There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and the otters and ferrets. The American Mink is larger and more adaptable than the European Mink. It is sometimes possible to distinguish between the European and American mink; a European Mink always has a large white patch on its upper lip, while the American species sometimes does not. Thus, any mink without such a patch can be identified with certainty as an American Mink, but an individual with a patch cannot be certainly identified without looking at the skeleton. Taxonomically, both American and European Minks used to be placed in the same genus Mustela ("Weasels"), but most recently the American Mink has been re-classified as belonging to its own genus Neovison.
The American Mink's fur has been highly prized for its use in clothing, with hunting giving way to farming. Its treatment has also been a focus of animal rights and animal welfare activism. American Mink have found their way into the wild in Europe (including Great Britain) and South America, after being released from mink farms by animal rights activists or otherwise escaping from captivity.
American Mink are believed by some to have contributed to the decline of the less hardy European Mink through competition (though not through hybridization—native European mink are in fact closer to polecats[disambiguation needed ] than to their North American cousins). Trapping is used to control or eliminate feral American Mink populations.
Mink oil is used in some medical products and cosmetics, as well as to treat, preserve and waterproof leather.