Female chacma baboons form strong, equitable, and enduring social bonds

Analyses of the pattern of associations, social interactions, coalitions, and aggression among chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana over a 16-year period indicate that adult females form close, equitable, supportive, and enduring social relationships. They show strong and stable preferences for close kin, particularly their own mothers and daughters. Females also form strong attachments to unrelated females who are close to their own age and who are likely to be paternal half-sisters. Although absolute rates of aggression among kin are as high as rates of aggression among nonkin, females are more tolerant of close relatives than they are of others with whom they have comparable amounts of contact. These findings complement previous work which indicates that the strength of social bonds enhances the fitness of females in this population and support findings about the structure and function of social bonds in other primate groups

Triadic awareness predicts partner choice in male–infant–male interactions in Barbary macaques

Social knowledge beyond one’s direct relationships is a key to successful maneuvering of the social world. Individuals gather information on the quality of social relationships between their group companions, which has been termed triadic awareness. Evidence of the use of triadic awareness in natural contexts is limited mainly to conflict management. Here we investigated triadic awareness in wild Barbary macaques (Macaca sylvanus) in the context of bridging interactions defined as male-infant-male interactions whereby a male (actor) presents an infant to another male (receiver) in order to initiate an affiliative interaction with that male. Analyses based on 1,263 hours of focal observations on ten infants of one wild social group in Morocco supported the hypothesis that males use their knowledge of the relationship between infants and other adult males when choosing a male as a partner for bridging interactions. Specifically, (i) the number of bridging interactions among initiator-infant-receiver triads was affected by the strength of the infant-receiver relationship and (ii) when two males were available as bridging partners, a male was more likely to be chosen as the receiver the stronger his social relationship with the infant in comparison to the other available male was. This demonstrates that non-human primates establish triadic awareness also of temporarily rather dynamic infant-male relationships and use it in naturally occurring affiliative context. Our results contribute to the discussion about the mechanism underlying the acquisition of triadic awareness and the benefits of its usage and lend support to hypotheses linking social complexity to the evolution of complex cognition

The Function of Mounts in Free-Ranging Barbary Macaques (Macaca sylvanus)

Generally, non-reproductive sex is thought to act as “social grease”, facilitating peaceful co-existence between subjects who lack close genetic ties. However, specifc non-reproductive sexual behaviors may fulfill different functions. With this study, we aimed to test whether non-reproductive mounts in Barbary macaques are used to: (i) assert dominance, (ii) reinforce social relationships, and/or (iii) solve conflicts. We analyzed non-reproductive mounts (N = 236) and post-mount behavior in both aggressive and non-aggressive contexts, in 118 individuals belonging to two semi free-ranging groups at La Montagne des Singes (France). As predicted by the dominance assertion hypothesis, the probability to be the mounter increased with rank difference, especially in aggressive contexts (increasing from 0.066 to 0.797 in non-aggressive contexts, and from 0.011 to 0.969 in aggressive contexts, when the rank difference was minimal vs. maximal). The strength of the social bond did not significantly predict the proportion of mounts across dyads in non-aggressive contexts, providing no support for the relationship reinforcement hypothesis. Finally, in support of the conflict resolution hypothesis, when individuals engaged in post-conflict mounts, (i) the probability of being involved in further aggression decreased from 0.825 to 0.517, while (ii) the probability of being involved in grooming interactions with each other increased from 0.119 to 0.606. The strength of the social bond between former opponents had no significant effect on grooming occurrence and agonistic behavior after post-conflict-mounts. Overall, our findings suggest that non-reproductive mounts in Barbary macaques have different functions that are not affected by the strength of the social bond