Influence of Seasonality on Activity Patterns, Feeding Behavior, Ranging, and Grouping Patterns in Taï Chimpanzees

Lowland rain forest chimpanzees (Pan troglodytes verus) of the Taï National Park, Ivory Coast, responded to the minor dry season (July and August) of 1988 in a predictable manner by spending more time feeding, feeding more frequently on lower quality food items, reducing day range and party size, and spending more time solitarily and less time in mixed groups than during the rainy season. These behaviors are consistent with a response to scarce resources. My findings do not support Boesch's (1991, 1996) hypothesis of bisexually bonded chimpanzees. Females spent 45% of time alone and associated with males in mixed parties only 18% of their time. This major discrepancy in our results probably stems from differences in the time of year when our studies were conducted, the year in which my study was conducted (potentially scarcer resources than on average), and methodological differences: focal animal sampling of males and females equally. Although Boesch (1991, 1996) and Steiner (1996) have demonstrated that Taï parties are usually larger and more mixed, Taï chimpanzee social structure—party size and composition—during this study closely resembles that found at other study sites.