Sexual Dimorphism Affects Herd Composition in African Antelopes

Abstract

Herd behaviour is a crucial aspect of antelope development and survival. Understanding determinants of differences in herd composition is necessary to predict patterns of habitation, social interaction, and life history; thus, the possibility of sexual dimorphism acting as a dictator of herd size and composition in African antelope was explored. Sexual dimorphism is a key factor in determining intersexual and intrasexual interactions, which can create selection pressures driving divergence in behavioural and social traits. Consequently, it was predicted that sexually dimorphic species would exhibit increased social behaviour and be found in larger groups when compared to sexually monomorphic species. Two closely related species, sexually dimorphic impalas and non-sexually dimorphic hartebeests were compared using 60 camera trap photos obtained through the WildCam Gorongosa project to determine if there was a difference in herd size and the number of young observed. It was discovered that impalas were found in larger groups than hartebeests and that there was no difference in the proportion of offspring. This discrepancy can be attributed to sexually dimorphic females needing to group together for protection against predation as they lack horns for self-protection. Group size differences can imply tendencies to inhabit different habitats and exhibit unique social interactions within the herd while foraging. These findings are key in understanding herd behaviour in African antelopes and can be applied to accurately track and monitor antelope species’ success in relation to conservation.