Travel routes and planning of visits to out-of-sight resources in wild chacma baboons, Papio ursinus

Abstract

The ability of animals to plan their foraging journeys and to approach resources in a goal-directed way may play a key role in cognitive evolution. Furthermore, optimal foraging theory assumes that animals are adapted to take least-effort routes between resources. Empirical evidence for these beliefs is largely lacking, however. We followed a group of chacma baboons over full days during a 16-month field study. We used GPS to investigate route linearity, travel speed and inter-resource distances, and the degree to which movement was guided by direct visual stimuli from the resources. During the dry season the study group travelled rapidly to sparse fruit sources and waterholes along linear paths over large distances. Inter-resource distances were larger than distances from which the resources could be seen. Seed resources, although situated closer to the sleeping site than fruit sources, were bypassed in the mornings and consumed predominantly in the afternoons, when movements were less linear, slower and shorter. During the rainy season, the animals left their sleeping sites earlier when visiting restricted and patchily distributed fig trees than when visiting abundant and evenly distributed fruit resources. However, travel speed and route linearity were not always associated with goal directedness, because the baboons approached the single sleeping site, presumably a vital resource, slowly and indirectly. Our results suggest that baboons plan their journeys, actively choosing between several out-of-sight resources and approaching them in an efficient, goal-directed way, characteristics commonly used as diagnostic for the presence of a cognitive map and episodic memory.