The Social Behavior of Brown Spider Monkeys (Ateles hybridus) in a Fragmented Forest in Colombia

Abstract

Forest fragmentation and habitat loss are two of the main drivers of wildlife population declines. Animals exposed to habitat disturbances must develop behavioral strategies to adapt to novel, rapidly fluctuating socioecological challenges. Understanding the behavioral flexibility of endangered primates as a response to ecological challenges, e.g., anthropogenic habitat disturbance, is a key element in the design of successful conservation initiatives for remaining populations. We studied the social behavior of a group of 11 adult and subadult brown spider monkeys (Ateles hybridus) living in a recently isolated and densely populated forest fragment in the Magdalena River Valley, Colombia, and compared their behavior to that of other wild spider monkey populations. From June 2009 to July 2010 we assessed diet, activity budgets, and the rates of affiliative and agonistic interactions initiated and received by adult male and female spider monkeys. The diet of our focal group was quite different from that in most previous studies of Ateles: leaves accounted for ca. 40 % of their diet, and fruits represented barely half of their diet, suggesting that this population has had to adjust its feeding strategies to the local ecological challenges. We found no sex differences in the time males and females spent resting, moving, and socializing, but females tended to invest more time in feeding than males did. Male-to-female aggression was the most common agonistic interaction, and same-sex aggressions were almost absent. We found no significant differences in rates of grooming or embracing between the different types of dyads. The resemblance of our results to those of similar studies in less disturbed habitats suggests that spider monkeys might adapt to certain levels of ecological and social disturbance, at least initially, and are a starting point to understand better the initial effects of fragmentation on the behavioral repertoire of these primates.