A member of the family Mustelidae, which also includes weasels, mink, ferrets, martens, sables, fishers, badgers, and wolverines. Otters are found worldwide except in Australia, Madagascar, and on the islands of the South Pacific. Most inhabit freshwater lakes and rivers. The sea otter (Enhydra lutris), however, inhabits the waters and shores of the northern Pacific Ocean from southern California to the Kurile Islands.