Abstract
Complex societies are suggested to generate complex communication. However, tests of this hypothesis rarely go beyond a superficial examination of social and communicative complexity. For a systematic approach, we first have to define what we mean by complexity. What defines social complexity, and what defines communicative complexity? What aspects of social complexity correlate with what aspects of communicative complexity? We reviewed the hypotheses put forward for the evolution of the diverse vocal communicative repertoires and variation within meerkats and four other mongoose species. The obligate group living species, meerkats, dwarf mongoose, and banded mongoose, in comparison to the solitary slender mongoose and the facultative social yellow mongoose show a wider variation in signal use. However, group size within the social mongoose species does not correlate to vocal repertoire size and is rather explained by differences in their social organization and also by the ecology of the species. For example, meerkats and dwarf mongoose seem to have evolved vocal systems based on many discrete call types, while banded mongoose show a more graded system with fewer call types, though the amount of information conveyed to receivers may be the same in both cases. The comparison of vocal complexity in the different mongoose species emphasizes the importance of identifying correlations of communicative variation with specific social contexts and taking the ecology of a species into account. Ultimately, the function of signals has to be considered from both the producer and receiver side, and in the natural habitat of a species, if we are ever to understand what explains the variation, complexity, as well as potential limitations in animal communication.
Manser, Marta