Sexual behaviour during ovarian cycles, pregnancy and lactation in group-living stumptail macaques (Macaca arctoides).

Sexual interactions were studied in a large, well-integrated group of stumptail macaques, continuously living together. Copulations with the highest-ranking male and with young males were equally distributed over the ovarian cycle. Copulations with other adults males also occurred during all cycle phases, but were most frequent peri-ovulatory. This was most distinct in conceptive cycles. Copulatory activity continued during early pregnancy, but was virtually absent during the middle and latter part of pregnancy and during lactation. Fluctuations in copulation frequency could be attributed to fluctuations in female attractivity (as measured by directed male masturbations), but not in proceptivity (spontaneous presents) or receptivity (acceptance ratios). However, hormonal influences on attractivity could be overruled by social factors. With regard to the expression of heterosexual behaviour, stumptail macaques seem to be less hormone-dependent than other primate species studied, both in the laboratory and under more natural circumstances.