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


Catalytic cooperators: individual effects on hunting and patrolling among male chimpanzees

IAN C. GILBY1 and MICHAEL L. WILSON2,3.

1Department of Evolutionary Anthropology, Duke University, 2Department of Ecology, Evolution and Behavior, University of Minnesota, 3Department of Anthropology, University of Minnesota

Thursday 4:15-4:30, Galleria South Add to calendar

For chimpanzees, both group-level hunts of monkeys and territory defense appear to present a collective action problem. In both cases, cheaters (non-participants) may experience the benefits of success without paying the costs of joining the collective effort. Previous work at Kanyawara (Kibale National Park, Uganda) has shown that two particular males have a catalytic effect on group hunts. Here, using 32 years of long-term data, we show that the same phenomenon exists among male chimpanzees of the Kasekela community in Gombe National Park, Tanzania. Upon encountering potential prey (red colobus monkeys), a hunt was significantly more likely to occur if at least one of two ‘impact’ males was present in the chimpanzee party. This effect remained after statistically controlling for party size and the presence of sexually receptive females (χ2 = 7.17, p = 0.007). We also report a significant temporal correlation between rates of hunting and border patrols (r = 0.27, p<0.0001), which suggests that similar phenomena may affect both forms of collective action. We test this prediction by asking a) whether certain males are more likely to participate in patrols, and b) if these are the same males that catalyze hunting behavior. The results of this study have important implications for our understanding of the dynamics of cooperation in humans’ closest living relative.

This study was funded by the National Science Foundation (DBS-9021946, SBR-9319909, BCS-0452315, LTREB-1052693), the National Institutes of Health (R01 AI50529, R01 AI58715, P30 AI 27767), The Jane Goodall Institute and Duke University.

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