Effects of Group Composition and Mating Season on the Agonisitic and Affiliative Behavior of Rhesus Macaques (Macaca mulatta)

The purpose of this study was to determine what, if any, were the effects of group composition and mating season on grooming and aggression in captive rhesus macaques (Macaca mulatta). Three groups of rhesus macaques were observed during the summer of 2003. The behavior of these three groups was compared in order to determine if any group differences were present. The following January, two of these groups (one had been disbanded) were observed again to determine if behavior varied in the mating season.

The results suggest that the number of intergroup fights has an inverse relationship to intragroup aggression. In addition, because the group with only one male showed significantly less grooming than the other two groups, grooming appears to be used by males to gain access to reproductive females. Findings also revealed that male aggression towards other males increased during the winter mating season (P=0.023) suggesting that there is male competition for access to reproductive females during the mating season.

Further research is recommended to assure that these results are indicative of a species approach to behavior and not merely individual differences in personality.