Social dynamics of male muriquis (Brachyteles arachnoides hypoxanthus)

Abstract

We investigated patterns of sociality among wild male northern muriquis (Brachyteles arachnoides hypoxanthus) to explore some of the possible ways in which within-group scramble competition might shape their social and mating strategies. The 13 adult males in our study group spent an average of 54.5′4.2% of their time in proximity to at least one other adult male. They were more likely to associate with one another, but not with adult females, when they were resting than when they were feeding. Embrace rates were positively related to the proportion of time males spent in proximity during resting. Males that associated closely with one another tended to interact more often, although individual differences in male social styles and rates of interactions were apparent. Young adult males had significantly higher social maintenance rates than the oldest males in our sample, but no other effects of age were detected in any of our other behavioral comparisons. In roughly 20% of all dyads, one male valued the association significantly more than the other. Males tended to value associates with higher mating success than themselves, and to share access to the same females on the same days with their closest associates. Neither of the two pairs of maternal brothers in our study group were important associates to their kin, but brothers shared copulations in the same polyadic copulation partnerships with one another. Although still preliminary, our findings suggest that muriqui males differentiate among their possible social partners in ways that may minimize the variance in their mating success under the unusual conditions imposed by scramble competition for reproductive opportunities.