Simultaneous classification by rank and kinship in Japanese macaques

To assess evidence of the ability of Japanese macaques, Macaca fuscata, to recognize the rank and kin relationships of other individuals, we analysed the recruitment of allies in the context of agonistic confrontations. Both mature and immature macaques preferentially directed their recruitment attempts to individuals ranking higher than their opponent and to individuals that were not the kin of their opponent. They were also able to combine the two criteria. These results suggest that Japanese macaques can recognize third-party rank and kin relationships, and provide observational evidence supporting the notion that nonhuman primates can simultaneously use multiple criteria in classifying the social relationships between group companions.