AN EXPERIMENTAL STUDY OF COLLECTIVE PERFORMANCE AT A FORAGING TASK IN TONKEAN MACAQUES

Abstract

The exchange of information regarding the environment is continuous within social groups of non-human primates. As an outcome, knowledge and decisions are socially distributed. However, we lack evidence regarding the processes through which collective achievements are produced. The study aimed to analyze group performance in Tonkean macaques (Macaca tonkeana) in an experimental foraging task. Eight young individuals were used as subjects. They were released in a 1-acre wooded area during 5-min tests either singly or in subgroups of two, three or four individuals. They had to discover a fruit, whole or in scattered portions. The fruit was to be found either alone or in company of a snake. Results showed that subgroups located baited spots generally sooner than single individuals. The number of spots visited until finding the incentives was weaker as the number of subjects increased. Snake presence could increase finding latency and induce more cohesion among individuals. The balance between competition and snake effects appeared to differ between sexes. Performances improved through conspecifics' visual monitoring, stating the role of information transmission in the foraging task. While subjects behaved selfishly and did not actively communicate, subgroups proved to be effective information units and everyone of their members obtained benefits from them. Cognitive performances occurred in situation, they should be assessed simultaneously at the individual and group levels.