Post-conflict reunions and reconciliation in long-tailed macaques

Abstract

In gregarious species, friendly post-conflict reunions between former opponents have been interpreted as ‘reconciliatory’ interactions whose function is to repair social relationships that were disrupted by aggression. An experiment on 10 pairs of captive long-tailed macaques, Macaca fascicularis, demonstrated the validity of this interpretation. Prior aggression reduced the ability of opponents jointly to exploit a resource relative to baseline, whereas friendly reunion after conflict restored this ability to baseline levels. Reconciliation appeared to work both by reducing the dominant opponent's aggressive motivation, and by reducing the subordinate's fear. The results support the hypothesis that friendly reunions are part of a homeostatic behavioural mechanism that maintains group integrity despite inevitable conflicts of interest between group members.