Temporal Dynamics of Group Size and Sexual Segregation in Ibex

Group size is an important variable describing behavioural ecology of animals. A variety of factors such as habitat characteristics, life history, spatio-temporal resource dynamics, population density, predation risk, competition with kin, and social learning often determine group size in large mammals. We studied temporal dynamics of group size in Siberian Ibex (Capra sibirica) in a protected area in Mongolia. We measured monthly and yearly variations in typical group size and used the sexual segregation and aggregation statistic to assess sexual segregation. Ibex formed the largest groups in November and smallest groups in July. However, group sizes did not significantly differ between the sexes. There was marked sexual segregation during the summer months and within all years segregation increased with temperature. We show that grouping behaviour is a complex phenomenon and is probably determined by a combination of factors, such as species’ life history, habitat and environmental characteristics, and behavioural strategy against predation risk.