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Palagi, E., Cordoni, G., & Borgognini Tarli, S. (2006). Possible roles of consolation in captive chimpanzees (Pan troglodytes). Am J Phys Anthropol, 129(1), 105–111.
Abstract: Empathy is a necessary prerequisite for the occurrence of consolation. The term “consolation” contains a hypothesis about function, which is distress alleviation. The present study aims to confirm the occurrence of consolation in captive chimpanzees via the post-conflict/matched-control method (PC-MC) and to suggest its possible roles. We collected 273 PC-MC pairs in the group of Pan troglodytes housed in the ZooParc de Beauval (France). We confirmed the presence of consolatory contacts (mean level of consolation, 49.5% +/- 22.3% SEM) in the colony. Consolation rates were significantly higher than reconciliation levels (mean level of reconciliation, 28.9% +/- 16.8% SEM). The level of consolation was greater in the absence of reconciliation than in the presence of it, suggesting that consolation might be an alternative behavior. As friendship and relatedness did not influence the occurrence of consolation, they did not seem to be the best prerequisites for this behavioral mechanism, at least in this chimpanzee colony. Affinitive contacts with third parties were significantly more frequent when the victim called attention to itself during severe aggressions by screaming. These high-pitched sounds seem to be useful in eliciting aid from conspecifics, as occurs in young humans. The occurrence of consolation reduced the likelihood of further attacks among group-members. From this perspective, both victims and consolers most likely gain potential advantages by interacting with each other when aggression is particularly severe, reconciliation is not immediate, and consequently social stress reaches high levels.
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Previc, F. H. (2002). Thyroid hormone production in chimpanzees and humans: implications for the origins of human intelligence. Am J Phys Anthropol, 118(4), 402–3; discussion 404–5.
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Baker, K. C., Seres, E., Aureli, F., & De Waal, F. B. (2000). Injury risks among chimpanzees in three housing conditions. Am. J. Primatol., 51(3), 161–175.
Abstract: Meeting the psychological needs of chimpanzees (Pan troglodytes) can be a challenge given their aggressiveness on the one hand and the complexity of their social lives on the other. It is unclear how to balance the need to provide opportunities for species-appropriate behavior against potential risks of injury chimpanzees may inflict on each other. This study evaluates the suggestion that simpler social environments protect chimpanzees from wounding. Over a two-year period all visible injuries to 46 adult males, 64 adult females, and 25 immature chimpanzees were recorded at the Yerkes Regional Primate Research Center. Approximately half of the subjects were mother-reared, and the rest were nursery-reared. Housing included compounds containing about 20 chimpanzees, interconnected indoor-outdoor runs for groups of up to 12 individuals, and smaller indoor-outdoor runs for pairs and trios. Annual wounding rates were calculated for serious wounds (extensive injuries and all those requiring veterinary intervention) as well as for minor wounds. Compound-housed chimpanzees incurred the highest level of minor wounding, but serious wounding levels were not affected by housing condition. Even with a period of dominance instability and elevated levels of wounding in one compound, compound chimpanzees were not injured more than those in smaller social groups over the long term. Nursery-reared females in moderate-sized groups were wounded more than mother-reared females. Also, nursery-reared males and females were wounded less often when paired with mother-reared companions. Overall, this study indicates that maintaining chimpanzees in pairs and trios would not be an effective means for reducing injuries. The management of wounding in chimpanzee colonies is influenced more by the sex and rearing composition of a colony.
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de Waal, F. B., & Seres, M. (1997). Propagation of handclasp grooming among captive chimpanzees. Am. J. Primatol., 43(4), 339–346.
Abstract: A grooming posture previously reported for two wild chimpanzee (Pan troglodytes) communities developed spontaneously in a captive group of the same species. This offered a unique opportunity to follow the propagation of a new social custom. The posture consists of two partners grasping hands--either both right hands or both left hands--and raising the arms in an A-frame above their heads while mutually grooming with their free hands. The propagation of this pattern was followed over a 5 year period. In the beginning, handclasps were always initiated by the same adult female. This female initiated the posture mainly with her adult female kin. In subsequent years, these relatives became frequent participants in the posture with each other as well as with nonrelatives. Over the years the posture increased in frequency and duration and spread to the majority of adults and also to a few adolescents and older juveniles. The pattern persisted after removal of the apparent originator.
