Description: The American mink usually has dark brown fur, looking black when wet. It has small and variable white patches on the chin, throat, chest and groin, which are more evident on a carcass. The American mink also has a short fluffy tail. It is of similar size to ferret or polecat and thus much smaller than an otter.
Size: Average 37cm head & body, tail 18cm.
Weight: Kittens 100-160g at birth. Adult males 800-1,500g & females 500-800g.
Lifespan: Average 10-12 years in the wild.
Breeding: The female has one litter a year, and young mink are born blind and hairless, in litters of 4-6, in May. They begin to take meat from 5-6 weeks and reach adult size by the autumn. They can breed at one year old.
Habitat: Rivers and wetland (also coastal in counties with coastline).
Diet: Mink eat a wide range of mammals, birds and fish, typically about a third of the diet coming from each. In some areas they also eat invertebrates, such crayfish (in coastal areas they eat crab).
General Ecology: The mink’s success is in part a result of its ability to exploit a very wide range of prey, and especially to take advantage of any species that is locally or seasonally abundant. Mink are strictly territorial, with males occupying exclusive ranges of 1-6 km in length. Females have smaller territories within or overlapped by those of males. They use their scats to mark the boundaries of their territory, and the neighbourhood of their den, which is usually within 10m of water.
Distribution and main sites: From the first official sighting on the river Teme in the far south-west of the county, the species has now spread into every major river catchment in Shropshire. The seemingly most frequent records are for the River Severn and its immediate larger tributaries, as well as the Shropshire Union Canal and the meres in and around Ellesmere, both at the north of the county.
Conservation Status: An invasive non-native species which is listed on Schedule 9 of the Wildlife and Countryside Act, 1981 (as amended), which makes it illegal to distribute or allow the release of mink into the wild. In the early years of its establishment in Britain and Ireland, mink appeared to do little serious damage, despite much concern about their potential impact. However, in Shropshire, water voles (largely confined to strips of waterside habitat) have proved to be very vulnerable.
Unlike some other counties, no serious attempts have been made to remove mink from river systems where water voles might be favoured are known.
Threats: Not applicable. As an invasive non-native it is subject to local attempts at eradication.
Action: Not applicable. As an invasive non-native it is subject to local attempts at eradication.
Main recording methods: Droppings are the most easily found and identifiable field sign. Footprints are also reasonable common in sand, mud and snow alongside watercourses. Mink rafts with clay floors, enclosed in a tunnel, for footprints reveal when mink are present are used for control programmes. See (link) for field sign details.
Their scat often contain bones and fur and are long and twisted in shape, with tapered ends. They are approximately 6-8cm long, 10cm thick, greenish, black, brown in colour. The key distinguishing feature from otter droppings is the smell which is foul, like burnt rubber and/or rotten meat (cf. otter droppings which are (sickly) sweet smelling).
Did you know?
Because of their fondness for water, captive American Mink may enter kettles or other open water-containing vessels.
Notoriously feisty, they have also been known to see off cats in confrontations.
Text – Robert Mileto, but largely using https://www.mammal.org.uk/species-hub/full-species-hub/discover-mammals/species-american-mink/ (accessed January 2020).
Mammal Society field signs guide
© Shropshire Mammal Group 2020