Dissertation: The Impact of Hunting by Chimpanzees (Pan troglodytes) on Demography and Behavior of Red Colobus Monkeys (Procolobus badius) in the Kibale National Park, Uganda.

Yale University, New Haven CT

Investigators

Abstract

Predation strongly affects primate social evolution, and chimpanzees and red colobus monkeys have a particularly intriguing predator-prey relationship. Chimpanzees regularly prey on various mammals, but red colobus are their preferred prey wherever these two species co-occur. There are extensive data on hunting frequency and prey offtake for several sites, but few on the impact of predation on red colobus social structure and population density and on their responses to chimpanzees. This research will provide data on red colobus behavioral ecology and the impact of chimpanzee predation on red colobus group size, group composition, and population density at Ngogo, Kibale National Park, Uganda. These data will address questions about primate social evolution, red colobus anti-predation strategies, and the sustainability of predation by chimpanzee. Ngogo has the largest known chimpanzee community; predation there is unusually intense and might have caused a long-term decline in the red colobus population, but demographic data are inadequate to be sure. Monthly censuses along four transects, conducted for 21 months, will provide data on population density and group size and composition. These data, plus previous census data and data on the chimpanzees, can assess the relationship of group size to predation pressure and whether the population has declined. Data on group composition will test hypotheses about anti-predation strategies (e.g., infant and juveniles survive better in groups with many adult males). Data on ecology will examine tradeoffs between foraging efficiency and protection (e.g., feeding competition increases with group size, but individuals are safer in larger groups). Experimental playbacks of chimpanzee vocalizations to red colobus, plus observations of responses to naturally occurring vocalizations and to chimpanzee proximity, will address hypotheses about anti-predation strategies. This research will improve our understanding of how predation influences primate behavior and of the implications of hunting by chimpanzees for human evolution.