Does male mate choice select for female colouration in a promiscuous primate species?
The traditional view of sex roles and sexual selection emphasises the evolution of male ornaments as a result of female mate choice and male-male competition. Female ornaments are now receiving more attention, although their roles in mating decision are still less well understood, especially considering cases in which colourful ornaments are expressed by both sexes. In this study, we analysed whether female skin colouration (luminance and redness of the face and hindquarters) influenced male mate choice and sexual behaviours in relation to intra-cycle (cycle phase), inter-cycle (number of consecutive cycles, conceptive nature of the cycle), and inter-individual (age, social rank, weight, and parity) variation in a captive population of Japanese macaques (Macaca fuscata). Males did not preferentially choose darker/redder females. Moreover, males did not appear to use female skin colouration to apportion their mating efforts on the most fertile period of the menstrual cycle or during cycles that lead to conception, or to discriminate between females. To our knowledge, our study is among the few to report a lack of male choice for female colouration in a species where both sexes potentially display ornamentation. While female colouration appeared to contain information about intra-cycle, inter-cycle, and inter-individual variation in fecundity, this study further demonstrates that this trait may not have been sexually selected and that males mated regardless of such variation across females. This study adds to the growing research on the role and evolution of female colouration in the context of sexual signalling and mate attraction.