We studied post-aggression mechanisms in a captive group of western gorillas (Apenheul Primate Park, The Netherlands) and compared them with those of wild mountain gorillas (Gorilla beringei). We found the same trend for reconciliation that wild mountain gorillas show: reconciliation occurred only between adult male-female dyads, while it was absent in the other sexage class combination. There were both solicited and nonsolicited contacts; the latter finding is in contrast with the result obtained in wild mountain gorillas, in which consolation was absent. Immature females were more likely to offer consolation toward both related and unrelated individuals. Consolation did not reduce the likelihood of further attacks among group members. It may be that, as the α-male plays a fundamental role in preventing the spread of conflicts throughout the entire group, triadic contacts become ineffective for the function. The levels of consolation were higher in absence of reconciliation than in its presence, suggesting that consolation may function as an alternative mechanism in stress reduction of the victim.

Most theories on the function of play have focused on ultimate rather than proximate benefits. Play peaks during juvenility but, in some species, it is present in adulthood as well. In primates, social play and grooming often show a matched pattern because they bring individuals into close contact and favor social cohesion. In Pan, researchers have widely documented anticipation of competition at feeding time. Chimpanzees limit aggression over food by grooming (celebration), whereas bonobos use sociosexuality as a reassurance mechanism. We examined the function of play in the context of conflict prevention in the Apenheul bonobo colony. We analyzed the distribution of social play, grooming, and sexual contacts in periods around feeding and in a control condition. Adult-adult and adult-immature play frequencies were significantly higher during prefeeding than in any other condition, thus not supporting the commonly held view that social stress suppresses play. Further, there is a significant positive correlation between adult-adult play and rates of cofeeding. During feeding, adults engaged in their highest levels of sociosexual behaviors, whereas an increase in grooming rates occurred in prefeeding, though not significantly compared to the control rates. In conclusion, bonobos apparently cope with competition and social tension via 2 different mechanisms of conflict management: play to prevent tension, e.g., prefeeding, and sociosexual behaviors as appeasement and reassurance mechanisms once a tense situation emerges.

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