Genetic and cultural evidence suggests a refugium for killer whales off Japan during the Last Glacial Maximum
Olga A. Filatova, Ivan D. Fedutin, Ekaterina A. Borisova, Ilya G. Meschersky, Erich Hoyt
During glacial periods, some animals moved to warmer regions that remained ice-free – so-called ‘glacial refugia’. Glacial refugia often preserved high levels of diversity; in contrast, areas recolonized after the glaciers receded tended to have lower levels of diversity because the populations there were descended from only a few colonizers. In the northwestern Pacific Ocean, most coastal waters were covered by floating ice during the Last Glacial Maximum (‘Ice Age’), and only the areas from northern Japan south remained ice free. We examined the genetic diversity and call variation of killer whales from this area off northern Japan to test whether it could have served as a refugium for killer whales during the Ice Age. We found that these whales had much higher genetic diversity and produced calls that differed from those of killer whales occurring further north off Kamchatka and the adjacent western North Pacific. We conclude that the waters around Japan may have served as a glacial refugium for killer whales during the Ice Age, preserving higher genetic and vocal diversity in this area compared to areas further north that were recolonized after the glaciers retreated.
Injuries and skin condition of Indo-Pacific humpback dolphins (Sousa chinensis) in the northern South China Sea
Agathe Serres, Wenzhi Lin, Binshuai Liu, Mingli Lin, Mingming Liu, Songhai Li
Indo-Pacific humpback dolphins are subject to intense human activity in the northern South China Sea. The analysis of photographs taken in five different locations indicated that 10.6% of dolphins presented human-induced injuries with higher rates for Jiangmen, Hainan, and Sanniang Bay suggesting that these areas should be the subject of more research. Skin conditions were observed on 47% of dolphins, with orange patches being the most frequent. Orange patches were significantly less prevalent in summer and fall than in winter and spring, in females than in males, as well as with calves relative to older age classes. Seasonal patterns may be linked to water temperatures, while demographic patterns may be associated with immune defenses. These findings allow for a better understanding of the potential impact of human activities on Indo-Pacific humpback dolphins and should inform further conservation measures.
High similarities in dorsal fin ratios of common bottlenose dolphins (Tursiops truncatus) in the Caribbean Sea
Carlos A. Niño-Torres, Jose A. Olvera-Gómez, Eric Ramos, Delma N. Castelblanco-Martínez, María P. Blanco-Parra, Laura J. May-Collado, Rita Sellares
Dorsal fin is the most notable features in dolphins playing an important role in swimming stability. The dorsal fin shape could change depending on where the dolphin’s lives. We compared dorsal fin across bottlenose dolphin in eight coastal regions in the Caribbean. Finding that coastal bottlenose dolphins across the Caribbean have very similar dorsal fin shape, having low and triangular shapes, two traits which are different with the oceanic dolphins. Nevertheless, differences in dorsal fin proportions were found between dolphin´s that live very close supporting the hypothesis that subgroups could be present even within extremely short geographical distances.