Otter Otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the weasel family Mustelidae, which also includes badgers, honey badgers, martens, minks, polecats, and wolverines. The word "otter" derives from the Old English word "otor" or "oter". This, and cognate words in other Indo-European languages, ultimately stem from the Proto-Indo-European language root *wódr̥, which also gave rise to the English word "water". An otter's den is called a holt or couch. Male otters are called dogs or boars,
Sea otter was more closely related to the earless seals. Genetic analysis indicates the sea otter and its closest extant relatives, which include the African speckle-throated otter, European otter, African clawless otter and oriental small-clawed otter, shared an ancestor approximately 5 Mya (million years ago). Fossil evidence indicates the "Enhydra" lineage became isolated in the North Pacific approximately 2 Mya, giving rise to the now-extinct "Enhydra macrodonta" and the modern sea otter, "Enhydra lutris". One related species has been described, "Enhydra reevei", from the Pleistocene of East Anglia. The modern sea otter evolved initially in northern Hokkaidō and Russia, and then spread