Conférences et séminaires » Séminaire présenté par Riccardo PANSINI, IPHC-DEPE
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Partner choice, cooperation and markets in three wild groups of vervet monkeys
Par : Riccardo PANSINI, Doctorant, IPHC-DEPE, Equipe Ethologie Evolutive
Date : mardi 7 décembre 2010 à 13h30
Lieu : IPHC, Salle de réunion du DEPE, bât.60
Over the course of three years, I performed field experiments with three groups of wild vervet monkeys in South Africa. The experiments involved at least two or more individuals belonging to two classes repeatedly operating feeders in order to get access to limited quantities of food. Partner choice could be analysed so that the feeders had to be handled simultaneously by a member of each class to return a shareable reward. Before the experiment, I calculated proximity networks based on distances of nearest neighbours and social networks based on behavioural parameters such as grooming, contact-sitting and social play. The recurrent partner associations observed before the experiment only partly predicted the forming of cooperative partnerships during the experiment. While most of the tested subjects cooperated with other partners, they preferred to do so with specific combinations of individuals and tended not to mix with other group members outside these preferred partnerships. This caused the relatively homogenous networks we observed before the experiment to differentiate since the food sharing partners selected each other limiting their choice. Interestingly neither sex nor age classes explained the specific partner matching. Kinship could not explain this matching either. Rather, higher ranking individuals cooperated with others higher ranking, and lower ranking ones with others of lower rank. Individuals belonging to same hierarchical categories segregated as predicted by socio-ecological models describing more despotic groups feeding on patchy resources.
After the experiment, to test market theory models, I analyse whether the social networks modified because of the cooperation events. During the training phase, the monkeys became able to discriminate between the values of the contribution to the cooperation across classes. Because one social class was less numerous than the other, its members are expected to become in demand as cooperation partners.