Behavioral responses of free-ranging female rhesus macaques to new males

This research project, conducted at Cayo Santiago, Puerto Rico, studied 48 free-ranging female rhesus macaques (Macaca mulatta) for 13 months to assess the response strategies of females to new males. Rhesus macaque society is composed of a stable core of multi-generational matrilines, with males generally transferring from their natal group at puberty, and migrating periodically throughout their lives. A female, therefore, will always be familiar with her female group members, but will be unfamiliar with recently transferred or peripheral males in her group. Matched pairs of females of varying age, rank, and parity, from two social groups, were followed across the entire reproductive cycle, to observe interactions with males. Hypotheses were developed from several models predicting female response to males under certain conditions (intra-group competition model, inter-group competition model, mate choice model, infanticide model, group history model), and the behavioral data were analyzed to test the hypotheses. Results indicate that all females do not follow the same strategies when interacting with males, and neither do all females of the same relative rank, age, reproductive state, or maternal experience. The major effect on a female\u27s response to males demonstrated in this project was her group membership. The model proposed to explain the results generated by this research is a group history model which relies on behavioral flexibility over a female\u27s lifespan and suggests that as a the nature of a female\u27s social group changes and evolves, her relationships with, and responses to, different categories of males will change also