Activity budgets and behavioural synchrony in a wild equid living in a fission-fusion social system

Abstract

Variation in activity budgets among individuals of different age-sex classes and reproductive status may lead to decreases in behavioural synchrony (i.e., individuals performing the same behaviour at the same time in the same group) in social species. Here, we assessed the costs of behavioural synchrony in terms of time allocated to feeding behaviour among individuals of different age-sex classes and reproductive status in the kiang (Equus kiang), a poorly known wild equid that inhabits the Tibetan Plateau. Our study was conducted in Eastern Ladakh (India), during summer and fall. Our results showed that groups were highly synchronized, and that individuals in groups were particularly synchronized when feeding. Despite a slight sexual dimorphism, males and females had similar activity budgets. Males in groups, however, spent less time feeding than solitary males, and females in groups with foals spent less time feeding and more time standing than females in groups without foals. We suggest that group formation in males and the presence of foals for females incur behavioural costs by lowering their time spent feeding. Because these costs occur at a predictable time of the year, it could be profitable for adult kiangs not to form permanent groups year-round. Individuals with divergent needs might benefit from the loose social system observed in kiangs, which could be a key feature of their adaptation to a highly seasonal environment.