Social complexity and hormonal influences on sexual behavior in rhesus monkeys (Macaca mulatta).

Rhesus females in multi-animal groups mate only during the mid-follicular and periovulatory portions of their ovarian cycle, whereas females in pair-tests often mate at all cycle phases. We investigated the influence of social context on hormonal mediation of rhesus sexual behavior by observing the same males and females in both pair-tests and in single male/multi-female group-tests. Five intact adult female rhesus were tested with each of four males during their follicular, periovulatory, and luteal cycle phases as verified by steroid radioimmunoassay. Male initiated behaviors of approach, hiptouch, mount, and ejaculation were significantly above luteal levels during periovulatory group-tests, with periovulatory approach and hiptouch frequencies also significantly above follicular levels. Approach did not vary with the female's cycle phase in pair-tests and both follicular and periovulatory frequencies of hiptouch, mount, and ejaculation were higher than luteal levels. Pair-test frequencies were greater than group-test frequencies at all cycle phases, except for male approach, where the difference depended upon female cycle phase. When group-tested, females approached the male, presented, and handslapped most frequently during periovulatory tests. In pair-tests, females approached and handslapped equally during follicular and periovulatory tests and lower luteally, but presents did not vary cyclically. Females approached males significantly more frequently during pair- than group-tests, but there were no consistent differences between the two social conditions for present and handslap. In group-tests, periovulatory females were approached and threatened by other group females significantly more often that they were at other cycle phases.(ABSTRACT TRUNCATED AT 250 WORDS)