Abstract

Communication is inherent to social relationships. Previous papers addressed the correlation between social and communicative complexity, and the origin of sociality in rodents. In subterranean social species, as the number of animals in the same burrow increases, so do interindividual contact rates. This is because of limitations in actually used tunnel length and diameter, leading to an increasing number of agonistic situations probably resulting in time loss, threatening, and fighting with danger of injuries. To avoid this, social species are expected to have an increase in the number of particular vocalizations. Comparison of the adult vocal repertoire of 12 species through regression and phylogenetically independent contrasts suggests three main conclusions: social species increase their repertoire both in number and categories of vocal signals in relation to solitary species, although the coefficient was smaller in the PIC model; the number of agonistic vocalizations was also different between solitary and social species, with the latter displaying higher numbers of these calls; the percentage of agonistic vocalizations in relation to total repertoire was similar between social and solitary species, with no significant relationship between this parameter and the social structure. These results imply that agonistic vocalizations have also increased in number in social species, indicating the importance of these calls in the establishment of new relationships. As repertoire changes are essential to cope with new and frequent kinds of interactions sociality originates, these results suggest that at least for these organisms, communicative changes, especially at the level of agonistic signals, could be a necessary condition to fulfill in the path to the possibility of group living.