Kin-oriented redirection among Japanese macaques: an expression of a revenge system?

Abstract

The ability to recognize the close associates of other group members may permit the display of redirected aggression against the relatives of the former aggressor. However, the dominance structure and the kin-based alliance system of macaque society are expected not to favour the occurrence of this kin-oriented redirection. Nevertheless, within 1 h of being the victim of an attack, Japanese macaques, Macaca fuscata, were more likely to attack the former aggressor's kin than without such a conflict. The conditions under which the victim redirected against the former aggressor's kin were investigated. This kin-oriented redirection did not occur preferentially either after conflicts between individuals with unstable and/or uncertain dominance relationships or after conflicts with individuals that were unlikely to intervene in favour of their kin. Victims redirected against individuals that were younger than the former aggressor and often subordinate to the victim. They also redirected in an opportunistic way by joining polyadic interactions against the former aggressor's kin. The possibility that this kin-oriented redirection may have a long-term function in changing the aggressive attitude of the aggressor towards the victim is also discussed. In addition, the victim's kin also displayed a form of kin-oriented redirection. They were more likely to attack the kin of an individual after it had attacked their own kin.