Jean-Paul Crampe

Jean-François Gerard

Michel Goulard

Cyril Milleret

Georges Gonzalez

Richard Bon
email: richard.bon@univ-tlse3.fr

Year-round sexual segregation in the isard, a nearly monomorphic polygynous herbivore

Keywords: Caprini, Grouping patterns, Habitat use, Mountain ungulates, Spatial distribution 1998

. In addition, we analysed the social interactions recorded between group members. As expected, habitat segregation was low throughout the year, with a maximum during the early lactation period. However, social and spatial segregation was consistently high, contradicting the predictions of the current prevailing hypotheses, while suggesting social causes were predominant. The scarcity of social interactions outside the mating season makes unlikely the hypothesis that males segregate to improve their reproductive success. We rather suspect that higher social affinities within than between the two sexes are at work. However, this hypothesis alone is probably insufficient to account for spatial segregation. Our results should revive the debate regarding the causes of sexual segregation.

Introduction

'I am not convinced that the answers to the underlying reasons for sexual segregation will be achieved by focusing on mechanisms of forage intake and digestion. By definition this approach will fail to explain sexual segregation in species that are not strongly dimorphic… and cannot, therefore, increase our understanding of a more universal explanation' (Main, al., 2001(Main, al., , 2004;;[START_REF] Peterson | Male group size, female distribution and changes in sexual segregation by Roosevelt elk[END_REF], (3) males avoiding females to prevent aggressive male-male interactions linked to the presence of the opposite sex ('male avoidance of females' MAFH; [START_REF] Morgantini | Sex differential in use of the physical environment by Bighorn Sheep (Ovis canadensis)[END_REF][START_REF] Prins | Condition changes and choice of social environment in African buffalo bulls[END_REF]. In order to reduce male sexual harassment (SHH), it was also hypothesized that females would modify their movement and association with males according to their reproductive status ('sexual harassment hypothesis' SHH; [START_REF] Sundaresan | Male harassment influences female movements and associations in Grevy's zebra (Equus grevyi)[END_REF]. It is worth noting that sexual dimorphism in body mass is not a prerequisite for sexual segregation to occur under these social hypotheses.

The bulk of the studies dedicated to sexual segregation concentrates on large and sexually dimorphic species [START_REF] Bowyer | Sexual segregation in ruminants: definitions, hypotheses, and implications for conservation and management[END_REF][START_REF] Du Toit | Sex differences in the foraging ecology of large mammalian herbivores[END_REF][START_REF] Macfarlane | Sexual segregation in Australian marsupials[END_REF] and the extent to which the degree of sexual dimorphism in body mass/size plays a key role in explaining segregation is seldom addressed (but see [START_REF] Ruckstuhl | Sexual segregation in ungulates: a comparative test of three hypotheses[END_REF][START_REF] Ruckstuhl | Sexual segregation in vertebrates: proximate and ultimate causes[END_REF][START_REF] Garnick | Inter-and intraspecific effects of body size on habitat use among sexually-dimorphic macropodids[END_REF]. [START_REF] Mysterud | The relationship between ecological segregation and sexual body size dimorphism in large herbivores[END_REF] reported a positive relationship between ecological segregation and body-size dimorphism for browser species but not for intermediate and grazer species. [START_REF] Illius | The Allometry of Food Intake in Grazing Ruminants[END_REF] predicted a sexual segregation in grazers when males are at least 20% larger than females, in periods of food restriction (see [START_REF] Ruckstuhl | Sexual segregation in ungulates: a comparative test of three hypotheses[END_REF].

Monomorphic species are appropriate models to test existing hypotheses regarding the origin of sexual segregation outside the rut period [START_REF] Lewis | Sex-specific foraging behaviour in a monomorphic seabird[END_REF][START_REF] Ruckstuhl | Sexual segregation in ungulates: a comparative test of three hypotheses[END_REF][START_REF] Sims | Differences in habitat selection and reproductive strategies of male and female sharks[END_REF]. According to the RSH, irrespective of sexual dimorphism in body mass and because parental care is exclusive to females in ungulates, habitat segregation would peak when lactating females restrict themselves into areas that limit the risk of predation on their offspring. No ecological and spatial segregation would occur past the weaning period according to the GCH, WSH and PH. The ABH predicts that when both sexes are similar in body mass, outside the lactation period, they should associate freely [START_REF] Ruckstuhl | To synchronize or not to synchronize: a dilemma for young bighorn males?[END_REF][START_REF] Barboza | Sexual segregation in dimorphic deer: a new gastrocentric hypothesis[END_REF][START_REF] Neuhaus | The link between sexual dimorphism, activity budgets, and group cohesion: the case of the plains zebra (Equus burchelli)[END_REF][START_REF] Ruckstuhl | Sexual segregation in ungulates: a new approach[END_REF], 2002, 2009;[START_REF] Lewis | Sex-specific foraging behaviour in a monomorphic seabird[END_REF][START_REF] Staniland | Sexual segregation in seals[END_REF]Wearmouth and Sims, 2008: p. 143).

The SHH is valid only during the period of sexual activity and then restricted to the period of rut which span a short period of time in temperate latitude and mountain habitat. When species adopt a polygynous mating system, the SFH suggests that males would benefit from sparring interactions in all-male groups outside the rut [START_REF] Ruckstuhl | Sexual segregation in ungulates: a new approach[END_REF]. Such interactions, if any, would occur during spring and summer when resources are plentiful and permit energetically costly activities. The FAMH predicts that when males are dominant and address agonistic acts to females, these latter would avoid males and engage in intra-sex agonistic interactions more frequently than in same-sex groups.

The two species of the Rupicapra genus, the Alpine chamois (R. rupicapra) and the isard or Pyrenean chamois (R. pyrenaica), are polygynous and have well-defined mating and birth seasons [START_REF] Krämer | Soziale Organisation und Sozialverhalten einer Gemspopulation (Rupicapra rupicapra L.) der Alpen[END_REF][START_REF] Corlatti | Rutting behaviour of territorial and nonterritorial male chamois: is there a home advantage?[END_REF]. In contrast to what prevails in many other Caprini and despite geographical variation in body size, they are nearly monomorphic in many characters [START_REF] Pépin | Factors affecting the relationship between body mass and age in the izard[END_REF][START_REF] Bocci | Even mortality patterns of the two sexes in a polygynous, near-monomorphic species: is there a flaw?[END_REF]Pérez-Barbería et al., 2010;Ferreti et al., 2014; Fig. 1) with both sexes similar in mass, except in summer-early autumn when males are heavier than females (Fig. 2; [START_REF] Crampe | La masse corporelle comme indicateur de la condition physique hivernale de l'Isard Rupicapra pyrenaica (Artiodactyla, Bovidae)[END_REF][START_REF] Loison | Agespecific survival in five populations of ungulates: evidence of senescence[END_REF][START_REF] Pérez-Barbería | Differences in body mass and oral morphology between the sexes in the Artiodactyla: evolutionary relationships with sexual segregation[END_REF][START_REF] Bassano | Body weight and horn development in Alpine chamois, Rupicapra rupicapra (Bovidae, Caprinae)[END_REF][START_REF] Garel | Sexspecific growth in Alpine chamois[END_REF]Pérez-Barbería et al., 2010;[START_REF] Rughetti | Seasonal changes in sexual size dimorphism in northern chamois[END_REF]. Rupicapra sp. are thus a valuable model to work out the origin of sexual segregation [START_REF] Ruckstuhl | Sexual segregation in ungulates: a comparative test of three hypotheses[END_REF].

