title: Lethal aggression in Pan is better explained by adaptive strategies than human impacts.
abstract: Observations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates. Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning. To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (n = 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.
authors.affiliation: 1] Department of Anthropology, University of Minnesota, 395 Humphrey Center, 301 19th Avenue South, Minneapolis, Minnesota 55455, USA [2] Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St Paul, Minnesota 55108, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Wilson
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Christophe
authors.initials: C
authors.lastname: Boesch
authors.affiliation: 1] Division of Neurobiology, Ludwig-Maximilians Universitaet Muenchen, Germany [2] Centre for Research and Conservation, Royal Zoological Society of Antwerp, Belgium.
authors.forename: Barbara
authors.initials: B
authors.lastname: Fruth
authors.affiliation: Primate Research Institute, Kyoto University, 41-2 Kanrin, Inuyama, Aichi 484-8506, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Furuichi
authors.affiliation: 1] Department of Evolutionary Anthropology, Duke University, 104 Biological Sciences Building, Box 90383, Durham, North Carolina 27708-0680, USA [2] School of Human Evolution and Social Change, Arizona State University, PO Box 872402, Tempe, Arizona 85287-2402, USA.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Gilby
authors.affiliation: Primate Research Institute, Kyoto University, 41-2 Kanrin, Inuyama, Aichi 484-8506, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Hashimoto
authors.affiliation: School of Psychology and Neuroscience, University of St Andrews, Westburn Lane, St Andrews, Fife KY16 9JP, UK.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Hobaiter
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Gottfried
authors.initials: G
authors.lastname: Hohmann
authors.affiliation: Wildlife Research Center, Kyoto University, 2-24 Tanaka-Sekiden-Cho, Sakyo, Kyoto, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Itoh
authors.affiliation: Division of Biological Anthropology, Department of Archaeology &Anthropology, University of Cambridge, Henry Wellcome Building, Fitzwilliam Street, Cambridge CB2 1QH, UK.
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Koops
authors.affiliation: Zoology Department, Makerere University, P.O. Box 7062, Kampala, Uganda.
authors.forename: Julia N
authors.initials: JN
authors.lastname: Lloyd
authors.affiliation: 1] Primate Research Institute, Kyoto University, 41-2 Kanrin, Inuyama, Aichi 484-8506, Japan [2] Japan Monkey Center, 26 Kanrin, Inuyama, Aichi 484-0081, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Matsuzawa
authors.affiliation: Department of Anthropology, University of Michigan, 101 West Hall, 1085 S. University Avenue, Ann Arbor, Michigan 48109, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Mitani
authors.affiliation: Gombe Stream Research Centre, The Jane Goodall Institute - Tanzania, P.O. Box 1182, Kigoma, Tanzania.
authors.forename: Deus C
authors.initials: DC
authors.lastname: Mjungu
authors.affiliation: The Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, Illinois 60614, USA.
authors.forename: David
authors.initials: D
authors.lastname: Morgan
authors.affiliation: Department of Anthropology, MSC01-1040, Anthropology 1, University of New Mexico, Albuquerque, New Mexico 87131, USA.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Muller
authors.affiliation: Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Roger
authors.initials: R
authors.lastname: Mundry
authors.affiliation: Wildlife Research Center, Kyoto University, 2-24 Tanaka-Sekiden-Cho, Sakyo, Kyoto, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Anthropology, Iowa State University, 324 Curtiss, Ames, Iowa 50011, USA.
authors.forename: Jill
authors.initials: J
authors.lastname: Pruetz
authors.affiliation: Department of Evolutionary Anthropology, Duke University, 104 Biological Sciences Building, Box 90383, Durham, North Carolina 27708-0680, USA.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Pusey
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Riedel
authors.affiliation: Department of Anthropology, Washington University in St Louis, Campus Mailbox 1114, One Brookings Drive, St Louis, Missouri 63130, USA.
authors.forename: Crickette
authors.initials: C
authors.lastname: Sanz
authors.affiliation: University of York, Department of Psychology, Heslington, York, YO10 5DD, UK.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Schel
authors.affiliation: Zoology Department, Makerere University, P.O. Box 7062, Kampala, Uganda.
authors.forename: Nicole
authors.initials: N
authors.lastname: Simmons
authors.affiliation: Department of Anthropology, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Michel
authors.initials: M
authors.lastname: Waller
authors.affiliation: Department of Anthropology, Yale University, 10 Sachem Street, New Haven, Connecticut 06511, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Watts
authors.affiliation: Department of Anthropology, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Frances
authors.initials: F
authors.lastname: White
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Roman M
authors.initials: RM
authors.lastname: Wittig
authors.affiliation: 1] School of Psychology and Neuroscience, University of St Andrews, Westburn Lane, St Andrews, Fife KY16 9JP, UK [2] Université de Neuchâtel, Institut de Biologie, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Zuberbühler
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, 11 Divinity Avenue Cambridge, Massachusetts 02138, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Wrangham
mesh_terms: D000349:Africa; D000374:Aggression / Q000502:physiology* / Q000523:psychology*; D000818:Animals; D000835:Animals, Wild / Q000502:physiology / Q000523:psychology; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D005502:Food; D006802:Human Activities; D006801:Humans; D008297:Male; D008954:Models, Biological; D019974:Pan paniscus / Q000502:physiology / Q000523:psychology; D002679:Pan troglodytes / Q000502:physiology / Q000523:psychology; D011156:Population Density; D012726:Sexual Behavior, Animal / Q000502:physiology