Deposited in DRO : 22

Although secondary sexual adornments are widespread in male primates, few studies have examined female choice for these characters. The mandrill (Mandrillus sphinx) presents an extreme example of sexual dimorphism, with males exhibiting an array of striking adornments. The most dominant adult male in a group exhibits the brightest and most extensive red coloration, while other males are less brightly colored. I examined whether female mandrills show a preference for brightly colored males using data on peri-ovulatory sexual behavior during the 1996 mating season for all males aged 8+ yrs (n = 5) and all parous females (n = 9) living in a semi-free-ranging colony at CIRMF, Gabon. Results showed that brightness of male coloration was significantly positively correlated with time spent within 2m of females, female responsibility for proximity, number of sexual presentations received, % approaches accepted by females, and % inspections that females cooperated with. Females also groomed only the brightest male. Behaviors indicative of female preference did not correlate significantly with male dominance rank, and partial correlations confirmed that the influence of male color on female behavior was stronger than that of male rank. When the influence of male dominance rank was controlled, correlation coefficients between female behaviors and male mating success were high and positive. In further support of the hypothesis that females show mate choice for brightly colored males, independent of dominance rank, I report an unusual case where the alpha male fell in rank without loss of coloration. This male experienced no significant change in female responsibility for proximity, sexual presentations received, or female reaction to approaches or inspections, although he was no longer observed to mate. These preliminary observations suggest that female mandrills attend to differences in male secondary sexual characters, and show mate choice in favor of brightly colored males. As brightly colored males are also dominant, this reinforces the influence of male-male competition on male reproductive success, and may explain the very high reproductive skew in males of this species, and the extraordinary appearance of male mandrills.