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Aureli, F., & de Waal, F. B. (1997). Inhibition of social behavior in chimpanzees under high-density conditions. Am. J. Primatol., 41(3), 213–228.
Abstract: This is the first study to investigate the short-term effects of high population density on captive chimpanzees (Pan troglodytes). Subjects of the study were 45 chimpanzees living in five different groups at the Yerkes Regional Primate Research Center. The groups were observed under two conditions: 1) when they had access to both the indoor and outdoor sections of their enclosures; 2) during cold days when they were locked into the indoor runs, which reduced the available space by more than half. Under the high-density condition, allogrooming and submissive greetings decreased, but juvenile play increased. Remarkably, the rate of various forms of agonistic behavior, such as aggression, bluff charge, bluff display, and hooting, occurred less frequently under the high-density condition. This general decrease in adult social activity, including agonistic behavior, can be interpreted as an inhibition strategy to reduce opportunities for conflict when interindividual distances are reduced. This strategy is probably effective only in the short run, however. Behavioral indicators of anxiety, such as rough scratching and yawning, showed elevated rates, suggesting increased social tension under the high-density condition.
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Koski, S. E., Koops, K., & Sterck, E. H. M. (2007). Reconciliation, relationship quality, and postconflict anxiety: testing the integrated hypothesis in captive chimpanzees. Am. J. Primatol., 69(2), 158–172.
Abstract: Reconciliation is a conflict resolution mechanism that is common to many gregarious species with individualized societies. Reconciliation repairs the damaged relationship between the opponents and decreases postconflict (PC) anxiety. The “integrated hypothesis” links the quality of the opponents' relationship to PC anxiety, since it proposes that conflicts among partners with high relationship quality will yield high levels of PC anxiety, which in turn will lead to an increased likelihood of reconciliation. We tested the integrated hypothesis in captive chimpanzees (Pan troglodytes) in the Arnhem Zoo, The Netherlands. We applied the standard PC/matched control (MC) method. Our results mostly support the integrated hypothesis, in that more valuable and compatible partners (i.e., males and frequent groomers) reconciled more often than less valuable and weakly compatible partners (i.e., females and infrequent groomers). In addition, PC anxiety was higher after conflicts among males than among females. Emotional arousal thus appears to be a mediator facilitating reconciliation. However, in contrast to the predictions derived from the integrated hypothesis, PC anxiety appeared only in aggressees, and not in aggressors, of conflicts. This suggests that while relationship quality determines PC anxiety, it is dependent on the role of the participants in the conflict.
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Langergraber, K., Mitani, J., & Vigilant, L. (2009). Kinship and social bonds in female chimpanzees (Pan troglodytes). Am. J. Primatol., 71(10), 840–851.
Abstract: A large body of theoretical and empirical research suggests that kinship influences the development and maintenance of social bonds among group-living female mammals, and that human females may be unusual in the extent to which individuals form differentiated social relationships with nonrelatives. Here we combine behavioral observations of party association, spatial proximity, grooming, and space use with extensive molecular genetic analyses to determine whether female chimpanzees form strong social bonds with unrelated individuals of the same sex. We compare our results with those obtained from male chimpanzees who live in the same community and have been shown to form strong social bonds with each other. We demonstrate that party association is as good a predictor of spatial proximity and grooming in females as it is in males, that the highest party association indices are consistently found between female dyads, that the sexes do not differ in the long-term stability of their party association patterns, and that these results cannot be explained as a by-product of the tendency of females to selectively range in particular areas of the territory. We also show that close kin (i.e. mother-daughter and sibling dyads) are very rare, indicating that the vast majority of female dyads that form strong social bonds are not closely related. Additional analyses reveal that “subgroups” of females, consisting of individuals who frequently associate with one another in similar areas of the territory, do not consist of relatives. This suggests that a passive form of kin-biased dispersal, involving the differential migration of females from neighboring communities into subgroups, was also unlikely to be occurring. These results show that, as in males, kinship plays a limited role in structuring the intrasexual social relationships of female chimpanzees.
