The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Rhesus macaques (Macaca mulatta) use snake postures to identify intensity of threat

STEPHANIE F. ETTING1,2 and LYNNE A. ISBELL1,3.

1Anthropology, University of California, Davis, 2Anthropology, University of California, Berkeley, 3Animal Behavior Graduate Group, University of California, Davis

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When predators are detected, prey must make decisions about how to respond. The decision on which strategy to adopt is based on a cost-benefit analysis of risk level. The Threat-sensitivity hypothesis predicts that prey should match their response to their predation risk, with high-risk predator encounters eliciting stronger evasive responses than low-risk encounters. Primates are known to vary in their responses toward different types of snakes or snakes in different contexts. We asked if primates are sensitive specifically to different threat levels presented by snakes as revealed by the snake’s posture. In a series of experiments, we presented snake models in different postures to captive rhesus macaques (Macaca mulatta) at the California National Primate Research Center. We found that rhesus macaques respond more strongly to snake models in striking pose relative to a coiled posture, and more to a coiled posture than to an extended traveling snake. Thus, macaques perceived intensities of threat that parallel our own perception of intensities of threat from snakes. Additionally, a partially covered snake evoked a response comparable to that of the striking snake, suggesting that when conditions limit opportunities for complete risk evaluation, primates respond as if they are under high risk.

Research funded by the Department of Anthropology, University of California, Davis, CA, 95616

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