semi-arid with a wet season from November to April, an early dry season from May to July and a late dry season from August to October. The long term mean annual precipitation is 600 mm (CV=25%).

Availability of water to animals is primarily from rainwater collected in natural depressions.

However, most of these do not hold water during the late dry season, when water is artificially supplied in about 50 waterholes spread throughout HNP. Numerous artificial waterholes are located in the study area. We analysed only data from the two most contrasting seasons i.e.

the wet and late dry season (dry season hereafter).

In the study area, the average lion density is 3.5 lions/100 km 2 (Loveridge et al., submitted). Wild dogs, cheetahs and leopards are also present in the study area. Collars were programmed to take hourly fixes at night between 4 pm to 6 am. We computed individual home ranges (HRs) using 95% isopleths of location based kernels using the reference smoothing factor h ref as recommended by [START_REF] Frank | Lions, Conflict and Conservation in eastern and southern Africa. A Background paper for the Eastern and Southern African lion conservation Workshop[END_REF]. Only locations within these 95% HRs were used in the following analyses. RSFs comparing used GPS locations to random ones are now often used to study animal habitat selection (e.g. Thaker et al. 2011;Davidson et al. 2012). However, the definition of random locations proves to be a problem as they should represent a sample of locations that could have been used by the animal, i.e. they have to be accessible to it. For territorial species, it implies that random locations are drawn from within each individual HR. In addition, fine scale successive GPS relocations have a high degree of spatio-temporal correlation which can prove troublesome in RSFs (Manly et al., 2002;[START_REF] Lele | Selection, use, choice and occupancy: clarifying concepts in resource selection studies[END_REF]. Sub-sampling the data set to select locations with low correlation has been often done but it results in high loss of information [START_REF] Fieberg | Correlation and studies of habitat selection: problem, red herring or opportunity?[END_REF] and correlation between successive relocations is often informative in itself [START_REF] Dray | The exploratory analysis of autocorrelation in animal-movement studies[END_REF]. Therefore, we chose to generate random points with the same patterns of correlation as the used ones. For each individual hyaena, we split the dataset into successive nights (producing a total of 1503 nights), defining night paths as all successive fixes between 4 pm and 6 am. We generated five random paths for each used night path by randomly moving it and rotating it within the individual HR (every of its fixes staying within the HR). Each random path contained the same number of fixes as the associated used path.

Spotted hyaena GPS data and random locations

Each random point of each random path was assigned the same date and time as its corresponding used location within the associated used path.

Environmental data

A vegetation map was designed based on three Landsat images from August and November 2002 and April 2003 with a resolution of 30 m (Chamaillé-Jammes, unpublished work). Six vegetation types were defined with increasing woody plant density: grassland, sparsely bushed grassland, bushed grassland, bushland, bushed woodland and woodland.

Grassland was the most open (higher visibility) vegetation class and was used as the reference in the following analyses. Each location (used and random) was assigned to a vegetation type.

In we assigned a moon illumination index equal to the moon fraction if the moon was below the horizon at the time of the location, 0 otherwise.

Risk of lion encounter

During the course of the study, 43 lions were equipped with GPS collars (see Loveridge et al., 2007 for details). For each night in the hyaena data set, we used lion GPS locations to first build lion Movement based Kernels Density Estimator (MKDE) to calculate individual HR using data from the whole year preceding a given night. For each lion, we also computed successive 5% MKBE isopleths for the month preceding a given night. The risk of encountering a given lion at a given hyaena location (used or random) was calculated as 100 minus the smallest isopleth HR value in which the location was lying. For a given lion, if the hyaena location was not within the monthly MKDE but within the yearly one, then the risk of encountering this lion was assigned to 0. If the hyaena location was not within either of these HR, then the risk was set to unknown. Thus, for a given lion, the risk ranged from 0 (location within 95% HR or within yearly MKDE only) to 95 (location within 5% HR). We assigned the risk of encountering a lion as the maximum risk across all individual lions HR in which each location (used and random) fell. All locations with a risk unknown were removed for the following analyses leaving a sample size of 13 582 used and 66 447 random locations for wet season and 10 471 used and 49 676 random locations for the dry season.

Prey habitat preference

Prey densities were estimated in the Main Camp area by using line transect surveys carried out in September/October (end of the dry season) and in May (end of the wet season). We used most available roads as transects. Details of the methodology used to analyse the data are provided in Chamaillé-Jammes et al. (2009). We calculated the kilometric abundance index for each prey species encountered during road transect counts [START_REF] Vincent | Kilometric index as biological indicator for monitoring forest roe deer populations[END_REF][START_REF] Maillard | The Kilometric Index as a monitoring tool for populationsoflargeterrestrialanimals:afeasibility test in Zakouma National Park, Chad[END_REF]. This index represents an encounter rate per kilometer of road driven and was taken as a proxy for the rate at which lions encounter individuals of each species of prey when moving through the environment. To avoid any bias linked to the probability of detection of an animal depending on habitat type, we used only observations located within 100 m of transects. We then converted the abundance index into biomass by multiplying the unit mass (i.e., average mass of individuals in a population- [START_REF] Cumming | Ungulate community structure and ecological processes: body size, hoof area and trampling in African savannas[END_REF] by the abundance of each of the prey species. We calculated the total prey kilometric biomass by adding the kilometric biomass of all species excluding elephants (Loxodonta africana) encountered for each vegetation type. Data were analysed using Distance Sampling software [START_REF] Thomas | Distance 6.0. Research Unit for Wildlife Population Assessment[END_REF].

Resource selection function

Contrary to compositional analysis [START_REF] Aebischer | Compositional analysis of habitat use from animal radio-tracking data[END_REF], RSFs allow to include multiple and continuous variables into habitat selection analyses (Manly et al., 2002). The interest of mixed conditional -or not-logistic regression in habitat selection studies has been recently emphasised (Manly et al., 2002;[START_REF] Duchesne | Mixed conditional logistic regression for habitat selection studies[END_REF]. By using the individuals as sample unit and a match design, we can eliminate issues with data auto-correlation [START_REF] Gillies | Application of random effects to the study of resource selection by animals[END_REF][START_REF] Duchesne | Mixed conditional logistic regression for habitat selection studies[END_REF]. We used mixed case control logistic regressions between each used hyaena location against the five corresponding random locations with hyaena individual ID as random factor. We built one model for the wet and one model for the late dry season. As predictors, we included the risk of encountering lions, vegetation type and distance to the closest artificial waterhole for the dry season model or to the closest open area for the wet season model as simple effect variables (see Figure 1).

We also included the following double interactions: risk of encountering lions and vegetation type, risk of encountering lions and distance to water / open area, risk of encountering lions.

In order to investigate how hyaena response to the risk of encountering lions was mediated by the interaction between the vegetation type and the night brightness, we also included the triple interaction between the risk of encountering lions, vegetation type and moon illumination index into the model (see Figure 1). This produced a set of 37 models for each season. We use the Akaike criterion information (AIC) to select the models best fitting the data, defined as those within ΔAIC ≤ 2 of the best model (Burnham & Anderson, 2002). All statistical analyses were conducted in the R software version 3.0.2 (R development Core

Team, 2013) using the function 'mclogit' from the 'mclogit' package.

RESULTS

Prey habitat selection

During both seasons, prey biomass kilometric index (excluding elephants) was highest in grassland, sparsely bushed and bushed grassland (Figure 3a Based on AIC, one model was best explaining hyaena habitat selection. The best model included the triple interaction between the risk, vegetation type and moonlight and the interaction between the risk and distance to an open area (Table 1). The open grassland habitat was the most preferred one, followed by sparsely bushed grassland and woodland. The three other habitats types, bushed grassland, bushland and bushed woodland were similarly less preferred compared to open grassland (Figure 4a). Overall, hyaenas selected for locations (Figure 5a). During full moon nights, grassland was avoided when the risk of encountering lions increased while selection for other habitats (except bushed woodland) showed the opposite trend (Figure 6a). However, during moonless nights, hyaenas showed little response to lion encounter risk while in grassland (Figure 6c). In other habitat types, independent of the moon phase, predation risk had a negative impact on selection (woodland and bushland) or little impact (bushed grassland and bushed woodland) except for sparsely bushed grassland

where selection was positively correlated to the risk (Figure 6a andc). Thus locations with high risk of encountering lions where only avoided in particular conditions: during bright nights in grassland with high visibility and in dark night in woodland with important canopy cover. In other conditions and habitats, hyaenas tended to use the same locations as lions do.

In both full moon and moonless conditions, hyaena preferred habitat switched from grassland at low risk to sparsely bushed grassland as the risk increases.

Dry season habitat selection

Based on AIC, there was only one best model which was the same as for the dry season (Table 1). During the dry season, the most preferred habitat was grassland followed by woodland and sparsely bushed grassland (Figure 4b). The three other vegetation types were equally less preferred compared to grassland. Hyaenas preferred location close to artificial waterholes and the risk of encountering lions had a positive effect on site selection irrespective of the distance to artificial waterhole (Figure 5b). During full moon nights, only the preference for grassland decreased with increasing risk of lion encounter. Hyaenas tended to select the same areas as lions do in all other habitats, and the positive effect of encounter risk was particularly strong in sparsely bushed grassland and much weaker in woodland and bushed grassland (Figure 6b). During moonless nights, the risk of encountering lions had a positive effect on location selection in all habitat types but woodland, for which the effect was negative (Figure 6d). Independently of the lion encounter risk, all habitat types with bushes or canopy cover had a higher probability of selection during full moon nights than during moonless ones, with more open habitats having a higher probability of selection (sparsely bushed grassland > bushed grassland > bushland > bushed woodland > woodland).

DISCUSSION

We showed that there is clear need to consider the interaction between the risk of encountering lion, the vegetation type and the moon phase to grasp the full picture of hyaenas spatial adjustment the risk of predation. We found that habitat selection in hyaenas is influenced by the risk of encountering lions and that they react differently to their predator depending on environmental variables such as habitat type and moonlight conditions.

We expected hyenas to show an overall avoidance of lions in order to reduce their predation risk like prey or other carnivores do (Creel et al., 2005;Ritchie & Johnson, 2009;Valeix et al., 2009), but also to limit competition for live prey and carrion. Indeed, competition for resources can influence species habitat use [START_REF] Acevedo | The Iberian ibex is under an expansion trend but displaced to suboptimal habitats by the presence of extensive goat livestock in central Spain[END_REF]. Contrary to this classical hypothesis, hyaenas did not show a general avoidance of lions and rather preferred locations also intensively used by them. Our results were not contrasted between the two seasons, despite the fact that finding food is more difficult during the wet season, when prey are dispersed and carcasses less easy to find.

We showed that artificial waterholes during the dry season are key habitat features for hyaenas. Prey concentrate in large numbers around these waterholes when all natural ones are dry, resulting in high availability of food in these areas. In addition, hyaenas clearly preferred open grasslands to any other habitat type. These results validate the hypothesis that hyaenas select for patches rich in prey, as prey also favour these open habitats. The high variability found in prey kilometric index in woodland is explained by the low sampling effort for this habitat (only 1.9 km per transect were in woodland, against more than 50 km per transect for the other habitat types). Waterholes also play a major role in structuring lion space use in HNP. Lion spend most of their time close to waterholes throughout the year and most of their kills are located within 2 km of waterholes (Valeix et al., 2009). The non-avoidance of locations with high encounter risk of lions close to waterholes or open areas is thus probably a consequence of both predators selecting for areas rich in prey where competition for food is less intense. Our results did not support our hypothesis that hyaenas should avoid lions in areas poor in prey because encounters can be costly in terms of food. On the contrary, hyaenas appeared to also select for areas intensively used by lions even when in mediocre patches and do not avoid lions in habitat types poor in prey (e.g. bushland). This pattern can result from the same mechanism as previously: both lions and hyaenas are looking for prey in the same areas independently of each other. But it could also result from the fact that they are attracted to each other, with one species actively following the other. In areas poor in prey, hyaenas or lions might actively seek each other to benefit from kills or carcasses via kleptoparasitism and scavenging. Both species are efficient hunters (Holekamp et al., 1997;Hopcraft et al., 2005) but also take advantage of any scavenging opportunity (Schaller, 1972;Honer et al., 2002). Lions have been shown to respond very quickly to sounds of hyaenas making a kill or squabbling around a carcass (Kruuk, 1972;Kiffner, Waltert & Meyer, 2007) and they often steal carcasses from them (Trinkel & Kastberger, 2005). Hyaenas are also attracted to lion kills and can make use of pieces of skin and bones left behind by lions, as well as chase them away (Kruuk, 1972). We recorded all the carcasses used by hyaenas during the study based on GPS data (Chapter 2) and found that large carcasses (elephant, buffalo -Syncerus caferand giraffe -Giraffa camelopardalis-) were on average 3.3 km away from artificial waterholes and 58 out of 73 carcasses were more than 500 m away from water.

However, most of the carcasses (55 out of 73) were within 100 m of an open area. So while our hypothesis that hyaenas and lions attract each other at the same carcasses far from water during the dry season might be valid, it is not supported by the pattern of carcasses locations during the wet season. It is possible that during the wet season, both hyaenas and lions select for areas locally rich in prey rather than increasing their kleptoparatism activity. Monthly MKDE is a relatively fine scale estimation of the probability of a lion being at a location. However, lions in HNP have been shown to move to a different area after most of their kills (Valeix et al., 2011). This behaviour would induce monthly MKDEs to have several cores, i.e. several areas used intensively by lion during the preceding month. It would allow hyaenas to use such areas only after the departure of lions and thus with a low risk of encountering them. This would explain why hyaenas selected for locations in risky areas.

We found that hyaena response to the risk of encountering lions was mediated by the habitat type and the moon illumination. This is in accordance with the fact that the risk of encountering a predator is not equivalent to the risk of predation, and that the actual risk depend on habitat [START_REF] Hebblewhite | Spatial decomposition of predation risk using resource selection functions: an example in a wolf-elk predatorprey system[END_REF] and predator strategy (Atwood, Gese & Kunkel, 2009). There is no consensus on the impact of moon illumination on lion activity patterns. [START_REF] Packer | Fear of Darkness, the Full Moon and the Nocturnal Ecology of African Lions[END_REF] concluded that in the Serengeti and Ngorongoro, lions tend to hunt more during dark nights, while a recent study in Moremi Game Reserve, Botswana showed that lion activity was not influenced by the moon illumination index (Cozzi et al., 2012). However, even if lion hunting success is lower in bright light conditions (Van Orsdol, 1984;Funston, Mills & Biggs, 2001b), they have a better chance to spot hyaenas.

Thus bright nights in open habitats should be more risky for hyaenas than dark ones. Our results are in accordance with this hypothesis as hyaenas avoided grassland during full moon nights when the risk of encountering lions was high. However, they increased their preference for this habitat rich in prey during moonless nights when they are far less conspicuous to lions. While Prugh at al. [START_REF] Prugh | Does moonlight increase predation risk? Metaanalysis reveals divergent responses of nocturnal mammals to lunar cycles[END_REF] argue that for prey, foraging efficiency and predator detection increases with moonlight and off balances the increase detectability by predators, this does not seem to hold true for hyaenas. It is also possible that hyaenas hunting success in grassland is higher during moonless night, when prey might be more confused by the darkness.

In woodland, the visibility was also high (visibility in grassland was on average more than four times higher than in bushed habitats and about two times higher in woodland, unpubl. data) and the risk of ambush relatively low compared to bushed habitats. As a result, hyaenas avoided woodland when the risk was high only during moonless nights, i.e. in extremely dark conditions when the tree canopy is obscuring the little light coming from the stars. As a cursorial predator, hyaenas rely primarily on sight to detect and hunt their prey, thus bright conditions should be advantageous [START_REF] Prugh | Does moonlight increase predation risk? Metaanalysis reveals divergent responses of nocturnal mammals to lunar cycles[END_REF]. Extremely low light conditions in woodland during moonless nights might have a negative impact on prey detection and can prove dangerous for long chases (Broekhuis et al., 2013). It thus makes sense for hyaenas to avoid encountering lions in such unfavorable conditions.

In bushy habitats, hyaenas selected for locations also used by lions, and this was barely impacted by the moon illumination. This is in accordance with results from Broekhuis et al. (2013) and Vanak et al. (2013) both concluding that subordinate predators were more likely to be found close to lions in dense vegetation. Thus, even though these habitat types are ideal for ambushed predators as lions (Funston et al., 2001b), they also provide concealment for hyaenas making them less sensitive to the risk of predation by lions. Figure 7 summarizes our understanding on the joint effect of habitat type, hyaena hunting success, lion encounter risk and moon illumination on habitat selection in hyaena.

Our results show that contrary to the classic hypothesis that hyaenas avoid lions, they do so only in extremely risky conditions: either in very open areas during full moon or in habitat with high canopy cover during dark nights. The rest of the time, hyaenas and lions use the same areas. However, hyaenas seem to select habitat in order to not being detected by lions rather than seeing them first. Hyaenas thus limit their risk of predation by avoiding lions in risky conditions and selecting safer habitats when the risk of lion presence increases. This pattern is very similar to that of prey (Thaker et al., 2011) but more complex as hyaenas can also benefit from staying close to lions. In HNP, hyaenas do not avoid areas intensively used by lions to establish their dens either (Chapter 5), but their pattern of den attendance suggests that they rather avoid lions temporally. Our results suggest that if hyaenas do avoid lions, they might do so at very fine spatial and temporal scales and in a highly dynamic way. The response of hyaenas to the risk of encountering lions shows that the actual risk of predation is a combination of several factors in which habitat type and night brightness play an important role. We thus encourage future research on the influence of predation risk on habitat selection of both predator and prey to take these two parameters into account.

INTRODUCTION

Interactions among species regulate natural populations and shape community structure.

Inter-specific killing is an extreme case of interference competition among carnivores [START_REF] Polis | The ecology and evolution of intraguild predation: potential competitors that eat each other[END_REF] and has been shown to occur amongst a very wide range of species (Palomares & Caro, 1999). Predation by other carnivores is one of the main causes of juvenile mortality in some species (see Mills & Biggs, 1993 for wild dogs, Lycaon pictus; [START_REF] Laurenson | Extrinsic factors and juvenile mortality in cheetahs[END_REF]Mills & Mills, 2013 for cheetahs, Acinonyx jubatus) and might thus impact on population dynamics and recruitment. In studies of predator avoidance, some suggested that individuals may use long term knowledge of their predators' space use [START_REF] Fuller | Non-overlapping ranges of coyotes and wolves in northeastern Alberta[END_REF] but recent work (Broekhuis et al., 2013) suggests that their response can be reactive rather that predictive.

