Florent Laroche

From semantic reverse-engineering to virtual reality tool box for digital heritage objects

Keywords: Digital heritage, reverse-engineering, history

The national project ReSeed aims to offer an alternative allowing both semantic (2D sources) and physical (3D) modeling for our scientific, technical and industrial heritage; while guaranteeing authenticity and integrity of knowledge. The digital integration of heterogeneous knowledge is ambitious; the project team then demonstrated that designing a unique tool is not possible. ReSeed's proposal is one digital container of self-structured knowledge created simultaneously with the digital double of the heritage object studied. Considered as an "Augmented Historical Reality" defined by a virtual tool instead of the usual "paper" procedures, ReSeed nonetheless remains a tool for asset decision support.

The recent democratization of the digital world has allowed new possibilities for capitalizing, analyzing and enhancing our heritage, tangible or intangible, in order to face the lack of the Humanity knowledge. Today, digital techniques are invading the field of cultural heritage for studies, conservation and valorisation, and they are constantly developing. In a few years, fields of use of digital techniques have become numerous and diversified: volume scanning (artefacts, monuments, landscapes), virtual restitution, databases, multiple requests and artificial intelligence aiming to coordinate representation: 2D (map), 3D (volume), 3D + t (dynamic) with information (archive, printed text, sound, image, movies, …). The main rules applied today are practical rules of feasibility. They are evaluated essentially from the point of view of their technical efficiency and specifications are mostly functional. However, if data acquired are intelligible and interoperable, they are rarely presented to the public or to experts. This low use can be explained because of the big amount of data to be handled, which greatly exceeds the capacities of current computers and the skills of those carrying this knowledge. Indeed, the use of digital tools for different types of cultural heritage projects and programs involves multiple professional and scientific communities: architects, heritage' curators, historians, archaeologists, geographers, computer scientists, engineers and etc. Communities with diverse interests appear to be involved in the projects: owner of the heritage in question and its projects, consultants and implementing companies, academics and research projects, institutions and conservation rules, etc. Beyond simply using 3D tools for graphical visualizations, new approaches and tools allowing the semantic linking of objects through databases must fit as new standards. The ReSeed project aims to offer an alternative allowing both semantic (2D sources) and physical (3D) modeling, without going through a filtering process, synonymous of loss of information and knowledge.

Nowadays, reverse engineering is widely used in manufacturing industries in order to record geometrical data from the products. However, digitizing physical data does not provide any knowledge about the products. Capitalizing this know-how and knowledge is critical to advance tomorrow's products. The aim of those researches is to develop methods and technologies for the heritage and museological field in the new field of the so called Digital Humanities. These innovative researches are interdisciplinary: both Human Sciences and Engineering Sciences.

Two approaches have been identified:

-Classical knowledge management based on semantic sources -Computer assisted design and scanning tools The ReSeed project aims for the development of a new technology: a tool and an interoperable format in order to digitize both semantic and physical data about objects. Before applying the process on industrial production cases, we decided to experiment our approach on existing assets, related to identified knowledge and whose intrinsic value is firmly established: ReSeed will be tested on the industrial cultural heritage. In the end, in case of success of the ANR ReSeed program, a cycle between the past and the present knowledge will be established. Actually, protecting, analysing and understanding these objects from the "past heritage" may turn them into "present capital". The transposition of past knowledge into contemporary form, readable and intelligible in our present socio-technical system, may become a source of inspiration to anticipate our future. However, new technical and epistemological issues arise: what (s) new methodology (s)? What scope for digital tools? Which interoperable data formats? What new professions? How to validate the results? 1. From the capture of traces of the object: here it is a question of capturing and storing 3D type elements, documentations, analyzes, archives… Two processes are put in parallel: the ability to digitize the object and the possibility of capitalizing the associated knowledge to allow its analysis and understanding (as shown by the previous figure) 2. By way of digital modeling of the physical object for processing and exploitation for purposes of expertise and chaining of knowledge. The point here is to link the elements together, by setting up, for example, a "knowledge container": associating documentation and archives with the geometry and the operating of the object. 3. Until it is valorised and stored for next human generations by viewing and using the data for transmission and mediation purposes. It is about exploiting the container of knowledge at different levels: from mediation for the general public, to the analysis tool for research in history, including the curious amateur; and in different situations: on a heritage site, in a museum, at a distance, etc.

The major scientific barrier lies in the interoperability of these 3 phases, which are often compartmentalized.

Scientifically speaking, ReSeed's proposal is a digital container of knowledge which is self-structured all along the creation of the digital twin of the heritage object studied. The purpose of the ReSeed technological tool is to be an asset decision support thanks to the digital integration of heterogeneous knowledge. It is a virtual tool that replaces a "paper" catalog (with a research tool and not an inventory base): it can be defined as "Historical Augmented Reality". Functionalities provided by the system are detailed in the figure below:

Several scientific prototypes have been developed both for capturing 3D historical traces or historical archives and also the "ReSeed App". In addition, a first prototype software based on augmented reality for smartphone and also available through virtual reality for standalone computer has been developed for mediation purposes. The prototype is applied to a use case coming from a national scientific collection (French meridian observatories) managed by the Ministry of Culture. ReSeed technology supports more than 20 GB of cloud of points and data archives which are streamed in real time on the internet. To try the prototype, go to the project website: https://reseed.ls2n.fr/fr/the-project/prototype-reseed/

More information www.reseed.fr

This article is published within the framework of the European symposium "Heritage for the Future, Science for Heritage: A European Adventure for Research and Innovation" which will be held on 15 and 16 March 2022 at the Musée du Louvre and the National Library of France (François Mitterrand). This symposium is organized with the support of the European Commission and in partnership with the

French Ministry of Culture, the French National Centre for Scientific Research (CNRS) and the universities of Paris-Saclay and Cergy Paris. To feed the symposium programme, a Call for Papers was launched in June 2021 and addressed to researchers, doctoral students, and various actors who contribute to the production, valorisation, dissemination and applications of knowledge such as heritage professionals, political decision-makers, international organisations etc. As a result of this Call

for Papers, some proposed communications have been selected for publication on the symposium website in the form of short articles.