Like many other Caprini, chamois are mountain-dwelling intermediate feeders [START_REF] Hofmann | Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system[END_REF][START_REF] Garcia-Gonzalez | Trophic utilization of a montane/subalpine forest by chamois (Rupicapra pyrenaica) in the Central Pyrenees[END_REF] that live in open-membership groups [START_REF] Pépin | Group dynamics and local population density dependence of group size in the Pyrenean chamois, Rupicapra pyrenaica[END_REF]. Sexual segregation is known to occur [START_REF] Berducou | Social grouping patterns of a dense population of chamois in the Western Pyrenees National Park, France[END_REF][START_REF] Gerard | Social affinities as the basis of the social organization of a Pyrenean chamois (Rupicapra pyrenaica) population in an open mountain range[END_REF][START_REF] Bonenfant | Testing sexual segregation and aggregation: old ways are best[END_REF], peaking in spring and summer [START_REF] Shank | Inter-and intra-sexual segregation of chamois (Rupicapra rupicapra) by altitude and habitat during summer[END_REF] and relaxed in early winter [START_REF] Gerard | Social affinities as the basis of the social organization of a Pyrenean chamois (Rupicapra pyrenaica) population in an open mountain range[END_REF][START_REF] Pérez-Barbería | Seasonal variation in group size of Cantabrian chamois in relation to escape terrain and food[END_REF][START_REF] Herrero | Grouping pattern in a forest-dwelling population of Pyrenean chamois[END_REF][START_REF] Bonenfant | Testing sexual segregation and aggregation: old ways are best[END_REF], coinciding with the period of parental care and rut, respectively. However, its intensity may also vary according to populations. Over the whole annual cycle, mixed-sex groups have been reported to form 20-25% of the observed groups (lone animals included) in some Pyrenean chamois populations (Pérez-Barbería and Nores, 1994: Table 2; Herrero et al., 2002: Table 3;[START_REF] Dalmau | Habitat selection and social behaviour in a Pyrenean chamois population (Rupicapra pyrenaica pyrenaica)[END_REF] Table 1) but 8-12% in others (Richard-Hansen et al., 1992). [START_REF] Crampe | Site fidelity, migratory behaviour, and spatial organization of female isards (Rupicapra pyrenaica) in the Pyrenees National Park, France[END_REF]. Only positive and negative standard deviations (error bars, with sample sizes above and below) are drawn for males and females respectively for the sake of clarity. Grand means (males vs females); Sep-Oct: 28.0 vs 23.0 kg (ratio 1.22); Nov-May: 22.4 vs 22.6 kg (ratio 0.99).

In this paper, we investigate the annual variation of social, spatial and habitat components of segregation and its inter-annual pattern using a 12 consecutive year survey of a Pyrenean chamois population. We propose an original statistical method derived from the 'sexual segregation and aggregation statistic' which permits controlling for habitat, spatial and social components in the degree of segregation. A modified version of the segregation coefficient (Conradt, 1998b) allows a comparison with former studies. The rates of social interactions between individuals of the same and of opposite sex were calculated to test social hypotheses.

We were able to test the WSH, RSH, PH, SFH, FAMH, MAFH, SHH. We discuss the GSH, ABH, and SAH considering the quasi-monomorphism of the studied species and the observed patterns of the different components of sexual segregation.

Material and Methods

Study area and population

The study was conducted in 'Clot-Cayan', a South-facing slope of 355 hectares situated in the Marcadau valley (42°51' N, 0°10' W) within the Pyrénées National Park (PNP), France.

Lower elevation follows the valley bottom, ranging from 1,500 to 1,620 m asl. Higher elevation corresponds to a 3.5 km-long ridge and ranges between 2,150 and 2,428 m asl.

Climate is hemiboreal to boreal according to elevation ('Dfb' to 'Dfc' in Köppen's classification; [START_REF] Peel | Updated world map of the Köppen-Geiger climate classification[END_REF], with mean annual snowfall of ca. 6 m at 1,850 m. Below 2,000 m in elevation, the area is a mosaic of grassland, coniferous woodland and alpine heathland, interspersed with screes and cliffs. Above 2,000 m, trees and screes become rare and the slope is covered mainly by high-elevation grassland, along with some alpine heaths and cliffs.

The Pyrenean chamois population has been free from any harvest since 1956 [START_REF] Crampe | Site fidelity, migratory behaviour, and spatial organization of female isards (Rupicapra pyrenaica) in the Pyrenees National Park, France[END_REF]. The individuals are wintering in Clot-Cayan from November to April, as the sunfacing slopes afford snow-free foraging areas during mild periods in winter. At this season, population density can reach 80 animals/km 2 . From May to October, about half of the individuals emigrate from the study area, extending the range occupied by the population to ca. 100 km 2 [START_REF] Crampe | Site fidelity, migratory behaviour, and spatial organization of female isards (Rupicapra pyrenaica) in the Pyrenees National Park, France[END_REF]. Births generally occur mostly from mid-May to early June with a peak during the 3rd week of May [START_REF] Richard-Hansen | Social environment of isard kids, Rupicapra pyrenaica during their ontogeny[END_REF][START_REF] Ruckstuhl | On the suckling behaviour of Alpine chamois Rupicapra rupicapra rupicapra[END_REF][START_REF] Pépin | Variability of spring habitat selection by isards (Rupicapra pyrenaica)[END_REF]. The rut, as defined by the frequency of courtship behaviour, extends from mid-October to late December. No large predators were present, but golden eagle (Aquila chrysaetos) and red fox (Vulpes vulpes) occasionally killed neonates or adults hampered by deep snowpack (JPC, personal observation).

Data collection

Data were collected by visual observation by JPC from August 1997 to June 2009 (143 consecutive months) along standard transects and at vantage points, using 10 x 40 binoculars and a 30 x 75 binocular spotting scope. Individuals were considered to belong to the same group when at a distance < 50 m apart (Pérez- [START_REF] Pérez-Barbería | Seasonal variation in group size of Cantabrian chamois in relation to escape terrain and food[END_REF][START_REF] Pépin | Group dynamics and local population density dependence of group size in the Pyrenean chamois, Rupicapra pyrenaica[END_REF]. The location of every group sighted (solitary individuals included) was plotted on a square grid of 1,167 cells overlaying a panoramic photograph of the area [START_REF] Crampe | Site fidelity, migratory behaviour, and spatial organization of female isards (Rupicapra pyrenaica) in the Pyrenees National Park, France[END_REF]. Following [START_REF] Berducou | Social grouping patterns of a dense population of chamois in the Western Pyrenees National Park, France[END_REF], animals were assigned to four age-sex classes according to morphological criteria, i.e., kids (< 1 year old; small body size, horns absent or very short), yearlings (≥ 1 and < 2 years old; larger body size, horns not higher than ears), adult males and females (≥ 2 years old; horns higher than ears in both sexes, more curved at the extremity and thicker in males than females). Pyrenean chamois groups often fuse and split up in the course of the day [START_REF] Pépin | Group dynamics and local population density dependence of group size in the Pyrenean chamois, Rupicapra pyrenaica[END_REF], and successive field surveys were separated by at least two days. Therefore, the data collected on group size and composition were considered as independent.

During the field surveys, the interactions occurring within any sighted group were recorded using an instantaneous recording method. On the basis of the repertoire given by [START_REF] Lovari | Behavioural repertoire of the Abruzzo chamois, Rupicapra pyrenaica ornata Neumann, 1899 (Artiodactyla: Bovidae)[END_REF], these interactions were assigned to four categories: mild aggression (threat, side display), severe aggression (butt, hook, chase), play-like behaviour (short run, hop), and sexual behaviour (courtship, copulation). When a given individual addressed a series of different acts to the same group member, only the first act of the series was taken into account. When the individual interacted with a new member in a short period of time in the same spotted group, the interaction was registered as a novel occurrence.

