Communication signals provide key information for conspecific recognition, mate choice and rival assessment. The painted goby Pomatoschistus pictus and the common goby P. microps are two closely-related sand goby species, often sympatric and with an overlapping breeding season. In this study we staged male–male and male–female interactions and compared visual, tactile and acoustic behaviour in both species. Sound production in the common goby is here accounted for the first time. We observed some differences in visual behaviour and a striking divergence in the use of tactile and acoustic communication during courtship and agonistic interactions. We further describe differences in drumming signals with social context in the painted goby. This study suggests a divergence in communication in two closely-related sand goby species and emphasizes the importance of further research concerning the role of multimodal communication in closely-related species.
Whistles are acoustic signals produced particularly during social interactions. Here, we compare whistles by bottlenose dolphins from three Mediterranean areas (Croatia, Sicily and Sardinia) to investigate the presence of acoustic divergence and to discuss the possible causes of variability. Whistle parameters differ significantly between populations, but PCA highlights that the majority of variability is due to a limited number of frequency parameters. Cluster and DFA show that the Croatian population is acoustically divergent from the western populations of Sicily and Sardinia. This divergence could be consistent with geographical isolation, and a possible genetic differentiation between populations, and/or an adaptation to the acoustic environment. Moreover, in a comparison of whistle parameters of different Mediterranean populations with those of previously published Atlantic populations, it was revealed that the Sicilian population was acoustically closer to Atlantic populations. Our results represent a contribution to identifying acoustically differentiated populations of bottlenose dolphins in the Mediterranean.