Female aggression: Testing the Hera Hypothesis. A study of female competition over access to males in rhesus monkeys (Macaca mulatta)

Abstract

Two semi-free ranging groups of rhesus macaques (Macaca mulatta) were observed over a nine month period on Morgan Island, South Carolina. The purpose of this study was to determine if the presence of males, rather than overall increased activity during the breeding and birthing seasons, resulted in higher rates of female-female aggression. This study was a test of the Hera Hypothesis: a model developed by the author in 1991 that predicted the existence of female intra-sexual competition. Repeated measures of affiliative behaviors and physical and non-physical aggression between subject and target monkeys were recorded and associated with the presence or absence of a male. Aggressive behavior was hypothesized to be a measure of female competition over mates, an arena mainly considered to be the domain of males alone. This study demonstrates that female rhesus monkeys do not aggress against each other more intensely when in the presence of a potential mate. In light of this I can only conclude that female rhesus monkeys do not use aggression as a means of competition over access to mates.