Description

American mink are a member of the mustelid family whose other members include weasel, otter and badger. They all have a musk gland which they use to secrete a pungent oil to mark their territories. Mink are ferret sized, twice the size of a stoat and half the size of an otter. Male mink measure approximately 60 cm in length, including the tail and weigh between 1 – 2 kg. Females are smaller at approximately 45 cm, including the tail and weigh between 0.5-0.8 kg. They are most commonly known to have dark brown/black fur with a little white chin patch, however their colours can vary. This is because when they were farmed for their fur more unusual colours were more valuable, e.g. blue-grey, silver and albino.

Habitat

Mink are semi-aquatic animals and the best places to see them are in wetland environments such as streams and rivers, lakes, broads, marshes and sea coasts where they find much of their prey, though they may also be frequent in more open situations. Mink are territorial; an average mink territory size along a linear waterway may be up to 5km for a male and 1km to 3km for a female. Mink are excellent swimmers and divers and can stay under water for some time.

Click image to enlarge.

Diet

American mink are carnivores and eat a wide range of prey including birds, rabbits, fish, and game, as well as water voles. Because of their wide range of prey they can thrive in many different habitats eating whatever food is available in that area, this can include domestic fowl. They are an opportunistic, generalist predator able to adapt their feeding behaviour according to prey availability and once they have reduced one food source they simply move onto another.

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Mink diet in 1st year of colonisation, River Soar, Leics. Researched by © Chris Strachan

Mink Calendar

Mink will breed during the spring (February to April) with males travelling vast distances in search of a mate, they will try to mate with any female mink they find and then move on in search of another. A female mink will look for a den site once she has mated to raise her young; den sites are usually cavities in tree roots at the water’s edge, rabbit burrows or in a pile of rocks. However they will make a den practically anywhere, e.g. under/in sheds, windmills, reed/sedge stacks, under cattle grids and we have seen them in a thatched roof on a boat house. The young (known as kits) are born in late April to June after a gestation time of 40-75days, with a typical litter size being 3-4 kits, some litters can be larger but this is rare. Kits are entirely dependent on the mother’s milk for 3-4 weeks, and are weaned after 6-7 weeks. From August to October juvenile mink will become independent, their mother will discourage them from the den and they will leave to find their own territories. Mink are very capable hunters during the winter and do not hibernate and both male and female mink will take winter-surviving water voles before they have had a chance to breed.

EARLY SPRING
February - March

Male mink are searching for females to mate with.

They will try to mate with multiple females.

Often several male mink can be caught in one
location as they move into a territory to find the female.

Summer
May – August

Female mink will be in a den rearing their kits.

As the kits are weaned, the female
will bring food back to the den.

Prey carcases left in one area could
be a sign that a den is close by.

Autumn
September – November

Kits will now be dispersing in search of their own territories.

A kit can travel vast distances within a year to find a territory.

A juvenile female can reach adult weight at approximately
4 months and males between 9 and 11 months of age.

Winter
December – February

Mink do not hibernate and
will continue to hunt for food.

Females and this year’s juveniles
are small enough to get into a
water vole burrow;
taking winter-surviving water voles
before they can
breed can be catastrophic.

Mink differences from Otter

If you do not know the species well it can sometimes be difficult to tell a mink from an otter especially if you only have a brief sighting. Useful points are:

  • Size – a mink is ferret sized, half the size of an otter.
  • Female mink 45 cm, male 60 cm inc tail. Female otter 90 cm, male 120 cm.
  • Female mink 0.5 – 0.8 kg, male 1 – 2 kg. Female otter 7 kg, male 10 kg.
  • Colour – for mink dark brown fur is most common but they vary from grey to black with a little white chin patch. Otters are medium brown with a large pale bib but can look almost as dark as mink when their fur is wet.
  • Tail – a mink tail is the same diameter along its length while an otter’s has a broad base and tapers to a point.
  • Swimming – with mink the whole body is visible, with an otter most of the time only the head shows.

© Paul Sergent

© Ken Billington

Mink

Otter

© Snowdonia National Park Authority

Mink

Otter