Progesterone levels in seasonally breeding, free-ranging male Macaca thibetana

Abstract

Progesterone, a “female” hormone, modulates sexual behaviors in male mammals. This modulation is well documented in laboratory animals, but it is as yet unknown whether progesterone is associated with testosterone and/or sexual behaviors in primates living in their natural environments. In this study, we collected a total of 426 fecal samples and approximately 453 h of behavioral data from five male Tibetan macaques (Macaca thibetana) to study relationships between males’ progesterone and testosterone levels and sexual behaviors. Our results showed a negative correlation between fecal testosterone and progesterone levels. Both hormones seasonally varied. For three of the five subjects, we also found that copulatory and sexually motivated behaviors were negatively correlated with fecal progesterone levels. While not significant for the other two males, this study provides insight into the relationship between progesterone and the sexual behaviors of male primates living in a natural environment.