Sex and group differences in feeding on animals by wild chimpanzees in the Mahale Mountains National Park,Tanzania

Sex differences in animal prey intake were revealed by fecal analysis among wild chimpanzees of the large-sized M-group (ca. 100 members) in the Mahale Mountains National Park, Tanzania: prime adult or old males feed more on vertebrates, while adult females more onCamponotus ants. By contrast, such differences were not obvious in the neighboring, small-sized K-group (ca. 20–30 members), despite the similar environment in which the two unit-groups lived. Such sex and group differences may be explained in terms of various factors, either ecological or social, or both, but social factors seem most responsible in particular for the group differences. It seems likely that increased capture rate of vertebrates per unit-group in the larger-sized M-group results in increased per capita intake of meat among prime adult or old males. Also, the more frequent interactions among prime adult or old males of M-group appear to reduce the frequency of theirCamponotus ant-fishing behavior.