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Koski, S. E., & Sterck, E. H. M. (2007). Triadic postconflict affiliation in captive chimpanzees: does consolation console? Anim. Behav., 73(1), 133–142.
Abstract: Consolation is a triadic postconflict interaction between a conflict participant and an uninvolved third party. The term consolation implies stress alleviation. Consequently, consolation may be an effective mechanism to alleviate postconflict stress. However, this assumption has not been tested. We tested whether consolation alleviates postconflict stress in captive chimpanzees, Pan troglodytes. In addition, we examined whether consolation is a substitute postconflict interaction for reconciliation. We collected 643 postconflict-matched control pairs on aggressees and 576 on aggressors. Consolation occurred equally frequently with aggressees and aggressors. However, we found no evidence that consolation alleviated stress, regardless of the identity of the consoler. In addition, consolation was also directed to conflict participants with no evident postconflict stress. Furthermore, we found no evidence for consolation being a substitute for reconciliation. The occurrence of consolation did not depend on the occurrence of reconciliation and consolation was not more prevalent with the sex class that reconciled less often or had the highest postconflict stress levels. We conclude that consolation is a postconflict interaction in its own right, the function of which is not likely to be connected to stress alleviation of the consoled individual. We propose that the function of triadic postconflict affiliation, previously labelled as consolation, should be reassessed with regard to the third parties' reasons to affiliate with conflict opponents.
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Hopkins, W. D., Taglialatela, J. P., & Leavens, D. A. (2007). Chimpanzees differentially produce novel vocalizations to capture the attention of a human. Anim. Behav., 73(2), 281–286.
Abstract: Chimpanzees, Pan troglodytes, produce numerous species-atypical signals when raised in captivity. We examined contextual elements of the use of two of these vocal signals, the `raspberry' and the extended grunt. Our results demonstrate that these vocalizations are not elicited by the presence of food, but instead function as attention-getting signals. These findings reveal a heretofore underappreciated category of animal signals: attention-getting sounds produced in novel environmental circumstances. The invention and use of species-atypical signals, considered in relation to group differences in signalling repertoires in apes in their natural habitats, may index a generative capacity in these hominoid species without obvious corollary in other primate species.
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Mitani, J. C. (2009). Male chimpanzees form enduring and equitable social bonds. Anim. Behav., 77(3), 633–640.
Abstract: Controversy exists regarding the nature of primate social relationships. While individual primates are frequently hypothesized to form enduring social bonds with conspecifics, recent studies suggest that relationships are labile, with animals interacting only over short periods to satisfy their immediate needs. Here I use data collected over 10 years on a community of chimpanzees, Pan troglodytes, at Ngogo, Kibale National Park, Uganda, to investigate whether male chimpanzees establish long-term social relationships and to determine the factors that affect variation in relationship quality and the stability of social bonds. Kinship and dominance rank influenced the quality of relationships. Maternal brothers and males of the same dominance rank class groomed each other more equitably than did unrelated males and males that were dissimilar in rank. In addition, males that formed strong social bonds groomed more equitably than did males that displayed weaker bonds. Social bonds were stable over time, with relationships in one year predicting those in subsequent years. Kinship and the quality of social relationships affected bond stability. Maternal half siblings and males that groomed each other equitably maintained longer-lasting bonds than did nonkin and males that groomed each other unevenly. Virtually all of the males established at least one enduring relationship with another individual. The most enduring bonds formed between a few pairs of maternal brothers and dyads that maintained balanced grooming interactions. These results indicate that male chimpanzees maintain long-lasting and equitable social bonds whose formation is affected by maternal kinship and the quality of social relationships.
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