UNEXPLAINED SEXUAL SEGREGATION IN POLYGAMOUS UNGULATES - A DEFENSE OFAN ONTOGENIC APPROACH

Two processes are generally mixed when considering ungulate sexual seg regation: the social segregation which appears to be a rule in polygam ous ungulate species and the spatial segregation which is facultative. Early in life, there is evidence that males and females exhibit diffe rent levels of activity and patterns of interaction which could lead t o behavioural incompatibility. It is proposed that juvenile females, d ifferently motivated than males to interact socially, may soon avoid t he pseudo-sexual and agonistic male behavioural components, as body an d behavioural dimorphism increase with age, the behavioural incompatib ility would be intensified. Since adults often interact agonistically with or avoid them, juveniles will attend to interact with same-sex pe ers of similar status. Because social experiences are occurring since early stages of development i.e., during sensitive periods, a social a uto-segregation by sex/age classes is expected. Then population would be structured in coherent socio-spatial set of compatible individuals, sharing similar constraints and properties, Around the birth period, females become asocial promoting a temporal social segregation. Costs linked to gestation and lactation may make females more dependent on w ater and rich food resources, Female with offspring are also likely to select areas where the risks of predation are reduced, sometimes at d etriment to energy intake, while other animals exhibit opportunistic f eeding behaviour, resulting in seasonally ecological segregation. Body growth channels a lot of energy for males which are expected to use t he best feeding areas. However, indirect competition for the same reso urces may result in a spatial segregation between the sexes, Sex- and age-specific activity budgets are suspected to favour social and spati al segregations, The social segregation among males and females use ex clusive ranges. Whether spatial segregation results in ecological segr egation would however depend on habitat heterogeneity, population dens ity, local ecological conditions and the biological cycle periods. It is suggested that spatial segregation will occur not only between the sexes but also among males. If populations are structured in coherent socio-spatial units, spatial segregation among individuals of age and sex classes may result from indirect interactions between sets of indi viduals (of same age and sex class), that may be translated as an indi rect competition between individuals. Studies on ethogenesis are consi dered as fundamental as they allow to know on what basis social and sp atial segregations are set up. In particular, studies on behavioural d evelopment could highlight how social segregation between adults may r esult from a process that originates much earlier in the life of anima ls. By considering the role of behaviour, we defend the idea that soci al and spatial segregations may be logically distinguished.