We are interested in the understanding of animal societies. We investigate proximate and functional aspects on group coordination (leadership and group decisions) and in particular, communication and cognition in mammals. With a comparative approach we identify what selective factors favor communicative complexity (e.g., vocal repertoire size, variation in call structure within call types, call combinations, etc…) and the underlying cognitive mechanisms. We focus on phylogenetic closely related or sympatric living species showing variation in their social structure. Based on behavioural observations of habituated animals in their natural habitat we test specific hypotheses with field experiments, and also on captive animals.