Temporal cognition in Taï chimpanzees

Despite appealing support for theories that argue that social complexity is the main force driving primate brain-size evolution, it is still unclear how great apes were able to afford the evolution of larger and more expensive brains than sympatric species. Comparative phylogenetic studies suggest that the costs of evolutionary brain enlargement were overcome by a permanent increase in net energy intake, renewing interest in the role of ecological complexity in primate brain-size evolution. As relatively larger-brained primates, like chimpanzees, show less seasonality in their net energy intake than smaller-brained species, larger brains are proposed to provide a ‘cognitive behavioural flexibility’ that facilitates the consumption of nutritious foods during periods of food scarcity (cognitive buffer hypothesis). To date, it remains unclear what this cognitive flexibility entails. In this chapter, I will provide evidence for a variety of mechanisms of temporal cognition that chimpanzees employ to gain first access to newly ripened, energy-rich fruit in a competitive and complex rainforest environment.