, Volume 47, Issue 1, pp 6–13 | Cite as

Demographic influences on the behavior of chimpanzees

Original Article


Recent research has revealed substantial diversity in the behavior of wild chimpanzees. Understanding the sources of this variation has become a central focus of investigation. While genetic, ecological, and cultural factors are often invoked to explain behavioral variation in chimpanzees, the demographic context is sometimes overlooked as a contributing factor. Observations of chimpanzees at Ngogo, Kibale National Park, Uganda, reveal that the size and structure of the unit group or community can both facilitate and constrain the manifestation of behavior. With approximately 150 individuals, the Ngogo community is much larger than others that have been studied in the wild. We have taken advantage of the unusual demographic structure of this community to document new and intriguing patterns of chimpanzee behavior with respect to hunting, territoriality, and male social relationships. Chimpanzees at Ngogo hunt often and with a considerable degree of success. In addition, male chimpanzees there frequently patrol the boundary of their territory and engage in repeated bouts of lethal intergroup aggression. By forming two distinct subgroups, male chimpanzees at Ngogo also develop social bonds above the level of dyadic pairs. While the sheer number of chimpanzees contributes to differences in hunting, patrolling, mating, and subgrouping at Ngogo, the demographic situation may also constrain behavioral interactions. At Ngogo, male chimpanzees who are closely related genetically through the maternal line do not appear to affiliate or cooperate with each other. Demographic constraints may be responsible for this finding. In this paper, I use these examples to illustrate how the demographic context affects the possible range of behavioral options open to individuals and ultimately contributes to the explanation of behavioral diversity in chimpanzees.


Chimpanzee Pan troglodytes Behavior Demography 



Toshisada Nishida furnished me my first opportunity to study wild chimpanzees at Kasoje, and I am indebted to him for giving me that chance and for his subsequent support and encouragement. I am grateful to Juichi Yamagiwa for inviting me to participate in the COE Symposium honoring Toshi on the occasion of his retirement. My fieldwork at Ngogo has been sponsored by the Uganda Wildlife Authority, Uganda National Council for Science and Technology, and the Makerere University. I thank G. I. Basuta, J. Kasenene, and the staff of the Makerere University Biological Field Station for logistic support and three anonymous reviewers for their comments on the manuscript. None of the work that I have conducted at Ngogo would have been possible without the help of my friend and collaborator, David Watts. Our field research at Ngogo has been supported by grants from the Detroit Zoological Institute, L.S.B. Leakey Foundation, National Geographic Society, the NSF (SBR-9253590, BCS-0215622), University of Michigan, and Wenner-Gren Foundation to me and L.S.B. Leakey Foundation and National Geographic Society to David Watts.


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Copyright information

© Japan Monkey Centre and Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of AnthropologyUniversity of MichiganAnn ArborUSA

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