“…In addition, the polar bear (Ursus maritimus) and the sea otter (Enhydra lutris) are counted among the marine mammals. For information on the sensory biology of the polar bear, the reader is referred to Nachtigall et al (2007); for the sea otter, to Murphy et al (1990) and Ghoul and Reichmuth (2012); for marine mammals in general, to Supin et al (2001), Dehnhardt (2002) and Thewissen and Nummela (2008). All major clades of marine mammals also include species that live fully or partly in fresh water, such as the Baikal seal (Pusa sibirica), two families of river dolphins (Iniidae and Platinistidae), dolphins of the genera Sotalia, Sousa and Orcaella, and the manatees (Trichechus).…”