Genetic inference of group dynamics and female kin structure in a western lowland gorilla population (Gorilla gorilla gorilla)

Abstract

Dispersal and grouping patterns form the foundations of social interactions in group-living mammals and are the outcomes of a complex interplay between inbreeding avoidance, kin cooperation and competition, predation pressure and food resource distribution. In species where both sexes disperse, the potential for kin-biased associations would seem limited. In one such species, the western lowland gorilla (WLG), short-term data suggest that female kin associations may be present due to directed local dispersal decisions, but monitoring of groups over longer timescales is needed to better elucidate this pattern. Using autosomal genotyping of 419 faecal samples representing 85 unhabituated gorillas collected non-invasively over 5 years in a 132 km2 section of Loango National Park, Gabon, we investigated the dynamics of WLG group composition, social structure and patterns of dispersal. By revealing two group dissolutions, one group formation and the movement of 13 gorillas between groups, this study demonstrates the utility of genetic analysis as a way to track individuals, groups and population dynamics on a larger scale than when monitoring the behaviour of a limited number of habituated groups or through one-time genetic sampling. Furthermore, we find that females are found in groups containing their female kin more often than expected by chance, suggesting that dispersal may not impede female kin associations in WLGs.