Variation in Rhesus Macaque (Macaca mulatta) Vocalizations: Social and Biological Influences

Rhesus macaques (Macaca mulatta) are the most widely studied nonhuman primate. While some work has been done on both vocal communication and the role of the neuropeptides, oxytocin, and vasopressin in the behavior of these highly social primates, key questions remain unanswered. In this study, seven rhesus macaques (four adult females and three adult males) were given a dose of either saline (control), oxytocin, or vasopressin. After being given this treatment, they were placed in close proximity to a conspecific who had not received any such treatment and the two monkeys were allowed to interact for five minutes. A variety of data, including the number of vocalizations that occurred in each session was recorded. Analysis showed that there were significant relationships between the number of vocalizations the female macaques produced and both the sex of the other individual in the room, and whether the female macaque had received saline, oxytocin, or vasopressin prior to the trial. These results have implications on the study of rhesus macaque communication and the study of the effects of oxytocin and vasopressin on promoting social behavior.