Ecology and nesting patterns of chimpanzees (Pan troglodytes) in Issa, Ugalla, western Tanzania

This thesis reports on a twenty month study of chimpanzees in the Ugalla region, the first long term study of this population. Very little research has been conducted on chimpanzees living in savannas and Ugalla is one of the driest habitats were chimpanzees are found.;Because of the large size of the region (>3,300 km2) I selected an area of 48km2 for the study. The chimpanzees were neither habituated nor provisioned. Thus, the methods I used were ecological and ethno-archaeological. However, behavioral data were collected ad libitum when the apes were observed.;I describe the ecology of the study area with emphasis on the climate and vegetation. I conducted a phenological study and found that the high seasonality of the habitat affected the availability of chimpanzee plant foods. For example, fruit was available in the forest during the rainy season but not during the dry season. In contrast, fruit was available in woodland throughout the year, although estimated relative abundance was higher during the rainy season than during the dry season within this vegetation type. It was found that seventy five percent of the number of species confirmed to be eaten by the chimpanzees came from woodland.;I obtained detailed quantified data on the physical characteristics of nests and nesting trees. I compared physical characteristics of trees selected for nesting versus other suitable trees that were not used for nesting to infer patterns of selectivity by the chimpanzees. Statistically significant differences of the physical characteristics investigated were found between trees used and not used for nesting within a nesting site, and between trees of nesting sites and trees of nearby places not used for nesting. Data indicate that chimpanzees extensively used the woodland for feeding and for nesting. Comparisons are made with those savanna study sites for which data are available. Finally, implications for early hominin behavioral ecology are given.