The Function and Determinants of Reconciliation in Pan troglodytes

Reconciliation (the postconflict affiliative reunion between former opponents) may mitigate costs of aggressive conflict by repairing the opponents' relationship and reducing stress. We showed that postconflict levels of self-directed behavior were lower after reconciliation than when reconciliation did not occur in chimpanzees (Pan troglodytes) at Chester Zoo, providing support for a stress-alleviating function for reconciliation. Further, we investigated the effects of multiple factors on the occurrence of reconciliation using generalized linear mixed models. We performed 2 separate analyses, a traditional analysis and a targeted analysis. The former included variables previously used to assess the occurrence of reconciliation in primates, i.e., conflict characteristics, sex combination, and a simple measure of relationship value. The latter included species-specific variables such as the occurrence of consolation ( postconflict affiliation from a bystander to the recipient of aggression); initiation of the conflict with a bluff display; and measures of relationship value, compatibility, and security specific to the study group. Whereas the traditional analysis showed that female-female dyads and valuable partners were most likely to reconcile, the targeted analysis showed that reconciliation was less likely to occur when consolation took place or when aggression was initiated with bluff displays. Further analyses revealed that the effect of sex-combination on reconciliation was due to its intercorrelation with bluff display. This study highlights the importance of considering variables specific to the study species and group when investigating the determinants of reconciliation and warns against premature interpretation of results without due consideration for all other possible determinants.