Segregation is not only a matter of sex in Alpine ibex, Capra ibex ibex

Abstract

We assessed social, spatial (using grids of 100×100, 200×200 and 500×500m) and habitat (vegetation) segregation between sex and age classes in two Alpine ibex populations (Sous-Dine and Bargy), with, respectively, 27 and ca. 120 animals at least 1 year old, during the rut (15 November–15 January), winter (16 January–15 April), spring (16 April–May), birth period (June–July) and summer (August–14 November). We hypothesized that ‘behavioural incompatibility’, the idea that (1) females are less motivated than males to interact socially and (2) females avoid some components of the social behaviour of males, leads to social segregation in ungulates (‘social affinity’ hypothesis). We considered habitat segregation to be a by-product of social segregation. Spatial segregation tended to decrease, but not significantly, with increasing grid size. Several of our predictions were verified: (1) social and spatial segregation were greater than habitat segregation, except during the birth period when sexual segregation peaked; (2) intersexual social segregation increased with male age; and (3) social segregation, but not habitat segregation, increased between males distant in age. In contrast, the expectation that (4) spatial segregation between the sexes and male age classes would be low in winter, because few areas were free of snow, was confirmed at Sous-Dine but not at Bargy. Differences in behaviour and motivation are likely to be the main factors leading to social segregation not only between the sexes but also between males distant in age. Further analyses are needed to explain how social segregation can generate spatial segregation.