Rebecca Rimbach
email: rrimbach@gmail.com

Kirsty-Jane Hartman

Catherine Currin

Carsten Schradin

Neville Pillay

Females of solitary-and group-living sister species of African striped mice show a similar social structure following experimentally imposed group-living

Keywords: communal breeding, group formation, social behavior, solitary-living, group-living, social flexibility

Social systems vary within and between species, ranging along a continuum between solitaryliving to complex societies. Social systems are emergent properties of interactions between individuals, and these interactions are often modulated by hormones. We investigated the behavioral and hormonal consequences of experimentally imposed social grouping in two sister species of the African striped mouse Rhabdomys, one of which (R. pumilio) is group-living in its natural xeric environment, while the other (R. dilectus) is solitary-living in its mesic environment.

We compared social behavior of triads of age-matched, unfamiliar females of each species, and measured their serum corticosterone and testosterone concentrations in comparison to solitarily housed controls. On Day 1, triads of both species displayed mainly amicable behavior. Aggression was rare, but R. pumilio females showed more aggression than R. dilectus females. Triads of both species shared nests from Day 2 onwards, and amicable behavior increased over time. Neither species differed in hormonal concentration compared to their solitary controls, but R. dilectus had 1.3x higher serum corticosterone than R. pumilio. Serum testosterone did not differ between species or treatments. Neither corticosterone nor testosterone concentration measured at the end of the experiment was related to the duration of amicable behavior shown between triad members at the end of the study. In sum, both species established a similar social structure when housed in non-kin triads in captivity. Both displayed high amicability and little aggression, indicating that environmental factors, such as resource distribution and duration of the breeding season, may be more important determinants of social organization in striped mice than social tolerance.

Introduction

Variation in social systems occurs both between and within species [START_REF] Lott | Intraspecific variation in the social systems of wild vertebrates[END_REF][START_REF] Kappeler | Constraints and flexibility in mammalian social behaviour: introduction and synthesis[END_REF]). This variation is underpinned by the environmental conditions and is physiologically mediated. The mechanisms leading to the formation of the observed variety of social systems are still not well understood [START_REF] Kappeler | Constraints and flexibility in mammalian social behaviour: introduction and synthesis[END_REF]). The social system of a species is created by the behavior of individuals, with whom they group (social organization), with whom and how they interact (social structure), with whom they mate (mating system) and who they care for (care system; [START_REF] Kappeler | A framework for studying social complexity[END_REF]. One important component of all forms of sociality is the nature of the interactions between individuals [START_REF] Hinde | Interactions, relationships and social structure[END_REF].

Group-living is typically associated with frequent interactions between group members and these interactions can be both amicable (e.g. grooming, body contact) and agonistic (e.g. chasing, fighting) [START_REF] Silk | The adaptive value of sociality in mammalian groups[END_REF][START_REF] Kappeler | Constraints and flexibility in mammalian social behaviour: introduction and synthesis[END_REF]. Aggression can occur over access to resources or mating partners, and to establish a social hierarchy [START_REF] Creel | Social dominance and stress hormones[END_REF][START_REF] Silk | The adaptive value of sociality in mammalian groups[END_REF]. Group size can influence rates of agonistic interactions, for example, occurrence of agonistic interactions between female primates increases with group size [START_REF] Wheeler | Rates of agonism among female primates: a crosstaxon perspective[END_REF]. Typically, individuals are less tolerant of unrelated individuals (especially of the same sex) than of relatives [START_REF] Th | Female sociality[END_REF]. Interactions between individuals of solitary species are generally less well-studied [START_REF] Kappeler | Evolution of primate social systems[END_REF], but studies have revealed that great diversity exists also in solitary mammals [START_REF] Woodroffe | Badger sociality -models of spatial grouping[END_REF]. For example, males of some solitary species form alliances [START_REF] Lührs | Simultaneous GPS tracking reveals male associations in a solitary carnivore[END_REF], some solitary foraging species form 'spatial groups' or sleeping associations that are characterized by home-range overlap and friendly interactions among members [START_REF] Wiens | Social structure of the solitary slow loris Nycticebus coucang (Lorisidae)[END_REF][START_REF] Dammhahn | Females go where the food is: does the socio-ecological model explain variation in social organisation of solitary foragers?[END_REF][START_REF] Lührs | Simultaneous GPS tracking reveals male associations in a solitary carnivore[END_REF][START_REF] Graw | Social organization of a solitary carnivore: spatial behaviour, interactions and relatedness in the slender mongoose[END_REF], and others show social tolerance at food or water sources [START_REF] Elbroch | Adaptive social strategies in a solitary carnivore[END_REF][START_REF] Tichon | Social interactions in striped hyena inferred from camera trap data: is it more social than previously thought?[END_REF]. There is a dynamic feedback between how constituent individuals behave towards each other, which leads to a particular social organization of a population, and in turn affects the behavior of individuals in that population [START_REF] Kappeler | Evolution of primate social systems[END_REF][START_REF] Schradin | The evolution of intraspecific variation in social organization[END_REF]. To date, it is still poorly understood how differences in social tolerance relate to interspecific variation in social systems.

