American mink  (Mustela vison)

The introduced American mink has a slender body, short legs and a tail that is about a third of the body length (2). The thick, glossy fur can vary in colour, but is generally dark brown or black, and becomes darker in winter (6).

American mink, native to North America, were first introduced to fur farms in Britain in 1929; the first official record of escapees breeding in the wild was in 1957 (3). Following many accidental and deliberate releases, the species is now widespread and common throughout Britain and much of Europe (4). In Britain they are spreading in terms of range and numbers, extending into East Anglia and Yorkshire (4). However, in some areas of England the population is declining, this may be due to the return of the native otter (Lutra lutra) (4).

Lives in aquatic habitats, but can spend some time away from water and can even live near urban areas (4).

This semi-aquatic species is a versatile opportunistic predator (2), preying on rabbits (Oryctolagus cuniculus), water voles (Arvicola terrestris), and many other mammals, as well as a range of fish, birds, eggs, crayfish, and a variety of invertebrates (4). This species has had a devastating effect on native species; it has been implicated in the precipitous decline of the water vole, and poses a serious threat to game birds, fish and birds nesting on offshore islands (4). Although it can be active at any time during the 24-hour period, the activity of the American mink tends to peak at night and at dusk (4). They are solitary and territorial, with the male home range overlapping several female ranges (4). Mating occurs once a year (2), between February and April (4). During this time males leave their territories and increase their range in search of females (2). A single litter of 4-7 young is produced between April and May (4). When they reach 13-14 weeks of age, the young disperse away from the place of birth (4).

Other than preying on our native fauna, the American mink may also carry Aleutian disease, a virus of fur farms that can be transmitted to native carnivores (4).

Eradication of mink throughout Britain is unlikely and would be extremely expensive (2), however populations remain low where regular culling is carried out on a local basis. Sensitive areas could be fenced off (3), and on previously predator free islands, such as Harris, which supports internationally significant populations of nesting sea birds; eradication of mink is essential (3). It is now apparent that in areas where otters have made a recovery, mink have been declining (3), this is certainly encouraging news.

For more on mammals see The Mammal Society:
http://www.abdn.ac.uk/mammal/index.shtml

Information authenticated by Dr Pat Morris, with the support of the British Ecological Society
http://www.britishecologicalsociety.org/