Chez les oiseaux, les espèces aux aptitudes cognitives avancées, et celles faisant face aux coûts et aux bénéfices de la vie en groupe, sont particulièrement intéressantes pour étudier l'émergence de formes complexes de socialité. Dans ma thèse, j'ai étudié les mécanismes comportementaux sous-jacents à la diversité et la dynamique des relations sociales dans un groupe de corbeaux freux captifs, une espèce de corvidé monogame et coloniale. J'ai montré que les freux peuvent former des relations en dehors du contexte reproducteur et changer de partenaire au cours de leur vie. De plus, j'ai montré : une certaine résilience de la structure sociale face aux variations temporelles des relations, de la composition du groupe et du sex-ratio; et l’absence d’effets stabilisateurs des relations de dominance sur la structure. Mon travail démontre que la structure sociale chez le corbeau freux est plus qu’un simple agrégat de paires, et forme la base d’une organisation sociale aux multiples niveaux. / Numerous avian species are good candidates to study the emergence of complex forms of sociality, in particular the species showing advanced cognitive skills, and the one living in groups all year long, coping with the costs and benefits of group living. In my thesis, I investigated the proximate mechanisms underlying the diversity and dynamic of social relationships in captive adult rooks, a colonial and monogamous corvid species. I found that rooks have the ability to form non-reproductive social bonds and several pair bonds throughout their life. In addition, I found: that the group social structure was flexible enough to allow temporal variations of relationships, group composition and sex-ratio; and that dominance relationships do not have any long lasting effects on the stabilisation of the structure. Overall, my work demonstrates that rooks social structure extends far beyond a simple aggregation of reproductive pairs, and may be acknowledged as a multi-level social organisation.

The Spotted hyena (Crocuta crocuta) is a gregarious carnivore known for its strictly structured hierarchical rank relationships. At the zoo of Borås a clan, consisting out of two Spotted hyenas, are participating in an ex-situ program. In order to successfully enact conservational work, within zoos, sustainable management of zoo populations is of importance, and the behavioral aspect is vital in enabling welfare. In this study, I observed social interactions and activity in the Spotted hyenas at the zoo of Borås, for ten continuous days. The study aimed to investigate the dominance relationship and daily activity of the individuals. Furthermore, if this correlates with concentrations of testosterone. I performed two different observational studies, one focusing on social and agonistic behaviors, and the other on general behaviors. A third method, blood sampling, was intended to be performed but due to non-optimal conditions it was not executed. The results implied that the two individuals were highly nocturnal, with activity peaks to be observed during the first half of the night and at dawn. The individuals spent the majority of the time, 60.6%, resting which signifies that they are active during shorter periods. They were highly social with each other, but force measurements and aggressive displays did occur, mainly during the night. Sansa was the one taking initiative in conflicts, which suggests attempts in dominating Arya. Further, this indicates that the activity and dynamic of the individuals resembles that of a wild population, along with corresponding with previously performed studies and behavioral descriptions.