Many species use dens to protect their young [START_REF] Tannerfeldt | Exclusion by interference competition? The relationship between red and arctic foxes[END_REF][START_REF] Theuerkauf | Selection of den, rendezvous, and resting sites by wolves in the Bialowieza Forest, Poland[END_REF][START_REF] Carter | Ecology of the red fox (Vulpes vulpes) in an agricultural landscape. 1. Den-site selection[END_REF]. Several studies have shown that dens may be selected based on environmental features such as thermal insulation [START_REF] Kaneko | Variations in Badger (Meles meles) Sett Microclimate: Differential Cub Survival between Main and Subsidiary Setts, with Implications for Artificial Sett Construction[END_REF], soil type [START_REF] Way | Eastern coyote denning behavior in an anthropogenic environment[END_REF] forest composition [START_REF] Norris | Forest composition around wolf ( Canis lupus) dens in eastern Algonquin Provincial Park, Ontario[END_REF] and distance to water [START_REF] Henner | A multiresolution assessment or raccoon den selection[END_REF]. Less is known about how predation risk influences den selection. It has been suggested that some species select dens as a function of their risk of predation. For instance, [START_REF] Way | Eastern coyote denning behavior in an anthropogenic environment[END_REF] suggested that coyotes (Canis latrans) select dens in dense cover to hide pups from wolves (C. lupus). [START_REF] Carter | Ecology of the red fox (Vulpes vulpes) in an agricultural landscape. 1. Den-site selection[END_REF] argue that red foxes (Vulpes vulpes) breeding dens have more entrances than do non breeding dens in order to protect the pups from predation. However, there seems to be no existing knowledge on how species use their dens depending on the previous whereabouts of their competitors/predators.

Dens play an essential role in spotted hyaena (Crocuta crocuta) ecology (Kruuk, 1972).

Cubs are born and raised in such dens, depending on them for safety and survival during the first year of their life (Hofer & East, 1993). Despite this, most cub mortality at dens is due to lions (Panthera leo, Mills, 1990;Watts & Holekamp, 2009) . Spotted hyaenas (hyaenas hereafter) are large predators (~ 60 kg) living in groups called clans (Kruuk, 1972). Together with lions, they are the largest and most numerous predators in Africa and lions are a main cause of mortality for both adult and juvenile hyaenas (Kruuk, 1972). All adult females in a hyaena clan raise their litters together in a communal den. They do not excavate their own dens, but rather use holes dug by aardvarks, warthogs or porcupines (Kruuk, 1972). Only cubs can enter the narrow tunnels where they are protected from harsh weather conditions, other clan members and predators. Dens usually have several entrances allowing cubs to gain access as fast as possible at the slightest hint of danger. In the open savanna of Eastern Africa, dens are the center of social interactions between clan members (Kruuk, 1972;Cooper, 1993).

Thus, it is common for at least one adult member of the clan to be present at the den.

However, when lions approach, adult hyaenas usually run away probably to lure the lions away [START_REF] East | Functions of birth dens in spotted hyaenas (Crocuta crocuta)[END_REF]Cooper, 1993) while cubs remain hidden inside the den.

Cubs remaining outside the den are frequently killed (Cooper, 1993). It is therefore crucial for hyaenas to find dens safe from lions.

This work is one of the first studies of hyaenas in a wooded savanna. In this habitat, such as Hwange National Park, Zimbabwe, very little is known about den sites themselves. Finding dens in densely wooded areas is difficult, and so is behavioral monitoring, but recent developments in radio-telemetry allow for long-term tracking of animal movement and space use. We expected that hyaenas would select dens in areas with a low probability of lion presence and providing protection from predators, using specific dens when lions are not present in the area. In particular, we predicted that (1) hyaena dens would be located outside of lion core home ranges (HRs) and that they should avoid denning close to waterholes as these are foci of lion activity (Valeix, Loveridge, et al., 2009). We also expected that (2) hyaenas should select for dens with several entrances and in dense vegetation. Finally, we predicted (3) that presence of lions in the vicinity of den for a given period should decrease the likelihood of the den being visited during the same period and that hyaenas also respond to past lion presence around a den.

METHODS

Study area

Hwange National Park (HNP) covers an area of approximately 14,600 km 2 in northwestern Zimbabwe (19°00'S, 26°30'E). The study area (≈ 1500 km 2 ) is located in the northern part of HNP characterized by Kalahari sand soils. The vegetation is primarily woodland and bushland savanna, interspersed with small patches of grassland (Rogers, 1993). HNP is semiarid with a wet season from November to April and a dry season from May to October. The long term mean annual precipitation is 600 mm. Availability of water to animals is primarily from rainwater collected in natural depressions. However, most of these do not hold water during the dry season, when water is artificially supplied in about 20 waterholes spread throughout the study area. In the study area, the average hyaena density between 2009 and 2012 was 9 hyaenas/100 km 2 and lion density was 3.5 lions/100 km 2 (Loveridge, Davidson, et al., 2007).

Spatial data and den sites identification

During the course of this study, from July 2009 to August 2012, eight adult female hyaenas were equipped with GPS radio-collars (African Wildlife Tracking, UHF 407, GPS collar with UHF download and VHF transmitter). There was no evidence that these individuals had dependent cubs at the time of capture. Collars were set up to take hourly GPS from 18:00 to 6:00 and one fix at 10:00, 12:00 and 16:00 making a total of 17 fixes per 24h. Collar accuracy was about 16 m in wooded area. We defined HRs and cores using 95% and 50% Kernel isopleths respectively using the reference smoothing factor h ref as recommended by Hemson et al.(2005). HR estimation was done over the whole hyaena dataset (individuals were monitored for at least 3 consecutive months). Based on their HR location and overlap, the eight hyaenas belonged to four different clans. As individuals were often not seen for extended periods of time, their reproductive status could not be assessed.

During the study, 18 lions (11 males and seven females) from different social groups were fitted with GPS radio-collars. GPS collars were programmed to take hourly fixes during the night from 18:00 to 07:00. At least one individual per pride or coalition was collared in the study areas and individuals from the same pride/coalition spent most of their time together (Valeix, Loveridge, et al., 2009). We thus monitored 11 coalitions and seven prides, each of them during at least several consecutive months. As lions are territorial, there is thus very little chance of lion presence not accounted for in our analysis.

Hyaenas were immobilized by a professional team either with a standard mix of 500 mg Ketamine (Kyron laboratories Pvt. Ltd, Ben-rose, RSA) and 200 mg Xylazine (Rompun;

Bayer, Leverkusen, Germany) or of 80 mg Zoletil (Virbac RSA, Halfway house, RSA) and 4 mg Medetomidine (Zalopine, Wildlife Pharmaceuticals, Karino, RSA). Drugs were then reversed with 16 mg of Yohimbine (Rx drug, Kyron Labs, Benrose, RSA). Full recovery was ensured by staying with the animal until it would walk away normally. All hyaenas were adults aging between 3 to 8 years. Details on lion immobilization and collaring are provided in Loveridge et al. (2007). Radio-collars were replaced or removed within the framework of long-term monitoring protocols. Relevant animal care protocols were followed during capture and collaring of carnivores (Wildlife Drugs Sub-committee of the Drugs Control Council of Zimbabwe and Zimbabwe Veterinary Association, Wildlife Group, and licenses to acquire, possess and administer game capture drugs/dangerous drugs), and permissions were provided by the appropriate agencies (Zimbabwe Parks and Wildlife Management Authority).

Clusters of locations from hyaena GPS data (areas where hyaenas spent at least three consecutive hours at night within a 50 m radius circle) were visited on foot to search for dens, i.e. holes in the sand where signs of hyaena presence, such as tracks, scats, urine, pieces of bones or regurgitated pellets were found. Day locations were discarded to avoid identifying day rest sites. Potential den sites were visited as soon as possible after cluster detection, and no investigation was made after the rainy season started. Out of 281 clusters detected, we visited 263 and found 32 dens. We added 25 dens detected by other means (during walks to investigate clusters, information given by other scientists, game rangers, etc) to this data set, making up to 57 dens actually used by hyaenas. All dens were too small for adults to enter, thus could not be considered as adult resting sites. Areas around dens were most often showing marks of intensive use by several adult hyaenas (trampled vegetation, lying places, etc.) thus all dens were considered as communal dens.

As hyaenas do not excavate their own dens, we defined 51 additional control holes encountered ad hoc during walks to investigate GPS clusters or during other activities. All control holes fell within hyaena territories.

Predation risk by lions

We defined two levels of predation risk: the long-term risk of encountering lions and the actual presence of lions in the vicinity of a den. We first defined a long-term risk of encountering lions using all lion GPS data over our study period. We calculated HR for each lion (95% Kernel isopleths). Each den and control was then coded as 1 (or 0) if it was located (or not) within the HR of at least one lion. We repeated this procedure for HR cores (50% Kernel isopleths). The analysis was conducted for male and female lions separately. As all dens and controls (but one) were located within at least on lion HR, we focused our analysis on HR cores.

We then quantified the presence of lions in the vicinity of a den at different spatiotemporal scales, representing the actual risk of encountering lions nearby the den. We defined ring buffers of 3 km, 1.5 km, 1 km and 500 m around dens and calculated the number of days per seven days period, i.e. week, when lions were found within the buffer. For each week, we also quantified the presence of lions at four temporal levels: during the week of interest as well as during the week, the two weeks and the month preceding the week of interest.

Den selection

For each den and control hole, we recorded the number of entrances and each entrance's width and height (in cm). Entrance width and height were not taken into account in the selection analyses as they most likely are a result of a den being used, rather than part of a selection process. We defined habitat type as bushed-grassland, bushland, woodland or woody-bushland. Classification was based on the dominant vegetation immediately surrounding the den.

The visibility at each den was assessed using two 50 cm x 50 cm white boards attached to a pole. The first board was set at 10 to 60 cm and the second at 100 to150 cm corresponding to the heights of a standing hyaena and a standing lion respectively. One person stood at the den/hole (central point) holding the visibility board while a second person walked away from it in each of the four cardinal directions. The distance at which each board could no longer be seen was measured using a handheld GPS device (Garmin GPSmap 60CSx; Garmin, Olathe, Kansas, USA) with an accuracy of about 4 m. The distances in each cardinal direction were then averaged to give a mean visibility measure at each site. As there was a significant correlation between the mean visibility of the two heights (Pearson: n=109, ρ=0.84, p<0.0001), only the mean visibility for the lower height was used.

We used generalized linear models with a binomial error structure and logit-link function to predict the probability of a hole being selected as a den (1) or not (0; control hole) by hyaenas depending its location within lion and hyaena HR cores. We used the same method with number of entrances, visibility distance and distance to the nearest waterhole as explanatory variables. We selected the best supported models based on the AICc criterion (Burnham & Anderson, 2002). We used model averaging to calculate estimates based on all models within ΔAICc<2

Den use

For dens discovered using GPS data (n=32), we used the following criteria to define periods of potential den use. Each den was associated with a collared hyaena. For each day, we calculated the minimum distance from the hyaena to the den; then, we considered that the den was potentially visited on days when minimum distance < 500 m (hyaenas travel an average of 1 km/h at night). A period of use was defined as at least five potential visits, two consecutive ones being separated by less than a week (see Appendix 5.1 for details). Based on this definition, we reduced our sample size from 32 to 27 dens actually used (i.e. an individual was consistently active in its vicinity). We also defined weekly den use by splitting the dataset into seven days periods. A den was considered as used if it was approached at least four days out of the seven.

For each den, we defined the duration of each period of use (in days) as well as the average duration of a period of use and the total duration of use being the sum of all periods of use.

We used linear mixed models to detect any effect of predation risk proxies on den use using distance to waterhole, number of entrances and visibility as explanatory variables. We defined individual hyaena ID and den ID nested within individual ID as random variables for the analyses of average length of a period of use and the total length of use. We then used generalized linear mixed models with a binomial error structure and the same random variables to model the effect of lion presence within a given distance of the den (3 km, 1.5 km, 1 km and 500 m) and during a given period (same week, two weeks earlier and a month earlier) on the likelihood of this den being used during a given week (i.e., the den was approached at least four days).

Estimates are given with ± standard deviation (SD) unless stated otherwise. Statistical analyses were performed in R 3.0.2 (R development Core Team, 2013) and packages 'lme4' and 'MuMIn '.

RESULTS

Den characteristics

Half of the dens (47.4% out of 57) were located within hyaena core ranges (Figure 1), with 42.1% and 56.1% of the dens located in core HRs of female and male lions respectively (Figure 1). Dens had an average of 1.5 ± 1.1 entrances, ranging from 1 to 7. There was no difference in entrance height between dens (42 ± 10 cm) and controls (40 ± 14 cm, F 1,144.93 = 0.64, p = 0.42), while entrance width (53 ± 18 cm) was significantly larger in dens (46 ± 10.2 cm, F 1,140.57 = 9.19, p = 0.003). Dens were located in areas where average distance of visibility was 23 ± 11 m and on average at 2335 ± 1180 m from the nearest waterhole. The dominant habitat was woody-bushland for 76.5% of the dens, bushland for 21.6% and woodland for 13.7%.

Den selection

Dens were not more likely to be located within hyaena core HRs than were controls (z = 0.15, p = 0.88, Figure 1). Holes within both female pride and male lion core HRs were not less likely to be selected as dens than those outside lion core HRs (female: z = 0.94, p = 0.35; male: z = 0.74, p = 0.46, Figure 1). The two models best explaining den selection by hyaenas included distance to water and number of entrances, both having a positive effect on den selection (Table 1 & 2, Figure 2).

Patterns of den use

On average dens were used 1.8 ± 0.2 times (range 1-3) and for a length of 45.2 ± 5.8 days (range 12-108 days) over the four years of study. Around half of the dens were used more than once (15 of 32). We did not find any evidence that den use, in terms of duration of each period of use, average and total period of use duration was influenced by distance to water, number of entrances or visibility. However, we found that the likelihood of a den being visited during a given week decreased with increasing lion presence in its vicinity (Table 3, Figure 3a). The negative effect of lion presence was stronger when they were closer to the den. For a given week, the negative effect of lion presence within a given radius on the likelihood of the den being approached by hyaenas was still significant when considering the presence of lions during the weeks preceding the week of interest (Table 3, Figure 3b). Lion presence had the strongest effect during the two weeks before the week of interest, followed by their presence during the preceding week, the week of interest and lastly the preceding month. Therefore, hyaenas were sensitive to the actual presence of lions at least up to 3 km of their potential dens and for at least a month after their passage.

DISCUSSION

Hyaenas select and use their dens depending on both habitat features and predation risk.

We found that den entrances are larger than these of control holes which is in accordance with results from Kruuk (1972) who observed that cubs enlarge the entrances. Contrary to our expectations, dens did not tend to be located within hyaena core HRs. This could be explained by a different denning behavior of hyaenas in wooded savanna compared to open ecosystems.

Despite the fact that dens are described as centers of social life in the Serengeti (Kruuk, 1972), we never observed hyaenas gathering at dens in HNP. Nevertheless, we found no evidence of reproduction in our collared individuals during the study period and they might have only visited or approached the dens occasionally, while only females with cubs used them intensively.

Several species have been shown to avoid denning in areas intensively used by their predators, as is the case of both Cape foxes (Vulpes chama) and bat-eared foxes (Otocyon megalotis), who avoid black-backed jackals (Canis mesomelas; [START_REF] Kamler | Resource partitioning among cape foxes, bat-eared foxes, and black-backed jackals in South Africa[END_REF]. We therefore expected that lion spatio-temporal habitat use would influence den selection and use by hyaenas. Yet, we found that hyaenas did not seem to avoid denning within lion HRs or intheir core areas. The whole study area fell within at least one lion HR, thus hyaenas had no choice but to den in lion territories. However, hyaenas tended to select dens based on environmental variables, such as distance to waterholes, that lower their predation risk.

Several species such as coyotes [START_REF] Way | Eastern coyote denning behavior in an anthropogenic environment[END_REF] and raccoons (Procyon lotor, [START_REF] Henner | A multiresolution assessment or raccoon den selection[END_REF]) have been shown to select dens close to water sources. In semi-arid savannas, waterholes are key resources for water and prey but also attract predators (Valeix, Loveridge, et al., 2009). Here, we found that hyaenas avoid denning nearby waterholes, thus close to lions and prey concentrations. Yet, 74% of the dens were located within 3 km of a waterhole.

At this distance, they still can access prey and water easily and maybe the soil there is better for burrowing species to excavate. Our study area was located on Kalahari sands, which are not ideal for the construction of permanent burrows. Areas around waterholes might have soil other than deep sands, richer in clay or calcrete, making holes less susceptible to collapse.

Soil type has indeed been showed to influence den selection in red foxes, wolves and coyotes [START_REF] Way | Eastern coyote denning behavior in an anthropogenic environment[END_REF][START_REF] Theuerkauf | Selection of den, rendezvous, and resting sites by wolves in the Bialowieza Forest, Poland[END_REF]Macdonald et al., 2004;[START_REF] Carter | Ecology of the red fox (Vulpes vulpes) in an agricultural landscape. 1. Den-site selection[END_REF].

Hyaenas preferred dens with several entrances, thus providing easier escape routes for cubs. [START_REF] East | Functions of birth dens in spotted hyaenas (Crocuta crocuta)[END_REF] also showed that communal dens usually have more than one entrance. In addition, [START_REF] Moehrenschlager | Escaping Intraguild Predation: Mexican Kit Foxes Survive while Coyotes and Golden Eagles Kill Canadian Swift Foxes[END_REF] showed that kit foxes (Vulpes macrotis) were more likely to escape predators as the availability of refuge holes increased. Vegetation cover and density can also affect den selection [START_REF] Arjo | Characteristics of current and historical kit fox (Vulpes macrotis) dens in the Great Basin Desert[END_REF][START_REF] Kaartinen | Selection of den sites by wolves in boreal forests in Finland[END_REF]. However, we did not find any significant effect of vegetation density on den selection.

In hyaenas, consistent den use is mostly determined by female reproductive condition. If a female has dependent cubs, she will have to visit the den to nurse them at regular intervals for at least a year (Kruuk, 1972). However, several studies have shown that dens are central places in the social life of the clan (Kruuk, 1972;Mills, 1990;Cooper, 1993;Hofer & East, 1993) and that all clan members spend extended periods there with frequent visits. We do not know if the collared hyaenas had dependant offspring during the study period, but we can safely assume that if they spend long periods of time in the proximity of a den it most probably means that they were socializing at a den.

In Hwange, hyaenas use their dens for about 45 day periods and re use about half of them.

This pattern is similar to the one observed in the Masai Mara [START_REF] Boydston | Patterns of den occupation by the spotted hyaena (Crocuta crocuta)[END_REF], where hyaenas are known to vacate their dens and sometimes re use them later (Kruuk, 1972). In HNP, hyaena den attendance was influenced by the actual predation risk by lions with the increased presence of lions close to a given den having a negative effect on the probability of this den being approached by hyaenas. The effect of lion presence was immediate and decreased in strength with the distance of lions from the den. In addition, hyaenas adjusted their patterns of den attendance according to recent (up to at least a month) lion presence in the vicinity of the den. It is possible that they respond to cues of lion presence such as scent-marks, urine or scats. It is also possible that hyaenas remember lion presence.

