Development of female-dominance in lemurs coincides with androgenic development

Abstract

Female dominance over males is rare among mammals but common among adult lemurs. Due to the role androgens play in activating aggressive behavior in male mammals, they are likely candidates for organizing and/or activating elevated rates of female aggression directed at males in female-dominant species. Comparative data are generally consistent with an androgenic mechanism, but the details differ across species and remain poorly understood. Recent work in ring-tailed lemurs (RTLs) has implicated androgens in organizing female dominance during the prenatal period and activating it in adults, but the role of androgens from birth through adulthood is completely unknown. Using enzyme immunoassay, we assessed total androgen concentrations from 343 fecal samples collected from 9 female and 27 male wild ring-tailed lemurs aged 2 to 48 months and analyzed them using GLMM to account for repeated measurements. These preliminary data indicate that immature RTLs have mammal-typical developmental profiles of fecal androgens—males and females have low, indistinguishable levels of androgens during infancy and juvenility (sex: χ2 = 1.489, P = 0.22), followed by dramatic androgenic increases beginning just prior to sexual maturity (age: χ2 = 16.852, P < 0.001). This increase coincides with behavioral changes in dominance relationships, when subadult female RTLs assert dominance over male age-mates, and with the appearance of anogenital marking by both sexes. These data are consistent with previous hypotheses regarding the role of androgens in fetal and adult life, but suggest that the postnatal, prepubertal lifespan has not been targeted during the evolution of female dominance in lemurs.