Development of juvenile goitered gazelle social behavior during the hiding period.

In many ungulate species, social organization of adults is based on a linear dominance hierarchy, which in turn often positively correlates with age, body mass, and horn/antler size. In contrast to the social behavior of adults and specific mother-offspring interactions, the process of ungulate socialization in juveniles through contacts with other conspecifics is poorly understood, especially for hider species during their initial hiding period. Therefore, we investigated this process in goitered gazelle (Gazella subgutturosa), which is a typical hiding species, and analyzed all contacts between fawns and other conspecifics, omitting mother-young interactions, which are different by nature from other contacts and demands separate consideration. We found that apart from mothers, fawns interacted most often with nonmaternal adult females, less with other fawns and least with adult males and sub-adults. The frequency of the fawns' contacts with conspecifics other than their mother increased during May and early-June, reaching a maximum in late-June, when fawns had the most mobility and independence from their mothers. This frequency decreased in July, when fawns spent more time with their mothers and when they mostly followed the mother's behavior. The interactions of adult males and sub-adults of both sexes with fawns were the most aggressive in character, involving frequent displays of butting and chasing. Aggressive interactions were fewer between adult females and fawns, while fawn-fawn interactions had least aggressive displays. The main cause of interactions between fawns and other conspecifics were attempts of these young gazelles to suckle from other adults and sub-adults, especially frequently from nonmaternal females. Only fawn-fawn contacts were not linked to suckling and seemed to relate mostly to the development of social behavior and dominance hierarchies.

Antipredator strategy of female goitered gazelles (Gazella subgutturosa Guld., 1780) with hiding fawn.

In ungulates, predation is often a major cause of infant mortality and likely plays an important role in shaping maternal care strategies that favor progeny survival. The anti-predator strategies of ungulates can be broadly categorized into two groups, hiding infants and following infants. We studied the maternal behavioral strategies of goitered gazelle, which is a typical representative of a hiding species. We found that shortly after birth, goitered gazelle mothers (1) stayed at the greatest distances from their hiding fawns; (2) spent the shortest amount of time together with their fawns, and then only for suckling (during the active phase) which was also the longest inter-suckling intervals (during the hiding phase); (3) kept twins separated in different hiding places and suckled them individually one after the other; (4) changed fawns' hiding places after every active period, travelling with them during the whole suckling bout; (5) oriented their body and muzzle most often toward their hiding young during the fawn's hiding phase; and (6) demonstrated the highest level of vigilance during their approaches to their hiding fawns. The anti-predator strategy of goitered gazelle females was similar to that observed in some North American (Antilocapra americana, Odocoileus hemionus and Odocoileus virginianus) and Eurasian (Dama dama and Capreolus capreolus) ungulate species that also demonstrate hiding behavior. Females of these species live on different continents with disparate environments and different predatory threats, but share anti-predator strategies, which are likely the result of convergent evolution in Bovids and Cervids.

Seasonal dynamics of agonistic displays in territorial and non-territorial males of goitered gazelle.

Aggression serves a great variety of social functions, one of which is protection of individual territories from intruders. Territorial males of many antelope species show aggressive noncontact displays, and only rarely fight. It has been suggested that ungulate males tend to have more frequent and longer aggressive interactions with rivals of similar age or social status than with males of dissimilar status. In the present paper, we test whether territorial and non-territorial males behave in a similar manner and avoid fights, and whether or not they preferentially direct aggressive and longer agonistic interactions towards males of similar age or social status, rather than towards other classes of males. We found that territorial males usually avoided straight fights with peers, and instead mainly used noncontact displays in aggressive interactions. In contrast, non-territorial males used fights considerably more often, especially during the onset of territoriality in April to May, when these males had their most frequent aggressive interactions. Territorial bucks aggressively interacted most frequently with non-territorial males and significantly less often with other territorial males, but agonistic noncontact displays between territorial males lasted the longest. In contrast, non-territorial males addressed their aggressive noncontact displays and fights most often to peers and less frequently to sub-adults. Asymmetry in the social status of territorial vs. non-territorial males was likely responsible for the distinctively different agonistic behaviors shown by the two types of males, which in turn are likely due to the different costs and benefits each male can accrue from these aggressive interactions.

Roaring function in male goitered gazelles.

