Male-Directed Object Use by Proceptive Female Bearded Capuchin Monkeys (Sapajus libidinosus) in Captivity

Abstract

Some nonhuman primates use tools to modify the behavior of other animals in social contexts. For example, during their proceptive periods, female bearded capuchins (Sapajus libidinosus) in two wild groups throw stones and push branches toward males, which may function to draw male attention to the females. To further clarify the social and communicative relevance of this behavior, we recorded all occurrences of object use in a captive group (one adult male and four females) at Brasília Zoo, during 963 h of observation. Additionally, we recorded the occurrence of typical proceptive behaviors and quantified behavioral changes of the male associated with throwing behavior. All females threw objects, such as stones and sticks, at the male (N = 205 events). One of the females also pounded objects near the male (N = 72). The two forms of object use were associated with female proceptivity. Male-directed throws increased the chances of the male changing his behavior, particularly by shifting his attention to the thrower, supporting the hypothesis that throwing at the male function as a communicative act. However, females also used aimed throwing in affiliative contexts (N = 2) and interactions with humans (N = 102) and other animals (N = 61). Thus, our results show that aimed throwing is a flexible behavior, elicited in multiple social contexts and for different purposes. Moreover, our study demonstrates that considering the effects of object use on the behavior of potential targets can help us to understand how primates use objects to mediate communication.