Habitats and patch-based polygons

The grid used to locate the animals was projected on a digitised vegetation map established by the cartography service of the PNP within the framework of the NATURA 2000 European network. This map was based upon field records and used the CORINE Biotope typology as a reference. We simplified the typology to eleven habitat types for the present study: (1) cliff;

( The 11 habitat types made up a set of 98 patches in the study area. In order to assess spatial segregation, six patches covering 12-60 ha in surface area were divided into smaller units (≤ 10 ha). Then, we obtained a set of 114 patch-based homogeneous polygons (mean surface area: 3.12 ha; range: 0.18-8.83 ha) as regards habitat type and to which groups and individuals were assigned.

Testing for social segregation

We tested for social segregation, extending the procedure proposed by [START_REF] Bonenfant | Testing sexual segregation and aggregation: old ways are best[END_REF]. For a period where the population sex ratio and grouping patterns can be considered as stationary, these authors suggest using the 'sexual segregation and aggregation statistic'

= ⁄ , (1)
where χ 2 is the Pearson's independence chi-square calculated on the numbers of adult males and females in the groups (including at least, and possibly reduced to, one adult) and N is the total number of adults. The statistic varies from 0 when the sex ratio within each group is identical to the sex ratio in the whole sample, to 1 when mixed-sex groups are never found. If all the groups were large in size, the calculated Pearson's χ 2 would follow a standard χ 2 distribution under the (null) hypothesis that individuals associate independently of their sex.

However, as small-sized groups are common, [START_REF] Bonenfant | Testing sexual segregation and aggregation: old ways are best[END_REF] recommend computing the 95% confidence interval (CI) of SSAS expected under the null hypothesis of sexindependent association, by performing random permutations of the sexes of the sighted adults. An observed value of SSAS above or below the 95% CI then leads either to the conclusion that the sexes socially segregated or that they aggregated more than expected by chance, respectively.

In order to check that the null hypothesis was not rejected primarily because the sex ratio differed between the subsample of adults observed isolated (or only with kids and/or yearlings) and the subsample of adults observed with other adults, SSAS was calculated on all the sampled groups including at least (and possibly reduced to) one adult, but also on the groups including at least two adults. Moreover, we expected a seasonal variation of the grouping patterns, and population sex ratio fluctuated over the 12 study years. SSAS was thus computed for each month i of the annual cycle as

= (2)
where is the Pearson's independence chi-square and N ij the total number of adults sighted for month i and year j. Furthermore, the CIs of the expected values of SSAS i were computed performing 10,000 random permutations of the sexes within each month i and year i. In order to obtain an overall 95% CI for the 12 months of the year, CI was fixed at 1 -0.05/12 ≈ 99.6% for each month (Bonferroni correction).

This first procedure tested for sexual segregation on the basis of group composition.

However, it did not test whether social segregation was a mere consequence of sex-related differences in habitat use (habitat segregation) or space use (spatial segregation). Thus we computed two additional 95% CI, performing the 10,000 random permutations of the sexes of month i and year j inside each habitat and inside each patch-based polygon, respectively.

Testing for habitat and spatial segregation

Following [START_REF] Ficetola | Spatial segregation among age classes in cave salamanders: habitat selection or social interactions?[END_REF], we also used SSAS to test for habitat and spatial segregation. Accordingly, SSAS i (Eq. 2) was computed using the numbers of adult males and females sighted per habitat (instead of their numbers per group), then their numbers per patchbased polygon. As for social segregation, expected 95% CIs were obtained by permuting randomly the sexes of the sighted adults (N = 10,000 replicates). To investigate whether spatial segregation was a mere consequence of habitat segregation, the randomization procedure was further performed with permutation of the sexes within each month, year and habitat.

Decomposition of SSAS computed on habitats

When applied to the number of males and females sighted per habitat, SSAS i (Eq. 2) is based upon the sum of independence χ 2 , each of which is in turn a sum of terms corresponding to the different habitats. We used this peculiarity to calculate the contribution of each habitat type to the computed values of SSAS i , and thus identify the habitats that primarily contributed to habitat segregation (see Appendix S1).

Seasonal variation of the degree of sexual segregation

Bonenfant et al. ( 2007) stressed that SSAS is not a measure of sexual segregation or aggregation. Accordingly, we quantified the degree of the social, spatial and habitat segregation using a slightly modified version of the segregation coefficient SC proposed by Conradt (1998b), i.e.,

= 1 - + -1 + -1 (3)
where m k and f k are the numbers of adult males and females in the k th group (or patch-based polygon, or habitat), and M and F are the total numbers of adult males and females in the K sampled groups (or patch-based polygons or habitats). Because of its definition (Eq. 3), SC must be calculated, discarding the groups (polygons or habitats) that include a single adult. Its expected value is 0 when males and females aggregate (or use space or habitats) randomly (Bonenfant et al., 2007: Appendix B). It takes negative values ∈ -1, 0 when males and females aggregate more than expected at random, and positive values in the case of sexual segregation, reaching the maximum of +1 when the sexes never occur in the same groups (polygons or habitats; Conradt, 1998b).

SC was computed for each of the 143 study months, on the numbers of adult males and females sighted in the sampled groups (SC social ), in the patch-based polygons (SC spatial ) and in the different habitats (SC habitat ). Because in each case the SC values constituted a time series, the monthly variation of SC in the course of the annual cycle was tested as follows.

First, we computed the moving average of SC over the 143 study months, with a symmetric window of 13 months, giving a weight of ½ for the first and 13 th month and a weight of one for the others (see Fig. S1). We then subtracted this moving average from the time series to obtain a detrended time series. Finally, we performed an ANOVA to test for the effect of the month on the detrended value of SC, and checked that no temporal autocorrelation remained among residuals by using the Ljung-Box test with a lag of 12 months (the test being considered as not significant for P > 0.10). In the event of significant effect of the month, we further checked that the detrended value of SC consistently reached its yearly minimum between October and December (i.e., during the rutting months), performing a one-tailed binomial test with a probability of 3/12 = 0.25. Similarly, we tested whether the yearly maximum of the detrended value of SC consistently occurred between May and July (birth and early lactation periods) rather than during the six other non-rutting months, performing a one-tailed binomial test with a probability of 3/9 = 0.33.

Analysis of interactions

We estimated the overall initiation rate of interactions between males outside the rutting months, selecting the sighted groups that included at least two males, then fitting the generalised linear model (family: Poisson; link function: log)

I mm ~ offset(log(m)) + 1
where I mm is the number of interactions between males recorded in the group, and m the number of males in the group. Because of the offset and the log link, the estimate obtained corresponds to the initiation rate per male. The same procedure of data selection and the same generalised linear model were used for estimating the overall initiation rates of interactions between females, and between males and females.

In order to analyse the effects of group size, group composition and month on the initiation rate of mild aggressions between males outside the rut, we selected the sighted groups that included at least two males, then fitted the generalised linear model (family: Poisson; link function: log)

MA mm ~ offset(log(m)) + log(log(N)) + log(pm) + female + month
where the dependent variable MA mm is the number of mild aggressions between males recorded in the group. In this model, N is group size (kids and yearlings included), a variable that influences the number of immediate neighbours of the mean individual, especially when group size is small, hence the transformation in log(log(N)). Furthermore, the variable pm = (m-1)/(N-1) is the expected proportion of males among the neighbours of any given male in the group. Finally, female is a binary variable indicating whether at least one female was present in the group, and month, a categorical variable indicating the month of observation.

The same procedures of data selection and generalised linear model were used for the initiation rate of severe aggressions between males, and the initiation rates of mild and severe aggressions between females. The models were fitted using maximum likelihood, and the effect of the explanatory variables was tested using the Deviance ( ) test.

