1Department of Human Evolutionary Biology, Harvard University, 2Department of Anthropology, University of New Mexico, 3Kibale Chimpanzee Project, Kibale National Park, Uganda, 4Department of Anthropology, Bates University
Thursday 1:00-1:15, Ballroom B
Chimpanzee males are well known for their aggressive behaviors and in all study communities, males are consistently more aggressive than females. Differences also exist between individuals within each sex but there is little known about what shapes the development of these differences. We examined the extent to which sex and individual differences in aggressive play behavior are the result of exposure to aggression and/or innate predisposition. We used four years of behavioral data behavior from 2006-2009 from 28 non-adult individuals from the Kanyawara community of chimpanzees in Kibale National Park, Uganda. This included data from over 15,000 play bouts. We tested the hypotheses that (1) males are exposed to more aggression before adulthood than females, (2) males exhibit more rough-and-tumble play behavior than females and (3) individual variation in the amount of aggressive play is affected by the amount of exposure to aggression. We found no sex difference in the amount of exposure to aggression among our non-adult individuals, but young male chimpanzees did engage in aggressive play behavior significantly more than young females. We also found a positive correlation between exposure to aggression and the probability that subsequent play on the same day would be aggressive. Our results indicate that sex differences in aggression in chimpanzees may occur early in life and manifest themselves through differences in the frequency of rough-and-tumble play. We also suggest that individual differences in aggressive play may in part be mediated by differences in exposure to aggression.
Funding provided by Harvard University, Wenner Gren Hunt Fellowship (ZPM), and National Science Foundation grant 0849380 (RWW & ZPM).