Monkeys don't go for easy pickings

July 17, 2007

Animals' natural foraging decisions give an insight into their cognitive abilities, and primates do not automatically choose the easy option. Instead, they appear to decide where to feed based on the quality of the resources available and the effect on their social group, rather than simply selecting the nearest food available.

These findings by Elena Cunningham and Charles Janson, respectively from the New York University College of Dentistry and the State University of New York, have just been published in a special issue of the journal Animal Cognition. The articles in the issue look at the interaction of social and ecological factors and their influence on the evolution of primate intelligence.

The authors investigated whether a group of six white-faced saki monkeys, living on an island in Venezuela, used memory to travel to select feeding resources during a period of fruit abundance. The study looked at the resources available to the sakis and compared the observed distances traveled with predicted distances, using a combination of statistical analyses and computer models.

The monkeys’ daily foraging pattern consisted of frequent short feeding bouts and a few long feeding bouts. Surprisingly, the sakis traveled four times further than the predicted distances, suggesting that the sakis were extremely selective about the food they ate. The sakis preferred trees with abundant fruit and trees with water holes. When fruiting trees were abundant, the sakis traveled efficiently to the trees with the most fruit, ignoring closer, less productive ones.

Although the sakis took more risks by traveling further – by expending more energy and exposing themselves to predators for longer periods – choosing more fruit-rich sites allowed the group to limit feeding competition amongst themselves and to stick together to maintain intergroup dominance.

The authors conclude that primates’ travel decisions to feed take into account more than distance. Elena Cunningham commented, "They may also be based on value judgements of resource sites that take into consideration social as well as dietary needs and preferences. The monkeys’ foraging decisions may help to keep the group together."

Source: Springer