Finally, we used Monte Carlo simulations [START_REF] Manly | Randomization, bootstrap and Monte Carlo method in Biology[END_REF] to test whether males performing severe aggressions in mixed-sex groups were more likely to interact with a male than a female. Each elementary simulation consisted of drawing at random a recipient among the adult members of each mixed-sex group including at least two males and in which a male was observed performing a severe aggression. The result retained was the total number of males among the recipients. The simulation was performed 9,999 times, which gave us 9,999 numbers of males under the null hypothesis that none of the two sexes was a preferred recipient. The 9,999 numbers obtained and the number observed were then ranked together in decreasing order, and we finally estimated the probability of obtaining a number of males higher than or equal to that observed under the null hypothesis (one-tailed P-value) as P = r/10,000, where r is the rank of the observed number.

Monte Carlo simulations were made using Excel software. All the other statistical analyses, including those described in the previous sections, were performed using R 3.2.1 software (R core team, 2015).

Results

We observed a total of 27,409 groups over the 12 years of the study (611 -3131 per year; mean: 2284.1). Group size ranged from 1 to 47 (mean ± SE: 4.19 ± 0.03). Among the sighted groups, 26,953 (98.3%) included adult(s), whose number ranged from 1 to 35 with a mean (± SE) of 3.17 (± 0.02) roughly steady throughout the year (Fig. 3a). Furthermore, 40.3% of the groups with adult(s) included a single adult that could be a female (15.3%) or a male (25.0%), 41.6% included at least two adults but a single sex among the adults (female groups: 25.1%; male groups: 16.5%), and 18.1% included adults of both sexes. Unsurprisingly, relative frequency of the mixed-sex groups peaked during the rut (33.3% in November), while it dropped to a minimum during the parturition-lactation period (5.2% in June; Fig. 3b).

Overall, males represented only 39.2% of the sighted adults (N = 85,537), 35.9% in the groups containing ≥ two adults (N = 74,680), but 62.1% among the adults seen isolated or only with kids and/or yearlings (N = 10,857).

Test of social, spatial and habitat segregation

Social segregation was significant throughout the annual cycle, whether or not the groups with a single adult (and the solitary adults) were taken into account. In both cases, indeed, all the monthly values of SSAS computed on the numbers of adult males and females per group were higher than expected under the hypothesis of random association of sexes within each month and year (Fig. 4a,b; CI 1). The same was true when permutations were performed within each month, year and habitat (Fig. 4a,b; CI 2), and within each month, year and patchbased polygon (Fig. 4a,b; CI 3), showing that social segregation was not merely a consequence of sex-related differences in habitat and space use. Spatial and habitat segregation was also significant throughout the year. All the monthly SSAS values computed on the numbers of males and females in the patch-based polygons were higher than predicted, whether permutations were performed within each month and year (Fig. 4c, CI 1) or within each month, year and habitat (Fig. 4c, CI 2). Similarly, all the monthly SSAS values computed on the numbers of males and females in the 11 habitats were significantly higher than predicted by random permutation of sexes within each month and year (Fig. 4d).

Contribution of the habitats

Five of the 11 habitats contributed to 60.6 -85.6% (mean: 72.2%) of the monthly values of SSAS computed on the numbers of males and females per habitat (Fig. 5a). Three were grassland types: (1) the rocky mid-elevation grassland, proportionately more used by males than females from January to July (monthly mean: 39.9 vs 19.8%; Fig. 5b,c), ( 2) the (nonrocky) mid-elevation grassland, with relatively more females than males during most of the year (32.8 vs 20.3%), and (3) the high-elevation grassland with a higher proportion of females than males in June (16.8 vs 6.9%) but the opposite in September-October (15.2 vs 29.5%).

20

The fourth and fifth habitats primarily involved in habitat segregation were alpine heath, proportionally more used by males than females from August to December (10.4 vs 5.7%), and screes, more used by males during most of the year (5.4 vs 3.0%). Mountain pine forest and cliffs also contributed to habitat segregation in May-July (Fig. 5a), i.e., during the birth and early lactation periods, with females being more often observed than males in both habitats (mountain pine: 15.3 vs 6.9%; cliffs: 8.6 vs 1.8%; Fig. 5b,c). in the eleven habitats.

Inter-annual and monthly variation of the social, spatial and habitat segregation

Over 3), SC social , SC spatial and SC habitat are calculated discarding the groups, polygons or habitats that include a single adult.

Interactions between adults outside the rut

We observed 574 interactions between adults outside the rutting months, i.e., 0.0591 interaction per group including ≥ two adults (N = 9,712), and 0.0123 interactions per adult sighted in such groups (N = 46,780). Though males composed 38.4% of the sighted adults, they initiated 72.5% of the interactions, thus much more than chance might suggest ( = 277.6, P < 0.0001).

A total of 321 interactions were recorded between males, i.e., an initiation rate of 0.0196 interactions per male sighted in groups including ≥ two males (N = 16,277). These interactions included 72.0% mild aggressions, 22.1% severe aggressions and 5.9% play-like interactions. Surprisingly, initiation rates of mild and severe aggressions decreased as group size and the proportion of males in the group increased (Deviance tests, P < 0.005).

Furthermore, these two rates did not depend on the presence of females in the group (Deviance tests, P ≥ 0.30), but both varied between months (Deviance tests, P < 0.0001) with a peak in May-June.

A total of 154 interactions were recorded between females, i.e., an initiation rate of 0.0054 interactions per female sighted in groups including ≥ two females (N = 28,263). These interactions included 72.7% mild aggressions, 16.9% severe aggressions, 9.7% play-like interactions, and 0.6% sexual interactions. Initiation rates of mild and severe aggressions tended to decrease as group size increased (Deviance tests, P < 0.06), but increased or tended to increase with the proportion of females in the group (Deviance test: mild aggressions = 6.321, P = 0.012; severe aggressions: = 3.387, P = 0.066). The presence of males in the group had no significant effect on the initiation rate of mild aggressions ( = 0.521, P = 0.47), but increased the initiation rate of severe aggressions ( = 10.877, P < 0.001; Fig. S2).

Both rates varied between months (Deviance tests, P < 0.002), with enhanced values in June and September for mild aggressions, and from July to September for severe aggressions.

Finally, 99 of the observed interactions involved one male and one female. Though males composed 25.8% of the adults sighted in mixed-sex groups (N = 12,041), they initiated many more male-female interactions than chance alone would predict ( = 248.3, P < 0.0001).

Indeed, females initiated only four mild aggressions, i.e., 0.0004 interactions per sighted female (N = 8,929), whereas males initiated the other interactions, i.e., 0.0305 interactions per sighted male (N = 3,112). The interactions initiated by males included 46 sexual interactions, 37 severe aggressions, 11 mild aggressions, and one play-like interaction. Most of the sexual interactions (89.1%) were recorded in winter, with a decreasing frequency from January (54.3%) to March (13.0%). In contrast, most male-female aggressions were observed from February to April (severe aggressions: 70.3%; mild: 60.0%). The severe aggressions performed by males in mixed-sex groups including ≥ two males (N = 19) tended to be more preferentially addressed to males than females (observed frequency of male-male severe aggression: 7; expected frequency: 4.25; Monte Carlo test: P = 0.0859).

Discussion

Given the theoretical background that underpins the current hypotheses focusing on ecological factors, sexual segregation should be reduced in the nearly monomorphic Pyrenean chamois, except during the parturition-early lactation period. Our data collected during 12 years and the analyses performed in the present paper show that habitat segregation was low outside the parturition-lactation period, but also that social and spatial segregations consistently occurred throughout the year. [START_REF] Takada | Effects of the physical and social environment on flight response and habitat use in a solitary ungulate, the Japanese serow (Capricornis crispus)[END_REF] also found no sexual differences in habitat use in the nearly monomorphic Japanese serow (Capricornis crispus).

In this species, however, both females and males are solitary, except when females are accompanied by dependent offspring, and inhabit closed habitat, which perhaps explains the lack of habitat segregation. By contrast, chamois live in open-membership groups and use

both forested and open habitats all around the year during daytime.

