Evolution

Otters have been around for about 5-7 million years, when they evolved from a terrestrial weasel like ancestor. All 13 species of otter are part of the sub-family Lutrinae, which specifies them from the diverse carnivorous mammals in the Mustelidae family. Most Mustelidae are small animals with long bodies, short legs, round ears, and thick fur.  Some well-known Mustelidae's include weasels, wolverines, and badgers, martins, and otters. Otters differ from the other Mustelidae's because they have very dense, layered fur and are larger in size. Otters have gone through many adaptations overtime, some specific to certain otter species, and some are present in all otters. Sea otters evolved from species that were on land, to semi-aquatic freshwater species (other otter species), and then to sea life.  Sea otters are the only otters that developed fully webbed feet because they are the only fully aquatic species of otter. Sea otters also differ from the other Lutrinae because they don't build dens and burrows and they lack an anal scent gland. Sea otters are the only living member of the genus Enhydra, which derives from ancient Greek meaning "in water". The sea otter species is known as lutris, but there are three sub-species of sea otter determined by their geographic location, the Asian sea otter, the Northern (Pacific) sea otter, and the Southern (Pacific) sea otter.