Spatial memory during foraging in prosimian primates: Propithecus edwardsi and Eulemur fulvus rufus.

A variety of anthropoids travel efficiently from one food source to another, although there is disagreement over how this is accomplished over large-scale space. Mental maps, for example, require that animals internally represent space, geometrically locate landmarks, use true distance and direction, and generate novel shortcuts to resources. Alternately, topological or route-based maps are based on a network of fixed points, landmarks and routes so that one food patch can be linked with another. In this study we describe travel patterns between food sources for two prosimian species found in southeastern Madagascar, Propithecus edwardsi and Eulemur fulvus rufus. Both species are dependent on fruit and have large home range sizes. By comparing interpatch distances, patch size and turning angles, we found that both species prefer nearest neighbor food patches and P. edwardsi travels in relatively straight lines. The amount of backtracking seen in E. f. rufus may be linked to their large group size and dependence on large-crowned fruit trees. We suggest that the goal-oriented foraging of both prosimian species is dependent on a topological or route-based map. These are rare behavioral data relevant to ecological and social contexts of primate cognitive evolution.