Do Monkeys Avoid Areas of Home Range Overlap Because They Are Dangerous? : A Test of the Risk Hypothesis in White-Faced Capuchin Monkeys (Cebus capucinus)

Abstract

In social animals, areas where the home ranges of neighboring groups overlap are often underused. The Risk Hypothesis posits that the costs of intergroup conflict create a “landscape of fear,” discouraging the use of such shared areas. To test this hypothesis, we observed the behavior of white-faced capuchins (Cebus capucinus) in central vs. peripheral areas of their home ranges. If capuchins perceive areas of home range overlap as “risky,” we predicted they would change activity budgets, vocalization rates, and foraging behavior in these areas. A spatially explicit behavioral comparison based on nearly 100 h of focal follows revealed that capuchins socialize less in the periphery (vs. the center) of their home range. Time spent resting, foraging, and engaging in vigilance, as well as vocalization rates, varied in consistent ways across all four study groups, but these differences did not reach statistical significance. Fruit trees near range borders (vs. the center) contained more ripe fruit, and groups spent more time in these trees, with more individuals entering to feed and consuming more fruits. However, capuchins did not alter their foraging behavior in potentially risky peripheral areas in a manner consistent with predictions of optimal foraging theory: intake rates at patch departure were not significantly lower and groups depleted trees to a greater extent along the periphery vs. in the center of their range. These results suggest that while peripheral areas are perceived as risky and this “landscape of fear” contributes to behavioral changes, they also provide resources whose value may outweigh the cost of intergroup encounters.