Disruption of Sexual Behaviour By High Ranking Rhesus Monkeys (Macaca Mulatta)

We studied the association between social rank and sexual behaviour in a group of rhesus monkeys (Macaca mulatta) (10 males, 14 females) housed in two adjacent 15.25 x 15.25 m compounds which were separated by a solid metal wall. This wall had a small opening through which the monkeys could move from one compound to another. Because of the position of this opening, most monkeys in one compound were hidden from view of the monkeys that remained in the other compound. It was therefore possible for an observer to record whether sexual behaviour was initiated within or outside the field of view of the four highest ranking animals (two males and two females). About 2/3 of the mount sequences initiated by lower ranking males were begun when the dominant animals were out of view. Such behaviour was usually disrupted if dominant animals entered the compound in which it was taking place. Most disruptions of sexual behaviour were accomplished by means of aggression directed by a dominant animal toward one or both members of the consorting pair. In most such cases, the aggression was directed by a dominant male toward the female member of the consorting pair. This study demonstrates that dominant animals tend to interfere with the sexual behaviour of subordinate animals, and that lower ranking animals are likely to begin copulatory activity out of view of higher ranking males and females. These tendencies may account for previous findings of a strong relationship between frequency of copulatory activity and social rank in group-dwelling rhesus monkeys.

Affiliations: 1: Division of Neurobiology, Yerkes Regional Primate Research Center, and Department of Biology, Emory University, Atlanta, GA 30322, U.S.A.