Abstract: Some costs of conflicts remain after an aggressive interaction has been terminated. Postconflict management in social living animals can reduce those costs by means of a variety of interactions implemented after aggression (e.g.reconciliation, consolation, redirected aggression). Each post-conflict interaction (PCI) provides different advantages and disadvantages, although the functions may sometimes overlap. Individuals can therefore choose a PCI to achieve the most favourable outcome within a given conflict situation. We examined 876 dyadic aggressive interactions among 18 wild chimpanzees (Pan troglodytes verus) of both sexes in the Tai National Park, Céte d'Ivoire. We investigated which conflict-condition led to which type of PCI and related the choice of PCI to its advantages and disadvantages. Tai chimpanzees used reconciliation to resolve conflicts among high value partners and when approaching the former opponent was unlikely to entail further aggression. Consolation seemed to substitute for reconciliation, when were opponents low value partners or approaching the former opponent was too risky, such as when further aggression was likely. Tai chimpanzees renewed aggression after undecided conflicts and when losers were unexpected. They used redirected aggression after long conflicts, possibly because friendly PCIs were likely to fail. However, Tai chimpanzees continued with business as usual when conflicts were very short, and they avoided further interactions when the accessibility of the resource was unlimited. Tai chimpanzees appeared to follow a clear-cut evaluation process as they seemed to weigh advantages against disadvantages for the appropriate choice of PCI.

Abstract: Bonobos have been described as a relatively egalitarian and female dominant species. The exact nature and quality of their dominance relationships and the existence of female dominance are current topics of dispute. We investigated the consistency across social contexts, the stability in time, and the degree of expression of the competitive feeding ability and agonistic dominance in a captive group of bonobos. First, we examined whether the competitive feeding ranks and agonistic ranks differed in different dyadic contexts, triadic contexts and the whole group context. For some pairs of animals the dominance relationships with respect to competitive feeding altered with different group compositions. The agonistic dominance relationships changed accordingly. The competitive feeding ranks and agonistic ranks in the experiments correlated strongly with each other. The alpha position was occupied by a female, but not all females outranked all males. We suggest that females can profit from each others presence to gain inter-sexual dominance. Second, although the agonistic rank order in the whole group remained the same over at least five years, some dyadic competitive feeding ranks changed over time, resulting in a stronger female intersexual dominance. Third, the degree of expression of the behaviors used to quantify dyadic competitive and agonistic dominance was not high, in line with the popular 'egalitarian' epithet. Notwithstanding its low consistency across contexts, the dominance hierarchy in the whole group has a strong predictive value for other social relationships such as grooming. Given this strong effect of rank on other behaviours and given the strong dependency of rank on social context, the choice of the right party members may be a crucial factor in the fission-fusion processes of free-ranging bonobos.

Abstract: Biological market models explain variability in reciprocity and interchange between groups. In groups with a shallow dominance gradient, grooming will be mostly exchanged for itself (i.e. exchange will occur). In groups with steep dominance hierarchies, interchange is expected: individuals will groom higher ranking individuals to get access to limited resources or commodities such as support in conflicts, and grooming will be traded for these commodities. We examine patterns of reciprocity in grooming and support, and of interchange of grooming for support or for tolerance in six captive groups of bonobos. We test whether differences between groups in patterns of reciprocity and interchange can be attributed to differences in a measure of steepness of dominance hierarchies, which is based on dyadic agonistic interactions. We found that grooming was reciprocal in some, but not all groups. Support was highly reciprocal, but this was a side effect of dominance in most groups. Interchange between grooming and support was observed in some groups. Corroborating earlier findings, this was a side effect of individuals preferring high ranking individuals as grooming and support partners, possibly because these high-ranking individuals provide more efficient support in conflicts. There was no evidence for interchange of grooming for tolerance. Variability in grooming reciprocity was explained by differences in steepness of dominance hierarchies, as predicted by the biological market models. In groups with a shallow dominance hierarchy, grooming was more reciprocal. This was not true for reciprocity in support. There was some evidence that individuals groomed dominants more frequently in groups with a steep dominance hierarchy. The variation in interchange relations between grooming and support did not depend on the steepness of dominance hierarchies. We suggest that grooming in itself is a valuable commodity in bonobos, especially under captive conditions, which can be exchanged reciprocally. Bonobos may interchange grooming for another value equivalent, with food sharing as a very likely candidate. This interchange effects seem more dependent on potential to monopolise food than on steepness of dominance hierarchies per se.

Abstract: 1. The social relationships in a group of Icelandic horses without a mature stallion were studied. The horses were all familiar to each other. Mutual grooming and play relationships, spatial associations, dominance-subordinate relations and the effect of kinship on these relationships were analysed.TAGSTARTBRTAGEND 2. The social structure was clearly dominated by the behaviour of the adult mares. The horses preferred to form bonds within their social class (sex/age) and they kept close proximity with their friends. The group was effectively divided into two social subgroups, adult mares as one group and adult geldings and sub-adults as another group. The sub-adults and adult geldings formed associations, which were based on mutual grooming and play, while the adult mares did not play. Differences between the sexes were evident. Males played more than the females, had more playing partners and were more popular as playmates.TAGSTARTBRTAGEND 3. Aggression rates were low. The dominance hierarchy was linear. Adult mares ranked higher than adult geldings, sub-adults and the foals. Rank was significantly correlated with age. The closer the adult mares were in rank, the more they groomed with each other. Such relationships were not found amongst the other social group.TAGSTARTBRTAGEND 4. Kinship was calculated between all pairs of animals for up to 4 or 5 generations. Allogrooming and play frequencies and proximity were all positively correlated with kinship. Adult mares, which were close in the dominance hierarchy, were on average more related than those further apart.TAGSTARTBRTAGEND 5. The social relationships in the Icelandic herd were, to some extent, different from relationships reported from unmanaged and feral horse-herds with mature stallions and bachelors. Our results suggest that adult mares groom more in groups without a stallion. Furthermore, they have more preferred partners than in natural harems and their partners are other adult mares, not their weaned offspring as seems to be the case in feral herds. The sub-adults also seem to be more socially active in the absence of stallions. Interestingly, in the Icelandic group, the adult mares showed stallion like behaviours, like mounting and protecting foals. Only by studying the behaviour and the nature of the relationships of horses in groups of different compositions, can we expect to gain a comprehensive understanding about individual social strategies and cognitive capabilities of the species. Such knowledge is valuable for management and welfare of the horse.