Doctoral Dissertation Research: Play Signaling and Play Behavior in Free-ranging Rhesus Monkeys on Cayo Santiago
Carol Berman Principal Investigator
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This project will investigate the possible use of play signals for reducing potential social risks of play in free-ranging rhesus monkeys on Cayo Santiago, Puerto Rico by (1) identifying play signals (i.e., gestures that precede and predict the occurrence of play behavior) in addition to the well known play face, (2) examining whether specific play signals transmit information about specific types of play and/or are used at different distances from the receiver, and (3) examining whether signal frequency and intensity varies with aspects of the social relationship between the partners that are related to the risk that play will result in a negative outcome (aggression, refusal or maternal intervention). <br/><br/>Social play, and particularly play fighting, poses an interesting question of how players know that their partner's intentions are playful rather than aggressive. One way for potential play partners to avoid confusion about playful intentions is through the use of play signals. However, the fact that many species have more than one play signal and that some play signals vary within species, raises an additional functional question. If the function of play signals is to merely communicate playful intent, why do animals need a variety of play signals? Could different play signals represent different types of play much like words represent different activities or ideas? Do monkeys signal more vigorously when proposing potentially more risky types of play? Some primate species, including rhesus macaques, have exhibited evidence that young animals regulate their play behavior to avoid physical or social risk by self-handicapping and by refusing high intensity play. Both self-handicapping and play refusal imply knowledge about the risks of high intensity social play. In this study, the applicant will examine the extents to which rhesus monkeys understand the social risks of play and use signals flexibly in a manner that reduces risk. Play with opposite sex, unrelated and younger partners (particularly when their mothers are present) is more likely to have a negative outcome than play with same sex, related peers. Thus this study will test the prediction that variation in signaling frequency and intensity is associated with partner age, sex, relatedness and/or the presence of mothers. <br/><br/>The intellectual merits of this project involve increasing our understanding aspects of primate social cognition, including representational signaling, intentionality, knowledge about social risk and the use of foresight to avoid risk. The function of gestural signals, particularly play signals, has rarely been studied within the context of a naturally-organized social group. As such, it will contribute to our understanding of the evolution of social cognition. It will also provide critical data and hypotheses for experimentalists pursuing future research on this topic. <br/><br/>The broader impacts of this project involve the enhancement of the research on Cayo Santiago, the expansion of the use of post-conflict/matched control methodology to social communication, and the dissemination of findings to the public, zoo staff, and university students interested in evolutionary and cognitive ecology. It will also form the basis of a Ph.D. dissertation and provide opportunities for research participation for two local undergraduate students.