Recognizing and respecting claims over resources in free-ranging rhesus monkeys, Macaca mulatta

All socially living animals are confronted with the challenge of competing over limited resources. When resources are movable a relatively open empirical question concerns how potential competitors recognize that another individual has a claim on a resource and when such claims should be respected. Here we address these dual features of competition in free-ranging rhesus monkeys by creating a competitive foraging task involving two food options, and for each condition, manipulating different aspects of the competitor’s potential competitive advantage. Specifically, we focused on aspects of the competitor’s physical connection to the food, and his attentional state and proximity. Results show that if the competitor had a physical connection to the food, rhesus respected the competitor’s claim. Even when this connection had been temporarily relinquished, rhesus nevertheless respected the competitor’s claim so long as proximity and attention to the resource were maintained. If, however, the competitor maintained a physical connection to one food source, but attended away from the food, subjects no longer respected the competitive advantage. Lastly, if a physical connection was made to one food option, but the experimenter was proximate to the other option, subjects were at chance in their choice, suggesting that proximity and physical connection represent conflicting competitive cues. These results reveal that rhesus monkeys use a variety of cues when recognizing and respecting competitive advantages. We discuss these results in relation to recent research on the evolution and ontogeny of our concepts of property and ownership.