Integrating information about location and value of resources by white-faced saki monkeys (Pithecia pithecia)

Abstract Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezu-ela during a period of fruit abundance. The sakis ’ move-ments were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the pre-dicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were signiWcantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis ’ preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled eYciently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with ‘what ’ and ‘where ’ information gained from individual visits to resources. Although the sakis ’ foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intra-group feeding competition, maintain intergroup domi-nance over important resources, and monitor the state of resources throughout their home range. The sakis’ foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutri-tional considerations