American Mink
Neovison vison
Description 4
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:
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.
The American mink's winter fur is denser, longer, softer, and more close-fitting than that of the European mink. The winter fur's tone is generally very dark blackish-tawny to light-tawny. Colour is evenly distributed over all the body, with the lower side being only slightly lighter than the upper body. The guard hairs are bright and dark-tawny, often approaching black on the spine. The underfur on the back is very wavy and greyish-tawny with a bluish tint. The tail is darker than the trunk and sometimes becomes pure black on the tip. The chin and lower lip are white. Captive individuals tend to develop irregular white patches on the lower surface of their bodies, though escaped individuals from Tartaria gradually lost these patches. The summer fur is generally shorter, sparser and duller than the winter fur. The thick underfur and oily guard hairs render the pelage water-resistant, with the length of the guard hairs being intermediate between those of otters and polecats, thus indicating the American mink is incompletely adapted to an aquatic life. It moults twice a year, during spring and autumn. It does not turn white in winter. A variety of different colour mutations have arisen from experimental breeding on fur farms.
On land, the American mink moves by a bounding gait, with speeds of up to 6.5 km/h (4.0 mph). It also climbs trees and swims well. During swimming, the mink propels itself primarily through undulating movements of the trunk. When diving, it undergoes a state of rapid bradycardia, which is likely an adaptation to conserve oxygen. In warm water (24 °C (75 °F)), the American mink can swim for three hours without stopping, but in cold water it can die within 27 minutes. It generally dives to depths of 12 in (30 cm) for 10 seconds, though depths of 3 m lasting 60 seconds have been recorded. It typically catches fish after five- to 20-second chases.
The American mink relies heavily on sight when foraging. Its eyesight is clearer on land than underwater. Its auditory perception is high enough to detect the ultrasonic vocalisations (1–16 kHz) of rodent prey. Its sense of smell is comparatively weak. Its two anal glands are used for scent marking, either through defecation or by rubbing the anal region on the ground. The secretions of the anal glands are composed of 2,2-dimethylthietane, 2-ethylthietane, cyclic disulfide, 3,3-dimethyl-1,2-dithiacyclopentane, and indole. When stressed, the American mink can expel the contents of its anal glands at a distance of 12 in (30 cm). Scent glands may also be located on the throat and chest. The smell produced by these scent glands was described by Clinton Hart Merriam as more unbearable than that produced by skunks, and added it was "one of the few substances, of animal, vegetable, or mineral origin, that has, on land or sea, rendered me aware of the existence of the abominable sensation called nausea".
Sources and Credits
- (c) Aleksandar, some rights reserved (CC BY-SA), uploaded by Aleksandar
- (c) Zac Cota, some rights reserved (CC BY-NC), uploaded by Zac Cota
- (c) annagypsy, some rights reserved (CC BY-NC-SA), uploaded by annagypsy
- (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/American_mink
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