The Socioecology of Chimpanzee Foraging and Food-associated Calling Behavior

Abstract

Social-living is complicated. Living in groups can provide greater protection from predators, promote discovery and defense of food sources and improve access to mates. On the other hand, it can increase susceptibility to predators or pathogens and incite competition for resources. Because of these trade-offs, social systems can display high levels of diversity, both on an evolutionary time-scale as well as in response to short-term variation in social and ecological pressures. In this dissertation I investigate the foraging and food-associated calling behavior of chimpanzees (Pan troglodytes) in order to better understand the causes and consequences of grouping behavior. Chimpanzee social groups display high levels of short-term variability in both size and composition. Furthermore, individuals produce specific vocalizations in foraging contexts that are believed to further modulate these parties. Thus, this system provides a prime opportunity to examine the costs and benefits of sociality and how individuals respond to these trade-offs. Using a combination of captive experiments and observational field studies, I examine chimpanzee foraging decisions, the trade-off between foraging and socialization and the social and ecological correlates of food-associated calling behavior. Results from these studies expand current understanding of the foraging and social behavior of chimpanzees and suggest an alternative function for their food-associated rough-grunt vocalization. Furthermore, they highlight the challenges and benefits of social-living and the tactics individuals can employ to manipulate their social landscape.