While external drivers underpin social interactions, various internal factors, such as hormones and neuropeptides, modulate interactions between individuals (McCall and Singer 2012; [START_REF] Hofmann | An evolutionary framework for studying mechanisms of social behavior[END_REF]. Testosterone is an important modulator of social interactions, influencing aggression, territory defense, sexual behavior, and is itself influenced by social status [START_REF] Staub | The role of androgens in female vertebrates[END_REF][START_REF] Soto-Gamboa | Social cues and hormone levels in male Octodon degus (Rodentia): a field test of the challenge hypothesis[END_REF]. Some species show increased testosterone secretion in response to social interactions, and high concentration of testosterone can be linked to social aggression [START_REF] Wingfield | The "challenge hypothesis": theoretical implications for patterns of testosterone secretion, mating systems, and breeding strategies[END_REF][START_REF] Goymann | Distinguishing seasonal androgen responses from male-male androgen responsiveness -revisiting the challange hypothesis[END_REF][START_REF] Tibbetts | The challenge hypothesis across taxa: social modulation of hormone titres in vertebrates and insects[END_REF]. Testosterone also potentially increases risk-taking behavior because of its association with inhibition of the hypothalamus-pituitary-adrenal (HPA) axis that reduces anxiety [START_REF] Aikey | Testosterone rapidly reduces anxiety in male house mice (Mus musculus)[END_REF][START_REF] Mccall | The animal and human neuroendocrinology of social cognition, motivation and behavior[END_REF][START_REF] Raynaud | Experimental increase of testosterone increase boldness and decrease anxiety in male African striped mouse helpers[END_REF]. Glucocorticoid hormones, corticosterone or cortisol, are released via stimulation of the HPA axis in response to stressors, for example aggression from a conspecific [START_REF] Sapolsky | How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions[END_REF]. Glucocorticoid hormones mobilize glucose to provide energy in response to stressors, and increased circulating levels are considered as a stress response [START_REF] Rubenstein | Stress hormones and sociality: integrating social and environmental stressors[END_REF]. It has been proposed that a generalized endocrine profile of chronic stress does not exist, but social stress is associated with a glucocorticoid increase in many species [START_REF] Zayan | The specificity of social stress[END_REF][START_REF] Dickens | A consensus endocrine profile for chronically stressed wild animals does not exist[END_REF]. Solitary and social species experience social stress differently [START_REF] Blanchard | Animal models of social stress: effects on behaviour and brain neurochemical systems[END_REF]. For example, several social primate species mount a stress response when separated from conspecifics [START_REF] Zayan | The specificity of social stress[END_REF], and female yearling tuco-tuco, Ctenomys sociabilis, that live and breed alone have higher glucocorticoid levels than females that live and breed within their natal group [START_REF] Woodruff | Effects of social environment on baseline glucocorticoid levels in a communally breeding rodent, the colonial tuco-tuco (Ctenomys sociabilis)[END_REF]. In contrast, solitary species can experience stress in response to social interactions with conspecifics, such as in the golden hamster, M. auratus, which experiences immune-system decline in groups, with a shorter life span as group size increases [START_REF] Wommack | Repeated exposure to social stress alters the development of agonistic behaviour in male golden hamsters[END_REF]. Moreover, group-living animals can experience social buffering, displaying reduced corticosterone response to a stressful situation due to the presence of conspecifics to which they are socially bonded, potentially via inhibition of the HPA axis [START_REF] Sachser | Social relationships and the management of stress[END_REF][START_REF] Hennessy | Social buffering of the stress response: diversity, mechanisms, and functions[END_REF][START_REF] Young | Responses to social and environmental stress are attenuated by strong male bonds in wild macaques[END_REF].

The African striped mouse, genus Rhabdomys, is a small (adult body mass 30 -90g) diurnal, murid rodent, widely distributed throughout southern Africa, occurring in a variety of biomes from semi-arid deserts (160 mm rainfall per annum) to moist grasslands (700-1000 mm rainfall per annum) [START_REF] Skinner | The mammals of the southern African subregion[END_REF]. Our study considers two closely related species of Rhabdomys: R. pumilio occurring in xeric environments and R. dilectus in mesic areas of South Africa [START_REF] Rambau | Molecular genetics of Rhabdomys pumilio subspecies boundaries: mtDNA phylogeography and karyotypic analysis by fluorescence in situ hybridization[END_REF]. Molecular data places the divergence between the species at approximately 3.1 million years ago [START_REF] Du Toit | Biome specificity of distinct genetic lineages within the four-striped mouse Rhabdomys pumilio (Rodentia: Muridae) from southern Africa with implications for taxonomy[END_REF]). Distinct differences in sociality exist between these species in nature. R. pumilio in the arid Succulent Karoo is facultatively groupliving (Schradin andPillay 2003, 2004), and is socially flexible, switching to solitary-living under very low population density during the breeding season (but not during the non-breeding season) (Schradin et al. 2010a[START_REF] Schradin | Social flexibility and social evolution in mammals: a case study of the African striped mouse (Rhabdomys pumilio)[END_REF]. In free-living R. pumilio, individuals of both sexes have lower corticosterone concentrations after switching from group-living to solitary-living during the breeding season [START_REF] Schoepf | Endocrinology of sociality: comparisons between sociable and solitary individuals within the same population of African striped mice[END_REF]). Female R. pumilio which breed solitarily have lower baseline corticosterone concentrations when compared to their group-living counterparts, but do not differ in testosterone concentrations [START_REF] Hill | Alternative reproductive tactics in female striped mice: solitary breeders have lower corticosterone levels than communal breeders[END_REF]. Weanling R. pumilio show a more pronounced stress response to separation from their natal group compared to weanling R. dilectus, indicating that philopatry and group-living may be more important for young R. pumilio compared to young R. dilectus that typically disperse at weaning [START_REF] Mackay | Separation at weaning from the family is stressful for naturally group-living, but not solitary-living, male African striped mice Rhabdomys[END_REF]. The grassland species, R. dilectus, is solitary-living, with individual home ranges overlapping mainly with home ranges of the opposite sex [START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF]. While variation in hormonal response in R. pumilio has been well investigated, a comparison of the hormonal profile with the closely related R. dilectus is lacking.

In this study we investigated 1) whether R. dilectus, a naturally solitary-living species, tolerates conspecifics and forms groups under experimental conditions, 2) whether social interactions differ between both species and how interactions change over time when experimentally kept in groups, and 3) how circulating corticosterone and testosterone concentrations correlate with social behaviors and the social contexts (imposed group-living vs solitary-housed). First, we investigated whether or not three unrelated, unfamiliar conspecific female Rhabdomys display the social tolerance necessary to facilitate and initiate social group formation, and whether tolerance (nest sharing and amicability) of conspecifics is maintained over time in each species (referred to as stable groups in this study). We predicted that R. pumilio triads show less aggression and more amicable behavior compared to R. dilectus triads, and that these differences would occur already at the beginning of nest cohabitation. We hypothesized that associating with conspecifics would be more stressful physiologically for R. dilectus than R. pumilio. We predicted that 1) social groups of both species would have greater concentrations of corticosterone and testosterone than solitary-housed controls of both species, due to social stress and competition experienced in groups, 2) testosterone and corticosterone concentrations to correlate positively with aggression and to be higher in the more aggressive triads and species, and 3) testosterone and corticosterone concentrations to correlate negatively with amicable behavior.

Materials and Methods

Study Species

In the semi-arid Succulent Karoo, R. pumilio is facultatively group-living and usually forms social groups that consist of one breeding male, up to four closely related breeding females and their philopatric offspring (Schradin andPillay 2003, 2004). Group members share a nest, interact amicably and bask together at dawn and dusk, and defend a common territory, but forage solitarily during the day [START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF]. R. pumilio is socially flexible, switching to solitaryliving under very low population density during the breeding season, but not during the nonbreeding season (Schradin et al. 2010a[START_REF] Schradin | Social flexibility and social evolution in mammals: a case study of the African striped mouse (Rhabdomys pumilio)[END_REF]. Individuals of both sexes have lower corticosterone concentrations when solitary than in a group [START_REF] Schoepf | Endocrinology of sociality: comparisons between sociable and solitary individuals within the same population of African striped mice[END_REF]). Female R. pumilio which breed solitarily have lower baseline corticosterone concentrations when compared to their group-living counterparts, but the solitary breeders do not differ from the group-living females in testosterone concentrations [START_REF] Hill | Alternative reproductive tactics in female striped mice: solitary breeders have lower corticosterone levels than communal breeders[END_REF].

