Nonaggressive interventions by third parties in conflicts among captive Bornean orangutans (Pongo pygmaeus)
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Whereas orangutans are regarded as semisolitary animals in the wild, several studies have reported frequent social interactions, including aggression, among orangutans in captivity. As yet, there is a lack of knowledge about how they cope with aggression. In this report, we provide a number of new observations of interventions by third parties in aggressive interactions within a captive group of Bornean orangutans (Pongo pygmaeus) in the Tama Zoological Park, Japan. We observed that an adult female and a juvenile male orangutan intervened in aggressive interactions. The victim was a newly introduced juvenile female who was unrelated to anyone in the zoo. The ways in which the orangutans intervened were not aggressive, as the interveners simply aimed to separate the opponents, and these interventions did not lead to further aggression in almost every case. Our observations suggest that third parties can play an important role in managing aggressive conflicts among captive orangutans and, under conditions in which orangutans share limited space, nonaggressive interventions by third parties for settling conflicts appear. It is possible that orangutans may actively promote the peaceful coexistence of other individuals.
KeywordsPongo pygmaeus Captive group Third-party intervention Nonaggressive intervention
This study was permitted by the Tama Zoological Park. We thank the director, Mr. Toshimitsu Doi, and the staff: Ms. Mika Shimizu, Ms. Miwa Kosaka, and Ms. Takako Akikawa, for their kind support. We also thank Prof. Juichi Yamagiwa, Drs. Naofumi Nakagawa, Shohei Takeda, Noko Kuze, and Nobuyuki Kutsukake for their supervision and comments. Ms. Saika Yamazaki and Mr. Yuki Hanazuka helped us a great deal and we truly appreciate it. This work was supported in part by Global COE program A06 to Kyoto University from MEXT, Japan. The authors thank the editor, Prof. Nishida, and two anonymous referees for helpful comments on this manuscript.
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