Pest Of The Week – Mink

Originally from North America, the American mink (Neovison vison), was brought over to Scotland in 1938 for fur farming, the first mink escaped in the same year. Feral mink are now known to be present in most Scottish mainland counties and are also found on the islands of Arran, Skye and Lewis. Mink are indiscriminate predators, and survive on a wide range of native species including water voles, which have declined dramatically in the past few decades, decreasing across the UK by more than 96% since 1950. As well as water voles and other small mammals, mink are also known to predate a range of bird species. Other species, not closely associated with water, are also vulnerable to mink predation and have potentially reduced in numbers as a consequence.

American mink have short legs, a long thick neck and a broad head with short rounded ears. Male American mink measure approximately 58-70 cm in length and weigh between 0.9 kg and 1.6 kg. Females are slightly smaller at 46-57 cm in length and weigh between 0.7 kg and 1.1 kg. Their natural fur colour is dark brown/black with a white chin patch however in the UK their colour varies greatly. When American mink were farmed for their fur the more unusual fur colours (e.g. silver, purple-grey and albino) were more valuable. Their fur is very thick which helps them stay warm and dry.

American mink are semi-aquatic which means that they spend a lot of time in and around water. They are good, strong swimmers and have slight webbing between their toes which helps them swim quickly in the water. Although they will usually avoid swimming in strong currents, they have been found to swim across the sea to reach islands, sometimes up to 5 km off shore.

During spring (February to April) male American mink travel vast distances across the country – up to 20 km a day in search of a mate. They will try to mate with any female American mink they can find and afterwards will move on in search of another female. Female American mink are very territorial, defending their territories against other females however they will tolerate the presence of a male. Once a female has been mated she will make a den in a safe place where she is unlikely to be disturbed. This could be within an old rabbit warren or water vole burrow and is usually not far from water. Up to 10 young (known as ‘kits’) can be born in one litter (although the average is 4-6) and remarkably young from the same litter can have different fathers. This is a result of diapause, a biological feature known in many mustelid species which means that the female can ‘pause’ the development of individual young until they are all at the same developmental stage before pressing “start” again. The kits are born around June after a gestation time of 40-75 days. They are weaned at approximately 6 weeks and in July they leave the den for the first time and begin to explore their surroundings. From August to October, juveniles are discouraged from the den by their mother and will leave to find their own territories.

American mink are carnivores and eat a wide range of prey including rabbit, water vole, fish and ground nesting birds. As a result, they can survive in many different habitats eating whatever food they can catch. They are classed as opportunistic, generalist predators able to switch between prey sources when one food source becomes scarce. Because of their high metabolic rate, American mink have to eat approximately one third of their body weight every day to sustain themselves.

The Law
The American mink meets criterion 2 of the SNH Species Action Framework as an invasive non-native species which presents a significant risk to biodiversity. The Wildlife and Countryside Act 1981, as amended, makes it an offence to release mink or allow them to escape into the wild. The Mink Keeping (Scotland) Order 2003 prohibits the keeping of the species in Scotland except under licence

If you suspect you have a mink infestation in Edinburgh, Glasgow, Aberdeen, Dundee or Perth, call GRAHAM pest control today and we could help