The grassland species, R. dilectus, is solitary-living, with individual home ranges overlapping mainly with home ranges of the opposite sex [START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF]. R. dilectus occurs at lower population density than R. pumilio, indicating that lower population density promotes solitary-living [START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF]. The breeding season (7 months; October to April) of R. dilectus is more than double that of R. pumilio (3 months; August to November) [START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF][START_REF] Skinner | The mammals of the southern African subregion[END_REF].

Study Animals

Experiments took place in the Milner Park Animal Unit at the University of the Witwatersrand, Johannesburg, South Africa. The striped mice used in this study were from existing captive colonies. The naturally group-living species, Rhabdomys pumilio, originated from the Goegap Nature Reserve in the semi-arid Succulent Karoo of South Africa (average rainfall of 160 mm per annum, winter rainfall). The naturally solitary-living species, Rhabdomys dilectus, originated from the moist grassland in central South Africa (average rainfall of 700 mm per annum, summer rainfall). All individuals were F2 or F3 captive born.

Husbandry

We conducted experiments under partially controlled environmental conditions: 14:10 light: dark cycle (lights on at 05h00); 30-60% rH; and a room temperature of 24-28℃. We randomly formed approximately 40 breeding pairs per species simultaneously before experiments began. Breeding pairs were housed in clear Labotec™ cages (L x H x W: 425mm x 150mm x 240mm), containing a PVC nest-box (L x H x W: 98mm × 64mm × 77mm), ±3cm wood shavings, a handful of Eragrostis grass (± 20g) and ± 5g of paper tissue provided for nesting material. We provided a cardboard tube (L x D: 99mm x 38mm) and a small wooden block for chewing for enrichment.

The daily diet included 5g Epol® mouse cubes, approximately 5g fresh fruit or vegetables and approximately 2g millet per mouse (millet was gradually increased to 4g for pregnant and lactating females); water was provided ad libitum.

At 20 days of age, pups produced from the breeding pairs were weaned and housed alone for a further 30 days in Labotec™ cages, furnished and enriched as described. R. dilectus young typically disperse at weaning (around day 16), whereas R. pumilio young typically delay dispersal, although they disperse earlier when population density is low [START_REF] Willan | Life-history styles of southern African Mastomys natalensis, Otomys irroratus and Rhabdomys pumilio (Mammalia, Rodentia)[END_REF][START_REF] Schradin | The striped mouse (Rhabdomys pumilio) from the Succulent Karoo, South Africa: a territorial group-living solitary forager with communal breeding and helpers at the nest[END_REF][START_REF] Schradin | When to live alone and when to live in groups: ecological determinants of sociality in the African striped mouse (Rhabdomys pumilio, Sparrman , 1784)[END_REF]Schoepf and Schradin 2012a). Thus, solitary living at young age occurs naturally in both species. From these juveniles, we used a total of 40 R. pumilio and 40 R. dilectus females in this study. We focused our study on females because groups in R. pumilio are usually made up of multiple breeding females with one breeding male [START_REF] Schradin | Social flexibility and social evolution in mammals: a case study of the African striped mouse (Rhabdomys pumilio)[END_REF].

Experimental design

At approximately 43 days of age (one week prior to forming triads), we marked all striped mice using commercial hair dye (Innecto™, Pinetown, South Africa) to allow for individual identification. We assigned three unrelated, age-matched conspecific females randomly to a triad, and we formed a total of 10 triads per species. Each triad was housed together from approximately 50 days old to approximately 85 days old in an aluminum tank with a clear Perspex front (L x H x W: 460mm x 350mm x 300mm) and a wire-mesh lid. These tanks contained wood shavings for bedding, and grass and nesting material, as described under husbandry (above). Tanks contained three separate nest boxes of equal size (L x H x W: 100mm x 77mm x 63.5mm) to prevent forced cohabitation of the triad. The feeding regime followed the diet described above. Before we initiated behavioral data collection, we directly observed interactions for 20 min immediately after introducing the three mice into experimental tanks on Day 1, so that triads could be terminated if excessive fights occurred. We observed no fights in any of the triads during this period. Following this 20-minute direct observation period, we filmed the triads from 09h00-12h00 using Sony Handycam® video cameras; striped mice are most active during this period [START_REF] Pillay | Female mate preference and reproductive isolation in populations of the striped mouse Rhabdomys pumilio[END_REF]. We filmed triads on Days 1, 3, 6, 10, 15, and 21 of triad formation and we manually scored the behavior of females (Table S1) from video footage using a stopwatch. It was not possible to score behavior blindly for several reasons: due to the timing of birth within a species that allowed triad formation to start earlier for R. pumilio than for R. dilectus, because the same researchers were responsible for husbandry, individual markings, triad formation and filming and scoring of behavior; and because the marking of mice was visible in the video recordings. As age-matched controls for hormonal comparison to triads (below), we maintained ten females per species in solitary housing from 50 to 85 days of age. We marked these individuals and placed them in new cages on the same days as experimental triads. Control animals were housed in Labotec™ cages prepared as described above.

To investigate the initiation of group formation in the two species, we scored the three hours (09h00-12h00) of footage from Day 1 of triad formation, recording the frequency of all interactions between all members of the triad. We recorded dyadic interactions between members of each triad, including which animal initiated an interaction, which mouse they initiated the interaction toward, the manner of the approach (amicable or aggressive), and the response (aggressive or avoidance) of the approached mouse (Table S1). We calculated the frequency of aggressive approaches, amicable approaches, avoidance, and aggressive responses to an approach from these data from Day 1 (behaviors defined in Table S1).

We scored the duration of amicable and aggressive interactions between dyads within each triad from the video footage recorded on Days 1, 3, 6, 10, 15 and 21 of experimental triad formation, and we recorded the presence of nest cohabitation from direct observation. We recorded the duration of behaviors continuously for 15-minutes during the period of most activity of the three hours of video footage recorded for all triads on the 6 non-consecutive days over the 21-days of sampling. We used the same 15 min slots for each triad. We recorded nest cohabitation (yes/no) using direct observation at times when the mice were resting or asleep, usually between 14h00-15h00. This was done every day following the formation of triads and we used this information to confirm whether group formation had occurred in a triad (Schradin et al. 2010b;Schoepf and Schradin 2012b).

