Effects of the menstrual cycle, social grouping, and exogenous progesterone on heterosexual interaction in laboratory housed stumptail macaques (M. arctoides)

The effects of endogenous fluctuations in ovarian hormones during the female's menstrual cycle on heterosexual interaction was studied in groups of stumptail macaques. When 5 different trios of females were paired for 5 consecutive weeks with each of 5 males no aspect of male-female interaction changed as a function of phase of the menstrual cycle. Moreover, males usually preferred to copulate with the same female of each trio in consecutive tests, regardless of the ovarian condition of any of the females. It appeared that the most dominant females in the trios were sexually most preferred. Subcutaneous implantation of silastic capsules containing progesterone into the sexually most preferred females of each trio affected neither the males' sexual preference, nor the behavior of these females, nor the behavior of sexually non-preferred females in each trio. Likewise, progesterone in sexually preferred females had no effect on male-female interaction in pair tests. It is concluded that in stumptail macaques social factors are more important than ovarian hormones in regulating heterosexual interaction.