American mink
The American mink is a semiaquatic species of mustelid native to North America, though human introduction has expanded its range to many parts of Europe, Asia, and South America. Because of range expansion, the American mink is classed as a least-concern species by the IUCN. The American mink was formerly thought to be the only extant member of the genus Neovison following the extinction of the sea mink, but recent studies, followed by taxonomic authorities, have reclassified it and the sea mink within the genus Neogale, which also contains a few New World weasel species. The American mink is a carnivore that feeds on rodents, fish, crustaceans, frogs, and birds. In its introduced range in Europe it has been classified as an invasive species linked to declines in European mink, Pyrenean desman, and water vole populations. It is the animal most frequently farmed for its fur, exceeding the silver fox, sable, marten, and skunk in economic importance.
Evolution
As a species, the American mink represents a more specialized form than the European mink in the direction of carnivory, as indicated by the more developed structure of the skull. Fossil records of the American mink go back as far as the Irvingtonian, though the species is uncommon among Pleistocene animals. Its fossil range corresponds with the species' current natural range. The American minks of the Pleistocene did not differ much in size or morphology from modern populations, though a slight trend toward increased size is apparent from the Irvingtonian through to the Illinoian and Wisconsinan periods.Although superficially similar to the European mink, studies indicate the European mink's closest relative is the Siberian weasel of Asia. The American mink has been recorded to hybridize with European minks and polecats in captivity, though the hybrid embryos of the American and European minks are usually reabsorbed.
Subspecies
, 15 subspecies are recognised:| Subspecies | Trinomial authority | Description | Range | Synonyms |
| Eastern or little black mink N. v. vison | Schreber, 1777 | The smallest subspecies | Eastern Canada, west to Hudson Bay; south in the interior to the Catskill Mountains, New York and to northern Pennsylvania | altaica borealis nigrescens tatarica winingus |
| California lowland mink N. v. aestuarina | Ginnell, 1916 | Resembles N. v. energumenos, but smaller and has paler, less dense fur | The lowlands of west-central California; west to Petaluma and Marin Counties | |
| Aniak mink N. v. aniakensis | Burns, 1964 | |||
| Western or Pacific mink N. v. energumenos | Bangs, 1896 | A small and dark-coloured subspecies with dark sooty-brown fur. Males measure in total length and in tail length. | Western North America, from British Columbia south to the Sierra Nevada Mountains in California and the Rocky Mountains in New Mexico | |
| Vancouver Island mink N. v. evagor | Hall, 1932 | |||
| Everglades mink N. v. evergladensis | Hamilton, 1948 | The southern tip of Florida | ||
| Alaskan mink N. v. ingens | Osgood, 1900 | The largest subspecies, it resembles N. v. energumenos, but is lighter in colour. Males measure in total length and in tail length. | Northern, western and central Alaska; the northern Yukon and the northwestern Mackenzie Mountains; south to the Alaska Peninsula and to Fort Good Hope | |
| Hudson Bay mink N. v. lacustris | Preble, 1902 | It has dark chocolate-brown fur above with white on the chin and irregularly distributed on the breast and between the hind legs. Males measure in total length and in tail length. | The interior of Canada from Great Bear Lake and the western shores of Hudson Bay south through Alberta, Saskatchewan and Manitoba to southern North Dakota | |
| Mississippi Valley mink N. v. letifera | Hollister, 1913 | It has a light brown coat with white spots on the chin, throat and breast. Males measure in total length and in tail length. | Northern Wisconsin and northern South Dakota south to northern Illinois, northern Missouri and southern Kansas | |
| East Canadian mink N. v. lowii | Anderson, 1945 | |||
| Atlantic salt marsh mink or Florida Mink N. v. lutensis | Bangs, 1898 | A medium-sized subspecies, it has a pale russet to clay- or reddish-brown coat. Males measure in total length and in tail length. | The coasts of the southeastern United States from South Carolina to Florida | |
| Kenai mink N. v. melampeplus | Elliot, 1904 | Darker than energumenos, it has dark chocolate-coloured fur with slightly paler underparts and a white spot on the chin. Males measure in total length and in tail length. | The Kenai Peninsula and Cook Inlet | |
| Common mink N. v. mink | Peale and Palisot de Beauvois, 1796 | A larger and more robust form than N. v. vison; it has similar colouration. Males measure in total length and in tail length. | The Eastern United States, from the coast of New England south to North Carolina and in the interior to central Georgia and Alabama; westward through southern Pennsylvania and Ohio to Missouri and northeastern Texas | lutreocephala rufa |
| Island mink N. v. nesolestes | Heller, 1909 | Intermediate in size between N. v. ingens and N. v. energumenos, it has rather dark fur. The fur is Van Dyke brown, lighter on the cheeks and sides and darker on the tail. The underparts are walnut brown and white on the chin, with irregular white spots or areas on the throat, chest, inner legs and abdomen. Males measure in total length and in tail length. | Admiralty Island in the Alexander Archipelago | |
| Southern mink N. v. vulgivaga | Bangs, 1895 | It resembles N. v. mink, but is paler and smaller, with rich and lustrous light brown fur which darkens at the end of the tail. Males measure in total length and in tail length. | The coasts of Louisiana and Mississippi |
Description
Build
The American mink differs from members of the genus Mustela, as well as the other members of Neogale, by its larger size and stouter form, which closely approach those of martens. It shares with martens a uniformly enlarged, bushy and somewhat tapering tail, rather than a slender, cylindrical tail with an enlarged bushy tip, as is the case in stoats. The American mink is similar in build to the European mink, but the tail is longer.The American mink has a long body, which allows the species to enter the burrows of prey. Its streamlined shape helps it to reduce water resistance while swimming. The skull is similar to that of the European mink, but is more massive, narrower, and less elongated, with more strongly developed projections and a wider, shorter cranium. The upper molars are larger and more massive than those of the European mink. The dental formula is.
Domestic mink, which are bred in fur farms and are substandard genetically, have 19.6% smaller brains, 8.1% smaller hearts, and 28.2% smaller spleens than wild mink. The feet are broad, with webbed digits. They generally have eight nipples, with one pair of inguinal teats and three pairs of abdominal teats. The adult male's penis is long, and is covered by a sheath. The baculum is well-developed, being triangular in cross section and curved at the tip.
Males measure in body length, while females measure. The tail measures in males and in females. Weights vary with sex and season, with males being heavier than females. In winter, males weigh and females. Maximum heaviness occurs in autumn.