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This study investigated post-conflict (PC) behavior among wild chimpanzees (Pan troglodytes) of the M-group in the Mahale Mountains, Tanzania, and examined what types of behavior characterize the PC situation in this group, and the factors that influence the occurrence of PC affiliation between opponents soon after the end of an aggressive conflict (i.e.,(More)
Reconciliation in primates, a post-conflict affiliative interaction between former opponents, appears to have two functions: (1) to repair relationship damaged by aggression such that animals who share more valuable relationships are more likely to reconcile, and (2) to reduce the post-conflict uncertainty and stress of former combatants. The 'integrated(More)
Although it is difficult for observers to determine how non-human primates use olfaction in a natural environment, sniffing is one clue. In this study, the sniffing behaviors of wild chimpanzees were divided into six categories, and sex differences were found in most categories. Males sniffed more frequently than females in sexual and social situations,(More)
This article reports developmental changes relating to reconciliation and bystanders' affiliation with victims of aggression (i.e., consolation) among 3- to 5-year-old Japanese preschool children. Use of the post-conflict-matched control (PC-MC) method revealed that the frequency with which reconciliation and consolation were offered to a victim increased(More)
Use of leaves or sticks for drinking water has only rarely been observed during long-term study of wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale. Recently, however, we observed 42 episodes of tool-use for drinking water (73 tools and two cases of using "tool-sets") between 1999 and 2004. Interestingly, all of the performers were immature(More)
It is predicted that asymmetries in competitiveness (or resource holding potential (RHP)) would determine the outcomes of animal contests, but it has been difficult to estimate RHP in practice. In long-living animals, individual RHP changes as they age, making it necessary to quantify the individual trajectories of RHP rather than estimate a single(More)
Competition among males influences the distribution of copulations and should therefore influence the spread of sexually transmitted diseases (STDs). We developed a model to investigate STDs in the mating and social systems found in primates, and we tested predictions using comparative methods. In the model, groups were distributed on a square lattice in(More)
Many social animals have a species-specific repertoire of affiliative behaviours that characterise individualised relationships within a group. To date, however, quantitative studies on intragroup affiliative behaviours in social carnivores have been limited. Here, we investigated the social functions of the two most commonly observed affiliative behaviours(More)
A classic example of a sexually selected trait, the deep fork tail of the barn swallow Hirundo rustica is now claimed to have evolved and be maintained mainly via aerodynamic advantage rather than sexually selected advantage. However, this aerodynamic advantage hypothesis does not clarify which flight habits select for/against deep fork tails, causing(More)
For dominant individuals in cooperatively breeding species, the presence of subordinates is associated with both benefits (i.e. increased reproductive output and other group-living benefits) and costs (i.e. intrasexual competition on reproduction). The biological market theory predicts that dominant individuals are tolerant to same-sex group members when(More)