Do Responses of Wild Macaca nigra to Crop Defense Resemble Responses to Predators?

Although conservation-minded researchers advocate that growers use a variety of methods to defend crops from wildlife, we know little about the effects of such methods on the targeted species. We assessed effects of nonlethal crop defense (CD) methods used in Tangkoko Reserve, Sulawesi, Indonesia, on potentially stress-related behavior of Critically Endangered (CR) wild, crested macaques (Macaca nigra). We examined responses of three groups exposed to different amounts of CD, both immediately after being targeted and when only exposed to cues of targeting elsewhere in the forest. We analyzed 630 h of data from 33 adults of both sexes by using Generalized Linear Mixed Models. When not targeted, all groups and both sexes displayed fewer self-directed behaviors, males showed fewer affiliative behaviors, and two groups decreased aggression in months with more CD. When we compared behavior immediately after targeting with behavior unassociated with targeting, males in the most frequently targeted group showed increased aggression, whereas both sexes in the moderately frequently targeted group showed increased self-directed behaviors. We suggest that when not targeted, groups show a degree of behavioral inhibition during months in which CD targeting is relatively frequent. When targeted, the two regularly targeted groups displayed behavior consistent with increased stress. However, the groups appeared to respond in qualitatively different ways. We tentatively suggest that the macaques’ behavioral responses to CD (inhibition in low-risk conditions and signs of stress and/or motivational conflict in moderate-risk conditions) resemble typical responses of primates to perceived predators posing varying degrees of risk.