Dominance styles of female and male Barbary macaques (Macaca sylvanus)

Dominance styles can be understood as consequences of different competition regimes imposed by socio-ecological conditions. As vital resources differ for males and females of the same species, one might expect different competitive tactics, hence differential dominance styles in both sexes. This was investigated on the basis of dyadic competition over a food resource (peanut) or mating partner (estrous female) in the semifree ranging colony of Barbary macaques at 'Affenberg Salem'. Both, females and males competed over nuts. The dominant typically won the nut by eliciting the retreat of the subordinate with a ritualised assertive signal, the 'rounded-mouth threat face'. The competitive style in adult male dyads (AM-AM) differed from that of all other age-sex class combinations, including adult versus subadult males, and did not change with the kind of incentive: Use of threat faces and retreat was replaced by ignoring, tension, or recruitment behaviour, and in 1/5 of AM-AM dyads at least one nut was taken by a third party. In the few cases where a male did perform a threat face his rival responded by counter aggression, recruitment or appeasement/affiliation, or by taking the nut nevertheless. It is concluded that (1) dominance relations among adult females are stricter than those between males, indicating different dominance styles for the two sexes; (2) the 'egalitarian' competitive style of adult males was compatible with an absence of formalisation of dominance-subordination relations and did not indicate an absence of competition among them; (3) Adult males behaved as dominance oriented as females if the risk of injury was small (as in AM-SM dyads). The 'egalitarian' behaviour in AM-AM dyads is best understood as the result of a stalemate where the risks of escalation are high relative to the value of the resource. In sum, the results suggest that variance in power asymmetries and differential cost-benefit ratios of escalated competition may produce different dominance styles even within the same species.