Cécile Fruteau
| Date of PhD defense: | 21 December 2010 |
| Title of thesis: | Biological Markets in the everyday lives of Mangabeys and Vervets: an observational and experimental approach |
| ISBN: | 978 90 5668 267 5 |
| Promotores: | Prof.dr. Eric van Damme and Prof.dr. Ronald Noë |
Abstract:
. Cooperation between unrelated partners has long been an evolutionary paradox: why would organisms sustain severe costs in order to increase the fitness of a perfect stranger? The biological market theory (BMT) developed by Noë & Hammerstein, in which cooperative interactions between organisms are similar to market exchanges, provides a new framework to tackle this issue. In this thesis, we extensively tested the predictions derived from BMT and showed how they provide insights into the social interactions in two different primate species. We worked with free-ranging sooty mangabeys (Ivory Coast) and vervet monkeys (South Africa). We first investigated naturally occurring exchanges: grooming-grooming, grooming-infants and grooming-sex exchanges. For each set of exchanges, we tested predictions derived from the law of supply and demand and predicted that grooming investments would follow the fluctuating availabilities of the sought commodities. We also investigated how outbidding competition and effects such as sexual receptivity or infants maturity could affect the value of the commodity. We demonstrated that individuals invested large amount of grooming to obtain rare commodities. They also differentiated between partners they often interacted with and the rest of the group. We secondly investigated grooming exchanges in an artificial setup. The field experiments demonstrated that monkeys quickly modified grooming ratios and reduced aggressive behaviours to facilitate cooperation, suggesting they understand new market situations easily. We showed that they acquired self-control through a socially enhanced queuing-to-learn system.
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