The effect of inter-opponent distance on the occurrence of reconciliation in stumptail (Macaca arctoides) and rhesus macaques (Macaca mulatta)

Several studies have shown that affiliative contact between opponents increases after conflicts in a number of primate species. This study investigated the effect of inter-opponent distance on the occurrence of reconciliation in stumptail and rhesus macaques. Both species were represented by multi-male, multi-female groups housed in large outdoor compounds. Ten-minute focal animal observations during post-conflict (PC) and matched control (MC) samples were collected in which affiliative interactions and the inter-opponent distance at the beginning of each sample were recorded. A total of 251 and 541 PC-MG opponent pairs were obtained for stumptail and rhesus macaques, respectively. Inter-opponent distance was smaller in PC than in MC observations for both stumptail and rhesus macaques. Conciliatory tendency varied as a function of the initial PC-MG inter-opponent distance. In particular, the closer opponents were in PC compared to MC periods, the more likely they were to reconcile. When the inter-opponent distance was the same in PC and MC periods the conciliatory tendency of both species was notably reduced. These findings have implications for the estimation of conciliatory tendency and its use in comparative studies.