Habitat segregation

Habitat segregation peaked during the parturition and early lactation period as predicted by the 'reproductive strategy hypothesis' (RSH). Females occurred in mountain pine forests and cliffs more often than males and more often than during the rest of the year, as also reported in other Pyrenean chamois populations [START_REF] Pérez-Barbería | Seasonal variation in group size of Cantabrian chamois in relation to escape terrain and food[END_REF]. Moving to steep slopes [START_REF] Karsch | Desert Bighorn Sheep lambing habitat: parturition, nursery, and predation sites[END_REF] or where trees provide concealment [START_REF] Hamr | Disturbance behaviour of chamois in an Alpine tourist area of Austria[END_REF][START_REF] Scornavacca | Suckling behaviour and allonursing in the Apennine chamois[END_REF] offer protection for offspring against terrestrial carnivores and raptors, as found in sexually dimorphic mountain-dwelling herbivores [START_REF] Hutchins | Behavioural considerations in the management of mountaindwelling ungulates[END_REF][START_REF] Kohlmann | Antipredator constraints on lactating nubian ibexes[END_REF][START_REF] Corti | Relationship between predation-risk factors and sexual segregation in Dall's sheep (Ovis dalli dalli)[END_REF][START_REF] Grignolio | Predation risk as a factor affecting sexual segregation in Alpine ibex[END_REF][START_REF] Karsch | Desert Bighorn Sheep lambing habitat: parturition, nursery, and predation sites[END_REF][START_REF] Baruzzi | Catch me if you can: antipredatory behaviour of chamois to the wolf[END_REF]. Females with neonates may also avoid tourists walking on valley bottom and summit trails [START_REF] Cederna | The impact of tourism on feeding activities in an area of the Abruzzo National Park, Italy[END_REF][START_REF] Bon | Do lambs affect feeding habitat use of lactating female mouflons in spring within an area free of predators?[END_REF][START_REF] Ciuti | Ecological sexual segregation in fallow deer (Dama dama): a multispatial and multitemporal approach[END_REF].

It should further be noted that habitat segregation around parturition may also be explained by a change in females' gregariousness. Females become less social and isolate themselves from conspecifics as in wild sheep (Ovis spp.), moose (Alces alces), Nubian ibex (Capra ibex nubiana) and roe deer (Capreolus capreolus) [START_REF] Festa-Bianchet | Seasonal range selection in bighorn sheep: conflicts between forage quality, forage quantity, and predator avoidance[END_REF][START_REF] Miquelle | Sexual segregation in Alaskan moose[END_REF][START_REF] Bon | Do lambs affect feeding habitat use of lactating female mouflons in spring within an area free of predators?[END_REF][START_REF] Habibi | Group dynamics of the Nubian ibex (Capra ibex nubiana) in the Tuwayiq Canyons, Saudi Arabia[END_REF][START_REF] Cransac | An example of segregation between age and sex classes only weakly related to habitat use in mouflon sheep (Ovis gmelini)[END_REF][START_REF] Langbein | Investigations on periparturient behaviour in free-ranging mouflon sheep (Ovis orientalis musimon)[END_REF][START_REF] Maublanc | Ranging behaviour of roe deer in an experimental high-density population: are females territorial?[END_REF]. By using habitat neglected by non-lactating females and males, females in late gestation and during few days post-partum space away from conspecifics, facilitating mutual recognition, the formation of an exclusive bond and exclusive maternal care to their own offspring [START_REF] Bon | Do lambs affect feeding habitat use of lactating female mouflons in spring within an area free of predators?[END_REF][START_REF] Ciuti | Space use, habitat selection and activity patterns of female Sardinian mouflon (Ovis orientalis musimon) during the lambing season[END_REF][START_REF] Karsch | Desert Bighorn Sheep lambing habitat: parturition, nursery, and predation sites[END_REF].

Soon after post-partum isolation, lactating females group together (Vaucher, 1988;[START_REF] Karsch | Desert Bighorn Sheep lambing habitat: parturition, nursery, and predation sites[END_REF], venturing farther from escape terrain. In early summer, isard females in our study area occupied the habitats they used before parturition, predominantly (non-rocky) midelevated grassland. At the same time, males kept on using the rocky mid-elevated grassland, and slightly increase their frequentation of alpine heath, which however remains a rather minor habitat for them. Males were reported to use more forested areas and less often alpine meadows than females in Alpine and Apennine chamois (R. p. ornata) [START_REF] Shank | Inter-and intra-sexual segregation of chamois (Rupicapra rupicapra) by altitude and habitat during summer[END_REF][START_REF] Lovari | Seasonal habitat selection and group size of the Abruzzo chamois (Rupicapra pyrenaica ornata)[END_REF]Untherthiner et al., 2012), shrub and bush areas more than females in Pyrenean and Cantabrian chamois (R. p. parva) [START_REF] Pérez-Barbería | Sex, seasonal and spatial differences in the diet of Cantabrian chamois Rupicapra pyrenaica parva[END_REF][START_REF] Dalmau | Habitat selection and social behaviour in a Pyrenean chamois population (Rupicapra pyrenaica pyrenaica)[END_REF]. By contrast, [START_REF] Ferretti | Males are faster foragers than females: intersexual differences of foraging behaviour in the Apennine chamois[END_REF] found no sexual differences in summer habitat use.

In late summer, isard of both sexes increasingly used high-elevated grasslands as found in other Rupicapra populations (Hamr, 1984a(Hamr, , 1984b;;[START_REF] Crampe | Site fidelity, migratory behaviour, and spatial organization of female isards (Rupicapra pyrenaica) in the Pyrenees National Park, France[END_REF][START_REF] Nesti | Ranging behaviour and habitat selection of Alpine chamois[END_REF][START_REF] Papaioannou | Demographic characteristics, seasonal range and habitat topography of Balkan chamois population in its southernmost limit of its distribution (Giona mountain, Greece)[END_REF] and other mountain ruminants [START_REF] Mysterud | Plant phenology, migration and geographical variation in body weight of a large herbivore: the effect of a variable topography[END_REF][START_REF] Parker | Nutrition integrates environmental responses of ungulates[END_REF]. This habitat would support more nutritive protein-rich forage due the delayed green-up of vegetation in September-October [START_REF] Nesti | Ranging behaviour and habitat selection of Alpine chamois[END_REF]. This change in habitat use was steeper in males. This may reflect lower sensitivity to predation risks than in females.

Nevertheless, whether a higher sensitivity of females to predation risks is related to maternal care as predicted by the 'reproductive strategy-predation risk hypothesis' (RSH) is unclear because offspring are weaned or nearly in September-October. Female-biased sensitivity to risks, human disturbance or interference due to wild or domestic herbivores [START_REF] Hamr | Disturbance behaviour of chamois in an Alpine tourist area of Austria[END_REF]Ciuti and Appolonio, 2008) may be a response of sex per se, as indicated by a higher responsiveness of female black rhinoceros (Diceros bicornis) to predators [START_REF] Berger | Predation, sensitivity, and sex: why female black rhinoceroses outlive males[END_REF] and as also found in domestic sheep (Ovis aries) and humans [START_REF] Wojniusz | Prepubertal 54 gonadotropin-releasing hormone analog leads to exaggerated behavioral and emotional sex differences in sheep[END_REF]. Alternatively, a more intense use of high-elevation terrain by males may reflect a higher sensitivity of males than females to heat stress, when they attain their highest body mass, i.e., in the period of highest body mass dimorphism, in accordance with the 'weather sensitivity hypothesis' (WSH).

