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. Am. J. Primatol. 43:339–346, 1997. © 1997 Wiley‐Liss, Inc.
Descriptions of the formation of relatively large groups of unfamiliar chimpanzees (Pan troglodytes) in captivity are scarce in the literature. Nineteen chimpanzees from preexisting subgroups were introduced into a social group at the Yerkes Regional Primate Research Center. The group included two adult males, six adult females along with six dependent infants, and five unrelated juveniles, four of whom had been hand-raised in a nursery unit. Here we provide details on dyadic and multiparty introductions as well as technical details on the indoor/outdoor compound. The introduction process itself took more than 3 weeks, and was completed without major injuries. The introductions combined with 4 years of follow-up data on aggression, grooming, and affiliative behavior confirm that even chimpanzees from an environment that does not promote complex social skills can be formed into a large multimale- multifemale group. During the introductions, low rates of agonistic behavior among adult females were offset by high rates of affiliative behavior. The two adult males, however, showed contact aggression during the first 10 minutes, after which such behavior virtually disappeared, whereas affiliative behavior increased. Three months after their first introduction, the two males reversed dominance ranks within the group, and hierarchical stability has been maintained since. During the 4-year postintroductory period, grooming rates slightly decreased, but group cohesion was maintained. The frequency of aggression among all adults, including the males, increased during the 4-year period, but aggression was generally of low intensity after the first year. (C) 2002 Wiley-Liss, Inc
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. Am. J. Primatol. 51:161–175, 2000. © 2000 Wiley‐Liss, Inc.
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