At approximately Day 35 (85 days of age), we euthanized all subjects (triads and controls) through isoflurane inhalation and collected blood to measure serum corticosterone and testosterone. Mice were euthanized and blood collected within 2-3 minutes of first handling to minimize the effect of the stress of handling on the circulating corticosterone concentrations. Mice were confirmed dead by testing for a pulse, then immediately decapitated and we collected approximately 500µL of blood in an Eppendorf™ tube from the trunk of the animal. Following the methods described by [START_REF] Schradin | Seasonal changes in testosterone and corticosterone levels in four social classes of a desert dwelling sociable rodent[END_REF], we kept blood samples at room temperature for 1.5 hours to allow for coagulation before being centrifuged at 8000 rpm for 10 minutes. Subsequently, we pipetted the serum into another Eppendorf™ tube and centrifuged for a further 10 minutes at 8000 rpm. We then pipetted the serum into two different aliquots (20µL of serum for corticosterone, and 50µL for testosterone) which were stored at -20℃. We measured hormone concentrations using enzyme-immunoassays, performed at the University of Strasbourg, France, using commercial kits from IBL Hamburg, specific to each hormone, following the procedures validated for striped mice by [START_REF] Schradin | Seasonal changes in testosterone and corticosterone levels in four social classes of a desert dwelling sociable rodent[END_REF]. For both hormones, serial dilution of striped mouse sample pools (2 for each hormone) paralleled the standard curve and the slopes were not different [START_REF] Schradin | Seasonal changes in testosterone and corticosterone levels in four social classes of a desert dwelling sociable rodent[END_REF]. Intra-and inter-assay variability was determined with pools from wild striped mice. For testosterone, inter-assay variability for one pool with 6 samples was 15.6%. For corticosterone, inter-assay variability (5 samples) for two pools were 11.5% and 15.6%. Intraassay variability was only determined for corticosterone for both pools and was 10.2% (5 samples) and 4.6% (8 samples). Hormone concentrations are expressed as ng/ml of serum.

Data analysis

We analyzed all data in R v.3.6.2 (R Core Team 2019). We calculated the percentage of triads that shared a nest for each species and used a Fisher's Exact Test to assess whether the species differed in nest cohabitation. We terminated one R. dilectus triad on Day 4 due to excessive fighting, and the video footage of one R. pumilio triad was corrupted and not available for analysis of behavioral interactions. We did not consider the R. pumilio triad in the data analysis of the Day 1 interactions and excluded both triads from the analysis of the behavior over the 21-day sampling period, resulting in data set of n = 9 triads for both species for these analyses. However, we included both triads in the nest cohabitation percentage calculation. For the hormonal analysis, we excluded the R. dilectus triad that was terminated early, and thus we analyzed data from 9 R. dilectus triads (n = 27 individuals), 10 R. pumilio triads (n = 30 individuals), and 10 individually-housed controls per species.

Interactions on Day 1 of triad formation

We analyzed the frequency of the type of approaches (amicable or aggressive) and responses to an approach (aggressive or avoidance) on Day 1 using a multivariate analysis of variance (MANOVA). We used the square-root of the approach and response behaviors to reduce heteroscedasticity. We included species as a categorical predictor and we used the frequency of aggressive approaches, amicable approaches, avoidance of approaches, and aggressive responses to approaches as multiple response variables. We assessed species differences in the proportion of aggressive approaches to amicable approaches and the proportion of avoidance behavior to aggressive responses using Fisher's Exact Tests for Count Data.

Behavior during 6 non-consecutive days of sampling over 21 days

We used linear mixed models (LMMs), using 'lme4' package [START_REF] Bates | lme4: Linear mixed-effects models using S4 classes[END_REF], to analyze species differences and temporal changes in the duration of amicable and aggressive behavior displayed during the 6 days of observation during 3 weeks of the study. We fitted two LMMs, one for each behavior, with either aggression or amicable behavior as the response variable, and species and Day, and the interaction between species and Day as fixed factors in the model. We included Triad ID as a random effect. We used Wald Chi-square tests (type III) to calculate  2 statistics and p values using the 'car' package [START_REF] Fox | An R companion to applied regression[END_REF]. We assessed model assumptions by inspecting Q-Q plots and by plotting model residuals against fitted values.

Prior to running each model, we checked for multi-collinearity by calculating variance inflation factors [START_REF] Zuur | A protocol for data exploration to avoid common statistical problems[END_REF] for the predictor variables using the 'vif' function in the 'car' package [START_REF] Fox | An R companion to applied regression[END_REF]. Vifs did not indicate collinearity (all vifs<2).

Hormone concentrations

We analyzed the influence of species and treatment on corticosterone and testosterone concentrations using a LMM per hormone with Gaussian error structure. We used the square root of testosterone to reduce heteroscedasticity when fitting the model. In both models, we included species, treatment and their interaction as fixed factors. We included treatment group ID (i.e. triad and control group) and litter ID as random effects. We included litter ID to account for the litter from which females were derived having possible influences on group dynamics, as litter mates were assigned to different triads or as controls. We then performed post-hoc analyses using the 'emmeans' function from the 'emmeans' package [START_REF] Lenth | emmeans: estimated marginal means, aka least-squares means (version 1[END_REF] to determine pairwise differences in hormone levels between species and treatment groups. We adjusted p values using the Tukey method. Since corticosterone suppresses testosterone secretion in some species [START_REF] Soto-Gamboa | Social cues and hormone levels in male Octodon degus (Rodentia): a field test of the challenge hypothesis[END_REF][START_REF] Deviche | Regulation of plasma testosterone, corticosterone, and metabolites in response to stress, reproductive stage, and social challenges in a desert male songbird[END_REF], we used a Pearson's product-moment correlation to assess whether the two hormones were correlated (n = 77).

