Associations are more strongly correlated with space use than kinship in female eastern grey kangaroos

Abstract

Understanding the relationship between kinship and female social preferences in mammalian societies is frequently complicated by philopatric behaviour and variation in pairwise home range overlap. While the influence of space use on association patterns is increasingly being considered in studies using network analysis, methods are needed for generating null models that control for pairwise home range overlap. We investigated female associations in a wild population of eastern grey kangaroos, Macropus giganteus, a species with higher fission-fusion dynamics, to test the influences of home range overlap and kinship on pairwise association strengths. Genetic analysis revealed that females were highly philopatric and we found that association strengths were significantly correlated with home range overlap. To test for social preferences, we compared observed associations with random associations based on individuals' space use, simulated using Digiroo2. HWIG, a version of the half-weight association index that controls for among-individual variation in gregariousness was used for all analyses. Preferred associates had significantly higher pairwise relatedness than expected. Although some females had strong social relationships with some of their close kin, in general, space use had a much stronger correlation with association strengths than both pairwise relatedness and maternal lineage. This suggests that familiarity may play a key role in driving association patterns in female kangaroos. We recommend controlling for individuals' space use when undertaking studies on social preferences and social structure in general.