Although reconciliation in bonobos (Pan paniscus) has previously been described, it has not been analyzed heretofore by the postconflict (PC) match-control (MC) method. Furthermore, although reconciliation has been investigated before in this species, consolation has not. In this study we analyzed agonistic and affiliative contacts in all sex-class combinations to clarify and reevaluate the occurrence of reconciliation in bonobos via the PC-MC method. We also investigated the occurrence of consolation by analyzing the victims' triadic contact tendency (TCT), the influence of the sex of victims, and the relative occurrence of consolation and reconciliation. We collected 167 pairs of PC-MC observations in a captive group of bonobos (in Apeldoorn, The Netherlands). The conciliatory tendency (CCT) we obtained was tendentially lower than the mean value previously found for Yerkes captive chimpanzees. Close relationships, which were present in all female-female (FF) and some male-female (MF) dyads, positively affected reconciliation rates. When only adult PC-MC pairs (157) were considered, the mean TCTs and CCTs did not differ significantly. When we focused on types of PC affiliative contact, in the case of consolation we found a striking preference for sociosexual patterns. As to the relative occurrence of consolation and reconciliation, the highest level of the former was found in the absence of the latter. When reconciliation took place, consolation generally preceded it, suggesting that consolation may be a substitutive behavior. Our findings suggest that even if reconciliation remains the best option, consolation may be an alternative substitute for reconciliation that is used to buffer the tension originating from an unresolved conflict. Reconciliation and consolation are complex phenomena that are probably related to the life history of a group. Given that few studies have been conducted on this subject, we can not at this time make any generalizations regarding conflict resolution in certain species by comparing results among studies.

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.

The aim of this study was to thoroughly investigate social play and its modalities among adult bonobos. We evaluated how play intensity varies according to the sex-class combination of the playmates and we also performed an analysis on social locomotor-rotational movements (L-R play) and contact interactions (C play). Rough and gentle play sessions were performed with comparable frequencies by male-female and female-female adult dyads, with play signals unlikely when the playmates strongly differed in age and in rank position. L-R play rates did not differ according to the sex-combination of the players; in contrast, C play sessions were particularly frequent among females. Play faces (play signals) were significantly higher during C play than L-R play sessions, thus suggesting that playmates assess reciprocally yet safely their relationships by using facial displays to avoid any kind of misunderstanding. Play was positively correlated with grooming and contact sitting interactions, suggesting that it may be used as a social enhancer. Finally, we found no correlation between both play contexts (L-R and C play) and age, size and rank differences of the players. In conclusion, we suggest that bonobos with their egalitarian society, peculiar social structure, and playful tendency represent an attractive testing subject to examine empirically many emerging hypotheses on adult play behavior.

Many reports have claimed that the duration of the swelling cycle in female bonobos (Pan paniscus) is longer than that of chimpanzees, and that the bonobo maximum swelling phase is markedly prolonged. Field data on intermenstrual intervals (IMIs) in female bonobos are limited and restricted to interswelling intervals (ISIs), which are assumed to reflect the IMI, though a direct comparison between the duration of ISIs and IMIs is still lacking. Reports on bonobo sexual activity as a function of the swelling phase are often contradictory. Moreover, the function of female homosexual interactions (genito-genital (GG) rubbing) is still debated. This study examines the reliability of the ISI as an approximation of the IMI, and the attractivity of female sexual swellings for other individuals. An analysis of 51 ISI-IMI pairs showed that ISIs are a fair representation of the reproductive cycle. The cycle length was 35.6+/-1.1 SE days relying on the ISI, whereas it was 35.0+/-1.1 SE days considering the IMI. This result is similar to the cycle length reported for chimpanzees. Female homosexual interactions and copulatory rates were higher during maximum tumescence, suggesting that the sexual swelling may be attractive for both males and other females. Furthermore, the GG-rubbing was performed free of a hierarchical postural imposition, and was not correlated with affinitive interactions. We suggest that GG-rubbing, which is generally the most frequent female sexual interaction, is a tool for social assessments among females.

While dominance relationships have been widely studied in chimpanzees, in bonobos, dominance style and linearity of hierarchy are still under debate. In fact, some authors stated that bonobo hierarchy is nonlinear/ill-defined, while others claimed that it is fairly linear. In this paper, we test the hypothesis that a shift in group composition determines changes in linearity of hierarchy. To test this hypothesis, we collected data on one of the largest captive groups in the world, in the Apenheul Primate Park (The Netherlands). We investigated the linearity of the hierarchy in two different periods, with a shifting group composition. We used the corrected Landau's index and David's scores to estimate which animals were most dominant. The major overall result of our study is that hierarchy is fairly nonlinear in this group: during the first study period (eight adults), the hierarchy was nonlinear, whereas during the second one (six adults), it failed to reach statistical linearity. We argue that the reduction of the number of adults is the principal factor affecting linearity. We also found that dominance interactions were evenly distributed across sex classes in both study periods. Furthermore, no correlation was observed between age/body weight and rank. As for the overall dominance relationship between males and females, our results suggest that there is no exclusive female dominance in the Apenheul group. The dominance style of bonobos may be loose and differentially expressed in diverse groups or in the same group, along with shifting conditions.