Ecological differences between the sexes may occur at a finer spatial scale than the habitat patches considered in the present paper. [START_REF] Ferretti | Males are faster foragers than females: intersexual differences of foraging behaviour in the Apennine chamois[END_REF] did not detect any sexual difference in the microhabitats used by Apennine chamois in summer. However, a sex-related difference in diet remains possible. Males feed more on fibrous and less digestible/nutritive food than females in the monomorphic black rhinoceros [START_REF] Du Toit | Sex differences in the foraging ecology of large mammalian herbivores[END_REF], whereas no sexual differences in diet and selection of forage were found in feral horses (Equus caballus), males and females white-tailed deer (Odocoileus virginianus) of similar body mass, and scimitarhorned oryx (Oryx dammah) [START_REF] Lenarz | Lack of diet segregation between sexes and age groups in feral horses[END_REF][START_REF] Lagory | Niche differences between male and female white-tailed deer on Ossabaw Island, Georgia[END_REF][START_REF] Robinson | Grouping Patterns and Selection of Forage by the Scimitar-Horned Oryx (Oryx dammah) in the Llano Uplift Region of Texas[END_REF]. [START_REF] Pérez-Barbería | Sex, seasonal and spatial differences in the diet of Cantabrian chamois Rupicapra pyrenaica parva[END_REF] found that females have a less fibrous and more digestible/nutritive diet than males outside winter in the Cantabrian chamois. However, summer increase in body mass is higher in males than females in the Pyrenean chamois (Fig.

2), and in late summer Pérez-Barbería et al. (1998) found a higher kidney fat index in males than females in the Cantabrian chamois. Though moderate in Rupicapra species [START_REF] Morin | Older conservatives: reproduction in female Alpine chamois (Rupicapra rupicapra) is increasingly risk-averse with age[END_REF], the energy expenditure incurred to face offspring care may limit the capacity for females to store body reserves despite their more nutritive diet. Besides, males may be more efficient than females at allocating energy to fat and/or muscle growth when resources are plentiful and contain relevant nutrients [START_REF] Rughetti | Seasonal changes in sexual size dimorphism in northern chamois[END_REF][START_REF] Kernaléguen | Early-life sexual segregation: ontogeny of isotopic niche differentiation in the Antarctic fur seal[END_REF] and whether this also apply to sexually dimorphic species is not reported to our knowledge.

Social segregation

Outside summer and the rut period, the persistent social and spatial segregation in Pyrenean chamois when food resources become limiting and when body mass of both sexes is comparable cannot be accounted for by 'reproductive strategy', 'gastro-centric', 'weathersensitivity' and 'predation risk hypotheses', and considered as a by-product of habitat segregation [START_REF] Bowyer | Assessing sexual segregation in deer[END_REF][START_REF] Bowyer | Sexual segregation in ruminants: definitions, hypotheses, and implications for conservation and management[END_REF][START_REF] Main | Reconciling competing ecological explanations for sexual segregation in ungulates[END_REF]. The SSAS and SC indicate that social segregation is prominent even when controlling for habitat and spatial segregation, with and without isolated adults (Fig. 4). Whatever the level of sexual dimorphism, almost all Caprini are characterized by social segregation (Shackleton, 1997). Despite intra-specific variation, social segregation is salient in Rupicapra spp. (Richard-Hansen et al., 1992;[START_REF] Levet | Sociabilité et domaine vital d'isards (Rupicapra pyrenaica) mâles au printemps à Orlu (Ariège)[END_REF][START_REF] Bonenfant | Testing sexual segregation and aggregation: old ways are best[END_REF], reminiscent of what is found in highly sexually dimorphic herbivores [START_REF] Conradt | Habitat segregation in ungulates: are males forced into suboptimal foraging habitats through indirect competition by females?[END_REF][START_REF] Bon | Segregation is not only a matter of sex in Alpine ibex, Capra ibex ibex[END_REF][START_REF] Bonenfant | Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude[END_REF][START_REF] Calhim | Sexual segregation among feral goats: testing between alternative hypotheses[END_REF][START_REF] Loe | Testing five hypotheses of sexual segregation in an arctic ungulate[END_REF][START_REF] Villerette | Sexual segregation in fallow deer: are mixed-sex groups especially unstable because of asynchrony between the sexes?[END_REF]. This strongly suggests that social mechanisms contribute to drive sexual segregation as already advocated for a number of large mammals (e.g. Alpine ibex Capra ibex ibex, wild, feral and domestic sheep, red deer Cervus elaphus, sea lion Zalophus californianus wollebaeki, white-tailed deer, feral goat, and African elephant Loxodonta africana; [START_REF] Bon | Social tendencies of the Corsican mouflon Ovis ammon musimon in the Caroux-Espinouse massif (South of France)[END_REF][START_REF] Villaret | Social and spatial segregation in Alpine ibex (Capra ibex) in Bargy, French Alps[END_REF][START_REF] Cransac | An example of segregation between age and sex classes only weakly related to habitat use in mouflon sheep (Ovis gmelini)[END_REF][START_REF] Conradt | Habitat segregation in ungulates: are males forced into suboptimal foraging habitats through indirect competition by females?[END_REF][START_REF] Pendu | Interactions and associations between age and sex classes in mouflon sheep (Ovis gmelini) during winter[END_REF][START_REF] Bon | Segregation is not only a matter of sex in Alpine ibex, Capra ibex ibex[END_REF][START_REF] Wolf | Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)[END_REF][START_REF] Pérez-Barbería | Are social factors sufficient to explain sexual segregation in ungulates?[END_REF][START_REF] Calhim | Sexual segregation among feral goats: testing between alternative hypotheses[END_REF]Shannon et al., 2008;Singh et al., 2010;[START_REF] Alves | Sexual segregation in red deer: is social behaviour more important than habitat preferences?[END_REF][START_REF] Biggerstaff | Sexual segregation of forage patch use: Support for the social-factors and predation hypothesis[END_REF][START_REF] Bourgoin | Social behaviour as a predominant driver of sexual, age-dependent and reproductive segregation in Mediterranean mouflon[END_REF].

The 'social factors hypothesis' (SFH) postulates that in polygynous species, sexual selection should have retained males practicing sparring interactions to develop social skills that ultimately increase access to receptive females [START_REF] Main | Sexual segregation in ungulates: new directions for research[END_REF][START_REF] Pérez-Barbería | Sexual selection for fighting skills as a driver of sexual segregation in polygynous ungulates: an evolutionary model[END_REF]. The Pyrenean chamois is a polygynous species but our data are poorly consistent with this prediction: males interacted with conspecifics more often than females, as reported in Apennine chamois by [START_REF] Locati | Sexual differences in aggressive behaviour of the Apennine Chamois[END_REF], but social interactions were seldom observed in the present study. In addition, play-like interactions among males were especially rare and much less frequent than agonistic interactions, which were short lasting. [START_REF] Boschi | The spatial patterns of Alpine chamois (Rupicapra rupicapra rupicapra) and their influence on population dynamics in the Swiss National Park[END_REF] pointed out that hook-shaped horns are dangerous, leading sparring to be scarce. Rupicapra spp. avoid clashing and rather perform agonistic display, anti-parallel fight, and chase [START_REF] Locati | Sexual differences in aggressive behaviour of the Apennine Chamois[END_REF][START_REF] Rughetti | Seasonal changes in sexual size dimorphism in northern chamois[END_REF][START_REF] Corlatti | Rutting behaviour of territorial and nonterritorial male chamois: is there a home advantage?[END_REF].

