Behavioral diversity and agonism are higher in larger groups among wild Costa Rican capuchins

Abstract Biologists have long been interested in the causes, costs, and benefits of group living. Within species, group sizes vary and affect the behavior of group members. Yet, few studies have investigated how behavioral diversity—defined here as the number of distinct behaviors occurring in a given time period—and frequency of agonistic behaviors relate to group size. Here, we test the predictions of the Resource Distribution Hypothesis. To do so, we analyzed >65,000 behavioral scans collected over 15 yr in Sector Santa Rosa, Costa Rica, on 214 white-faced capuchins inhabiting eight social groups. We found that cross-sectional behavioral richness and diversity was higher in larger groups than in smaller groups and that individuals in larger groups exhibited significantly higher behavioral richness and diversity across the day (longitudinally). We also found that agonism frequency at the group level was higher in larger groups, suggesting increased competition. Understanding these relationships provides insight into group dynamics, patterns of interindividual competition, and potential constraints on group size.