Social rank and responses to feeding competition in rhesus monkeys

A group of rhesus monkeys (Macaca mulatta) living in a large enclosure received food which varied in desirability and spatial distribution. Feeding and agonistic behaviour of four hierarchical subgroups were analyzed. In general, there was less aggression and improved feeding rates with dispersed food than with piled food. The behaviour of high-ranking subjects was the most stable: they usually ate first, ate most, and showed little agonistic behaviour. The most subordinate subjects were also involved in few agonistic episodes, since they tended to remain on the periphery and eat little. However, subordinates obtained access earlier to a pile of the most highly prized food (banana pieces) than to piles of less attractive foods. Subordinates also obtained their highest feeding score when banana pieces were dispersed. This latter condition was associated with increased aggression. The feeding behaviour of intermediate-ranking subjects lay between that of dominants and subordinates, and the former were involved in more aggression. Behaviour in situations involving restricted food reflects cognitive processes in which several factors including attractiveness of the food, social status, and risks involved are evaluated.