Abstract

A key aspect of cooperation is the choice of partners with whom to cooperate, as this determines if an individual can establish a successful cooperative interaction and reduce the chances to be exploited. In most of the experiments on cooperation conducted so far, subjects had no opportunity to choose their cooperative partner, or the choice was reduced between two individuals. Non-human primates, however, live in complex social groups and can choose their social partner among several individuals. We presented a cooperative apparatus to a wild provisioned group of Barbary macaques, leaving them the choice to interact or not with the apparatus, and with any of their group companions. We used the same experiment used in captive studies on cooperation (Crawford, 1937), requiring two monkeys to pull a rope simultaneously in order to both get rewards. We found mixed evidence of cooperation in our study group and we discuss here the methodological and theoretical difficulties of running experiments with free-ranging animals.