Group Dynamics and Proximate Mechanisms of Female Reproductive Monopolization in a Cooperatively Bre

This thesis presents the results of a field study on the cooperative breeding system of wild moustached tamarins (Saguinus mystax; Callitrichidae, Primates), carried out in the Amazon rainforest of north-eastern Peru. The author employed a combination of detailed behavioural observations of wild tamarin monkeys with modern non-invasive techniques of genetic and endocrine analyses from faecal samples collected during field work. This combination allowed new insights into the biology of an unusual breeding system - cooperative polyandry - where a single female per group monopolizes reproduction and all group members (except youngsters) help with costly care for the twin offspring. The thesis focuses on the demographic and genetic background (group size and composition, sex ratio, genetic relatedness among group members) as well as the underlying physiological and behavioural mechanisms (reproductive endocrinology, social behaviour) of this fascinating system.