ABSTRACT Progressive urbanization has led to increased human–primate interactions, often resulting in aggression, especially when humans offer food. In Brasília National Park, the local capuchin monkeys are known for their intense interactions with the visitors at the Pedreira Pool. In this context, this study investigated factors predicting aggressive behavior between capuchins and humans. The sampling was conducted over a one-year period, and behaviors were recorded using “all events” sampling. Two binary logistic regression models were applied to predict when the monkeys and humans were most likely to be aggressive. A total of 722 encounters between capuchins and humans were observed during this study, totaling 616.5 hours of monitoring. Of these, 364 occurred during the dry season and 358 during the rainy season The monkeys were more aggressive toward the humans during the dry season, when the humans were either being aggressive toward the capuchins or photographing them, when food was involved, and when fewer humans were involved in the interaction. The humans were more aggressive toward the capuchins when the capuchins stole food or were being aggressive and when more children were present. Aggressive behavior in the capuchins was caused primarily by disputes over food and was exacerbated by aggressive human behavior toward the capuchins and attempts to photograph them. While offering food may reduce agonism in the short term, it may have contributed to a long-term increase in aggressive behavior by attracting the monkeys into more frequent contact with human visitors. The number of humans in close proximity during an encounter was a predictor of aggressive behavior in the capuchins toward the humans, which indicates that the monkeys assess the costs and benefits of approaching humans. Park administrators should prevent, or at least reduce, the entry of food into the park.
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