Invasive Alien Species in Northern Ireland

Mustela vison, American Mink

Mustela vison
© Laurie Campbell
Mustela vison
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Mustela vison Schreber 1777
 
Introduction
Mink are semi–aquatic fur-bearing mammals and are rarely found far from water. They prefer slow shallow rivers and lakes with lots of bankside vegetation. In some coastal areas mink may be found on rocky sea shores.
Mink were first farmed for their fur in Ireland in the early 1950s. Within ten years there were around forty mink farms or ranches across Ireland, housing thousands of animals. Since then there have been many escapes and deliberate releases. As a result, mink have become firmly established in the wild throughout Ireland.
Mink farming was banned in Northern Ireland in 2003. There are six mink farms still operating in the Republic of Ireland.
 
Description
Mink are members of the weasel family (Mustelidae). They have long, sinuous bodies, short legs with partly-webbed feet and a moderately bushy tail. The head is bluntly pointed with small rounded ears that are almost hidden in the fur. Males can measure 50–70cm from nose to tail and weigh up to 1½kg; females are smaller. The fur is dark chocolate brown (appears black) and made up of long, hard, shiny guard hairs with a short undercoat of slightly lighter soft dense fur. White patches are usually seen on the chin, chest and belly.
 
Country of origin
Canada and North America.
 
Current distribution
American mink have been introduced to many countries across the world since the 1920s – Argentina, Iceland and most mainland European countries have breeding populations. American mink are widespread in Britain and are present on a number of offshore islands including Lewis, Harris, Mull, Islay and the Isle of Arran.
 
Location in Ireland
Mink are widespread throughout Ireland. In Northern Ireland they are more common in counties Tyrone and Fermanagh. The first documented escape of farm–bred mink occurred in 1961 when thirty mink escaped from a fur farm near Omagh, County Tyrone and became established in the surrounding countryside. Mink have also escaped over the last fifty years at various locations in the Republic of Ireland.
 
Life cycle
Mink are solitary, territorial animals, both males and females select an area of land (territory) that they will defend. A male will not tolerate another male within its territory, but is usually less aggressive towards females. Within its territory a mink will have several dens to shelter in, usually in the roots of riverside trees, amongst boulders or in old rabbit burrows. Although mainly nocturnal, mink are often seen during the day.
Mating takes place between February and early April; up to six young are born about 30 days later, depending on food and weather conditions. The kids are born deaf, blind and hairless but grow quickly and are weaned by the time they are eight weeks old. They remain with their mothers during the summer, but move away to find their own territories in the autumn.
Mink are fast, agile carnivores and will eat anything that they can catch and kill. Their diet is made up of fish mainly, birds (coots and moorhens), young rabbits, rats and crayfish.
 
Wildlife and habitat impacts
Mink may pose a serious threat to ground–nesting birds, particularly colonies of seabirds nesting on islands.
 
Human impacts
If the opportunity arises, mink will kill and eat game birds and ornamental fowl.
 
Key vectors
Mink were intentionally introduced into Ireland for fur farming. Many animals accidentally escaped from these farms and in some cases were intentionally illegally released.
Mink farms are still operating in the Republic of Ireland. In 2003 animal activists released mink in Co. Laois.
 
What you can do as an individual
Report mink sightings to CEDaR, Botany Department, Sciences Division, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down BT18 0EU. Tel: 028 9039 5256, email cedar.info[at]nmni.com.
A survey has been recently undertaken to assess the extent of damage caused by mink and the level of mink control being exercised in Ireland. To find out more about the survey contact Conall Hawkins, Tel: 0879284842, email: minkresearch[at]yahoo.com.
 
Management measures
Trapping and culling are the most effective methods for controlling mink. Control of mink should only be undertaken if their activities are actually causing problems. Where a problem arises, only legal methods of control must be used.
When undertaking control measures, special care must be taken to avoid harming any wildlife species protected under the Wildlife (NI) Order 1985.
 
Further information
Links
Northern Ireland's Mammals, Amphibians & Reptiles
Mink Survey
Centre for Conservation Science . CCS
Global Invasive Species Database
 
Literature
Hayden, T. and Harrington, R. (2000). Exploring Irish Mammals. Town House and Country House Ltd., Dublin.
 
Text written by:
Angela Ross, Curator of Vertebrates, Ulster Museum