Sexual segregation reported in many wild ruminants is generally assumed to result from either different habitat choices by adult males and females or ‘social factors’. In this framework, we studied group composition and habitat use of mouflon sheep (Ovis gmelini) over an annual cycle in the low-mountain range of Caroux-Espinouse (continental France). The analysis of group composition revealed segregation outside the rut, not only between the sexes, but also between the young (2-3 years) and old rams ( 4 years). Moreover, ewes, young rams, and old rams exhibited some differences in patterns of habitat use in the mid-rutting and lambing seasons, but showed similar patterns in winter and summer. These results, juxtaposed with those of studies of interactions and proximity between individuals within groups, suggest that segregation between age-sex classes has a strong social basis in mouflon sheep.