Abstract # 2108 Event # 164:

Scheduled for Saturday, June 23, 2007 08:30 AM-08:45 AM: Session 15 (North Main Hall E) Oral Presentation

Food Depletion Time Predicts Contest Competition and Punishment in Captive Rhesus Macaques (Macaca mulatta)

R. L. Chancellor and L. A. Isbell
University of California, Davis, Department of Anthropology, Davis, CA 95616, USA
     Current ecological models agree that clumped food resources elicit aggressive competition, yet they disagree about what constitutes clumped resources. We conducted an experiment on 15 multimale-multifemale groups (range: 50-110) of captive rhesus macaques (Macaca mulatta) at the California National Primate Research Center in which we varied both food depletion time (temporal clumping) and interfood distance (spatial clumping) independently to test which factor more significantly influenced two forms of aggression, contest competition and punishment. At interfood distances of 1-6 m, two same-sized apple pieces ranging from 1-30 g, were offered to the monkeys simultaneously during each of 297 trials. Aggression was recorded five minutes before the arrival of the food, when the food arrived, and five minutes after. Data were pooled after testing for cage effects. For 24 combinations of food size/interfood distance, we conducted multiple regression tests on the mean scores of aggression. Results of the independent effects of food size (a proxy for food depletion time) revealed that food size significantly predicted both contest competition and punishment respectively [F(1,22)=12.02, p=0.002; F(1,22)=7.71, p=0.01]. Interfood distance did not significantly predict either contest competition or punishment [p>0.05]. These results suggest that short-term temporal distribution of food may be a better predictor of within-group aggression than its spatial distribution.