Vocal communication in social groups

Vocal communication plays a particularly important role in the regulation of social interactions and in the coordination of activities in many mammals and birds that are organised into social groups. Previous research on the function and evolution of vocal signals has mainly considered dyadic interactions of a signaller and its addressed receiver. However, in social groups it is likely that additional individuals attend to dyadic communication and that they use this information to their own benefit, sometimes with severe costs to the signaller. To improve existing communication models, benefits and costs of vocal communication caused by bystanders must therefore also be considered. Here we discuss vocal communication in social groups and identify the effect of additional individuals on signalling interactions, concentrating on audience effects, eavesdropping and group coordination. First, review of the existing literature reveals that the presence of an audience, i.e., additional individuals within the signalling range, clearly affects the outcome of communicative interactions, and that individuals modulate their signalling behaviour according to the presence of bystanders or a particular category of bystanders in a variety of contexts. Second, social knowledge acquired by eavesdropping on the communicative network within a group influences not only future actions, but can also provide individual benefits for eavesdroppers, whereas mutual eavesdropping can structure cooperation and alliance formation, and, hence, contribute to long-term group stability. Third, communicative networks also provide a means to facilitate the maintenance of group cohosion and decision-making processes. In conclusion, cost-benefit analyses at the level of dyadic interactions reveal clear differences with communication networks, where repeated interactions with multiple partners are considered. Future communication models and empirical studies should therefore consider the composition of the entire communication network as well as the effects of repeated interactions to fully understand signalling interactions in social groups