Primates show a wide range of different types of vocalizations and vocal repertoires. The aim of our research program is to identify how phylogeny, social system and habitat interact during evolution in influencing the structure and usage of vocalizations and repertoires. Theory predicts that the habitat should shape the sound transmission characteristics of vocalizations while variation in visibility should affect signal usage. In addition, there should be an interplay between the characteristics of the social system and the structure and diversity of signals used to maintain this system. For instance, species with a high reproductive skew should exhibit a higher degree of sexual dimorphism in calls and specific calls used in male-male interactions. Finally, the phylogenetic descent is expected to impose some general constraint on the repertoire structure. We study closely related baboon subspecies whose phylogeography is well established. We can thus control for phylogenetic decent in our analysis. Using observational and experimental methods, we will determine and analyse the usage and function of different vocalisations in several, carefully chosen baboon populations. By comparing populations living in different social systems and in various habitats within and between baboon sub-species, we aim to link differences and similarities in vocal communication to their determining factors. Our long-term goal is to gain insights into evolutionary constraints and ecological plasticity of primate vocal communication.