Sexual interactions (46 events in 12 years) were rarely observed past December, as could be expected since the rut is seasonal in chamois as in all mountain-dwelling species. In addition, we did not find that the rate of aggression between males increased in the presence of females. Accordingly, the 'sexual harassment hypothesis' (SHH) and the 'male avoidance of females hypothesis' (MAFH) do not apply. Inter-sex agonistic interactions were also rare (56 events), as reported in Apennine chamois by [START_REF] Lovari | Behavioural repertoire of the Abruzzo chamois, Rupicapra pyrenaica ornata Neumann, 1899 (Artiodactyla: Bovidae)[END_REF], and mainly observed in winter, perhaps in relation to the scarcity of resources and thus to competition for food. Males were almost always the initiators of such interactions, and the rate of severe conflicts among females increased in the presence of males, which is compatible with the FAMH [START_REF] Weckerly | Are large male roosevelt elk less social because of aggression?[END_REF][START_REF] Biggerstaff | Sexual segregation of forage patch use: Support for the social-factors and predation hypothesis[END_REF]. However, we have to be cautious with this result because chase interactions among females in mixed-sex groups were noticed only on 11 occasions in 12 years. The instantaneous recording method used in the study is perhaps a limit to test this hypothesis. Whether co-occurring within the same groups affects foraging efficiency or vigilance level for each sex as reported in white-tailed deer [START_REF] Biggerstaff | Sexual segregation of forage patch use: Support for the social-factors and predation hypothesis[END_REF]) cannot be checked with our data. But assessing social interference between the sexes requires controlling for familiarity, which plays a role in attraction [START_REF] Pérez-Barbería | Are social factors sufficient to explain sexual segregation in ungulates?[END_REF], whereas males and females seldom group together. The lack of familiarity had previously been mentioned as source of conflict among females themselves (Festa-Bianchet, 1998).

Alternatively, as postulated by the 'social affinity hypothesis' (SAH) proposed by Bon and Campan (1996), prevalence of same-sex groups may reflect intra-sex attraction or affinity [START_REF] Gerard | Social affinities as the basis of the social organization of a Pyrenean chamois (Rupicapra pyrenaica) population in an open mountain range[END_REF]) and maintenance of spatial proximity [START_REF] Wolf | Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)[END_REF] without overt affiliative interactions [START_REF] Macfarlane | Boys will be boys: social affinity among males drives social segregation in western grey kangaroos[END_REF]. [START_REF] Coe | Sexual segregation and its ontogeny in squirrel monkey social structure[END_REF] found higher intra-sex than inter-sex spatial proximity in penned squirrel monkey (Saimiri sciurus), mirroring the social segregation described in field studies of this species.

Higher intra-sex spatial proximity is also documented in mixed-sex groups of wild and domestic sheep, and in feral goat (Le [START_REF] Pendu | Spatial structure and activity in groups of Mediterranean mouflon (Ovis gmelini): a comparative study[END_REF][START_REF] Michelena | An experimental test of hypotheses explaining social segregation in dimorphic ungulates[END_REF][START_REF] Calhim | Sexual segregation among feral goats: testing between alternative hypotheses[END_REF]. Higher social attraction for same-sex peers was experimentally found in domestic sheep [START_REF] Michelena | An experimental study of social attraction and spacing between the sexes in sheep[END_REF][START_REF] Pérez-Barbería | Are social factors sufficient to explain sexual segregation in ungulates?[END_REF] together with a spatial separation of groups of females and males [START_REF] Pérez-Barbería | Why do polygynous ungulates segregate in space ? Testing the activity-budget hypothesis in Soay sheep[END_REF]. More recently, Griffith et al.

(2014) found that wild male and female minnows (Phoxinus phoxinus), which are similar in morphology, tend to segregate socially and spatially when introduced in artificial channels. [START_REF] Villerette | Sexual segregation in fallow deer: are mixed-sex groups especially unstable because of asynchrony between the sexes?[END_REF] found a strong tendency of fallow deer (Dama dama) mixed-sex groups to split up into single-sex groups, without group asynchrony being a major cause of fission. [START_REF] Macfarlane | Boys will be boys: social affinity among males drives social segregation in western grey kangaroos[END_REF] reported no avoidance of one sex by another in western grey kangaroo (Macropus fuliginosus) but a higher intra-sex attraction particularly in males. [START_REF] Wolf | Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)[END_REF] concluded that segregation probably reflects a social preference for same-sex conspecifics outside the rut. Although our present data cannot disentangle the respective role of avoidance from attraction, these studies and our own give support to the hypotheses relying on social mechanisms.

We suspect that cryptic mechanisms linked to sex per se, i.e., sexualisation of behaviour, totally or partially decoupled from sexual mass dimorphism, may partly drive the sexual segregation found in adults. Group living outside the rut is based on non-sexual social attraction and interactions. Sexual differences in behaviour may be dependent on sex-limited gene expression, perinatal action of steroid and corticosteroid hormones [START_REF] Meaney | The sexual differentiation of social play[END_REF][START_REF] Beery | Same-sex social behavior in meadow voles: multiple and rapid formation of attachments[END_REF][START_REF] William | Genetic and molecular insights into the development and evolution of sexual dimorphism[END_REF]. Interestingly, Soay sheep lambs castrated within three days after birth segregate socially and spatially from both females and noncastrated males [START_REF] Jewell | Survival in a feral population of primitive sheep on St. Kilda, Outer Hebrides, Scotland[END_REF] despite no segregation in habitat [START_REF] Ruckstuhl | The effects of castration, sex ratio and population density on social segregation and habitat use in Soay sheep[END_REF]. The 'social factor hypothesis' (SFH) hardly accounts for such a segregation. The Soay sheep experiment illustrates how physiological mechanisms may influence the development of social behaviour, social affinity at the individual level and also aggregation and spatial patterns at a population-wide level. In the case of Soay sheep, however, it is difficult to disentangle the relevancy of the 'activity budget hypothesis' (ABH) and of hypotheses implying social mechanisms as castrated males outweigh entire males, increasing the sexual dimorphism. On the other hand, non-social behaviour such as response to environmental stressor [START_REF] Carter | Developmental consequences of oxytocin[END_REF] and social behaviour may be differently regulated by neuropeptides such as oxytocin and vasotocin in females and males [START_REF] Beery | Same-sex social behavior in meadow voles: multiple and rapid formation of attachments[END_REF][START_REF] Goodson | Deconstructing sociality, social evolution and relevant nonapeptide functions[END_REF].

We did not investigate the activity budget of adult males and females in the present study. [START_REF] Pérez-Barbería | Reproductive parameters, kidney fat index and grazing activity relationships between the sexes in Cantabrian chamois Rupicapra pyrenaica parva[END_REF][START_REF] Dunbar | Sex differences in feeding activity results in sexual segregation of feral goats[END_REF]. Although the 'activity budget hypothesis' (ABH) as stated does not account for the intense social segregation observed, we cannot preclude that despite the monomorphism in body mass during more than 6-7 months, sexual differences of metabolic rate or other physiological mechanisms induce different feeding patterns [START_REF] Lewis | Sex-specific foraging behaviour in a monomorphic seabird[END_REF], which could make both sexes less synchronous in their activities and thus mixed-sex groups more labile [START_REF] Alves | Sexual segregation in red deer: is social behaviour more important than habitat preferences?[END_REF][START_REF] Griffiths | Sexual segregation in monomorphic minnows[END_REF]. For instance, males may have a greater muscle/fat ratio and thus for the same body mass, greater energetic demands due to higher metabolic activity of muscles [START_REF] Romey | Sex and the selfish herd: sexual segregation within nonmating whirligig groups[END_REF]. Data collected in the same environment, excluding the influence of gestation and lactation and controlling for group size would be required to test the hypotheses of diet selectivity and activity budget [START_REF] Pérez-Barbería | Why do polygynous ungulates segregate in space ? Testing the activity-budget hypothesis in Soay sheep[END_REF].