To establish the relationship between the hormonal profiles and social behavior, we calculated the total duration of amicable and aggressive behavior shown by each of the 18 triads during the 15-minute observation slot on Day 21, which were the behavioral data collected closest in time to when the endocrine measurements were taken. Both species showed no aggressive behavior on Day 21, and thus we did not examine the relationship between aggressive behavior and endocrine levels. We fitted two LMMs with Gaussian error structure. We used hormone concentration (corticosterone or square root of testosterone) as the response variable and included the duration of amicable behavior on Day 21, its quadratic term, species, and the interaction between behavior and species as fixed factors.. We included triad ID as random effect in both LMMs. We checked model assumptions by inspecting Q-Q plots and by plotting model residuals against fitted values and by using the 'performance' package [START_REF] Lüdecke | performance: an R package for assessment, comparison and testing of statistical models[END_REF].

Results

Females of both species cohabited nests, with all three females sharing one nest from Day 2 for 100% of R. pumilio triads (10 of 10 triads) and 90% of R. dilectus triads (9 of 10 triads; Fisher`s Exact Test: p > 0.99). One R. dilectus triad did not cohabit a nest and was terminated on Day 4 due to excessive fighting.

Interactions on Day 1 of triad formation

Species was not a significant predictor (F1,14 = 1.03, p = 0.43) of the type of approaches and responses to an approach on Day 1 of triad formation (Fig. 1A). Triads of R. pumilio showed a total of 2015 approaches (359 aggressive and 1656 amicable approaches) and triads of R. dilectus showed a total of 1556 approaches (234 aggressive and 1322 amicable approaches). Triads of R. pumilio showed a total of 832 responses (753 avoidance and 79 aggressive responses) and triads of R. dilectus showed a total of 635 responses (538 avoidance and 97 aggressive responses). There was a species difference in the proportion of aggressive approaches to amicable approaches (Fisher's Exact Test for Count Data: P = 0.03, odds ratio = 1.22, 95% CI = 1.02 -1.47; Fig. 1B) and in the proportion of avoidance behavior to aggressive responses (P = 0.0009, odds ratio = 1.72, 95% CI = 1.24 -2.39; Fig. 1B). Both species showed more amicable approaches than aggressive approaches, but in R. pumilio proportions were more skewed towards aggressive approaches compared to R. dilectus (Fig. 1B). Both species showed more often avoidance behavior compared to aggressive responses, and again, in R. pumilio proportions were more skewed towards aggressive responses compared R. dilectus (Fig. 1B). Behavior over 21 days Species was not a significant predictor of amicable behavior duration (χ 2 1 = 0.04, p = 0.83), nor was there a significant interaction between species and Day (χ 2 5 = 4.49, p = 0.48). Day was a significant predictor of duration of amicable behavior (χ 2 5 = 53.56, p < 0.001; Fig. 2A). Post hoc tests revealed that amicable behavior duration was significantly lower on Day 1 than the subsequent days (p < 0.0001), and the duration of amicable behavior on Day 21 was significantly greater than on Day 3 (p = 0.01) and Day 6 (p = 0.02; Fig. 2). In both species, amicable behavior occurred more frequently than aggressive behavior during the study (Fig. 2B). Species (χ 2 1 = 0.009, p = 0.92), Day (χ 2 5 = 0.00, p = 1.00) and their interaction (χ 2 5 = 5.55, p = 0.35; Fig. 2B) did not affect aggressive behavior. Testosterone and corticosterone were not correlated (Pearson's product-moment correlation: t = -1.42, df = 75, p = 0.15, r = -0.16). Species ( 2 1 = 3.86; p = 0.049) was a significant predictor of circulating corticosterone concentrations. R. dilectus had higher corticosterone concentrations (mean ± SD: control: 2038.2 ± 1215.7 ng/ml, triad: 2644.7 ± 566.7 ng/ml) than R. pumilio (control: 1896.4 ± 655.9 ng/ml, triad: 1838.2 ± 641.0 ng/ml). Treatment ( 2 1 = 1.06; p = 0.30) was not a predictor of corticosterone concentrations, nor was there an interaction between species and treatment ( 2 1 = 2.09; p = 0.14). Pairwise comparisons of corticosterone concentrations between species and treatment groups showed no significant differences (all P>0.09; Fig. 3A). Both species had similar testosterone concentrations (R. dilectus: control: 0.71 ± 0.36 ng/ml, triad: 0.56 ± 0.28 ng/ml; R. pumilio: control: 0.62 ± 0.13 ng/ml, triad 0.75 ± 0.36 ng/m). Testosterone concentration was not significantly predicted by species ( 2 1 = 1.70; p = 0.19), treatment ( 2 1 = 0.11; p = 0.76), or an interaction between species and treatment ( 2 1 = 2.08; p = 0.14; Fig. 3B). Neither corticosterone nor testosterone concentration showed a relationship with the duration of amicable behavior shown between triad members on Day 21 (Table 1; Fig. 4). The marginal R 2 considers only the variance of the fixed effects, while the conditional R 2 takes both the fixed and random effects into account.

Discussion

Surprisingly, females of both the group-living and the solitary-living species of the African striped mice formed stable non-kin groups characterized by amicable interactions with corticosterone and testosterone levels comparable to their solitary controls. Overall, aggression was rare and both species showed more amicable approaches than aggressive approaches and more avoidance behavior than aggressive responses. But in R. pumilio proportions were more skewed towards aggressive approaches and aggressive responses compared R. dilectus.

Nest cohabitation occurred in all R. pumilio triads and 90% of R. dilectus triads, and in all those triads already by the second day of triad formation. Nest cohabitation was then maintained for the remaining duration of the study. We had not expected the naturally solitary-living R.

dilectus to form groups as readily as the natural group-living R. pumilio. Sharing a nest with conspecifics requires social tolerance and is often used as an indication of group-living [START_REF] Andrews | Season affects tolerance of cohabitation by deer mice[END_REF][START_REF] Rusu | Kin-preferential cooperation, dominance-dependent reproductive skew, and competition for mates in communally nesting female house mice[END_REF]Schradin et al. 2010a;Schoepf and Schradin 2012b).

Our study thus indicates that differences in the social organization between both Rhabdomys species under natural conditions may not be due to species differences in social tolerance. The similarity in social interactions between both species implies that environmental factors, such as resource distribution and the duration of the breeding season, could be more important determinants of social organization in free-living Rhabdomys than social tolerance [START_REF] Schradin | When to live alone and when to live in groups: ecological determinants of sociality in the African striped mouse (Rhabdomys pumilio, Sparrman , 1784)[END_REF][START_REF] Schradin | Intraspecific variation in the spatial and social organization of the African striped mouse[END_REF]. However, we studied both species in a single context (non-kin triads)

and results may vary if, for example, the number of animals per cage was decreased or increased, in the presence of a male or when studied under semi-natural conditions.

