Androgens in a female primate: relationships with reproductive status, age, dominance rank, fetal sex and secondary sexual color

Abstract

A comprehensive understanding of the role of androgens in reproduction, behavior and morphology requires the examination of female, as well as male, hormone profiles. However, we know far less about the biological significance of androgens in females than in males. We investigated the relationships between fecal androgen (immunoreactive testosterone) levels and reproductive status, age, dominance rank, fetal sex and a secondary sexual trait (facial color) in semi-free-ranging female mandrills, using samples collected from 19 reproductively mature females over 13 months. Fecal androgens varied with reproductive status, being highest during gestation. Fecal androgens began to increase at 3 months of gestation, and peaked at 5 months. This pattern is more similar to that found in a platyrrhine than in other cercopithecine species, suggesting that such patterns are not necessarily phylogenetically constrained. Fecal androgens did not vary systematically with rank, in contrast to the relationship we have reported for male mandrills, and in line with sex differences in how rank is acquired and maintained. Offspring sex was unrelated to fecal androgens, either prior to conception or during gestation, contrasting with studies of other primate species. Mean facial color was positively related to mean fecal androgens across females, reflecting the same relationship in male mandrills. However, the relationship between color and androgens was negative within females. Future studies of the relationship between female androgens and social behaviour, reproduction and secondary sexual traits will help to elucidate the factors underlying the similarities and differences found between the sexes and among studies.