Multilevel analysis of the foraging decisions of western chimpanzees (Pan troglodytes verus) and resource scarcity in a savanna environment at Fongoli, Senegal

Abstract

Savannas are the hottest, driest, and most open environments occupied by wild chimpanzees (Pan troglodytes). Chimpanzee subsistence strategies are poorly understood in these habitats and, thus, current knowledge primarily resides within the theoretical domain. To address this gap, we empirically test food and habitat selection hypotheses by examining the foraging decisions of chimpanzees in a savanna mosaic environment at Fongoli, Senegal. The foraging behavior of Fongoli chimpanzees was examined in relation to the macronutrient composition of their foods. As predicted under an energy maximizing strategy, individuals often selected foods that were energy-rich and easy to consume. However, this strategy was a poor predictor for some important foods. Fongoli chimpanzees may select lower quality foods at times to minimize risk of heat stress. At the level of habitat selection, this study asked how the foraging behavior of adult male Fongoli chimpanzees changed with predation risk. We tested for this sensitivity by measuring food intake among relatively risky and safe habitats. Elevated risk of predation did not fully deter adult males from feeding in these habitats, but during such visits they ingested more ripe fruit, an energy-rich food. The third level of analysis addresses landscapes-scale habitat selection processes. Our analysis merges findings on Fongoli chimpanzee food and habitat selection with information on the species’ distribution and remotely-sensed land cover to evaluate relationships between landscapes and the species’ range. We show that accessibility to drinking water sources, anthropogenic habitat disturbance, and habitat physiognomy are associated with the species’ distribution in southeastern Senegal. This study highlights the importance of concurrently examining chimpanzee foraging behavior at several levels to understand interconnected factors that shape their subsistence strategies.