Sexual segregation in Eurasian wild sheep

Sexual segregation, a widely observed phenomenon in vertebrates, is commonly categorized into habitat and social segregation. A universal explanation for sexual segregation is, however, lacking and debated. Causes of segregation and their division into proximate and ultimate causes is also highly debated, and the relative contributions of habitat and social factors to segregation are also seldom quantified. We studied the Eurasian wild sheep in trans-Himalayan rangelands to identify these causes and estimate the contributions of habitat and social components to sexual segregation. We observed male, lactating, and nonlactating female groups feeding during 3 springs and summers. The 3 groups strongly segregated and differed in their activity budgets, partly because of antipredation risks, with lactating females being the most vigilant (40% of the time). At the feeding habitat scale, males selected the patches of highest quality. We found that the social component contributed the most to segregation (70%) as compared with habitat segregation (30%). This is the first study that quantifies the contribution of habitat and social components to sexual segregation. We emphasize the role of antipredator behavior of lactating females on activity budgets and selection of relatively poor-quality sites as compared with other groups and illustrate that the usual division into proximal and ultimate causes of sexual segregation is not as clear-cut as usually presented. Copyright 2010, Oxford University Press.