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American mink

The American mink (Neovison vison) is a semiaquatic species of mustelid native to North America, though human intervention has expanded its range to many parts of Europe and South America. Because of range expansion, the American mink is classed as a least-concern species by the IUCN. Since the extinction of the sea mink, the American mink is the only extant member of the genus Neovison. 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. 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 American mink's closest relative is the Siberian weasel (kolonok) 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. As of 2005, 15 subspecies are recognised. The American mink differs from members of the genus Mustela (stoats and weasels) 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 slenderly terete 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 (constituting 38–51% of its body length). 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 whilst 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 3.1.3.13.1.3.2. 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. It generally has eight nipples, with one pair of inguinal teats and three pairs of abdominal teats. The adult male's penis is 2.2 in (5.6 cm) long, and is covered by a sheath. The baculum is well-developed, being triangular in cross section and curved at the tip. Males measure 13–18 in (34–45 cm) in body length, while females measure 12–15 in (31–37.5 cm). The tail measures 6–10 inches (15.6–24.7 cm) in males and 6–8 in (14.8–21.5 cm) in females. Weights vary with sex and season, with males being heavier than females. In winter, males weigh 1–3 lb (500–1,580 g) and females 1–2 lb (400–780 g). Maximum heaviness occurs in autumn.

[ "Predation", "Mink", "Pseudamphistomum truncatum", "Southern river otter", "Neovison", "Mustela lutreola", "Genus Mustela" ]
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