Does participation in intergroup conflict depend on numerical assessment, range location, or rank for wild chimpanzees?

Citation
Ml. Wilson et al., Does participation in intergroup conflict depend on numerical assessment, range location, or rank for wild chimpanzees?, ANIM BEHAV, 61, 2001, pp. 1203-1216
Citations number
74
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ANIMAL BEHAVIOUR
ISSN journal
0003-3472 → ACNP
Volume
61
Year of publication
2001
Part
6
Pages
1203 - 1216
Database
ISI
SICI code
0003-3472(200106)61:<1203:DPIICD>2.0.ZU;2-G
Abstract
Male chimpanzees, Pan troglodytes, engage in cooperative territorial defenc e and sometimes kill members of neighbouring communities. Observations of i ntergroup interactions suggest that escalation of aggression depends on num erical assessment, with lethal attacks occurring when numerical advantage r educes the costs of attacking. To gain a better understanding of the factor s guiding participation in intergroup conflict, we conducted a series of pl ayback experiments with the Kanyawara chimpanzee community of the Kibale Na tional Park, Uganda. We tested whether the response to the playback of the 'pant-hoot' call of a single extragroup male depended on the number of adul t males in the listening party, the location of the speaker relative to the territory edge, and each male's agonistic rank. These playbacks elicited c ooperative responses, with the nature of the response depending on the numb er of adult males in the party. Parties with three or more males consistent ly joined in a chorus of loud vocalizations and approached the speaker toge ther. Parties with fewer adult males usually stayed silent, approached the speaker less often, and travelled more slowly if they did approach. In cont rast to many territorial species, the location of the simulated intruder di d not affect the response. Although high-ranking males might be expected to benefit more from repelling outside males, both high- and low-ranking male s showed a similar pattern of response. Each male responded as if he benefi ted from repelling intruders, but only if he had strength in numbers. This pattern of response is consistent with cooperation based on mutualism. (C) 2001 The Association for the Study of Animal Behaviour.