Social preferences influence the short-term exchange of social grooming among male bonobos
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The emotional mediation hypothesis proposes a mediating role of social bonds in the exchange of services. This model predicts that the form of short-term exchange of services depends on the relationship between the individuals involved. Here, we test this prediction in the exchange of grooming among males in a wild bonobo community for which close relatedness could be excluded. As bonobo males hardly engage in food sharing or agonistic support, grooming is mainly exchanged for grooming. While overall grooming, both given and received, correlates across dyads and within sessions, the form of grooming exchange within a given session differs according to dyadic association preferences. Individuals with a higher tendency to associate, ergo more familiar individuals, exhibit larger time differences and reduced reciprocation in consecutive grooming bouts than less familiar individuals. These results support the idea that emotional components are involved in the exchange of services between unrelated individuals.
KeywordsSocial bonds Emotional mediation hypothesis Reciprocity Short-term contingency Tit-for-tat Grooming Primates, great apes Pan paniscus Altruism Biological market
We thank the members of the LuiKotale Bonobo Project, ICCN and Barbara Fruth for support through various stages of the project. We furthermore thank Roger Mundry for statistical support, Catherine Crockford, Mimi Arandjelovic, Sarah Till Boysen and two anonymous reviewers for their helpful comments on the manuscript.
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