Interestingly, this "ghost of lion presence" was strongest when lions had been present during the past two weeks, suggesting that hyaena's decision to attend a den is based on an integrated knowledge of lion presence rather than their immediate presence in the vicinity. On the other hand, none of the other variables tested (distance to water, number of entrances and visibility) seemed to influence den use patterns in terms of total and average duration of use and frequency of use.

Overall, den selection was influenced by proxies of predation risk (distance to waterholes and number of entrances) while knowledge of the current and past presence of lions was more important for den use. The presence of several dens in each clan HR may allow hyaenas to reduce risk of encountering lions by temporarily avoiding using dens when lions are in their vicinity. Thus, hyaenas respond to lions in a reactive way rather than in a predictive way, like cheetahs do (Broekhuis et al., 2013) and make use of dens in risky areas only when their main competitor/predator is absent. This shifting space use is similar to the pattern observed in prey responding to the presence of their predators (Fortin et al., 2005;[START_REF] Hernández | Foraging in the 'landscape of fear' and its implications for habitat use and diet quality of elk Cervus elaphus and bison Bison bison[END_REF]Valeix, Fritz, et al., 2009). Den use is therefore a dynamic process responding to the risk of predation by lions and can therefore be relevant for hyaena reproduction and dynamics.

congregate around pumped waterholes. This would be in accordance to observations in Chobe NP where birth peak is in June, 4 to 6 months before the birth peak of zebras foals which constitute easy prey (Cooper, 1993). As for the wet season, cubs would be born after a period of high prey availability during which pregnant females have easy access to large amount of food. It would be useful to monitor dens to determine number and age of cubs in order to validate our hypothesis, the recent development of camera trapping devices may offer more opportunities to do so.

INTRODUCTION

Understanding how animals move in landscapes characterized by a spatial and temporal heterogeneity is key to several behavioural processes such as foraging behaviour and habitat selection [START_REF] Fauchald | Using first-passage time in the analysis of area-restricted search and habitat selection[END_REF][START_REF] Fritz | Scale-dependent hierarchical adjustments of movement patterns in a long-range foraging seabird[END_REF], dispersal [START_REF] Bowler | Causes and consequences of animal dispersal strategies: relating individual behaviour to spatial dynamics[END_REF], and ultimately provides valuable insights into the spatial structure of populations and communities [START_REF] Revilla | Individual movement behavior, matrix heterogeneity, and the dynamics of spatially structured populations[END_REF], and individual performance [START_REF] Gaillard | Habitat-performance relationships: finding the right metric at a given spatial scale[END_REF]. The recent advances in this research field have prompted the emergence of a movement ecology paradigm [START_REF] Nathan | An emerging movement ecology paradigm[END_REF]. Most existing works have studied the influence of resources on animal movement and have demonstrated that, for example, predators may show an "area-restricted search" (ARS) behaviour when they expect the resources to be clumped, i.e. they intensify their search for food in rich patches by lowering their speed and increasing their path tortuosity, and display high speed oriented movement between such patches (e.g. Smith, 1974a;Smith, 1974b;[START_REF] Kareiva | Analyzing insect movement as a correlated random walk[END_REF][START_REF] Fauchald | Foraging in a hierarchical patch system[END_REF][START_REF] Bartumeus | Animal search strategies: a quantitative random-walk analysis[END_REF][START_REF] De Knegt | Patch density determines movement patterns and foraging efficiency of large herbivores[END_REF]Young & Van Aarde, 2010). For instance, African lions (Panthera leo) have been shown to display an ARS behaviour in the vicinity of waterholes, which are prey hotspots in savanna landscapes (Valeix et al., 2010). Other factors than resources have been shown to also influence animal movement patterns such as habitat type [START_REF] Bélisle | Influence of forest cover on the movements of forest birds: a homing experiment[END_REF], predation risk (Fortin et al., 2005;[START_REF] Fischhoff | Habitat use and movements of plains zebra (Equus burchelli) in response to predation danger from lions[END_REF] and social factors, e.g. mating opportunities [START_REF] Beier | Movement patterns of mountain lions during different behaviors[END_REF]. Additionally, animal movements can be further influenced by anthropogenic factors such as roads [START_REF] Blake | Roadless Wilderness Area Determines Forest Elephant Movements in the Congo Basin[END_REF] and refuse pits (Kolowski & Holekamp, 2008), or by the fear of humans [START_REF] Valeix | Behavioural adjustments of a large carnivore to access secondary prey in a humandominated landscape[END_REF].

For predators, resources, i.e. prey abundance and distribution, clearly affect movement patterns and the presence of other predators is also likely to have a strong impact. Within the African large carnivore guild, five species coexist and compete with each other. In addition to exploitation competition, interference competition is likely to be particularly strong in carnivores [START_REF] Linnell | Interference interactions, co-existence and conservation of mammalian carnivores[END_REF] reaching the extreme case of intraguild predation (Palomares & Caro, 1999;Caro & Stoner, 2003). Spatial avoidance has been demonstrated in subordinate species. For example, wild dogs (Lycaon pictus) are excluded from prey rich areas by competitively superior lions and spotted hyaenas (Crocuta crocuta, hyaenas hereafter, Thaker et al., 2011;[START_REF] Swanson | Cheetahs and wild dogs show contrasting patterns of suppression by lions[END_REF], and studies on cheetahs (Acinonyx jubatus) have revealed that they move away from recent lion locations (Durant, 2000;Broekhuis et al., 2013;Vanak et al., 2013). Nonetheless, the consequences of coexisting with other carnivores on movement patterns have been little studied. It can however be expected that a subordinate species will limit the time spent in risky areas intensively used by a dominant species by moving fast and straight through them, and move quickly away after encounters with the dominant species. The development of GPS telemetry combined with Geographic Information Systems (GIS) now allows researchers to investigate the relationship between animal movement and their environment and study spatial interspecific relationships.

Here, we used a unique dataset of simultaneous hourly GPS positions of nine hyaenas and 18 lions (Panthera leo) in Hwange National Park (HNP), Zimbabwe, to study the influence of the environment and lions on hyaena movement characteristics. The relationships between hyaenas and lions are complex as they compete for prey and both scavenge from each other's kills (Kruuk, 1972). They are also able to chase each other from carcasses (Cooper, 1991;Honer et al., 2002) and lions are known killers of hyaenas (Kruuk, 1972;Mills, 1990;Watts & Holekamp, 2009). Hyaenas are thus facing a trade-off between following their competitor to benefit from their food or avoid them to limit their kleptoparasitism and predation risk.

HNP ecosystem is highly seasonal with prey dispersed in the landscape during the wet season, whereas they congregate in large numbers at artificial waterholes during the dry season, resulting in a patchy distribution of areas of high resource abundance. In the dry season, the distance to a waterhole is therefore a good proxy for prey abundance. We first tested the effect of the distance to waterholes, vegetation type, season, and night brightness on hyaena movement. We predicted that hyaenas would adopt an ARS in the vicinity of waterholes in the dry season (i.e. lower speed, more tortuous paths). We further expected that during bright nights hyaenas would move more (higher speed, longer displacement) due to the increased visibility for detecting prey and hunting (Hayward & Slotow, 2009). We then investigated the spatio-temporal dynamics of hyaenas and lions relationships. We tested if hyaenas generally avoided lions as it is classically assumed. A priori, we can expect hyaenas to avoid lions at several spatio-temporal scales. At a large scale and in a predictive way, hyaenas should limit their home range (HR) overlap with lions. Within their HRs, hyaena should either avoid areas intensively used by lions (e.g. artificial waterholes areas) or use them when lions are absent.

At a finer scale, hyaenas should quickly move away after an encounter with lions, especially when away from food to reduce the predation risk.

METHODS

Study area

Hwange National Park (HNP) is located in north-western Zimbabwe (19°00'S, 26°30'E)

and covers an area of approximately 14 600 km 2 . The study area (≈ 1 500 km 2 ) is located in the northern part of HNP, in the Main Camp area, characterized by Kalahari sand soils. The vegetation is primarily woodland and bushland savanna, interspersed with small patches of grassland. HNP is semi-arid with a wet season from November to April, an early dry season from May to July and a late dry season from August to October. The long term mean annual precipitation is 600 mm (CV=25%). Availability of water to animals is primarily from rainwater collected in natural depressions. However, most of these do not hold water during the late dry season, when water is artificially supplied in about 50 waterholes spread throughout HNP. A total of 15 artificial i.e. actively pumped waterholes are located in the study area. In the study area, the average hyaena density is 9 hyaenas/100 km 2 (Chapter 2)

and the average lion density is 3.5 lions/100 km 2 (Loveridge et al., submitted). We contrasted movement data from the wet and late dry season (dry season hereafter) only, as the early dry season is transitional between the two other seasons. We thus worked with a total of 3 051 hyaena night (932 for the dry season and 1 460 for the wet season).

Hyaena and lion GPS data

Environmental data

We used a vegetation map built from three Landsat images from August 2002, November For each hyaena location, we extracted the corresponding vegetation class, the distance to the closest artificial waterhole (distance to water hereafter), and the distance to the closest road.

For distance to water, each location was assigned to a class of distance to water: "close" for locations within 2 km of water, "intermediate" for locations between 2 and 4 km from water, and "far" for locations further than 4 km from water. We also assigned a night brightness index to each hyaena location depending on the moon illumination index and the position of the moon on the horizon (if the moon was below the horizon at the time of the location, the index was set to 0). We classified night brightness into "dark" for moon index below 0.2, "intermediate" for index between 0.2 and 0.8 and "bright" for index above 0.8. Moon illumination index was extracted from http://aa.usno.navy.mil/data/docs/MoonFraction.php for our study location.

Risk of encountering lions

We built individual lion Movement based Kernels Density Estimator (MKDE) to estimate individual home range (HR) over the whole study period. MKDE method was developed by Benhamou et al. (2010;2011) and improves the spatial resolution of utilization distributions by taking advantage of movement information provided by the serial correlation between successive locations. For each hyaena paths, if both the starting and ending point of a step were located within at least one lion MKDE core (50% isopleths), it was assigned the value 1, if they were both outside a lion MKDE core, the step was assigned the value 0, otherwise the step was discarded. As the likelihood of being in a lion MKDE core was correlated to the distance to water (being close to water greatly increases the probability of being within a lion MKDE core, logistic regression, z value = -62.68, p<0.0001), we chose to use the distance to water only as a measure of both prey availability and lion encounter risk.

Hyaena movement characteristics

We defined the instantaneous speed (in m/h) as the distance (i.e. step length) between two successive hourly locations. Steps shorter than 50 m were removed from the analyses, after assuming that the hyaena was immobile. For each night, we calculated the total displacement (TD, in m) as the sum of all the step lengths for that night, and the net displacement (ND, in m) as the straight-line distance between the starting and the ending point of the night path.

Nights with at least one missing location were not taken into account. Path tortuosity is a key parameter to animal movement as it defines how the animal explores an area. For each night path, we defined a straightness index (SI) as ND/TD [START_REF] Batschelet | Circular statistics in biology[END_REF]. SI ranges from 0 (very convoluted path or path having the same starting and ending points) to 1 (straight line).

Each step and each night path were assigned to a class of distance to water as were GPS locations. Steps and paths with starting and ending points in a different class of distance to water were not included in subsequent analyses. We followed the same method to assign each step to an habitat type. As very few night paths occurred within the same habitat class, we did not use the habitat variable in the analyses of path properties. We first analysed the influence of distance to water, season, habitat, night brightness and the interactions between season and distance to water, season and habitat, and habitat and night brightness on step length using Linear Mixed Models (LMMs) with hyaena individual as a random factor. We built a set of 34 models and used the Akaike criterion information (AIC) to select the models best fitting the data, defined as those within ΔAIC ≤ 2 of the best model (Burnham & Anderson, 2002).

We then tested the influence of season, distance to water, moonlight (the maximum moon index of all steps constituting a night path was attributed to the path) and the interaction between season and distance to water on TD, ND and SI (on a total of 349 night paths) using LMM with hyaena individual as a random factor. We built a set of 10 models and selected the best ones based on the AIC.

Potential for dynamic interactions between hyaenas and lions

We first studied the level of static interactions between monitored hyaenas and lions, i.e.

their home range overlap. For each individual hyaena, we calculated the extent (percentage area) to which its 95% MKDE was overlapped by that of each lion 95% MKDE built over the hyaena data set period. We then assessed how often a collared hyaena was near a collared lion using an index of proximity with T αβ the proportion of simultaneous locations (± 10 min), and ST αβ the proportion of simultaneous locations that are within a given distance [START_REF] Bertrand | Effects of parturition on home ranges and social affiliations of female white-tailed deer[END_REF]. We computed Prox for the following distances: 5 km, 1 km and 200 m.

We also computed the dynamic interaction index (DI) defined by Long at al. (Long & Nelson, 2012). DI measures the cohesiveness of movement paths both in terms of path length and direction and gives an estimation of how the movement of two animals. The overall DI uses all simultaneous fixes irrespective of their distances which can have little meaning;

hence we also defined local DI indexes during encounter nights (see next section for encounter definition). Prox and DI were calculated using the R software functions provided by Long et al. (2014) on http://www.geog.uvic.ca/spar/DynamicInteraction/.

Dynamic interactions between hyaenas and lions

Environmental determinants of hyaena and lion encounters

We focused on encounters between the two predators, analysed when and where they occurred, and investigated the movements of hyaenas and lions before and after these encounters. We assumed that hyaenas and lions encountered each other every time they were within 200 m of each other. We tested for the influence of season on the location of the simultaneous fixes in relation to the closest artificial waterhole and closest road using ANOVAs and to habitat using Fisher's exact test.

All encounters occurring within a given night with the same lion were regrouped into a same encounter. We identified a total of 100 encounters between hyaenas and lions. Twelve of these encounters were located at carcasses identified from hyaena GPS clusters (cf Chapter 5 for detailed methods), and 53 additional encounters occurred at lions GPS clusters. Each of these clusters was composed on average by 29.4 ± 22.1 lion locations (± SD, range 6-87) and lions spent more than one night at the vast majority of them (59 out of 65). Previous work has used such clusters to identified lion kill sites (Tambling et al., 2010;Davidson et al., 2012).

We thus assumed that all these clusters represented feeding sites and that the associated encounters occurred at carcasses. For the 35 remaining encounters, we could not identify clusters and thus assumed that they did not occur near carcasses.

Hyaena and lion movements before and after an encounter

For each encounter, we studied the distances between each hyaena and lion simultaneous fixes during the 3 hours preceding the beginning of the encounter (i.e. the first simultaneous fix within 200 m), during the whole encounter, and for the 3 hours after the departure from the encounter (i.e. after the last simultaneous fixes within 200 m of each other). For encounters located at carcasses, we also calculated the distance between the carnivores and the carcass. For carcasses detected from lion cluster only (not confirmed in the field), we set the carcass position at the barycentre of the lion cluster. We counted the number of proximal fixes during each night of encounter. We further defined encounter type based on the movement characteristic of each species within the 3 h preceding and 3 h following the first proximal fix of the night. We identified four types of movement combination before and after the encounter: only one animal moved (H1L0: only the hyaena H moved, and H0L1: only the lion L moved), both animals moved (H1L1) or hyaena and lion moved very little (H0L0, see

Figure 1 for details on movement definition and Appendix 6.1 for examples of real movement patterns). When the encounter occurred before 9 pm or after 4 am, movement characteristics for the 3 h preceding or following the encounter respectively could not be defined. For these encounters only movements after and before were defined respectively.

All data extraction and analyses were performed with the R software version 3.0.2 (R development Core Team, 2013). When necessary, data were transformed (log and square root) to meet normality assumptions.

Dynamic interactions between hyaenas and lions

HR overlap between hyaena and lion averaged 16.8 % (SD= 19.6 %; range: 0.004-77) and hyaena HRs were overlapped on average by 10.4 ± 5.1 lion HRs. Most hyaena locations (90.9% of a total of 54,151 fixes) were simultaneous with at least one lion. Proximity indices were very small and decreasing when considering smaller threshold distance, ranging from 0.01 ± 0.03 at 5 km, 0.020 ±0.004 at 1 km to 0.0004 ± 0.0001 at 200 m showing that very few simultaneous fixes of hyaenas and lions were close to each other. Overall DI was also very close to 0 showing no overall cohesiveness of movement between hyaenas and lions (0.002 ± 0.02, range: 0.07 to 0.12).

Environmental determinants of hyaena and lion encounters

Out of the 270 proximal fixes of hyaenas and lions, we identified 100 encounters (first proximal fix of a given night, if other fixes were proximal during the same night, they were not accounted for) between hyaenas and lions. Most of the encounters (n=45) occurred during the wet season, 22 during the early dry season and 33 during the late dry season. When hyaenas encountered lions, they were on averaged at 3.4 ± 2.4 km from an artificial waterhole (range: 0.0-10.4, Figure 4a). As the dry season progressed, the encounters occurred closer to artificial waterholes (F 2,97 =6.5, p=0.002). Encounters were located at 4.3 ± 2.4 km from water (range: 0.03-10.4) during the wet season, 3.0 ± 1.4 km from water (range: 0.5-5.8, t=-2.2, p=0.03) during the early dry season and 2.5 ± 2.6 km from water (range: 0.0-9.6, t=-3.5, p<0.001) during the late dry season. Encounters were located at 6.6 ± 1 km (range: 0-4.2) from a road and season had no effect on this distance (F 2,97 =2.1, p=0.127). The majority of encounters occurred in bushland (n=41) followed by bushed grassland (n=22), grassland (n=13) and sparsely bushed grassland (n=13) then by bushed woodland (n=10) and only one encounter occurring in woodland (Figure 4b). When the encounter occurred at a carcass, it lasted from few hours to several nights (up to seven consecutive nights) whereas when no carcass was involved, there was only one proximal fix per night. From the encounters occurring at identified carcasses (n=12), 42% (n=5) were elephants, 33% (n=4) giraffes, 17%

(n=2) buffaloes and 8% (n=1) kudu.

Hyaena and lion movements before and after an encounter

We defined 13 types of encounter based on combinations of hyaena and lion movement both before and after the encounter, and an additional seven only based on movement before or after (see Appendix 6.1 for examples and Figure 5). Out of the 65 encounters that occurred at a carcass, 50 encounters (77%) where fully defined with movement before and after. Of these 50 encounters, the majority of them were of type H1L0-H1L0 (36%, n=18, hyaena came and went away, Figure 5 and Appendix 6.1) and of type H1L0-H0L0 (16%, n=8, hyaena came and stayed in the vicinity of the carcass, as the lion did, Figure 5 and Appendix 6.1). Out of the 35 encounters that occurred away from a carcasses, 29 encounters (71%) were fully defined and the majority were of type H1L1-H1L1 (48%, n=14, both hyaena and lion were moving before and after the encounter, Figure 5 and Appendix 6.1) and of type H1L0-H0L0 (14%, n=4, the hyaena approached and stayed close to the lion, Figure 5 and Appendix 6.1).