Spatial segregation

Bowyer (2004, p. 1040) stressed that 'one especially problematical aspect with the concept of social segregation is that it does not explain why sexes spatially segregate… any inclusive hypothesis for sexual segregation should be able to cope with the spatial attributes of this process' (see also [START_REF] Stewart | Sexual segregation in North American elk: the role of density dependence[END_REF]. Indeed, neither sexual differences in activity budget nor preferences to associate with same-sex conspecifics could alone explain spatial segregation, as they do not theoretically preclude both sexes from using independently the same areas [START_REF] Francisci | Male and female Alpine ibex: phenology of space use and herd size[END_REF][START_REF] Jakimchuk | Differential habitat use and sexual segregation in the Central Arctic caribou herd[END_REF]. Nonetheless, inter-sex avoidance might certainly promote spatial segregation [START_REF] Pérez-Barbería | Are social factors sufficient to explain sexual segregation in ungulates?[END_REF], and at least some other mechanisms not involving ecological factors might do the same.

In a number of gregarious Antilopini (including nearly monomorphic species), all-male groups would result to a large extent from the exclusion of their members by territorial males [START_REF] Leuthold | Types of Social Organization in African Ungulates[END_REF][START_REF] Dubost | The behavior of the male Antilope cervicapra L., its development according to age and social rank[END_REF][START_REF] Estes | The Behavior Guide to African Mammals: Including Hoofed Mammals, Carnivores, Primates[END_REF]. The same mechanism might be at work in Rupicapra spp.: part of the mature males is reported to be territorial during the rut, and territoriality is also suspected or reported in spring [START_REF] Levet | Sociabilité et domaine vital d'isards (Rupicapra pyrenaica) mâles au printemps à Orlu (Ariège)[END_REF][START_REF] Unterthiner | Sexual and seasonal differences of space use in Alpine chamois[END_REF] and summer [START_REF] Shank | Inter-and intra-sexual segregation of chamois (Rupicapra rupicapra) by altitude and habitat during summer[END_REF][START_REF] Hardenberg | Male Alpine chamois occupy territories at hotspots before the mating season[END_REF]. In the present study, a large proportion of the adults observed alone throughout the year were males. However, severe aggressions were seldom observed between males, and we cannot assert that spatial segregation was primarily caused by inter-male aggression. Another mechanism might be involved in spatial segregation. Mother-young bonds break down in Rupicapra sp. for both sexes when juveniles enter their second year of life. Males, however, eventually disperse farther from maternal ranges as in pronghorn [START_REF] Loison | Age-and sex-specific settlement patterns of chamois (Rupicapra rupicapra) offspring[END_REF]Barnowe-Meyer et al., 2013) -possibly revealing a weaker attachment to natal ranges and/or social bonds with familiar conspecifics, higher attraction for unfamiliar conspecifics -, and although sexdependent dispersal is not a pre-requisite to social segregation, it may contribute to spatial segregation. Finally, a model developed by [START_REF] Bon | Sexual segregation in ungulates: from individual mechanisms to collective patterns[END_REF] suggests that higher intra-sex than inter-sex attraction could amplify slight differences in habitat or space use, and thus lead to sexual segregation on a large spatial scale. Such a model, however, remains to be tested experimentally.

Conclusion

Our long-term observational data set showed, unexpectedly, high year-round sexual segregation in the Pyrenean chamois, a nearly monomorphic mammalian herbivore.

Segregation peaked during and following parturition as expected in species where parental care is exclusive to females. However, past offspring weaning, we found low habitat segregation whereas social segregation remained very high, which is hardly explained by current hypotheses relying on sexual dimorphism in body size. Social mechanisms that could promote social segregation are difficult to test in the wild. However, the fact that social segregation is prevalent in such a nearly-monomorphic species opens avenues regarding possible mechanisms linked to dispersal, social neuroscience, and collective patterns emerging from social and spatial mechanisms, and in our opinion should revive the scientific debate around sexual segregation.

Authors' statement. JPC: collected the data. GG, JPC and JFG: managed the data. JFG and MG: performed the data analyses. RB, JFG, GG, JPC, and CM: wrote the paper.

Declaration of competing interest

Fig. 1 .Fig. 2 .

 12 Fig. 1. Mean body length (a), shoulder height (b) and metatarsus length (c) of Pyrenean

Fig. 3 .

 3 Fig. 3. (a) Average size (± SE) of the sighted Pyrenean chamois groups (lone animals

Fig. 4 .

 4 Fig. 4. Monthly values of SSAS computed on the numbers of adult males and females sighted

Fig. 5 .

 5 Fig. 5. (a) Contribution of each habitat to SSAS values computed for testing habitat

Fig. 6 .

 6 Fig. 6. Monthly average of the values of SC social , SC spatial and SC habitat computed for each

  the 143 study months, SC social gave high values (mean ± SE: 0.70 ± 0.02), SC habitat SC habitat and SC spatial remained steady across the 12 years whereas SC social tended to decrease in 2006-2009 (Fig.S1a). Degree of social, spatial and habitat segregation varied significantly in the course of the annual cycle(Figs. 6 and S1b, c,

	low (positive) values (mean ± SE: 0.15 ± 0.01), and SC spatial intermediate values (0.45 ±
	0.01), indicating habitat segregation was low despite the high degree of sexual segregation
	revealed by group composition.

d; detrended SC social ; F11,119 = 11.525, P < 0.0001; Ljung-Box test: = 15.632, P = 0.21; detrended SC spatial ; F11,119 = 13.646, P < 0.0001; Ljung-Box test: = 13.080, P = 0.36; detrended SC habitat : F11,119 = 4.276, P < 0.0001; Ljung-Box test: = 17.345, P = 0.14). The minimum of the detrended values of the three coefficients generally occurred between October and December: 8/11 years for SC social , 7/11 for SC spatial and SC habitat (one-tailed binomial test: P = 0.0012 et P = 0.008, respectively). Furthermore, the maximum of the detrended values of the three coefficients occurred more frequently in May-July than chance alone would suggest: 9/11 years for SC social , 10/11 for SC spatial and 7/11 for SC habitat (onetailed binomial test: P = 0.0014, P = 0.0001 and P = 0.039, respectively).

  Contrasting results have been found in Rupicapra species outside winter. Pérez-[START_REF] Pérez-Barbería | Seasonal variation in group size of Cantabrian chamois in relation to escape terrain and food[END_REF] and[START_REF] Pérez-Barbería | Reproductive parameters, kidney fat index and grazing activity relationships between the sexes in Cantabrian chamois Rupicapra pyrenaica parva[END_REF] found that females Pyrenean chamois spent more time foraging than males, perhaps reflecting higher selectivity.[START_REF] Ferretti | Males are faster foragers than females: intersexual differences of foraging behaviour in the Apennine chamois[END_REF] did not detect any sexual differences in this respect, but[START_REF] Puorger | Plastic adaptations of foraging strategies to variation in forage quality in Alpine chamois[END_REF] found that males display higher bite rate and less step rate than females. In winter, snow cover restricts available space, food abundance and quality are low, and the short diurnal time is mostly dedicated to food acquisition and processing, enforcing similar activity budgets as in Cantabrian chamois and feral goat (Capra hircus) (Pérez

Acknowledgments

We are thankful to the direction of the Pyrénées National Park for allowing this study to be carried out, and to the park rangers from the Cauterets station for their help in the fieldwork.

We are grateful to Marco Festa-Bianchet who addressed helpful remarks and also to anonymous reviewers for their constructive comments. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

APPENDIX A Contribution of the habitats

For month i and year j, the Pearson's independence chi-square calculated on the numbers of adult males and females sighted in the eleven habitats is a sum of terms, each corresponding to a given habitat k:

Moreover, for month i, the computed for the habitats is

where is the total number of adults sighted for month i and year j (see Material and Methods). Substituting in Eq. (A2) by its expression (Eq. A1), it comes to

The absolute contribution of habitat k to is therefore

whereas its relative contribution to is