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Bystanders, parcelling, and an absence of trust in the grooming interactions of wild male chimpanzees

Kaburu, Stefano S. K., Newton-Fisher, Nicholas E. (2016) Bystanders, parcelling, and an absence of trust in the grooming interactions of wild male chimpanzees. Scientific Reports, 6 . Article Number 20634. ISSN 2045-2322. E-ISSN 2045-2322. (doi:10.1038/srep20634) (KAR id:54075)


The evolution of cooperation remains a central issue in socio-biology with the fundamental problem of how individuals minimize the risks of being short-changed (‘cheated’) should their behavioural investment in another not be returned. Economic decisions that individuals make during interactions may depend upon the presence of potential partners nearby, which o ers co operators a temptation to defect from the current partner. The parcelling model posits that donors subdivide services into parcels to force cooperation, and that this is contingent on opportunities for defection; that is, the presence of bystanders. Here we test this model and the e ect of bystander presence using grooming interactions of wild chimpanzees. We found that with more bystanders, initiators gave less grooming at the beginning of the bout and were more likely to abandon a grooming bout, while bouts were less likely to be reciprocated. We also found that the groomer’s initial investment was not higher among frequent groomers or stronger reciprocators, suggesting that contrary to current assumptions, grooming decisions are not based on trust, or bonds, within dyads. Our work highlights the importance of considering immediate social context and the in uence of bystanders for understanding the evolution of the behavioural strategies that produce cooperation.

Item Type: Article
DOI/Identification number: 10.1038/srep20634
Subjects: G Geography. Anthropology. Recreation > GN Anthropology
Q Science > QH Natural history > QH301 Biology
Q Science > QH Natural history > QH541 Ecology
Q Science > QL Zoology
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation
Depositing User: Nicholas Newton-Fisher
Date Deposited: 10 Feb 2016 10:56 UTC
Last Modified: 08 Dec 2022 23:07 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Newton-Fisher, Nicholas E..

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