Sex or power? The function of male displays in rhesus macaques

Abstract

Male behavioral displays (e.g., branch-shaking) are common across Anthropoidea, but their function remains unclear. We examined free-ranging rhesus macaques on Cayo Santiago, Puerto Rico, to test three major hypotheses for the function of male displays: (1) mate attraction, (2) mate guarding and (3) male–male dominance competition. Focal and ad libitum behavioural data were recorded for 21 adult males across 9 groups during the mating season. Display rates were calculated for each male in each context (i.e., agonistic, mating). In stable groups, males with high mating success displayed more during consortships than in other contexts and displays were more likely to follow than to precede copulation, whereas males in unstable groups were more likely to displays in agonistic contexts. These results suggest that mate guarding and male–male dominance competition are the primary functions of male display behaviours in rhesus macaques.