For encounters occurring at carcasses, the most common case was for hyaenas to approach lions already at the carcass (65.4%, type H1L0, Figure 6) and after they either both stayed (39.7%, type H0L0) or hyaena left leaving lions at the carcass (36.5%, type H1L0). On the contrary, when the encounter did not occur at a carcass, in most cases both hyaena and lion where moving before (56.3%, type H1L1, Figure 5 and after (67.7%) the encounter. Before an encounter when both species moved, hyaenas tended to move more than lions (Table 2). In addition, when one of the species at least was in the encounter area or stayed in it, lions moved less than hyaenas (Table 2).

Local DIs for encounter nights were also very low. When the encounter took place at a carcass local DI averaged -0.0009 ± 0.31 (ranging from -0.87 to 0.98) before the encounter and 0.025 ± 0.32 (ranging from -.97 to 0.99) after the encounter. For encounters away from carcass, local DI before averaged 0.037 ± 0.36 (ranging from -0.86 to 0.94) and -0.038 ± 0.35 (ranging from -0.98 to 0.82) after the encounter.

DISCUSSION

Hyaena movement characteristics

This study revealed that hyaenas move with an average speed of 1.5 km/h, which is two to three times quicker than what has been reported for lions in HNP (between 0.5 to 1 km/h; Valeix et al. 2010). Hence, hyaenas are highly mobile and can travel quite long distances in a night; on average their total displacement per night is 14.1 km and can reach up to 45 km, and their net displacement per night is 4.6 km reaching 30 km. For all parameters of movement, (speed, net and total displacements) hyaenas covered far greater distances than lions, more than 2.5 times the total distance travelled by lions (maximum TD of 5.4 km per night far from waterholes, Valeix et al. 2010). This is consistent with observations from the Serengeti where hyaenas follow migratory prey over very long distances (Kruuk, 1972;Hofer & East, 1993).

In addition, hyaenas had more tortuous paths than lions which is in accordance with the differences in foraging tactics between a sit and ambush predator versus a cursorial one.

Indeed, hyaenas do not stalk their prey from cover prey as lions do, but rather walk to them until they run away so they can identify a target and start the hunt (Kruuk, 1972;Cooper, 1990). This strategy of covering great distances also allows them to find carrion more efficiently.

Effects of resource distribution on hyaena movement

Herbivores tend to aggregate around waterholes in the HNP ecosystem and are not homogeneously distributed among habitat types. For instance, bushland and bushed woodland are amongst the poorest habitats in terms of prey abundance whereas grassland and sparsely bushed grassland are amongst the richest (Chapter 4). Hyaenas moved at lower speed when they were close to waterholes and in habitats preferred by prey, which is consistent with movement patterns influenced by patch prey richness. They also moved faster, and thus spend less time, in habitats with significant bush density that greatly reduces the visibility, and consequently where prey might be more difficult to encounter and catch. This could be consistent with the hypothesis of extensive search mode between prey rich patches [START_REF] Zollner | Search strategies for landscape-level interpatch movements[END_REF], but movement can also be influenced by other factors such as risk [START_REF] Valeix | Behavioural adjustments of a large carnivore to access secondary prey in a humandominated landscape[END_REF]. The fact that hyaenas tended to move less during dark nights is in contradiction with observations in Moremi, Botswana, where Cozzi et al. (2012) found that moon light had no influence on hyaena activity. However, it is possible that hyaenas experience higher hunting success when the night is bright, as they do not rely on ambush (Kruuk, 1972). Moving less during dark nights might also reduce their risk of encountering lions, known to have a higher hunting success during moonless nights (Funston, Mills & Biggs, 2001). As they pursue prey over long distances, moonlight might also give them an advantage. Lions have also been reported to move with lower speed and cover shorter net displacement when in the vicinity of waterholes (Valeix et al. 2010), which together with our results on hyaena speed, and hyaena TD and ND in the wet season confirm that waterhole are key loci for predators in general. However, we did not find that hyaena path straightness was influenced by the distance to water, contrarily to lions (Valeix et al. 2010), Hyaena movement patterns are thus influenced by patch richness but there are most probably other factors, such as the presence of a competitor/predator and they do not entirely show an ARS.

Hyaena interactions with lions

Every hyaena HR was overlapped by several lion HRs, resulting in a high potential for interactions between the two species. However, proximity index was extremely low indicating that interactions are rare. In addition, at least at the HR scale, hyaenas did not show any strong pattern of lion avoidance and our results thus do not support a general spatial avoidance between the two predators. In semi-arid savannas, waterholes constrain herbivores distribution, at least during the dry season [START_REF] Redfern | Surface-water constraints on herbivore foraging in the Kruger National Park, South Africa[END_REF]. In HNP, waterhole location and dispersion also greatly influence lions (Valeix et al., 2010;Valeix et al., 2011;Valeix, Loveridge & Macdonald, 2012) and hyaena ranging behaviour (see Chapter 2). Hyaenas thus cannot avoid lions at a large spatial scale as they also have to access water and prey during the dry season. The extremely low overall movement cohesiveness between hyaenas and lions do not show evidence of one species consistently following or avoiding the other one. Even before and after encounters, local DI values were very small indicating that the two species move almost independently of each other.

Over more than four years of monitoring, we found only 270 occurrences of hyaenas and lions within 200 m of each other. However, we only monitored a small sample of each hyaena clan (two individuals per clan), in which foraging group formation is a very dynamic process of fusion-fission (Kruuk, 1972;Cooper, 1990;Smith et al., 2008). In addition, some data within the study period is missing due to collars failure for both species. However, at the individual scale, our data provide a reasonable estimate of the rate of encounters with lions (on average, we detected 2.1 encounters per month and individual hyaena, ranging from 0 to 6.4). Some prey species have been shown to respond to their predator's presence within a 2 km radius (Valeix et al., 2009;[START_REF] Périquet | Individual vigilance of African herbivores while drinking: the role of immediate predation risk and context[END_REF], hence we believe that the 200 m threshold we used to define encounter is conservative. Nevertheless, we identified 100 nights with occurrence of encounters. These encounters occurred in the vast majority (65% of study encounters) at carcasses and not at random. In most cases, hyaenas, and less often lions, were attracted from over long distances to carcasses. In one case, a hyaena travelled 7.5 km in an hour to reach the carcass. In 11 occurrences, hourly GPS locations positioned hyaenas and lions arriving at the same time at the carcass. This suggests that both species can recognise cues of the other one killing a prey or feeding. This is in accordance with the fact that sounds from hyaenas scrambling at a carcass and those of a dying buffalo calf attract both lions and hyaenas (Mills, Juritz & Zucchini, 2001;Kiffner, Waltert & Meyer, 2007;Cozzi et al., 2013).

Most of the interactions (36%) away from carcasses occurs within 1km of artificial showing once again the importance of these landscape features into large carnivore ecology (see Chapter 2 & 4). Interestingly, encounters far from waterholes mainly occur near carcasses confirming the Chapter 4 hypothesis that away from these prey rich patches, predators are drawn together at carcasses. Interactions near carcasses could extend to several consecutive nights, with each time several simultaneous fixes within 200 m, conversely encounters away from food were always very short, with only one pair of proximal fixes and usually both species in movement before and after the encounter. Thus, it seems that the two species avoid spending time near each other when food is not at stake and if one is following the other, it is at more than 200 m away. Our results support the conclusion of numerous observations that hyaenas and lions compete at carcasses (Mills, 1990;Cooper, 1991;Honer et al., 2002;Trinkel & Kastberger, 2005). However, it was not possible in our study to identify parameters influencing kleptoparasitism attempt and success such as hyaena group sizes, prey species or carcass state. Indeed, if members of a lion pride or a coalition spent most of their time together (Davidson et al., 2012), hyaenas forage alone or in pairs and clan members join at carcasses (Kruuk, 1972;Cooper, 1990;Smith et al., 2008, Chapter 2). It is thus not possible to estimate hyaena group size during these interactions from our GPS data. As for prey species, it would have been necessary to visit the encounter site in the field but there is tendency for encounters to occur more often on large carcasses (e.g. elephant and giraffe).

To our knowledge, this is the first study providing details on how two large carnivore species move in relation to each other. Vanak et al. (2013) recently showed how subordinate species such as wild dogs (Lycaon pictus) and cheetahs were more likely to move away from lion locations. However, they did not study how these species moved simultaneously to lion movements nor how they reacted after encountering lions. Previous studies showed that cheetahs and wild dogs were likely to move away when hearing lion roars (Durant, 2000;[START_REF] Webster | African Wild Dogs as a Fugitive Species: Playback Experiments Investigate How Wild Dogs Respond to their Major Competitors[END_REF]. Similar work was conducted on hyaenas [START_REF] Watts | Responses of Spotted Hyenas to Lions Reflect Individual Differences in Behavior[END_REF][START_REF] Webster | Eavesdropping and Risk Assessment Between Lions, Spotted Hyenas and African Wild Dogs[END_REF]. However, predator's presence was simulated using broadcast of lion roars and no data were collected on the movement of the studied species after these simulated encounters and for how long their movement was affected.

Our results show that interactions between hyaenas and lions occurred at a very fine spatiotemporal scale, were extremely dynamic and most of the time related to food. While we acknowledge that hourly GPS locations allow for a very rough estimation of movement parameters, it proves to be enough to provide the first insights into how two large predator species interact with each other at an unprecedented scale. We therefore strongly encourage further research with more frequent GPS locations as well as monitoring several individual hyaenas per clan. Predators are the best wildlife managers.

George B. Schaller, The Serengeti Lion 1972

Gause's principle of competitive exclusion states that two species cannot permanently coexists unless they do things differently. The outcomes of competition for the same resources can sometimes result in local extinction of one species. However, when competition is reduced by means of evolutionary or behavioural shifts towards a different ecological realized niche competing species can coexist [START_REF] Pianka | Niche overlap and diffuse competition[END_REF][START_REF] Schoener | Resource partitioning in ecological communities[END_REF]. For example, [START_REF] Macarthur | Population ecology of some warblers of northeastern coniferous forests[END_REF] found that five closely related species of warblers (Dendroica spp.), which greatly overlapped spatially and consumed the same resources, coexisted by segregating their foraging in different portions of trees in a coniferous forest. Numerous studies have investigated the behavioural and ecological effects of interactions between intraguild species of small mammals [START_REF] Hughes | Predation risk and competition affect habitat selection and activity of Namib Desert gerbils[END_REF][START_REF] Palomares | Spatial relationships between Iberian lynx and other carnivores in an area of south-western Spain[END_REF] or in predator-prey systems (Creel et al., 2005;Valeix, Fritz, et al., 2009;[START_REF] Periquet | Individual vigilance of African herbivores while drinking: the role of immediate predation risk and context[END_REF] but comparatively little research has focused on large carnivore interactions. This lack of knowledge is partially due to the difficulties associated with simultaneous data collection on multiple carnivore species often elusive, nocturnal and occurring at low densities, but also to the fact that their interactions are very complex with unique mechanisms of competition such as kleptoparasitism and intraguild predation, that make the study of their coexistence complicated. Nonetheless, the importance of incorporating multiple predators in studies of ecosystem functioning is widely recognized [START_REF] Ives | A synthesis of subdisciplines: predatorprey interactions, and biodiversity and ecosystem functioning[END_REF][START_REF] Schmitz | Predator diversity and trophic interactions[END_REF] as disappearance of one species can have dramatic effects on the whole community [START_REF] Palomares | Positive effects on game species of top predators by controlling smaller predator populations: an example with lynx, mongooses and rabbits[END_REF][START_REF] Myers | Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean[END_REF]Estes et al., 2011;Ripple et al., 2014). Numerous examples come from the USA where the disappearance of wolves (Canis lupus) and thus the decrease in elk (Cervus elpahus) predation heavily impacted the landscape (Beschta & Ripple, 2006;Ripple et al., 2013).

results might be different if focusing on females having dependent cubs at the den.

For competing species with high spatial overlap, temporal segregation can promote coexistence. For instance sympatric black-backed and side-striped jackals (Canis mesomelas and C. adustus) use the same resources but show an almost complete avoidance in time (Loveridge & Macdonald, 2003). Both hyaenas and lions are nocturnal and I did not find any evidence of temporal segregation, even when considering the effect of moonlight which had no impact on their activity (Chapter 6, Loveridge, unpubl. data). Despite the fact that activity in African predators has been reported to decrease in cloudy nights with less visibility (Hayward & Slotow, 2009), activity patterns of hyaenas and lions were not impacted by moonlight in Moremi GR, Botswana, neither (Cozzi et al., 2012).

Additionally, I found that hyaena and lion diets overlap extensively across their range (Chapter 1) and in HNP in particular (Chapter 3), corroborating a strong potential for exploitative and interference competition (Hayward, 2006). Thus, as hyaenas do not avoid lions spatially nor temporally on a broad scale in HNP, I searched for mechanisms of their coexistence at a finer scale. I found that despite the fact that hyaenas and lions use the same areas, especially the ones rich in prey such as artificial waterhole areas (Chapters 2 and 6), hyaenas avoided locations with a high risk of encountering lions in conditions of extreme vulnerability (Chapter 4). In addition, they reacted to the recent presence of lions in the vicinity of their dens by lowering their attendance at these dens (Chapter 5). Finally, hyaenas reacted strongly to opportunistic encounters with lions (when no carcass was involved) by moving away immediately (Chapter 6). These results are in line with the reactive response of cheetahs to lion presence in Moremi Game Reserve, Botswana (Broekhuis et al., 2013).

Results from HNP also show that hyaenas respond to lions in the reactive way (response to the actual presence of lions) rather than predictive (based on the general knowledge of encounter risk with lions). These results also suggest that avoidance of competitor/predator within the large carnivore guild is a very dynamic process. Indeed, avoiding areas intensively used by lions would force hyaenas into areas poor in prey, while avoiding rich areas only when the risk of encountering lions is high allows hyaenas to benefit from them.

Synthesis & perspectives 225

Outcome of interactions between solitary species are somewhat simple: the larger is dominant.

For instance, tigers displace leopards from rich habitats to suboptimal ones [START_REF] Odden | Do tigers displace leopards? If so, why?[END_REF][START_REF] Harihar | Responses of leopard Panthera pardus to the recovery of a tiger Panthera tigris population[END_REF] and the larger pumas often kill bobcats [START_REF] Cashman | Diets of mountain lions in southwestern Arizona[END_REF][START_REF] Harveson | Prey use by mountain lions in southern Texas[END_REF]. However, between two social species as hyaenas and lions, interaction outcomes are strongly influenced by their group size and composition. Numerous studies showed that the more numerous the hyaenas were compared to lionesses, the higher chance they had to access or retain a carcass (Kruuk, 1972;Cooper, 1991).

Such relationships have also been shown between wolves and coyotes (Canis latrans, Atwood & Gese, 2008). In addition, the presence of at least one adult male lion completely tips the balance in the favours of lions, no matter how numerous the hyaenas are (Elliott & McTaggart-Cowan, 1978;Cooper, 1991;Trinkel & Kastberger, 2005). Thus social dynamics complexify the interactions between hyaenas and lions. In lion populations such as Etosha NP where males are with the pride most of the time, hyaenas might only rarely manage to chase lions from their kills, and thus benefit little from kleptoparatism, while losing much to the competitively superior lions.

While members of a lion pride spend most of their time together, the fusion-fission dynamic of hyaena clans ensure an ever-changing size and composition of their foraging groups. Kruuk (1972) suggested that hyaenas formed larger groups before hunting zebras (Equus quagga), a species with a well develop anti-predator strategy. To date, we do not know if they do the same before challenging lions at carcasses or simply recruit clan members as the interaction progresses.

Importance of artificial waterholes for hyaena ecology

In semi-arid savannas, as the dry season progresses, prey congregate in large numbers around the scarcely available surface-water sources [START_REF] Redfern | Surface water availability and the management of herbivore distributions in an African savanna ecosystem[END_REF]. This in turn attracts their predators for which water sources become focal points in of their activities. In HNP, lions have been shown to strongly select areas within 2 km of waterholes and most of their kills occur there (Valeix, Loveridge, et al., 2009;Davidson et al., 2012). I also found that artificial waterholes are structuring hyaena space use and movement (Chapters 4 and 6). Hyaena home range cores were located around waterholes and hyaenas also spend a lot of their time in areas close to them (Chapter 2). In addition, when close to waterholes where prey encounter probability is higher, hyaenas move slower and seem to adopt an "area-restricted search" behaviour (Chapter 6).

Synthesis & perspectives 226

Interestingly, waterhole areas were also visited often and for long periods during the wet season.

The majority of these areas are characterised by open vegetation, especially grasslands that are intensively used by prey species throughout the year.

As lions also concentrate their activities around waterholes (Valeix et al., 2010;Davidson et al., 2012), encounters with hyaenas are thus more likely to happen in their vicinity, especially during the dry season (Chapter 6). Waterhole areas are thus particularly risky for prey as the probability of encountering lions or/and hyaenas (and most probably other predators) is high.

Despite this, prey have to access water and thus use these areas, where they are known to adjust their behaviour to lion predation risk (Valeix, Fritz, et al., 2009;[START_REF] Periquet | Individual vigilance of African herbivores while drinking: the role of immediate predation risk and context[END_REF]. To which extent these behavioural adjustments modify their susceptibility to hyaena (and other carnivore species) predation is unknown. After a kill made in the vicinity of a waterhole, lions have been shown to move to another waterhole (Valeix et al., 2011). At this stage, we do not know if hyaenas do the same. Using a given waterhole when lions are in the vicinity could be advantageous for at least two reasons. First, hyaenas could chase the lions away from their kill, and in any case, would get early access to leftovers. Second, the presence of lions might induce behavioural or habitat shifts in prey (see Further research section) and thus make them more susceptible to hyaena predation. However, being close to lions can also include cost from kleptoparasitism and predation risk and hyaena might thus prefer to use a given waterhole when lions are not there.

