Invasive Alien Species in Northern Ireland

Mustela putorius furo, Feral ferret

Mustela putorius furo (Linnaeus, 1758)
The ferret is the domesticated form of the polecat. They have been used for hundreds of years to hunt rabbits and to kill mice and rats. Ferrets are still used for hunting rabbits but mostly they are kept as pets.
Ferrets are very good at escaping, if they can get their heads through a gap they can usually get the rest of their bodies through. Most escapee ferrets are either recaptured or they die within a few days. Those that survive may become established and breed in the wild.
Ferrets were introduced onto Rathlin Island, County Antrim a number of years ago in an attempt to control the rabbit population. In the1980s ferrets became established in County Monaghan – it is thought that this population developed from animals lost and abandoned by ferreters whilst rabbit hunting.
The ferret is a member of the weasel family and has a long, thin elongated body with short legs. Males can grow up to 60cm long including the tail, females are smaller – ferrets are similar in size and shape to American mink.
Domesticated ferrets have been selectively bred to produce a variety of coat colours including the well-known white (albino) form with pink eyes. Most feral populations have markings similar to the wild European polecat – dark brown outer fur with creamy yellow under fur on the body and a distinctive ‘bandit-like’ dark mask across the eyes.
Country of origin
Domesticated form of the western polecat Mustela putorius
Current distribution
Feral ferret populations have been reported from New Zealand, Australia, Europe and North America. In Britain ferrets appear to survive best on offshore islands where there are large numbers of rabbits, there are populations on Shetland, Mull, Harris, Islay and North and South Uist.
Location in Ireland
The only known ferret population in Northern Ireland is on Rathlin Island. There is also a population in North Monaghan in the Republic of Ireland – at present there is no evidence that this population has spread beyond County Monaghan.
Life cycle
Very little is known about the life cycle and habits of wild ferrets or their preferred habitat. They are believed to be mainly nocturnal and are therefore rarely seen. Rabbits are thought to be their main prey along with birds and rodents.
Wildlife and habitat impacts
Feral ferrets may pose a threat to ground-nesting birds, especially rare species such as the lapwing and corncrake.
Key vectors
Ferrets are excellent escape artists and have been accidentally introduced into the countryside by ferreters and pet owners. In some cases ferrets have been intentionally introduced to control rabbits biologically.
What you can do as an individual
Report ferret 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[at]
A survey is currently under way to determine the distribution of feral ferrets in Ireland. To find out how to contribute to the survey contact Daniel Buckley, Mobile: (00353) 86-36 91 982, email: ferretsurvey[at]
Management measures
Queen's University Belfast's Quercus Centre, supported by the Environment and Heritage Service, is carrying out an investigation into the wildlife management requirements for corncrake recovery on Rathlin Island. Radio-tracking wild ferrets and filming at lapwing nests are being carried out to determine if ferrets are a threat to ground-nesting birds.
Further information
Feral Ferret Survey
Hayden, T. and Harrington, R. (2000). Exploring Irish Mammals. Town House and Country House Ltd., Dublin.
See the Invasive Species Ireland web site for further information -
Text written by:
Angela Ross, Curator of Vertebrates, Ulster Museum