The curious case of rhesus macaques: despotism does not prevent third-party postconflict affiliation

Abstract

The ability to manage aggression in social animals is crucial for maintaining stable group dynamics. Triadic postconflict contacts (TC) are widespread behavioural strategies across mammal species consisting of affiliative contacts provided spontaneously by a third party or bystander towards the victim or the aggressor of a previous conflict (unsolicited triadic contacts, UTC) or upon request by one of them (solicited, STC). Depending on the target, the social context and the relationship quality shared by the interacting agents, TC's functions can range from bystander self-protection to victim comfort with the ultimate outcome of maintaining group cohesion. Evidence suggests that TCs are strongly affected by social styles, with despotic species engaging less frequently in such behaviours. Here, we tested hypotheses on the presence, modulation and possible functions of UTC and STC in a group of rhesus macaques, Macaca mulatta, a highly despotic species. For the first time, we found that bystanders spontaneously provided affiliation to both victims and aggressors. In contrast, we did not find any significant evidence for STC. Macaques seem to be sensitive to potential risks implied in providing postconflict affiliation to victims and aggressors (e.g. age, arousal). To some extent, UTC decreased the probability of bystanders being the target of redirection. UTC coincides with consolation when bystanders direct affiliation mainly towards ‘friend’ victims, when they perceive the negative affective state of the victim (measured by screaming), and when affiliation reduces the victim's distress (measured by self-scratching). Our data support the first two criteria but not the last one. Bystanders' spontaneous motivation to offer affiliation to victims of aggression in M. mulatta goes beyond the social constraints associated with the species' despotic style suggesting that several factors can affect the emergence of prosocial behaviours also in despotic-intolerant species.