Patterns of male–male association in mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica: effects of dominance rank and age

Abstract

Cooperative relationships among male primates are emerging as an important aspect of primate social behavior. What remains unclear is the extent to which male associations with coresident males vary within species, and what social and demographic factors drive these associations. This information provides an important contribution to our understanding of how cooperative relationships play an adaptive role in the evolution of male social and reproductive strategies. To examine the nature of male associations and the influence of social and demographic factors, including rank and age, we collected 1751 h of focal behavioral data on adult males in two large multimale–multifemale groups of mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica. Both groups inhabited upland forest area, were of similar size and sex ratio, and exhibited strongly linear male hierarchies. Based on observed spatial associations within 3 m proximity, dyadic patterns varied from strongly preferred to strongly avoided associations that were largely consistent among dyads over the study period. In contrast to reports from other mantled howler study sites, neither rank nor age differences among males predicted whether dyads spent any time in proximity to one another, nor the amount of time in proximity. However, higher-ranked males within dyads were more likely to maintain close proximity than their lower-ranked counterparts. Our results provide important data on the nature of male associations within mantled howler groups with linear dominance relationships, and are suggestive of the adaptive value of cooperative relationships.