Abstract: Dominance rank in female chimpanzees correlates positively with reproductive success. Although a high rank obviously has an advantage for females, clear (linear) hierarchies in female chimpanzees have not been detected. Following the predictions of the socio-ecological model, the type of food competition should affect the dominance relationships among females. We investigated food competition and relationships among 11 adult female chimpanzees in the Ta National Park, C+ete d'Ivoire (West Africa). We detected a formal linear dominance hierarchy among the females based on greeting behaviour directed from the subordinate to the dominant female. Females faced contest competition over food, and it increased when either the food was monopolizable or the number of competitors increased. Winning contests over food, but not age, was related to the dominance rank. Affiliative relationships among the females did not help to explain the absence of greetings in some dyads. However comparison post hoc among chimpanzee study sites made differences in the dominance relationships apparent. We discuss them based on social relationships among females, contest competition and predation. The cross-site comparison indicates that the differences in female dominance hierarchies among the chimpanzee study sites are affected by food competition, predation risk and observation time.

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: 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.

Abstract: Two experiments explored the duration of dogs' working memory in an object permanence task: a delay was introduced between the disappearance of a moving object behind a box and the beginning of the search by the animal. In experiment 1, the dogs were tested with retention intervals of 0, 10, 30, and 60 s. Results revealed that the dogs' accuracy declined as a function of the length of the retention interval but remained above chance for each retention interval. In experiment 2, with new subjects, longer retention intervals (0, 30, 60, 120, and 240 s) were presented to the dogs. Results replicated findings from experiment 1 and revealed that the dogs' accuracy remained higher than chance level with delays up to 240 s. In both experiments, the analysis of errors also showed that the dogs searched as a function of the proximity of the target box and were not subject to intertrial proactive interference. In the discussion, we explore different alternatives to explain why dogs' search behaviour for hidden objects decreased as a function of the retention intervals.