Large carcasses and carnivore coexistence: the role of elephants

The HNP elephant population is fluctuating around an average density of 2 individuals/km 2 obs.). Hyaenas do not hunt adult elephants but are known to kill young elephant calves (Salnicki et al., 2001). As the dry season progresses, elephants have to cover longer distances between water sources and food, and weak individuals (old, injured, diseased and new-born) often die

Synthesis & perspectives 227 during this period of the year (pers. obs.), providing carnivores with large amounts of carcasses to scavenge from. Because I did not know the amount of meat available to and eaten by hyaenas on each elephant carcass and could not rely on the amount of elephant hairs in scats to estimate the biomass eaten (Chapter 3), I did not estimate the importance of elephant in the hyaena diet in term of biomass. Nonetheless, I am confident that they constitute the bulk of their diet, especially during the dry season. As lion abundance increased over the past decade due to the implementation of a moratorium on the lion trophy hunting (Loveridge et al., 2010), hyaenas increased their use of elephant (and giraffe) carcasses (Chapter 3), which suggests an additional source of elephant (and other large species) carcasses provided by lions, as well as a switch from active hunting to scavenging. This is probably due to the fact that the number of males and of male coalitions has increased and now allows for larger prey to be hunted by lions and for lions to be more competitive when encountering hyaenas at carcasses. In addition, some lion prides and coalitions in HNP specialised on elephant hunting during the dry season, with one pride of two adult males and five adult females killing up to 30 juveniles and sub-adult over a 2-month period (pers. obs.). There is often enough food (including skin and bones) remaining on the carcass for hyaenas to use them for several nights by the time lions leave or are driven away.

During this period, hyaena density remained stable, which suggests that the availability of elephant carcasses thanks to elephant natural mortality already facilitated the coexistence between hyaenas and lions. The presence of alternative prey has already been suggested to stabilize coexistence between predators species killing each other [START_REF] Holt | Alternative prey and the dynamics of intraguild predation: theoretical perspectives[END_REF]. Hyaenas and lions are probably more likely to encounter each other at elephant carcasses (Chapter 6), but there is enough meat on the carcasses for both predators to eat one after the other. The additional source of food source also decreases the competition for live prey as hyaenas and lions would hunt less often.

Because elephant carcasses are large, both species usually stay a long time around them, feeding for several consecutive nights. This creates many opportunities for them to interact with each other. Patterns of hyaena habitat selection relative to the risk of encountering lions (Chapter 3) also suggest that the two species are surprisingly also drawn together in areas a priori poor in prey and I would be inclined to suggest this is due to the presence of large carcasses there.

Synthesis & perspectives 228

Effect of management decisions on large carnivore ecology and coexistence

Identifying drivers of resource selection at different spatial scales is essential for understanding species ecology and planning relevant management strategies [START_REF] Boyce | Relating populations to habitats using resource selection functions[END_REF]. I revealed that in HNP, artificial waterholes are structuring hyaena ecology, as already demonstrated for lions (Valeix et al., 2010;Valeix et al., 2011;Davidson et al., 2012), and consequently waterholes are important in the ecology of these carnivores' interactions. The presence of about 50 artificial waterholes in the Northern part of HNP makes water available throughout the year. Prey populations are thus not limited by water availability during the dry season, and concentrate around these water sources and this is particularly true for elephants.

Until the mid-80s, the HNP elephant population was controlled through annual culling. Since the culling operations stopped, the population nearly doubled. By supplying large amounts of meat, the elephant culling most probably allowed sustaining a large and healthy hyaena population.

This study suggests that hyaenas are not suffering from competition with lions, which may be partly due to the large availability of elephant carcasses, also a result of water management.

Indeed, if elephants are not limited by access to water during the dry season, they have to move daily between artificial waterholes and areas where they can feed. As the dry season progresses, the distance they have to walk to find places where there is enough food lengthen and the weaker individuals do not survive the journey, thus providing meat for both hyaenas and lions to Figure 1: After adult male lions killed a young giraffe, hyaenas quickly arrived and the carcass changed hands a number of times that night. These two pictures were taken with a 30-min interval. Lions and hyaenas interacted at this carcass for 2 consecutive nights (note GPS collars on both species).

Synthesis & perspectives 229 scavenge. It has been suggested that the elephants are now above the carrying capacity of HNP and that their population could be controlled by changing the way artificial waterholes are managed (Chamaillé-Jammes, Valeix & Fritz, 2007). This solution has been used in Kruger NP, without many effects on the elephant population to date. However, the decision of closing or opening artificial waterholes is likely to impact other species. Not only the lack of water can affect their population dynamics, but after the pulse of elephant carcasses availability, hunting pressure from predators might also increase. Rarer and less iconic species than elephants might be heavily impacted by changes in water availability and distribution, and I showed that hyaenas already prefer rare species such as roan (Hippotragus equinus) and sable (H. niger, Chapter 3).

Managers thus need to consider the relationships between species, especially apex predators and their effects on prey populations, before taking decisions susceptible to impact the whole ecosystem functioning.

Large carnivore conservation: what is at stake?

Carnivores are unique as that they are indicator, keystone, umbrella, flagship and vulnerable species at the same time [START_REF] Gittleman | Carnivore Conservation[END_REF]. No one has a neutral position towards large predators: they are either loved or hated. On the one hand, they are iconic species, sources of income through both non-consumptive (e.g. photography) and consumptive activities (e.g. trophy hunting, see Dalerum et al., 2008). On the other hand, they are a source of conflicts with human populations living alongside them [START_REF] Woodroffe | People and wildlife: Conflict or Coexistence[END_REF]. Conflicts arise mainly through livestock predation, for which retaliatory killing has become the most important source of mortality for large carnivores and raises concern about their survival [START_REF] Woodroffe | Edge effects and the extinction of populations inside protected areas[END_REF]Woodroffe et al., 2005). However, large carnivore effects on livestock can be small compared to those of mesopredators released by their extirpation such as jackals and coyotes (Canis latrans, [START_REF] Beinart | The night of the jackal: sheep, pastures and predators in the Cape[END_REF][START_REF] Sillero-Zuberi | Interactions between carnivores and local comminities: conflict or coexistence? In Carnivore Conservation[END_REF][START_REF] Treves | Evaluating lethal control in the management of human-wildlife conflict[END_REF]. Despite numerous efforts, there is a global decline in large carnivore populations around the world (Ripple et al., 2014). And because of their wide-ranging behaviour, apex predators need large conservation areas reducing the edge effects and their forays into adjacent lands [START_REF] Woodroffe | Edge effects and the extinction of populations inside protected areas[END_REF][START_REF] Woodroffe | Strategies for carnivore conservation: lessons from contemporary extinction[END_REF].

Synthesis & perspectives 230

In the community areas surrounding HNP, livestock predation by hyaenas and lions is widespread (unpubl. data). While lions kill cattle mostly in the wet season, hyaenas kill goats and sheep throughout the year. Losses can be extremely high for households raising livestock for subsistence. HNP is not fenced and nothing prevents large carnivores from roaming into adjacent communal lands. The presence of artificial waterholes and availability of numerous elephant carcasses maintain a high diversity and abundance of large carnivores within the protected area, but as the competition for space and food will increase in the protected area, subordinate species and individuals are likely to move outside the protected area (e.g. van der Meer, 2011). Thus, conservation efforts outside protected areas are crucial for large carnivore conservation [START_REF] Marker | Human Aspects of Cheetah Conservation: Lessons Learned from the Namibian Farmlands[END_REF]Hayward & Kerley, 2008).

Factors affecting large carnivore conservation are numerous and complex, ranging from ecology to the socio-economic and political situation [START_REF] Winterbach | Key factors and related principles in the conservation of large African carnivores[END_REF]. For instance, their wide-ranging behaviour put them into contact with human population outside protected areas where livestock predation is a major source of conflicts (Woodroffe et al., 2005). People attitude towards carnivores also varies between rural people raising livestock for subsistence and tourism operators for instance, and it is people behavior that ultimately determines large carnivores conservation success [START_REF] Woodroffe | Predators and people: using human densities to interpret declines of large carnivores[END_REF][START_REF] Linnell | Predators and people: conservation of large carnivores is possible at high human densities if management policy is favourable[END_REF]. Presence of large carnivores is essential to ecosystem diversity and functioning (Estes et al., 2011;[START_REF] Ritchie | Ecosystem restoration with teeth: what role for predators?[END_REF]. For instance, sea otter (Enhydra lutris) predation enhance kelp abundance by limiting herbivorous sea urchins [START_REF] Estes | Sea otters and kelp forests in Alaska: generality and variation in a community ecological paradigm[END_REF]. Each predator species has a different prey spectrum (Hayward & Kerley, 2008) and the interactions between them are complex.

Nonetheless, we still know very little about the impacts of such interactions between large carnivores on ecosystem functioning (Ritchie & Johnson, 2009;Ripple et al., 2014).

Conservation of the intact guild should thus be given a higher priority than this of single species [START_REF] Miller | The importance of large carnivores to healthy ecosystems[END_REF][START_REF] Worm | Biodiversity, productivity and stability in real food webs[END_REF].

Based on the results from the PhD, it is possible to identify major factors influencing coexistence between hyaenas and lions that can be modified through management and be use for conservation. The first point is that managers should pay particular attention to the lion sex ratio that can be affected by human activities well outside the protected area (PA). Trophy hunting around HNP has been show to influence lion population structure over the entire PA (Loveridge et al., submitted). If they are too few adult males, then kleptoparasitism from hyaenas might Synthesis & perspectives 231 negatively impact the lion population. Another factor to pay attention to is resources management that are susceptible to influence prey space use and aggregation, such as artificial waterholes.

Prey hotspots become key areas for predators where they are also more likely to encounter and thus compete with each other. Lastly, is it important to switch from programs focusing on single species to conservation efforts targeting entire ecosystems, as changes in abundance of a single carnivore species can have deleterious effects on numerous trophic levels. For instance, several studies [START_REF] Odden | Do tigers displace leopards? If so, why?[END_REF][START_REF] Harihar | Responses of leopard Panthera pardus to the recovery of a tiger Panthera tigris population[END_REF] showed that the recovering tiger population is forcing sympatric leopards to suboptimal habitats at the edges of PAs, where encounters with humans are more likely. [START_REF] Mattisson | Influence of intraguild interactions on resource use by wolverines and Eurasian lynx[END_REF] showed that in Scandinavia, wolverine (Gulo gulo) benefit from coexisting with lynx through increased scavenging opportunities. Thus controlling the lynx population to decrease depredation on the semi-domestic reindeer (Rangifer tarandus) could have a negative impact on wolverine populations.

Future research

Despite an increasing number of studies on large carnivore interactions, due to the wide spread use of GPS technology, many questions still remain unsolved. Several authors stressed the importance of the presence of a male lion at a carcass for the outcome of interactions with hyaenas (Cooper, 1991;Honer et al., 2002;Trinkel & Kastberger, 2005). Without the presence of a male, the outcome usually depends on group sizes of both lionesses and hyaenas. I could not test this hypothesis as it was not possible to estimate hyaena group size during their interactions with lions (defined using GPS data only), due to the fission-fusion dynamic of their society.

However, I believe that further research should focus on understanding the dynamics of group formation in hyaenas is crucial for their ecology and interactions with lions. For instance, knowledge of hyaena group size during each encounter identified in Chapter 6 would have greatly help to understand hyaena movement after interacting with lions. In addition, Pangle and Holekamp (2010b) showed that some individual hyaenas were more sensitive to risk than others in terms of vigilance behaviour and response to lion roar playback. It would be of interest investigating if hyaenas also show individual variations in their behaviour during real encounters with lions, such as it had been shown with coyotes and wolves (Atwood & Gese, 2008). Indeed, one might expect that high ranking individuals will tend to be leaders in attempting to steal kills

Synthesis & perspectives 232 from lions, while subordinate ones would tend to wait for lions to move off a carcass.

Effects of large carnivores on their prey have received a lot of interest and the importance of indirect effects such as habitat shifts and behavioural adjustments of herbivore species in response to the carnivore presence are now recognised [START_REF] Creel | Relationships between direct predation and risk effects[END_REF]. But when one prey adjusts its behaviour or habitat use to a given predator species, how does this impact its predation risk by another carnivore? Prey response to decreases in predation risk by one predator species might result in an increase of risk from another species (Pangle & Holekamp, 2010a) and prey have been shown to respond differently to different predator species (Atwood, Gese & Kunkel, 2009). For instance, elk shifting habitat to reduce their predation risk by cougar (Puma concolor) might increase their risk of predation by wolves (Atwood et al., 2009). Thus prey avoiding habitat with cover for ambushed lions (Valeix, Loveridge, et al., 2009) might be at higher risk from cursorial predators in open areas. We are starting to understand how prey react to predation risk by lions (Valeix, Loveridge, et al., 2009;[START_REF] Periquet | Individual vigilance of African herbivores while drinking: the role of immediate predation risk and context[END_REF][START_REF] Periquet | Influence of immediate predation risk by lions on the vigilance of prey of different body size[END_REF] and wild dogs (van der Meer, Pays & Fritz, 2012) but we virtually know nothing on their responses to the risk of predation by hyaenas. While both Kruuk (1972) and Thaker et al. (2011) suggested that prey response to foraging hyaenas was almost inexistent, this remains to be tested.

It is therefore crucial to maintain the carnivore guild as complete as possible as their effects on prey are more likely to be synergistic rather than additive.

Concluding remarks: The Lion King and the Hyaena Queen

Disney's Lion King surely did not do justice to hyaenas when they pictured them as " [not] essential, crude and unspeakably plain" stupid animals subordinated to lions. The work presented here certainly pictures a quite different side of hyaena ecology and behaviour. We do need to recognise their role as keystone predators in order to obtain a better knowledge of their impact on prey and sympatric predator populations. What The Lion King did get right though was "the circle of life", the connection between species sharing the same ecosystem. The importance of interactions within the apex predator guild and their effects on lower trophic levels are now widely recognised, but still far from understood no matter how crucial they are for ecosystem functioning and for their conservation.

Large carnivores fascinate us with their beauty, power and majesty. We have coexisted with

Synthesis & perspectives 233 them for most of our evolutionary time, but whether we will be able to do so future is entirely up to us. It will not happen without accepting losses on both sides, as conflicts will always occur where large carnivores, humans and livestock coexist. And no matter how hard we try to convince ourselves that we can replace large predators at the top of the food chain, we simply cannot reproduce the complexity of the effects they have on the ecosystems they live in.

You already know enough. So do I. It is not knowledge that we lack. What is missing is the courage to understand what we know and to draw conclusions.

Sven Lindqvist, Exterminate all the Brutes (1992) http://www.fanpop.com/clubs/hyenas-from-lion-king/images/15658383/title/hyenas-smarter-than-lions-d-fanart

Faculté

  Directeur : M. N. LEBOISNE Résumé Étant au somment de la chaîne alimentaire, les grands prédateurs ont la capacité d'influencer le fonctionnement des écosystèmes, y compris au sein de leur guilde. En Afrique, les lions (Panthera leo) et les hyènes tachetées (Crocuta crocuta, hyènes ci-après) sont les plus gros et les plus nombreux prédateurs, et les hyènes sont souvent considérées comme subordonnées aux lions. Néanmoins, notre compréhension de leurs interactions est très limitée, d'autant plus dans les milieux boisés. Ce travail vise à identifier les mécanismes permettant la coexistence des hyènes et des lions. L'hypothèse principale est que les hyènes évitent les lions à la fois dans l'espace et dans le temps. Une revue de la littérature montre que malgré leur fort potentiel pour la compétition d'exploitation (régimes alimentaires similaires) et d'interférence (kleptoparasitisme et prédation), les lions partagent la quasi-totalité de leur distribution avec les hyènes et leurs densités sont positivement corrélées. J'ai collecté des données sur l'écologie des hyènes et des lions durant 2.5 ans à partir d'observations directes et de colliers GPS dans le Parc National de Hwange (PNH), au Zimbabwe. PNH est caractéristique d'une savane dystrophique arborée semi-aride dominée par l'éléphant (Loxodonta africana). L'écologie de la hyène y est largement influencée par la localisation des points d'eau artificiels, des carcasses d'éléphants et des lions.

Figure 1 :

 1 Figure 1: Diagram of simplified ecosystem functioning and trophic cascade from large predators to vegetation though mesopredators and prey. Numbers next to arrow are referenced in the text. See Figure 2 for details on interactions within the large carnivore guild.

Figure 3 :

 3 Figure 3: Spotted hyaena in HNP.

Figure 4 :

 4 Figure 4: Hyaena taxonomy. Figure adapted from the IUCN Hyaena Specialist Group website (http://www.hyaenidae.org/hyena-myths.html, left panel) and Watts and Holekamp 2007 (right panel).

Figure 5 :

 5 Figure 5: Current distribution of spotted hyaenas[START_REF] Honer | Crocuta crocuta. IUCN Red List of Threatened Species[END_REF]

  Figure 6: a) Study area location (red circle) within Hwange National Park. The dotted polygon represents the area where lions, prey and vegetation are intensively monitored. b) Aerial view of an artificial waterhole showing vegetation structure with the open area directly surrounding the waterhole. c) Herds of elephants congregate at an artificial waterhole during the dry season.

Figure 1 :

 1 Figure 1: Distribution map of spotted hyaena (grey) and lion (red). Most of lion populations are nowadays restricted to protected areas. Total overlap in distribution is 94.9% of the lion range. Data from the IUCN database. (The population of Indian lions is omitted from this map).

Figure 2 :

 2 Figure 2: Diagram of the interactions between lions and hyaenas. Lined arrows represent positive effects and dotted ones represent negative effects.From the point of view of the spotted hyaenas, lions have a negative impact on live prey and both a positive (predation) and negative (scavenging) on the availability of carrion. Lions also have a direct negative effect on hyaenas through intra guild predation. Live prey and carrion availability both have a positive effect on hyaenas through predation and scavenging. Lions thus have a positive effect on hyaenas providing scavenging and kleptoparasitism opportunities. The situation is symmetrical from the point of view of lions except that there is barely any mortality directly due to hyaenas.