Most of the vocalizations of Antilopinae males are soft and usually only heard from a very close distance. The goitered gazelle is a rare exception to this rule, and during the rutting period territorial males of this species are among the noisiest antelopes. Rutting vocalization is such an essential part of the rutting behavior in goitered gazelle that adult males have a hypertrophic larynx, the muscle tissues of which increase considerably in size during the rut. We were interested in the frequency and variance with which male goitered gazelles emit their calls depending on an animal's age, reproductive status and time of the year in order to understand the main function of the rutting vocalizations. We found that roaring was mostly related to courting displays, while vocalizations during aggressive displays were less frequent in male-male interactions. Acoustic signals likely enhance courtship displays and also may aid in accelerating female ovulation, promoting synchronization of breeding cycles during the mating and birthing periods, which last only several days for most of the females in our population. We discuss the potential benefits of such behaviors and compare it to other species living in similarly extreme environments.

Sexual segregation in vertebrates: proximate and ultimate causes.

Sexual segregation is very common in vertebrates that live in groups. In this article, I will review proximate and ultimate causes of sexual segregation in social species and in particular in ungulates in which the bulk of research on the topic has been carried out. In most social ungulate species, males and females live in separate groups outside the breeding season, sometimes using different home ranges and types of habitat. In most of these species, males are larger than females. Dimorphism in body size can lead to sexual differences in ecology and behavior making it difficult for the two sexes to stay in the same group. It is important for our better understanding of the evolution of sociality, sexual dimorphism and different mating systems to determine why sexual segregation is so widespread not only in ungulates but also in other vertebrates. In this article, I discuss the ecology of the two sexes by reviewing proximate and ultimate causes of sexual segregation. To do this, I compare a range of studies of ruminants and include explanations for social segregation as well as for habitat segregation by gender. This leads into a review and updates current knowledge of the phenomenon. Although I present a number of different hypotheses, I focus in particular on predation risk, forage selection and activity budget and discuss the social-factors hypothesis. I stress that the key in solving the enigma of sexual segregation lies in clearly separating hypotheses that try to explain social segregation and habitat segregation, as well as in including experiments or model systems. To that end, I present a preliminary study on a test of the activity-budget hypothesis in three-spine sticklebacks and explain why I believe that shoaling fish are useful for analysing the underlying processes and mechanisms that lead to sexual segregation in animals. Lastly, I argue that it is unlikely that a single factor can explain social segregation or habitat segregation but that a model integrating different factors and different levels of segregation might succeed in describing proximate and ultimate causes of sexual segregation.

Sexual segregation in ungulates: a comparative test of three hypotheses.

In most social ungulate species, males are larger than females and the sexes live in separate groups outside the breeding season. It is important for our understanding of the evolution of sociality to find out why sexual segregation is so widespread not only in ungulates but also in other mammals. Sexual body size dimorphism was proposed as a central factor in the evolution of sexual segregation in ungulates. We tested three hypotheses put forward to explain sexual segregation: the predation-risk, the forage-selection, and the activity budget hypothesis. We included in our analyses ungulate species ranging from non-dimorphic to extremely dimorphic in body size. We observed oryx, zebra, bighorn sheep and ibex in the field and relied on literature data for 31 additional species. The predation-risk hypothesis predicts that females will use relatively predator-safe habitats, while males are predicted to use habitats with higher predation risk but better food quality. Out of 24 studies on different species of ungulates, females and their offspring chose poorer quality but safer habitat in only eight cases. The forage-selection hypothesis predicts that females would select habitat based on food quality, while males should prefer high forage biomass. In fact, females selected higher quality food in only six out of 18 studies where males and females segregated, in eight studies there was no difference in forage quality and in four studies males were in better quality habitat. The activity budget hypothesis predicts that with increasing dimorphism in body size males and females will increasingly differ in the time spent in different activities. Differences in activity budgets would make it difficult for males and females to stay in mixed-sex groups due to increased costs of synchrony to maintain group cohesion. The predictions of the activity budget hypothesis were confirmed in most cases (22 out of 23 studies). The heavier males were compared to females, the more time females spent foraging compared to males. The bigger the dimorphism in body mass, the more males spent time walking compared to females. Lactating females spent more time foraging than did non-lactating females or males. Whether species were mainly bulk or intermediate feeders did not affect sexual differences in time spent foraging. We conclude that sexual differences in activity budgets are most likely driving sexual segregation and that sexual differences in predation risk or forage selection are additive factors.