We expected R. pumilio to be more tolerant of conspecifics than R. dilectus, but initially on Day 1 R. pumilio showed a higher proportion of aggressive approaches and aggressive responses toward conspecifics than R. dilectus. Naturally occurring groups of R. pumilio typically consist of extended family members [START_REF] Schradin | The striped mouse (Rhabdomys pumilio) from the Succulent Karoo, South Africa: a territorial group-living solitary forager with communal breeding and helpers at the nest[END_REF], which are territorially aggressive towards striped mice of other groups [START_REF] Schradin | Territorial defense in a group-living solitary forager: who, where, against who?[END_REF], so using unrelated females here may have promoted aggression on Day 1. Importantly, amicable behavior was also common on Day 1 and consistently increased in the first week after the mice started cohabiting, remaining high throughout the second and third week of the study. Behaviors such as allogrooming facilitates social recognition of group members [START_REF] Kerth | Causes and consequences of sociality in bats[END_REF]) and the increasing duration of amicable behavior between group members over time may be the result of increased familiarity between group members. Importantly, amicable behavior was the predominant behavior displayed in triads of both Rhabdomys species, indicating not only social tolerance but social attraction facilitating group formation in both species. Female free-tailed bats, Tadarida teniotis, are more amicable toward familiar than unfamiliar conspecifics [START_REF] Ancillotto | Selective aggressiveness in European free-tailed bats (Tadarida teniotis): influence of familiarity, age and sex[END_REF]. Similarly, meadow voles, M. pennsylvanicus, that form unrelated communal nesting groups in winter, reduce agonistic and increase amicable interactions toward group-members, but display heightened aggression toward unfamiliar non-group members [START_REF] Kawata | Fluctuating populations and kin interaction in mammals[END_REF]). In captivity, but not in the wild, meadow voles readily form partner preferences for both same-sex and opposite-sex conspecifics [START_REF] Beery | Same-sex social behavior in meadow voles: multiple and rapid formation of attachments[END_REF][START_REF] Madrid | Variation, plasticity, and alternative mating tactics: revisiting what we know about the socially monogamous prairie vole[END_REF]). These differences in behavior between captive and wild individuals of the same species show that animals in captivity may exhibit behaviors that they do not normally exhibit under free-living conditions, highlighting the need to study species both in captivity and in the wild. It is important to note that the use of non-kin may have resulted in fewer differences between the species because neither species lived in their typical social organization (solitary or with extended family members), and it would be important to repeat this study using related females.

We expected R. dilectus to be more physiologically stressed during associations with conspecifics than R. pumilio, expressed as higher corticosterone concentrations in triads compared to solitary housed females. We found no support for this prediction, and triads of both species had similar corticosterone levels as solitary-housed controls of their own species.

With the exception of one R. pumilio triad, little aggression occurred after Day 1, which prevented analysis of the relationship between aggressive behavior and hormonal profiles.

Testosterone was not related to amicable behavior. We expected triads to have greater concentrations of testosterone than solitary-housed controls of both species, due to competition within groups. However, there was no difference in circulating testosterone concentrations between the two species, regardless of social setting (triad vs. solitary control). Similarly, previous studies found no differences in testosterone concentration between solitary and group-living female R. pumilio [START_REF] Schoepf | Endocrinology of sociality: comparisons between sociable and solitary individuals within the same population of African striped mice[END_REF][START_REF] Hill | Alternative reproductive tactics in female striped mice: solitary breeders have lower corticosterone levels than communal breeders[END_REF]. Together these studies do not support the hypothesis that testosterone has an important role in the regulation of social behavior of female Rhabdomys. However, it may be important to repeatedly measure testosterone throughout the process of triad formation when most aggression occurred to better assess species differences. It has been proposed that, in females, selection may have favored independence of aggression from testosterone concentration because elevated concentrations of testosterone could interfere with normal ovulation or produce detrimental maternal effects, such as a decrease in the expression of maternal behavior [START_REF] Gandelman | Reduction of maternal nest building in female mice by testosterone propionate treatment[END_REF][START_REF] Svare | Testosterone propionate inhibits maternal aggression in mice[END_REF][START_REF] O'neal | Experimentally-elevated testosterone, female parental care, and reproductive success in a songbird, the Dark-eyed Junco (Junco hyemalis)[END_REF]. Similar to findings in many other mammalian and avian species, our results indicate that female aggression might be independent of testosterone in contrast to male aggression [START_REF] Payne | The effect of sex hormones on the aggressive behaviour of the female golden hamster (Mesocricetus auratus Waterhouse)[END_REF][START_REF] Elekonich | Seasonality and hormonal control of territorial aggression in female song sparrows (Passeriformes: Emberizidae: Melospiza melodia)[END_REF][START_REF] Davis | The progesterone challenge: Steroid hormone changes following a simulated territorial intrusion in female Peromyscus californicus[END_REF][START_REF] Sannen | Urinary testosterone-metabolite levels and dominance rank in male and female bonobos (Pan paniscus)[END_REF][START_REF] Jawor | Females competing to reproduce: dominance matters but testosterone may not[END_REF][START_REF] Littlefield | Beyond aggression and dominance: the effects of social and environmental factors on fecal testosterone and fecal glucocorticoid levels in wild female Verreaux´s sifaka (Propithecus verreauxi)[END_REF]).