Figure 3 :

 3 Figure 3: a) Hyaena (line) and lion (dashed) densities versus prey densities. Regression line equations: log(hyaena density) = -4.11 + 0.97 x log(prey biomass) log(lion density) = -3.55 + 0.71 x log(prey biomass) b) Hyaena density versus lion density. Letters represent location codes corresponding to the Appendix 1.1 Regression line equation: log(hyaena density) = -4.11 + 0.97 x log(lion density)

Figure 5 :

 5 Figure 5: Mechanisms of interactions between spotted hyaenas and lions showing the key role of prey. Straight arrows figure positive impact while doted ones represent negative effects.

  prey density and biomass Body mass 120-400kgLarge prey density and biomassBody mass 400-600kgVery large prey density and biomass Body mass > 600kg

  HOFER, H. & EAST, M. L.(1995). Population dynamics, population size and the commuting system of Serengeti spotted hyenas. In Serengeti II: dynamics, management and conservation of an ecosystem, (ed. A. R. E. Sinclair and P. Arcese), pp. 332-363. The University of Chicago Press, Chicago. HOLEKAMP, K. E., SMALE, L., BERG, R. & COOPER, S. M.(1997). Hunting rates and hunting success in the spotted hyena (Crocuta crocuta). Journal of Zoology 242, 1-15. HONER, O. P., WACHTER, B., EAST, M. L. & HOFER, H. (2002). The response of spotted hyaenas to long-term changes in prey populations: functional response and interspecific kleptoparasitism. Journal of Animal Ecology 71, 236-246. HONER, O. P., WACHTER, B., EAST, M. L., RUNYORO, V. A. & HOFER, H. (2005). The effect of prey abundance and foraging tactics on the population dynamics of a social, territorial carnivore, the spotted hyena. Oikos 108, 544-554. HONER, O. P., HOLEKAMP, K. E. & MILLS, M. G. L. (2013). Crocuta crocuta. www.iucnredlist.org./details/5674/0 HOPCRAFT, J., SINCLAIR, A. R. E. & PACKER, C. (2005). Planning for success: Serengeti lions seek prey accessibility rather than abundance. Journal of Animal Ecology 74, 559-566. HUNTER, J., DURANT, S. M. & CARO, T. M. (2007). Patterns of scavenger arrival at cheetah kills in Serengeti National Park Tanzania. African Journal of Ecology 45, 275-281. STANDERS, P. E. (1998). Spoor counts as indices of large carnivore populations: the relationship between spoor frequency, sampling effort and true density. Journal of Applied Ecology 35, 378-385. SUNQUIST, M. & SUNQUIST, F. (2009). Family Felidae (Cats). In Handbook of the Mammals of the World Vol.1 Carnivores, (ed. D. E. Wilson and R. A. Mittermeir), pp. 54-168. Lynx Edicions, Barcelona. SWITALSKI, T. A. (2003). Coyote foraging ecology and vigilance in response to gray wolf reintroduction in Yellowstone National Park. Canadian Journal of Zoology 81, 985-993. TENDE, T., OTTOSSON, U., HANSSON, B., ÅKESSON, M. & BENSCH, S. (2010). Population size of lions in Yankari Game Reserve as revealed by faecal DNA sampling. African Journal of Ecology 48, 949-952. TERBORGH, J. (1992). Maintenance of diversity in tropical forests. Biotropica 24, 283-292. TILSON, R. L., VON BLOTTNITZ, F. & HENSCHEL, J. R. (1980). Prey selection by spotted hyaena (Corcuta crocuta) in the Namib desert. Madoqua 12, 41-49. TILSON, R. L. & HAMILTON III, W. (1984). Social dominance and feeding patterns of spotted hyaenas. Animal Behaviour 32, 715-724. TILSON, R. L. & HENSCHEL, J. R. (1986). Spatial arrangement of spotted hyaena groups in a desert environment, Namibia. African Journal of Ecology 24, 173-180. TREVES, A., PLUMPTRE, A. J., HUNTER, L. T. B. & ZIWA, J. (2009). Identifying a potential lion Panthera leo stronghold in Queen Elizabeth National Park, Uganda, and Parc National des Virunga, Democratic Republic of Congo. Oryx 43, 60. TRINKEL, M., FLEISCHMANN, P. H., STEINDORFER, A. F. & KASTBERGER, G. (2004). Spotted hyenas (Crocuta crocuta) follow migratory prey. Seasonal expansion of a clan territory in Etosha, Namibia. Journal of Zoology 264, 125-133. TRINKEL, M. & KASTBERGER, G. (2005). Competitive interactions between spotted hyenas and lions in the Etosha National Park, Namibia African Journal of Ecology 43, 220-224. TRINKEL, M. (2009). A keystone predator at risk? Density and distribution of the spotted hyena (Crocuta crocuta) in the Etosha National Park, Namibia. Canadian Journal of Zoology 87, 941-947. TRINKEL, M. (2010). Prey selection and prey preferences of spotted hyenas Crocuta crocuta in the Etosha National Park, Namibia. Ecological Research 25, 413-417. TUMENTA, P., KOK, J., VAN RIJSSEL, J., BUIJ, R., CROES, B., FUNSTON, P. J., DE IONGH, H. H. & UDO DE HAES, H. (2010). Threat of rapid extermination of the lion (Panthera leo leo) in Waza National Park, Northern Cameroon. African Journal of Ecology 48, 888-894. VALEIX, M., FRITZ, H., DUBOIS, S., KANENGONI, K., ALLEAUME, S. & SAÏD, S. (2007). Vegetation structure and ungulate abundance over a period of increasing elephant abundance in Hwange National Park, Zimbabwe. Journal of Tropical Ecology 23, 87-93. VAN DER MEER, E., MOYO, M., RASMUSSEN, G. S. A. & FRITZ, H. (2011). An empirical and experimental test of risk and costs of kleptoparasitism for African wild dogs (Lycaon pictus) inside and outside a protected area. Behavioral Ecology 22, 985-992. Chapter 2 Artificial waterholes structure Spotted hyaena ecology in a wooded savanna Stéphanie Périquet, Nolwenn Drouet-Hoguet, Julia Salnicki, Eléonore Hellard, Eloy Revilla, Simeon Mudimba, Marion Valeix and Hervé Fritz Status: In preparation for Wildlife Monographs

  savanna of Hwange National Park (HNP), Zimbabwe. HNP has two main characteristics: a very high density of elephants (Loxodonta africana) and extremely localised surface water availability where pumps are installed at waterholes during the dry season. These two parameters are likely to influence hyaena ranging behaviour and habitat selection. We gathered clan and population data for 10 years using callings, collected observations and equipped with GPs collars nine individuals from four different clans and followed them for four years to expand our knowledge of hyaena ecology in wooded savannas in comparison with more open ecosystems. We expected that the wooded vegetation coupled with water availability and spatial distribution imposed by human management would have an important impact on hyaena ecology. In particular, we hypothesized that artificial waterholes play a central role in shaping hyaena home ranges (HRs) and habitat selection and that HRs should expand during the wet season when prey are dispersed through HNP.

  zebra (Equus quagga), greater kudu (Tragelaphus strepsiceros) and impala (Aepyceros melampus, Chamaillé-Jammes et al. 2009). In the study area, the average lion density is 3.5 lions/100 km 2 (Loveridge et al. submitted). Wild dogs (Lycaon pictus), cheetahs (Acinonyx jubatus) and leopards (Panthera pardus) are also present.

Figure 1 :

 1 Figure 1: Location of HNP and study area (circled area). Black dots represent artificial waterholes and empty dots represent natural ones. The dotted polygon represents the area were prey abundance has been intensively monitored.

Figure 3 Figure 4 :

 34 Figure 3: a) Map of clan LKDE (thick lines 95% and dotted lines 50% core). b) Zoom on two individuals (thick lines and dotted line) from the Makwa clan. Each clan and individual is represented by a different symbol. Thick grey line represented HNP boundary with the protected area lying to the South West of it.

Figure 5 :

 5 Figure 5: Use of artificial and natural waterholes by hyaenas: a) frequency of use and b) duration of each visit (right panel) for each season. n gives the number of individuals used for the analysis as data were missing for some combinations of seasons and individuals. Some individuals only visited waterholes for very short periods (only one location per visit within 250 m of waterholes), it was thus impossible to calculate visit duration. Boxplot representation: thick lines are the median, boxes are the first (lower) and third quartiles, whiskers show the minimum and maximum values of the data.

  Zimbabwe Research Council and the Zimbabwe Parks and Wildlife Management Authority are kindly acknowledged for providing the opportunity to carry out this research.This study was supported by the HERD program (Hwange Environmental Research Development), funded by the ANR FEAR (ANR-08-BLAN-0022), the CNRS and the RP-PCP platform. Some GPS collars were funded by the National Geographic Society GRANT #C151-08, and Wilderness Wildlife Trust contributed to field expenses. The PhD fellowship for the principal investigator was provided by the ENS of Lyon and UCBL Lyon1. Our deepest thanks to Simon Chamaillé-Jammes and Nicolas Ganzin for the fieldwork and compilation for the vegetation map. We want to thank ZPWM rangers and Martin Muzamba for providing great assistance in the data collection in HNP. Relevant animal care protocols were followed, and approval was received from the appropriate agencies. Chapter 3 Large carnivore menus: foraging strategy shift in Spotted hyaena as a result of increased intraguild competition and facilitation with Lions Stéphanie Périquet, Marion Valeix, Jaelle Claypole, Nolwenn Drouet-Hoguet, Julia Salnicki, Simeon Mudimba, Eloy Revilla and Hervé Fritz Status: In preparation for Journal of Animal Ecology

  Hwange National Park, Zimbabwe, a moratorium on lion trophy hunting around the periphery of the park between 2005 and 2008 provided a unique opportunity to study the changes in hyaena diet and prey selection in two contrasted periods in terms of intraguild competition with lions. We combined scats and carcasses analyses (as in[START_REF] Bacon | Do GPS clusters really work? Carnivore diet from scat analysis and GPS telemetry methods[END_REF][START_REF] Tambling | Spatial and temporal changes in group dynamics and range use enable anti-predator responses in African buffalo[END_REF] and used estimated herbivore densities to assess hyaena diet composition and prey selection and tested two hypotheses: (1) intraguild competition with lions affects hyaena diet and prey selection, with an increase of competition leading hyaenas to avoid medium-sized prey and prefer small and very small prey eaten fast enough to minimize kleptoparasitism by lions. Intraguild competition increases hyaenas scavenging on very large prey killed by lions, with hyaenas forming larger foraging groups to reduce risk when accessing a carcass; and (2) hyaena diet and prey selection are mostly influenced by hyaena foraging group size with smaller prey taken by smaller groups, and scavenging of very large prey should not be influenced by hunting group size, thus implying a lack of response in hyaenas to the change in lion population.

a

  dry season from May to October. The long term mean annual precipitation is 600 mm (CV = 25%). Availability of surface water to animals is primarily from rainwater collected in natural depressions. However, most of these do not hold water during the dry season, when water is artificially supplied in about 50 waterholes spread throughout HNP. The herbivore community is largely dominated by elephants (Chamaillé-Jammes et al., 2009, see Figure1).The hyaena population density has been stable since 1999 with an average (± SD) of 9 (± 2) indiv./100 km² (See Chapter 2 for details). Lion trophy hunting occurred in areas surrounding HNP until 2004, when a moratorium banned lion hunting from 2005 to 2008. As a consequence, the lion population density which was just above 2 indiv./100 km² before 2005 has now reached 3.5 indiv./100 km² with a very strong increase in the fraction of male population and the density of male coalitions(Loveridge et al. submitted). In our study, we thus divided our study time-frame into two distinct periods: before 2005 with low competition pressure(period 1, 1999-2006) and after 2008 with high competition pressure(period 2, 2009-2013). Wild dogs, cheetahs (Acinonyx jubatus) and leopards (Panthera pardus) are also present in the study area.

  Figure 1: Prey community composition (in % of total number of individuals) during the two periods.

Figure 2 :

 2 Figure 2: Changes in hyaena a) foraging and b) feeding group sizes between two periods of contrasted competition with lions in Hwange National Park, Zimbabwe: period 1 (1999-2006) and period 2 (2009-2013).

Figure 3 :

 3 Figure 3: Evolution of hyaena diet composition (a,b) and prey preferences using the Jacob's selection index (c,d) between the period of low (grey) and high (empty) competition with lions estimated from scats (a,c) and carcasses (b,d) data. a and b show the difference in diet composition between the 2 periods i.e. for a given species: % in the diet during period of high competition -% in the diet during period of low competition. Negative Jacobs' indices indicate avoidance while positive ones indicate selection.

Figure 4 :

 4 Figure 4: Hyaena prey preferences in term of prey size classes based on a) scats and b) carcasses. Negative Jacobs' indices indicate avoidance while positive ones indicate selection.

Figure 1 :

 1 Figure 1: Comparison of hyaena (grey) and lion (white) diet composition (a,b) and prey preferences (c, d) from scat data (a, c) and carcasses data (b,d) for a period of low competition pressure from lions.

Figure 1 :

 1 Figure 1: Factors influencing habitat selection in hyaenas (in bold) and variables used as their proxies (in italic)

From

  July 2009 to October 2013, nine adult female hyaenas belonging to four different clans were equipped with GPS collars (African Wildlife Tracking, UHF 407, GPS collar with UHF download and VHF transmitter). Hyaenas were immobilized by a professional team s s la n d S p a r s e ly b u s h e d g r a s s la n d B u s h e d g r a s s la n d B u s h la n d B u s h e d w o o d la n d W o o d la n d

Figure 2 :

 2 Figure 2: Habitat type availability, ordered from lower to higher vegetation cover in the Main Camp area of HNP.

  and b). Common prey species (except for kudu -Tragelaphus strepsiceros -during the dry season) were encountered at a higher rate in these three open habitats as well (see Appendix 4.1 for details). Prey kilometric biomass and encounter rate were highly variable in woodland (Figure 3, Appendix 4.1).

Figure 3 :

 3 Figure 3: Prey kilometric biomass (averages with SD) excluding elephants during a) the wet and b) the dry season for each habitat type.

  within or very close to open areas (76% of used locations within 200 m of an open area). The risk of encountering lions had little impact on the strength of selection of location in open area but had a positive effect on selection strength when further way from an open area

Figure 4 :Figure 5 :Figure 6 :

 456 Figure 4: Hyaena habitat type preference a) during the wet season and b) during the dry season. Error bars show standard errors (SE). SE was so small for grassland that it is not visible on the figure.

Figure 7 :

 7 Figure 7: Diagram describing how the perceived predation risk, moonlight illumination and hyaena hunting success influence their habitat selection

Figure 1 :

 1 Figure 1: Location of dens (black squares) and control holes (grey squares). Thick black lines represent clans 90% kernels contour HR and greyed areas represent clan cores (50% Kernels). Hashed areas figure cores of individual lion HR. HNP lies Southeast of the thick grey line and triangles represent waterholes

Figure 2 :

 2 Effect of a) the number of entrances and b) the distance to water on the likelihood of a site being selected as a den. Estimates were calculated by model averaging on the two best logistic regression models. Dotted lines represent lower and upper confidence intervals.

Figure 3 :

 3 Figure 3: Likelihood of a den being used when lions are present within a given distance with different time lags.a) Effect on distance to lion during a given week on den use during the same week. Solid, dot-dash, dashed and dotted lines show the effect of lion presence within 500 m, 1 km 1.5 km and 3 km radii respectively. b) Time effect of lion presence within 1 km of the den. Solid, dot-dash, dashed dotted lines show the impact of lion presence during the same week, the preceding week, the two preceding weeks and the preceding month respectively. Graphs for other time frames (presence of lions on the week, two weeks and month preceding the week of interest) and for other distance (500 m, 1.5 km and 3 km) present the same patterns.

From

  July 2009 to October 2013, nine adult female hyaenas belonging to four different clans were equipped with GPS collars (African Wildlife Tracking, UHF 407, GPS collar with UHF download and VHF transmitter). Collars were programmed to take hourly fixes at night between 6 pm to 8 am i.e. 15 locations per night. Hyaenas were immobilized by a professional team either with a standard mix of 500 mg Ketamine (Kyron laboratories Pvt.Ltd, Ben-rose, RSA) and 200 mg Xylazine (Rompun; Bayer, Leverkusen, Germany) or of 80 mg Zoletil (Virbac RSA, Halfway house, RSA) and 4 mg Medetomidine (Zalopine, Wildlife Pharmaceuticals, Karino, RSA). Drugs were then reversed with 16 mg of Yohimbine (Rx drug, Kyron Labs, Benrose, RSA) using a Dan Inject J.M.SP.25 CO 2 powered dart gun. Full recovery was ensured by staying with the animal until it would walk away normally. Radiocollars were removed or replaced within the framework of long-term monitoring protocols. In the study area, 18 lions were also equipped with GPS collars between 2009 and 2013 (seeBenhamou et al., 2014 for details) with lion collars programmed to take hourly fixes at night between 6 pm and 7 am, providing a unique opportunity for simultaneous monitoring of both species. Relevant animal care protocols were followed during capture and collaring of carnivores (Wildlife Drugs Sub-committee of the Drugs Control Council of Zimbabwe and Zimbabwe Veterinary Association, Wildlife Group, and licenses to acquire, possess and administer game capture drugs/dangerous drugs), and permissions were provided by the appropriate agencies (Zimbabwe Parks and Wildlife Management Authority).

  2002 and April 2003 with a resolution of 30 m (Chamaillé-Jammes, unpublished work). Six vegetation classes were distinguished with increasing tree density: grassland, sparsely bushed grassland, bushed grassland, bushland, bushed woodland and woodland. Grassland was the most open (higher visibility) vegetation class and was used as the reference in all analyses.

Figure 3 :

 3 Figure 3: Effect of the interaction between season and distance to an artificial waterhole (a & c) and night brightness (b & d) on hyaena total (a & b) and net displacement (c & d). Error bars represent SE.

  Figure 5: Distribution of movement types a) before, b) afterand c) for the complete encounter between hyaenas and lions depending on encounter occurring at a carcass or not. Distributions of encounter types for the complete encounter was calculated using the fully defined (movement before and after) encounters only.

Figure 1 :

 1 Diagram synthesis of the results obtained during my PhD. Solid lines represent effects demonstrated in this study while dashed lines figure suspected effects.

(

  [START_REF] Fritz | Resource variability, aggregation and direct density dependence in an open context: the local regulation of an African elephant population[END_REF]. Elephants, like other herbivore species, are dispersed through HNP during the wet season. However, the availability of surface water is limited to the Northern part of the park in the dry season (including the study area of Main Camp). This results in high concentrations of elephants with densities locally reaching 4.4 indiv./km 2(Chamaillé-Jammes et al., 2009) and often hundreds of them seen at an artificial waterhole in the late afternoon (pers.

  WINNIE, J., JOHN A, CHRISTIANSON, D., CREEL, S. & MAXWELL, B. (2006). Elk decisionmaking rules are simplified in the presence of wolves. Behavioral Ecology and Sociobiology 61, 277-289. WORM, B. & DUFFY, J. E. (2003). Biodiversity, productivity and stability in real food webs. Trends in Ecology and Evolution 18, 628-632.

Table 1 :

 1 Diet composition in prey species for both predators. Proportions are averaged between all ecosystems with available data. n gives the number of studies mentioning the prey species.

