Talking more and fighting less? Conflict management through acoustic signals in a cooperatively breeding species

In the absence of conflict management, competition for limited resources can lead to heightened aggression and can negatively affect fitness. However, acoustic signals may serve as a management mechanism to deescalate such events. In this study, the functional significance of submissive cries and chatters as conflict escalation-avoidance behaviours in four wild groups of cooperatively breeding common marmosets, Callithrix jacchus , was investigated. By experimentally manipulating food availability and distribution, the four groups were exposed to contrasting competitive scenarios. Both calls were uttered unidirectionally between marmoset dyads to indicate dominance (chatter) or subordination (submissive cry). They were frequent during more (71%) and less (29%) competitive scenarios and were associated with reduced physical aggression. Despite increased aggression in the more competitive trials when only one out of four experimental feeding sites contained a food reward, high-intensity, physical aggression remained infrequent. Although chattering individuals had more access to food, this was not observed when the individuals uttered submissive cries. Under limited food availability, a group’s single breeding female chattered more often and used submissive cries less often than expected, while nonbreeding adult females showed the opposite pattern. Males uttered both call types less often than expected given their co-feeding opportunities. These findings are consistent with the social and breeding systems of common marmosets, in which female reproductive competition is high, leading females to vocalize more frequently during feeding-related interactions, while males invest heavily in cooperative infant care and vocalize less frequently. Results indicate that marmoset vocal signals can mediate foraging/feeding-related aggression effectively under limited resources, thereby supporting their role as escalation-avoidance behaviours in managing social conflict. By reducing the frequency of aggressive contests over food, these signals lower the risk of injury and destabilization of marmoset social relationships.