Female mate choice in Cayo Santiago rhesus macaques.

Abstract

Female mate choice, a potentially powerful selective force, has received little systematic attention in nonhuman primates. In this study, focal animal behavioral data collected during 12 months on 48 free-ranging female rhesus macaques in two social groups at Cayo Santiago were used to address two questions. First, what behaviors of estrous females signal preferences for particular males? Second, what criteria do females use in choosing mates? Mate choice behaviors should (a) be plausibly related a priori to mate choice and (b) correlate cross-dyadically with mating rate. Hypothesized mate choice criteria include (a) male dominance rank, (b) male age, (c) male breeding tenure, (d) prior nonsexual relationship with the choosing female and (e) degree of genetic relatedness to the choosing female. Three behaviors of estrous females--proximity maintenance (in one social group), cooperation with male sexual solicitations (hip-grasps), and restoration of proximity following attacks by other males--correlated cross-dyadically with hourly copulation rate during the female's fertile period, and therefore signalled mate choice. Females preferentially maintained proximity to less dominant (lower-ranking) males, even though they were attacked by males more frequently while accompanying lower-ranking males, but this appears to reflect different tactics required to complete matings with lower-ranking males rather than active preference for them. Females apparently used choice criteria that were independent of male dominance rank, and chose the same males in consecutive years. Females did not prefer older males over younger males. Data are equivocal on the issue of whether females chose males most likely to be sexually novel. There was little concordance between mating patterns and birth season heterosexual affiliative patterns. Females did not direct mate choice signals preferentially toward their unrelated male affiliates of the preceding birth season. Although natal males in both study groups experienced high copulatory success, fewer matings than expected by chance occurred between matrilineal relatives. Females directed mate choice signals preferentially toward unrelated natal males (i.e. those of other matrilineages) compared to related natal males.