			Lion			Hyaena
	Prey species	%	Range	n	%	Range	n
	Baboon	3.2 ± 1.6	0.1-6.7	4	0.8	0.7-0.8
	Blesbok	9.9 ± 6.4	3.5-16.3	2	-	-	-
	Buffalo	21.9 ± 3.5	0.1-61.7	23	7.3 ± 2.6	0.1-23.5	11
	Bushbuck	5.8 ± 1.8	0.0-21.1	15	8.4 ± 7.3	0.3-30.4
	Bushpig	1.8 ± 1.1	0.0-4.9	4	1.9 ± 1.1	0.4-4.2
	Duiker	2.5 ± 1.1	0.1-11.5	11	3.0 ± 1.3	0.2-7.4
	Eland	2.7 ± 0.5	0.5-5.9	17	2.5 ± 2.2	0.3-7.0
	Elephant	11.2 ± 5.8	2.2-34.0	5	6.3 ± 5.4	0.1-22.3
	Gazelles	3.1	3.1	1	9.9 ± 4.0	4.9-17.9
	Gemsbok	9.4 ± 7.5	1.1-32.0	4	41.3 ± 19.5	8.8-76.1
	Giraffe	7.2 ± 2.0	0.4-21.4	13	8.9 ± 5.8	0.6-31.6
	Grant gazelle	0.8 ± 0.2	0.2-1.3	4	0.4 ± 0.1	0.3-0.5
	Grysbuck	-	-	-	0.1	0.1
	Hartebeest	15.0 ± 5.1	0.6-81.3	15	1.3 ± 1.1	0.0-4.7
	Hippo	3.5 ± 2.3	0.1-10.2	4	0.1	0.1
	Impala	11.4 ±2.9	0.4-43.5	18	22.7 ± 7.1	0.9-57.4
	Kob	20.2 ± 5.0	2.1-37.7	7	-	-	-
	Klipspringer	-	-	-	0.8 ± 0.2	0.6-1.0
	Kudu	11.6 ± 2.2	0.4-33.9	17	5.2 ± 1.7	0.6-12.9
	Lechwe	0.5	0.5	1	-	-	-
	Nyala	8.3 ± 8.0	0.1-24.3	3	6.8 ± 6.2	0.6-13.0
	Oribi	1.3 ± 1.5	0.8-1.8	2	-	-	-
	Puku	1.2	1.2	1	-	-	-
	Reedbuck	4.4 ± 3.3	0.3-36.8	11	2.1 ± 1.1	1.0-3.2
	Rhino	0.3 ±0.2	0.2-0.5	2	0.4	0.4
	Roan	15.4 ± 4.5	0.3-35.0	8	0.4 ± 0	0.4
	Sable	2.1 ± 1.0	0.8-5.1	4	1.4 ± 1.2	0.2-2.5
	Springbok	12.8 ± 8.3	0.8-36.2	4	29.8 ± 23.5	2.5-76.6
	Steenbok	0.5 ± 0.4	0.0-1.3	3	1.8 ± 0.5	0.3-3.1
	Suni	-	-	-	14.4	14.4
	Thomson gazelle	13.3 ± 6.7	0.4-22.6	3	10.4 ± 5.5	1.3-20.2
	Topi	5.6 ± 3.8	0.9-17.0	4	5.8 ± 3.0	2.8-8.8
	Tsessebe	0.7 ± 0.2	0.1-1.3	5	4.5 ± 4.1	0.4-8.6
	Warthog	11.6 ± 2.0	1.1-35.5	25	5.1 ± 2.4	0.1-17.2
	Waterbuck	5.5 ± 0.9	0.1+14.9	22	2.9 ± 1.1	0.0-8.6
	Wildebeest	24.6 ± 3.8	2.6-60.6	19	28.3 ± 8.0	3.7-76.9	10
	Zebra	11.6 ± 1.7	1.0-37.5	23	17.5 ± 5.1	1.5-63.5	12
	Other	6.2 ± 1.6	0.2-26.9	17	12.2 ± 3.3	0.7-37.8

Table 2 :

 2 Diet composition in prey size classes for both predators. Proportions are averaged between all ecosystems with available data.

	Figure 4: Hyaena foraging group size versus lion adult pride size.
		Lion		Hyaena
	Prey class	%	Range	%	Range
	Very small	2.8 ± 0.1	06-12.3	5.6 ± 1.3	0.8-14.4
	Small	29.4 ± 6.6	2.7-62.3	31.8 ± 2.5	3.5-67.9
	Medium	45.1 ± 6.2	3.3-90.1	41.5 ±+ 8.6	4.7-89.4
	Large	20.1 ± 1.9	2.8-61.7	7.9 ± 0.1	1.4-23.5
	Very large	7.6 ± 0.4	1.3-21.9	14.0 ± 0.8	2.7-31.6
	Other	6.2 ± 0.2	1.1-26.9	13.2 ± 1.7	1.9-37.8

Table 3 :

 3 Dietary breadth and overlap for lions and hyaenas.

	Species	Levin's	Pianka's	% overlap
		index	index
	Hyaena	7.94	0.92	-
	Lion	7.06	0.82	-
	Both	-	0.43	68.5

Table 4 :

 4 Kleptoparasitism extent between hyaenas and lions. The total % of food

of kills at which the other species is present

  Elliott and loss takes both killed and scavenged carcasses into account. m gives the number of locations used.

		Hyaena	Lion
	% of total food loss	11.7 ± 1.3 (0.6-24)	16.7 ± 2.2 (0.6-30)
		n=6	n=3
	% 23 ± 1.4 (20-25.9)	55.9
		n=2	n=1
	%

of kill lost when the other species is present

		69.7 ± 2.2 (35.7-100)	34.6 ± 1.9 (0-57.1)
		n=5	n=6
	% of owns kills when both	64.9 ± 12.3 (41.5-92.3)	7.3
	species at kills	n=3	n=1
	%

of food obtained from the other species (kleptoparasitism and scavenging)

	11.6 ± 1.18 (4.5-20)	22.35 ± 1.8 (5.6-35.8)
	n=5	n=4

Table 5 :

 5 Hyaenas main causes of death.

	Location

Sample size (number of deaths recorded) % death caused by lions Other cause of deaths Lions as a leading cause of mortality? Time frame Reference Chobe NP

	Cooper (1991)	Trinkel & Kastberger (2005)	Mills (1990)				Henschel & Skinner (1991)	Frank (1986)	Watts & Holekamp (2009)						Frank et al. (1995)
	1986-1988	2000-2001	1972-1980				1982-1984	1979-1983	1988-2006						1979-1992
	Y	Y	N				Y	Y	Y	NA	NA				Y	Y	Y	N		Y			Y	Y	NA
	NA	NA	24% rabies	12% humans	3% rabies	20% rabies		30% humans	18% humans	10% humans	15% hyaenas	15% starvation	10% disease	5% humans	31% humans	31% humans	33% humans	18.2% hyaenas	15.9% starvation	17.9%	disease/starvation	14.3% hyaenas	7.2% humans
	53	71	12		9	13	66.7	60	27	15	15				69	69	67	10.2		46.4			44.4	50	individuals 10	killed
	13	Etosha NP NA	Kalahari NP 50		35 adults	15 juveniles	Kruger NP 6	Masai Mara GR 5	73	24 adults	49 juveniles				16	13 adults	3 juveniles	Serengeti NP NA		28			18 adults	10 juveniles	NA

Table 6 :

 6 Proportion of adults and juveniles in hyaena and lion diets.

Species Proportion of adults in the diet Proportion of juveniles in the diet

	Hyaena	0.66 (n=2232)	0.34 (n=1134)
	Lion	0.77 (n=4119)	0.23 (n=1221)

  would walk away normally. Radio-collars were replaced or removed within the framework of long-term monitoring protocols. Relevant animal care protocols were followed during capture and collaring of carnivores (Wildlife Drugs Sub-committee of the Drugs Control Council of Zimbabwe and Zimbabwe Veterinary Association, Wildlife Group, and licenses to acquire, possess and administer game capture drugs/dangerous drugs), and permissions were provided by the appropriate agencies (Zimbabwe Parks and Wildlife Management Authority).

	Ketamine (Kyron laboratories Pvt. Ltd, Ben-rose, RSA) and 200 mg Xylazine (Rompun;
	Bayer, Leverkusen, Germany) or of 80 mg Zoletil (Virbac RSA, Halfway House, RSA) and

4 mg Medetomidine (Zalopine, Wildlife Pharmaceuticals, Karino, RSA) using a Dan Inject J.M.SP.25 CO 2 powered dart gun. Drugs were then reversed with 16 mg of Yohimbine (Rx drug, Kyron Labs, Benrose, RSA). Full recovery was ensured by staying with the animal until Figure 2: Location of calling stations within hyaena HRs (thick lines: 95% isopleths, dotted lines: 50% isopleths). Large dots represent artificial waterholes and small dots represent natural ones. Empty squares figure calling stations. The thick grey line figures HNP boundary with the protected area lying at the Southwest.

it

Table 1 :

 1 Hyaena density estimated from calling surveys. Area sampled is the product of the number of calling stations by the area sampled at one station (i.e. 32.2 km 2 with a response radius of 3.2 km)

	Year	Number of calling stations	Number of hyaenas seen	Area sampled (km²)	Hyaena density (indiv./km²)
	1999	11	31	353.9	0.09
	2000	13	29	418.2	0.07
	2001	12	37	386.0	0.10
	2002	13	46	418.2	0.11
	2003	12	42	386.0	0.11
	2005	16	47	514.7	0.09
	2008	17	42	643.4	0.07
	2010	16	76	546.9	0.14
	2011	20	48	514.7	0.09
	2012	20	52	643.4	0.08

Table 2 :

 2 Global HR and core sizes for each individual and clan and average clan size estimated from calling survey.

			Individual		Clan	Average
	Clan	Individual	95% (km 2 )	50% core (km 2 )	95% (km 2 )	50% core (km 2 )	clan size
	Airstrip	Pilot Masinyana	263.2 134.1	60.9 21.2	177.7	24.3	8.7
		Cyclope	255.4	39.1
	Makwa	Julia	290.8	61.8	282.4	57.5	16
		Tom	275.2	52.8
	Guvalala	Incognito Nyarai	238.2 359.8	43.9 74.3	320.6	62.5	19
	Ngweshla	Decoration Damdubzo	161.6 175.4	18.8 32.4	178.6	28.2	12

Table 4 :

 4 Demographic and HR characteristics of several hyaena populations across Africa ordered by increasing prey density. Prey biomass of was calculated as the sum of each species density time 75% of their adult female weight when necessary. Parentheses below HR size gives SD, the number of individuals or clans used for HR estimation and the method used: minimum convex polygon (MCP).

	Location	Density (ind/km 2 )	Clan size	HR size (km 2 )	Prey (/km 2 ) density	Prey (kg/km 2 ) biomass	References
	Ngorongoro	1.5	60.1	26.1 (± 12.2, 16	89.1	4598.5	Kruuk 1972, Honer et al. 2005
				indiv., MCP)
							Frank 1986, Ogutu and Dublin
	Masai Mara	0.46	57.5	30.2 (± 6.9, 10 indiv., MCP)	19.2	4609.4	1998; 2002, Boydston et al. 2003, Kolowski et al. 2007, Kolowski and Holekamp 2009, Watts and Holekamp 2009,
							Pangle and Holekamp 2010
				239.8
	Hwange	0.09	11.3	(± 72.9, 4	14.3	7233	This study
				clans, LKDE)
	Kruger	0.12	14	130 (1 clan, MCP)	14.7	1999.4	Mills 1985, Henschel and Skinner 1990a; 1991
				30.8
	Serengeti	0.8	22-75	(± 11.8, 10 clans, MCP)	12.1	5414.9	Kruuk 1972, Hofer and East 1993a
	Kalahari	0.09	10	1095 (± 177, 6 clans,	4.5	546.7	Mills 1990
				MCP)
	Chobe	0.44	57.5	60 (1 clan, MCP)	1.6	2142.0	Cooper 1989
				327.5
	Etosha	0.056	9-18	(± 156.5, 3	0.7	NA
				clans, MCP)

  addition, for each location during the late dry season, we calculated the distance to the closest artificial waterhole and for each location of the wet season, the distance to the closest open area regrouping grassland, sparsely bushed grassland and bushed grassland. When artificial waterholes were located within open areas, these were not located only around waterholes, this is why we included distance to an open area as a proxy of prey abundance instead of distance to artificial waterhole during the wet season (see Appendix 4.2). Each

	location was also assigned to a moon illumination index ranging from 0 (new moon) to 1 (full
	moon).	Moon	illumination	index	was	extracted	from

http://aa.usno.navy.mil/data/docs/MoonFraction.php for our study location. For each location,

Table 1 :

 1 List of the five top models for predicting hyaena locations based on ΔAIC for the dry and wet season

	Model	ΔAIC
	Dry season
	risk x distance to water + moon x habitat x risk	0
	distance to water + moon x habitat x risk	7.2
	risk x habitat + risk x distance to water + moon x habitat	9.5
	risk x habitat + risk x distance to water + risk x moon	13
	distance to water + risk x habitat + moon x habitat	16.9
	Wet season
	risk x distance to open + moon x habitat x risk	0
	risk x habitat + risk x distance to open + moon x habitat	28.8
	risk x habitat + risk x distance to open + risk x moon	29.6
	risk x habitat + risk x distance to open	30.3
	distance to open + moon x habitat x risk	96.5

Table 1 :

 1 Models for den selection based on proxies of predation risk by lion. Best models are in bold. NB ENT number of entrances, VISIB average visibility distance, DWT distance to closest waterhole.

	Model

Table 2 :

 2 Averaged parameter estimates for den selection based on proxies of predation risk by lions.

	Parameter	Estimate	Adjusted SE	Lower CI	Upper CI
	Intercept	-1.29	0.70	-2.67	0.08
	DWT	0.0003	0.0002	-0.0001	0.001
	NB ENT	0.81	0.37	0.08	1.54

Table 3 :

 3 LRT tests and estimated values of the effect of lion presence within a distance on the den on the likelihood of the same den being use by hyenas at different time lags. LRT test columns show the p-value of the LRT test for the model including the lion effect against the null model, Estimate and SE columns give the value of the parameter estimate given by the model and its SE.

		SE	0.31	0.36	0.21	0.12
	500 m	LRT test Estimate	0.004 -0.51	0.014 -0.75	0.014 -0.46	0.022 -0.25
		SE	0.14	0.18	0.11	0.06
	1 km	Estimate	-0.25	-0.48	-0.32	-0.20
		LRT test	0.003	0.001	<<0.001	<<0.001
		SE	0.09	0.10	0.06	0.04
	1.5 km	Estimate	-0.20	-0.26	-0.19	-0.12
		LRT test	0.001	0.003	0.001	<<0.001
		SE	0.05	0.05	0.03	0.02
	3 km	Estimate	-0.17	-0.23	-0.15	-0.09
		LRT test	<<0.001	<<0.001	<<0.001	<<0.001
	Distance	time frame	same week	preceding week	2 preceding weeks	preceding month

Table 1 :

 1 Top five models that best explained hyaena movement patterns with distance to artificial waterhole (water), habitat, season and night brightness (moon) as explanatory variables.

	Response variable	Models	AIC	ΔAIC	ωAIC
	Log (Step length) water + habitat	28412.83	0.00	0.82
	water + habitat + moon	28417.62	4.79	0.07
	season x water + habitat	28418.19	5.37	0.06
	season + water + habitat	28420.07	7.25	0.02
	season + water + habitat + moon	28421.00	8.17	0.01
	√ (Net displacement) season x water + moon	4078.66	0.00	0.95
	season x water	4085.40	6.74	0.03
	season + water + moon	4087.39	8.72	0.01
	season + water	4094.09 15.42	0.00
	water + moon	4094.69 16.03	0.00
	√ (Total displacement) season x water + moon	4241.91	0.00	0.97
	season x water	4249.08	7.17	0.03
	season + water + moon	4251.67	9.76	0.01
	season + water	4258.84 16.93	0.00
	season + moon	4259.93 18.02	0.00
	Straightness null		128.96	0.00	0.75
	season		131.48	2.52	0.21
	water		136.02	7.06	0.02
	season + water	137.11	8.15	0.01
	moon		142.28 13.32	0.00

Table 2 :

 2 Speed (m/h; mean ± SD) for both hyaena and lion before and after each encounter type.

			Before encounter
		Hyaena		Lion
	Type	Mean ± SD	range	Mean ± SD	range	n
	H0L0	210 ± 203	3-673	77 ± 176	4.2-545	6
	H0L1	501 ± 1298	1-5293	1341 ± 886	12-2993	11
	H1L0	1466 ± 1430	0-5727	141 ± 311	0-1842	43
	H1L1	1169 ± 1194	1-4908	989 ± 1021	0-3943	24
			After encounter
	Type	Mean ± SD	range	Mean ± SD	range	n
	H0L0	246 ± 567	1.2-4022	76 ± 141	1-617	29
	H0L1	227 ± 352	0-1293	597 ± 612	4-1589	11
	H1L0	1131 ± 1224	1-5562	266 ± 863	0-4444	27
	H1L1	1004 ± 1103	0-5689	986 ± 972	2-4037