Inter-specific variation does not only occur in social systems, but also in hormone levels (Guindre-Parker 2018). Inter-specific variation in testosterone levels is best explained by differences in breeding season length and mating system [START_REF] Husak | Life history and environment predict variation in testosterone across vertebrates[END_REF]. While mean testosterone levels can vary between 0 and 5 ng/ml in mammals [START_REF] Husak | Life history and environment predict variation in testosterone across vertebrates[END_REF], variation in glucocorticoid levels is more extreme [START_REF] Chrousos | Glucocorticoid hormone resistance during primate evolution: receptor-mediated mechanisms[END_REF][START_REF] Guindre-Parker | The evolutionary endocrinology of circulating glucocorticoids in freeliving vertebrates: recent advances and future directions across scales of study[END_REF]. For example catarrhine primates have cortisol levels of around 300 ng/ml and some platyrrhine primates have 1000-2000 ng/ml [START_REF] Chrousos | Glucocorticoid hormone resistance during primate evolution: receptor-mediated mechanisms[END_REF][START_REF] Coe | Diurnal and annual variation of adrenocortical activity in the squirrel monkey[END_REF]. Similarly, house mice (Mus musculus) have basal corticosterone levels of between 100 and 150 ng/ml [START_REF] Veenema | Differences in basal and stress-induced HPA regulation of wild house mice selected for high and low aggression[END_REF], prairie voles (Microtus ochrogaster) of between 630 and 850 ng/ml [START_REF] Devries | Modulation of pair bonding in female prairie voles (Microtus ochrogaster) by corticosterone[END_REF], while female striped mice (R. pumilio) have up to 2000 ng/ml during the breeding season [START_REF] Schradin | Seasonal changes in testosterone and corticosterone levels in four social classes of a desert dwelling sociable rodent[END_REF][START_REF] Hill | Glucocorticoid levels predict subsequent social tactic in females of a facultatively social mammal[END_REF]. While several studies investigated inter-specific differences in stress response [START_REF] Crespi | Life history and the ecology of stress: how do glucocorticoid hormones influence life-history variation in animals?[END_REF], understanding variation in basal glucocorticoid levels received less attention [START_REF] Guindre-Parker | The evolutionary endocrinology of circulating glucocorticoids in freeliving vertebrates: recent advances and future directions across scales of study[END_REF][START_REF] Schoenemann | Repeatability of glucocorticoid hormones in vertebrates: a meta-analysis[END_REF]. One important first question would be whether very high basal levels observed in one species also occur in closely related species from another environment, allowing for an assessment of phylogeny versus environment on basal levels of glucocorticoids. We show that both Rhabdomys species have corticosterone concentrations that are higher than those of most mammals, indicating that the high corticosterone concentrations are a phylogenetic remnant of a common ancestor and we predict that other Rhabdomys species will share this trait with the two species examined here. Comparative studies of basal glucocorticoid levels in mammals would be needed to address why some species have such high basal glucocorticoid levels.

Conclusion

Ours is one of few studies assessing how social structure develops when two sister species, that naturally differ in their social organization, are experimentally forced to live in groups.

Surprisingly, we found a very similar social structure in both species, characterized by high amicability and little aggression, making cohabitation possible in 19 out of 20 triads. Whether R.

dilectus shows flexibility in its social organization under natural conditions, similar to R. pumilio, is unknown and needs to be studied in the future, but here we showed that this species has the capacity to do so. Ongoing studies in some parts of its range provide anecdotal information of R.

dilectus sometimes forming small social groups, but the reasons for, and the demographic composition of, such group-living are not always apparent [START_REF] Dufour | Habitat characteristics and species interference influence space use and nest-site occupancy: implications for social variation in two sister species[END_REF]).

Fig 1

 1 Fig 1 Aggressive and amicable approaches, aggressive responses and avoidance behavior between triad members on Day 1 (observation of 3 hrs) of triad formation in two species of Rhabdomys (beige = solitary R. dilectus, blue = group-living R. pumilio). (A) Frequencies of approaches and responses are shown. Columns indicate mean frequency and error bars show the standard error. (B) Percentages of approaches (aggressive vs. amicable) and responses (aggressive vs. avoidance) are shown. Boxplot center line represents the median, lower and upper box limits represent the 1 st and 3 rd quartile (IQR), whiskers minimum and maximum values of nonoutlier data (±1.5 × IQR) and outliers are indicated by small filled circles (n = 10 for R. dilectus triads, n = 9 for R. pumilio triads)

Fig. 2

 2 Fig. 2 Duration of (A) amicable and (B) aggressive behavior of two species of Rhabdomys (R. pumilio in blue and R. dilectus in beige) housed in triads over 21 days. Data (15 min observations per day) are displayed as mean and 95% confidence interval

Fig 3

 3 Fig 3 Serum (A) corticosterone and (B) testosterone concentrations of two species of Rhabdomys. Comparisons are shown between two treatments: triads (in yellow) and solitarily-housed females (controls, in green). Boxplots show median values as well as 1st and 3rd quartiles and points represent individual values (n = 27 for R. dilectus triads, n = 30 for R. pumilio triads, n = 10 for controls of each species)

Fig 4

 4 Fig 4 Serum corticosterone and testosterone concentrations in relationship to the duration of amicable behavior on Day 21 in triads of two species of Rhabdomys (R. pumilio in blue and R. dilectus in beige).

Table 1

 1 Results of the linear mixed models to test for an association between the total duration of amicable behavior shown in a triad on Day 21 and corticosterone and testosterone concentration of two species of Rhabdomys. Factors in bold type indicate significant predictors of hormone concentration

			Corticosterone			Testosterone
	Predictors	Estimates	CI	p	Estimates	CI	p
	(Intercept)	2545	2060 -3031	<0.0001	0.74	0.62 -0.87	<0.0001
	Duration amicable behavior	16	-426 -457	0.945	-0.05	-0.16 -0.06	0.386
	on Day21
	Duration amicable behavior on Day21 2	82	-`59 -324	0.505	-0.01	-0.07 -0.05	0.703
	Species[R. pumilio]	-797	-1345 --248	0.004	0.12	-0.02 -0.26	0.081
	Random Effects
	σ 2 / ICC	144398 / 0.66		0.03 / 0.23
	Marginal R 2 / Conditional R 2	0.317 / 0.767		0.119 / 0.323

σ 2 = variance of the random effect 'triad'; ICC = Intraclass coefficient of variation.

Acknowledgements

We thank Megan Mackay and Damian Ponsonby for help with sample collection and preparation.

We thank the staff at the Milner Park Animal Unit for their help with the animal maintenance. We thank two anonymous reviewers for their comments on an earlier version of the manuscript.

Author's contributions

Funding

This work was supported by the University of the Witwatersrand, the National Research Foundation (grant code: 87769), and the CNRS.

Data availability

All data analyzed during this study are included as supplementary information files.

Code availability Code will be uploaded as supplementary material during revision or upon acceptance.

Declarations

Supplementary Information Supplementary material is available KJH and CC coded behavioral data; CS measured hormone concentrations; KJH and RR performed statistical analyses; KJH and RR drafted the initial version of the manuscript and all authors gave final approval for publication; NP and CS raised financial support.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All animal protocols adhered to the guidelines set forth by the Animal Behaviour Society/Association for the Study of Animal Behaviour. This study was approved by the animal ethics screening committee at the University of the Witwatersrand (AESC number: 2012/28/2A).

Consent to participate Not applicable.

Consent for publication Not applicable.