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We assessed the level of genetic variability and population structure of the common bottlenose dolphin (Tursiops truncatus) in the tropical and subtropical portions of the southwestern Atlantic Ocean and compared the results with previous morphological findings. We analyzed 109 samples of common bottlenose dolphins that were sequenced for control region mtDNA and genotyped for seven polymorphic microsatellite loci. The results suggested that the species in this region can be separated in two major biological units, northern and southern, with an area of parapatry at southern Brazil. The northern unit seems to occur in a wide range of depths, including

The genus Kogia, which comprises only two extant species, Kogia sima and Kogia breviceps, represents one of the least known groups of cetaceans in the global ocean. In some coastal regions, however, stranding events of these species have been relatively common over the last decades. Stranding provides the opportunity to investigate the biology of these cetaceans and to explore the epidemiological aspects associated with the mortality of the organisms found on the beach. A number of disturbances (including pelagic fisheries, chemical pollution, boat strikes, and noise pollution) have been confirmed to pose a particular threat to the Kogia species. However, no study has yet investigated potential relationships between environmental conditions and stranding events. Here we analyse how a collection of environmental, physical, and biological variables, such as wind, sea surface temperature (SST), water depth, and chlorophyll-a, correlate to Kogia stranding events along the Brazilian coast. The results of our statistical analyses suggest that K. sima is more likely found in warm tropical waters, which provide an explanation for the high frequency of stranding in northeastern Brazilian coast. In contrast, K. breviceps appears to have a preference for temperate and productive waters. Wind speed results to be also an important factor for predicting Kogia strandings in Brazilian coast. Additionally, literature information in combination with our own data and analyses of stomach contents confirms that oceanic cephalopods constitute the primary nutritional source of both Kogia species. By using the available information as a qualitative proxy for habitat preference and feeding ecology, our study provides a novel and comprehensive assessment of Kogia stranding data in relation to environmental conditions along the Brazilian coast.

This report compiles the current information on morphology, genetics, stable isotopes, acoustics and parasites of bottlenose dolphins along the Southwest Atlantic Ocean (SWAO), which includes waters of Brazil, Uruguay and Argentina. The authors also briefly review the proposed taxonomy for the genus along the Atlantic coast of South America.