Thesis structure

Synthesis & perspectives

Acknowledgements / Remerciements

Acknowledgements / Remerciements Acknowledgements Remerciements Acknowledgements / Remerciements Acknowledgements / Remerciements Acknowledgements / Remerciements Acknowledgements / Remerciements ACKNOWLEDGMENTS This study was conducted in the framework of the HERD program (Hwange Environmental Research Development), funded by the CNRS INEE (''Institut Ecologie et Environnement'', ''Zones Ateliers'' programme, the Agence National de la Recherche FEAR project (ANR-08-BLAN-0022). The principal investigator salary was provided by the ENS of Lyon and UCBL Lyon1. ER was supported by the Spanish Ministry of Science and Innovation co-funded by FEDER (projects CGL2009-07301/BOS and CGL2012-35931/BOS). We thank Marion Valeix for her fruitful comments on early versions, as well as Nicholas Elliot for correcting the English and allowing us to improve this manuscript. We are grateful to Matt Hayward and an anonymous reviewer for providing helpful comments on a previous version of the manuscript. MILLS, M. G. L. & BIGGS, H. C. (1993). Prey apportionment and related ecologial relationships between large carnivores in Kruger National Park. Symposia of the Zoological Society of London 65, 253-268. MILLS, M. G. L., BIGGS, H. C. & WHYTE, I. J. (1995). The relationship bewteen rainfall , lion predation and population trends in African herbivores. Wildlife Research 22, 75-87. MILLS, M. G. L., JURITZ, J. & ZUCCHINI, W. (2001). Estimating the size of spotted hyaena (Crocuta crocuta) populations through playback recordings allowing for non-response. Animal Conservation 4, 335-343. MILLS, M. G. L., BROOMHALL, L. S. & DU TOIT, J. T. (2004). Cheetah Acinonyx jubatus feeding ecology in the Kruger National Park and a comparison across African savanna habitats: is the cheetah only a successful hunter on open grassland plains? Wildlife Biology 10, 177-186. MITCHELL, B., SHENTON, J. & UYS, J. (1965). Predation on large mammals in the Kafue National Park, Zambia. Zoologica africana 1, 297-318. MOSSER, A., FRYXELL, J. M., EBERLY, L. E. & PACKER, C. (2009). Serengeti real estate: density vs. fitness-based indicators of lion habitat quality. Ecology Letters 12, 1050-1060. OGUTU, J. O. & DUBLIN, H. T. (2002). Demography of lions in relation to prey and habitat in the Maasai Mara National Reserve, Kenya. African Journal of Ecology 40, 120-129. OGUTU, J. O., BHOLA, N. & REID, R. (2005). The effects of pastoralism and protection on the density and distribution of carnivores and their prey in the Mara ecosystem of Kenya. Journal of Zoology 265, 281-293. OTTICHILO, W. K., DE LEEUW, J., SKIDMORE, A. K., PRINS, H. H. T. & SAID, M. Y. (2001). Population trends of large non migratory wild herbivores and livestock in the Masai Mara ecosystem, Kenya, between 1977 and 1997. African Journal of Ecology 38, 202-216. PACKER, C. (1990). Serengeti lion survey. Report to TANAPA, SWRI, MWEKA and the Wildlife Division. PACKER, C., SCHEEL, D. & PUSEY, A. (1990). Why lions form groups: food is not enough. The American Naturalist 136, 1-19. PACKER, C., PUSEY, A., ROWLEY, H., GILBERT, D., MARTENSON, J. & O'BRIEN, S. (1991). Case study of a population bottleneck: lions of the Ngorongoro Crater. Conservation Biology 5, 219-230. PACKER, C., LOVERIDGE, A. J., CANNEY, S., CARO, T. M., GARNETT, S. T., PFEIFER, M., ZANDER, K. K., SWANSON, A., MACNULTY, D. R., BALME, G., BAUER, H., BEGG, C. M., BEGG, K. S., BHALLA, S., BISSETT, C., BODASING, T., BRINK, H., BURGER, A., BURTON, A. C., CLEGG, B., DELL, S., DELSINK, A., DICKERSON, T., DLONIAK, S. M., DRUCE, D. J., FRANK, L. G., FUNSTON, P., GICHOHI, N., GROOM, R., HANEKOM, C., HEATH, B., HUNTER, L. T. B., DEIONGH, H. H., JOUBERT, C. J., KASIKI, S. M., KISSUI, B. M., KNOCKER, W., LEATHEM, B., LINDSEY, P. A., MACLENNAN, S. D., MCNUTT, J. W., MILLER, S. M., NAYLOR, S., NEL, P., N'WENO, C., NICHOLLS, K., OGUTU, J. O., OKOT-OMOYA, E., PATTERSON, B. D., PLUMPTRE, A. J., SALERNO, J., SKINNER, K., SLOTOW, R., SOGBOHOSSOU, E. A., STRATFORD, K. J., WINTERBACH, C. W., WINTERBACH, H. & ACKNOWLEDGMENTS The Zimbabwe Research Council and the Zimbabwe Parks and Wildlife Management Authority (ZPWMA) are kindly acknowledged for providing the opportunity to carry out this research. This study was supported by the HERD project (Hwange Environmental Research Development), funded by the Agence Nationale de la Recherche (FEAR project ANR-08-BLAN-0022), and the Centre National de la Recherche Scientifique (Programme Zones Ateliers) and the RP-PCP platform. Some GPS collars were funded by the National Geographic Society GRANT #C151-08. The PhD fellowship for Stéphanie Périquet was provided by the ENS of Lyon and UCBL Lyon1. We want to thank ZPWMA rangers and Martin Muzamba for providing great help in the data collection in HNP. Our deepest thanks go to Javier Calzada for the early beginning of scat analyses. Relevant animal care protocols were followed, and approval was received from the appropriate agencies. ACKNOWLEDGMENTS The Zimbabwe Research Council and the Zimbabwe Parks and Wildlife Management Authority are kindly acknowledged for providing the opportunity to carry out this research. We thank Nicholas Elliot, Jane Hunt and Brent Stapelkamp for the collection of lion GPS data. This study was supported by the HERD project (Hwange Environmental Research Development), funded by the ANR FEAR (ANR-08-BLAN-0022), the CNRS, the RP-PCP platform and by the Hwange Lion Project supported by grants from The Darwin Initiative for Biodiversity Grant 162/09/015, The Eppley Foundation, Disney Foundation, Marwell Preservation Trust, Regina B. Frankenburg Foundation, The Rufford Maurice Laing Foundation, Panthera Foundation, and the generosity of Joan and Riv Winant. The principal investigator salary was provided by the ENS of Lyon and UCBL Lyon1. Our deepest thanks to Simon Chamaillé-Jammes and Nicolas Ganzin for the fieldwork and compilation for the vegetation map. ACKNOWLEDGEMENTS The Zimbabwe Research Council and the Zimbabwe Parks and Wildlife Management Authority are kindly acknowledged for providing the opportunity to carry out this research. We thank Nicholas Elliot, Jane Hunt and Brent Stapelkamp for the collection of lion GPS data. This study was supported by the HERD project (Hwange Environmental Research Development), funded by the ANR FEAR (ANR-08-BLAN-0022), the CNRS, the RP-PCP platform and by the Hwange Lion Project supported by grants from The Darwin Initiative for Biodiversity Grant 162/09/015, The Eppley Foundation, Disney Foundation, Marwell Preservation Trust, Regina B. Frankenburg Foundation, The Rufford Maurice Laing Foundation, Panthera Foundation, and the generosity of Joan and Riv Winant. The principal investigator salary was provided by the ENS of Lyon and UCBL Lyon1. Our deepest thanks to Marion Valeix and Nicholas Elliot for fruitful comments on previous versions of this manuscript.

ACKNOWLEDGMENTS

The Zimbabwe Research Council and the Zimbabwe Parks and Wildlife Management Authority are kindly acknowledged for providing the opportunity to carry out this research.

We thank Nicholas Elliot, Jane Hunt and Brent Stapelkamp for the collection of lion GPS data. This study was supported by the HERD project (Hwange Environmental Research Development), funded by the ANR FEAR (ANR-08-BLAN-0022), the CNRS, the RP-PCP platform and by the Hwange Lion Project supported by grants from The Darwin Initiative for Biodiversity Grant 162/09/015, The Eppley Foundation, Disney Foundation, Marwell Preservation Trust, Regina B. Frankenburg Foundation, The Rufford Maurice Laing Foundation, Panthera Foundation, and the generosity of Joan and Riv Winant. The principal investigator salary was provided by the ENS of Lyon and UCBL Lyon1. Our deepest thanks to Simon Chamaillé-James and Nicolas Ganzin for the fieldwork and compilation for the vegetation map.

Abstract / Résumé

Structure of the thesis

Appendix 1.2 Data on locations, predators and prey extracted from publications.

For density, biomass and diet estimates, hippos were never accounted for as well as baboons, other apes, ostriches and other large birds. Body mass refers to 75% of adult female weight, which was used to estimate prey biomass.

ABSTRACT

Large carnivore diets are influenced by several factors such as prey abundance and vulnerability and habitat characteristics related to hunting or escape. Hunting group size also affects prey selection as larger groups can hunt large prey and better protect kills from kleptoparasitism. However, intraguild competition and predation risk can also influence large predator diet. We collected scats and feeding site data, identified from GPS clusters of spotted hyaenas in Hwange National Park, Zimbabwe, to assess whether the hyaena diet composition and prey preferences changed with changes in the lion population. We compared these two parameters between two contrasting periods, one with low and one with high lion densities.

As hunting group size can be a key determinant of hyaena foraging, and also changed with time, we also tested for the effect of hunting group size on diet. We found that during the period of high competition with lions, hyaenas use and preferences for very large prey increased while that of medium and small sized prey decreased, despite an increase in foraging group size. The use of elephant and giraffe, the two largest herbivores in our system, greatly increased during the high competition period while that of buffalo and zebra decreased. We interpret these results as a switch from active predation to scavenging from natural carcasses and lion kills as the risk of kleptoparasitism from lions and intraguild predation increased. We also found that scat data largely underestimated elephant whilst feeding sites overestimated very large and large-sized prey and underestimated very small ones. Our findings support the hypothesis that the intensity of competition between large carnivores can affect their diet, prey preferences and foraging strategies and thus may impact prey populations and possibly ecosystems functioning.

KEYWORDS

Appendix 3.2

Diet comparison and overlap between hyaenas and lions during a period of low competition pressure from lions

We used data published in [START_REF] Davidson | Seasonal Diet and Prey Preference of the African Lion in a Waterhole-Driven Semi-Arid Savanna[END_REF] to compare lion and hyaena diet and prey preferences. Lion data were collected during a period of low competition from lion due to trophy hunting in the areas surrounding HNP that reduce the number of adult males in the lion population [START_REF] Davidson | Lion ecology and socio-spatial impacts of trophy hunting in Zimbabwe[END_REF]. For the comparison, we thus used only scats and carcasses collected from hyaenas during the same period (1999)(2000)(2001)(2002)(2003)(2004)(2005). This analysis were not included in the draft as no data was available for lion diet during period preventing us to analyse the effect of increased competition of diet overlap between the two species.

We computed the percentage of diet overlap between the two species of carnivores as (Krebs, 1989) where and are the proportion of food item i in species j and k diets, respectively. We then used Pianka's niche overlap index (Pianka, 1973) Chapter 4

Habitat selection in Spotted hyaena: hiding from Lions or spotting them first? Hyaenas preferred not being seen rather than detecting lions first and were willing to take more risks in dense habitats. Hyaenas thus limit their risk of predation by avoiding lions in risky conditions and selecting for safer habitats when the risk of lion presence increased. Our results show that predators habitat selection is also influenced by the trade-off between resource availability and predation risk.

KEYWORDS

Crocuta crocuta, moon illumination, Panthera leo, predation risk, RSF, waterhole Here we present a vegetation map of the study area with a 30 m resolution and six vegetation classes.

Open areas regroup grassland, sparsely bushed grassland and bushed grassland vegetation classes.

The thick grey line figures HNP boundary. Squares represent artificial waterholes and circles natural ones.

Hyaena clan home ranges are also represented.

ABSTRACT

Inter-specific killing is common among carnivore species and is likely to be a major driver of their spatial ecology and habitat selection. Here, we show how den selection and attendance at, and proximity to, dens by spotted hyaenas is influenced by the risk of predation by lions. We studied 57 dens in the semi-arid savannah of Hwange National Park, Zimbabwe.

Hyaenas did not avoid denning in lion home ranges or their cores, but den selection was affected by environmental proxies of predation risk. Hyaenas preferred dens far from waterholes, which are intensively used by lions, and with numerous entrances presumably providing many escape options for cubs. Den attendance pattern was not influenced by proxies of predation risk. However, as the presence of lions in the vicinity of a den increased during a given week, the likelihood of a hyaena moving close to that den during that week decreased (regardless of its current state, used or unused). This effect was stronger when lions were closer to the den. In addition, hyaenas adjusted their patterns of den attendance according to recent (up to at least a month) lion presence in the vicinity of the den. They avoided using dens in a given week as the presence of lions during the preceding weeks increased. Hyaenas thus selected their dens based on proxies of predation risk but used them depending on their actual knowledge of lion presence (current or past) in the area. Hyaena denning behaviour is therefore very dynamic and appears to be driven, at least in part, by the presence of their main competitor.

KEYWORDS

Crocuta crocuta, Hwange National Park, Panthera leo, predation risk Appendix 5.1

Den use definition method

Here we provide more details on our method to define den periods of use in case this design was to be repeated in other studies.

Each black cell represents a day when the minimum distance from hyaena to the den was less than 500 m. We thus considered that the den was visited on these days. Grey cells figure days included in the period of use based on the following definition: they are at least 5 visits per period of use and each successive visit occurred within 7 days of the previous one.

The following figure gives some examples.

A: the den was only visited three times, thus was not considered as used.

B: the den was first visited 3 times but the next visit took place more than 7 days after the one in day 6. Thus the den was considered as used once for 5 days.

C: the 5 visited all occurred within 7 days of the previous ones and the den was considered as used for 7 days.

D: the den was used twice, first 5 days than 7. Its total length of use is thus 12 days and average length of use is 6 days.

Appendix 5.2

Den site characteristics and denning seasonality

The following results are not presented in the draft as they do not involve response the predation risk by lions. However, we believe that they are worth mentioning to provide a general knowledge of hyaena denning behaviour in wooded savannas. We did not seek to present extensive data on hyaena social behaviour at dens, as direct observations were not possible due to their remote location inaccessible by car. Details on such behaviour have been extensively studied in the Serengeti and Ngorongoro (Kruuk, 1972;[START_REF] East | Functions of birth dens in spotted hyaenas (Crocuta crocuta)[END_REF]Hofer & East, 1993;[START_REF] Hofer | Siblicide in Serengeti spotted hyenas: a long-term study of maternal input and cub survival[END_REF], Masai Mara [START_REF] Holekamp | Provisioning and Food Sharing by Lactating Spotted Hyenas, Crocuta crocuta (Mammalia: Hyaenidae)[END_REF][START_REF] Boydston | Patterns of den occupation by the spotted hyaena (Crocuta crocuta)[END_REF] as well as in Chobe (Cooper, 1993). Here, we rather simply provide basic description of den location, characteristic and attendance patterns in HNP.

We tested if hyaenas preferred particular types of vegetation to establish their dens using Fisher's exact test to compare habitat type between dens and control holes. We studied the effect of season on the likelihood of a den being used (as defined in this Chapter) using LRT test based on generalized mixed effects models with den identity as a random factor and a binomial error structure.

There was no habitat selection for den site (Fisher test, p=0.65). On average, dens were used 1.8 ± 0.2 times (range 1-3) and for a length of 45.2 ± 5.8 days (12 to 108 days).

Season had a significant impact on den use (LRT test p<0.0001, model deviance 9261.5, null model deviance 9299.9). Dens were more likely to be used during the early dry season than during the late dry season (z=-5.78, p<0.0001). However, there was no difference in the likelihood of a den being used during the early dry and the wet season (z=-1.16, p=0.24).

We found that hyaenas tend to make more use of their dens during the early dry and wet seasons which seems odd as prey availability is probably at its lowest during these two seasons as they are dispersed through the park. We do not have data to link den attendance to the presence of very young cubs, but hyaenas use their dens more frequently when they have small cubs [START_REF] East | Functions of birth dens in spotted hyaenas (Crocuta crocuta)[END_REF]. Thus during the early dry season, cubs are born a couple of month before prey are easier to find and catch i.e. during the late dry season when they

ABSTRACT

Movement is a key factor in ecological and behavioural processes such as foraging behaviour and space use. Its characteristics can be influenced by landscape features, resource distribution and predation risk. Studying movement requires fine scale monitoring of animals locations that is now possible thanks to telemetry data. Despite the widespread development of GPS telemetry and radio-collars, very few fine scale detailed studies exist on large carnivore movement. As for other species, their movement patterns are also likely to be influenced by competition and predation risk. In addition, in semi-arid savannas where surface water availability influences prey distribution, large carnivore movement ecology is also likely to be constraint by the spatial distribution of artificial waterholes. We studied spotted hyaena (Crocuta crocuta) movement ecology in the semi-arid wooded savanna of Hwange National Park (HNP), Zimbabwe, thanks to hourly GPS locations from radio-collars.

We found that hyaenas concentrate their time and movement in areas less than 2 km away from artificial waterholes where prey are easily encountered. Habitat structure also impacted hyaena movement patterns, with hyaenas moving faster in bushy habitat than in grassland and woodland. GPS collars deployed simultaneously on lions (Panthera leo), in the study area allowed us to characterise encounters between the two species. Most of them occurred at carcasses where hyaenas and lions stayed in close proximity at least for a few hours and up to several nights. Encounters away from food were very short (less than 1 h) and both species moved away rapidly after being in contact. Hyaenas and lions were also more likely to encounter each other close to artificial waterholes, especially during the dry season. This is the first study providing details on hyaena movement patterns and dynamic of spatial interactions between two apex predators.

KEYWORDS

artificial waterholes, Crocuta crocuta, dynamic interaction, feeding sites, movement, Panthera leo

RESULTS

Hyaena movement characteristics

Hyaena speed (when active) averaged 1.5 km/h (SD = 1.3; range = 0.1-10.0) for a total displacement per night of 14.1 km (SD = 7.4; range= 0.1-45.3 km) and a net displacement per night of 4.6 km (SD = 4.3; range: 0.0-30.0 km). The average straightness index was 0.3 (SD = 0.3; range = 0-1).

The best model predicting speed included distance to water and habitat (Table 1). Hyaenas moved faster when further from water and in habitats with a bushland layer (bushland, bushed woodland, and bushed grassland, Figure 2). The variables that were most influential in determining the total and net displacements included the interaction between season and distance to water as well as the night brightness (Table 1). TD and ND increased as the distance to water increased in the wet season only (Figures 3a and3c). Hyaenas covered longer TD and ND during dark nights (Figures 3b and3d). The straightness index was best predicted by the null model and was thus not influenced by season, distance to water or night brightness (Table 1).

Speed (m/h) In this PhD work, I investigated the effects of coexisting with sympatric lions on spotted hyaena ecology in a semi-arid wooded savanna by using a unique combination of direct observations and GPS data to obtain simultaneous fine scale spatio-temporal data on hyaenas and lions. To my knowledge, this is the first extensive work focusing primarily on hyaenas and using simultaneous data from lions. Figure 1 summarizes the effects of lions and human management on hyaena ecology in HNP that I identified during this study.

Hyaenas responses to lions: dynamic interactions at the heart of carnivore coexistence

While some studies have shown that hyaenas are competitively inferior to lions, losing their kills to them, and often incapable of stealing those of lions (Honer et al., 2002;Trinkel & Kastberger, 2005), others have concluded the opposite with hyaenas capable of negatively impacting lions (Kruuk, 1972;Cooper, 1991). With lions more than three times bigger than hyaenas (average adult male lion weight = 200 kg; average adult female hyaena weight = 60 kg) and one of the main causes of hyaena mortality (Chapter 1), I first expected hyaenas to spatially and temporally avoid lions. Indeed, subordinate species have been commonly shown to spatially avoid dominant ones to reduce competition pressure and predation risk. For instance, Egyptian mongooses (Herpestes ichneumon) and common genets (Genatta genatta) avoid habitats intensively used by their main competitor, the Iberian lynx (Felis pardina, [START_REF] Palomares | Spatial relationships between Iberian lynx and other carnivores in an area of south-western Spain[END_REF]. However, the results presented in this study do not support the hypothesis of general avoidance of lions by hyaenas.

Geographic range of hyaenas and lions overlap extensively and their densities are also positively correlated through their range (Chapter 1). Thus, high densities of lions do not seem to have a negative effect on hyaena populations (Chapter 1). This result is in accordance with those of Creel and Creel (1996), and is explained by the fact that both species reach high densities in areas rich in prey [START_REF] Carbone | A Common Rule for the Scaling of Carnivore Density[END_REF]Hayward et al., 2007). In HNP, hyaena home ranges are largely overlapped by those of lions and they both select for the same habitats and patches, which are rich in prey (Chapter 4). This demonstrates that there is no general spatial segregation between them. I then investigated den site selection by hyaenas and expected them to select for low risk areas to establish their dens. Indeed, competition with lions appears to result in lower reproductive success in hyaenas in the Masai Mara (Watts and Holekamp 2008), and lions have been observed killing hyaena cubs at dens in HNP [START_REF] Teichmann | Spotted hyaena research[END_REF]. I did not find any evidence supporting this hypothesis (Chapter 5), however