Friday, 2 November 2012

Identifying Invasive Species - American Mink

Hi all,

My name is Fiona and I’m the volunteer Arthur mentioned a few blog posts ago.  I’m thoroughly enjoying my time here and in the interest of sharing we decided it would be a nice idea to let you all know a little about what I’ve been doing.

My focus over the last little while has been on Neovison vison A.K.A the American Mink.  Many of you will recognise these as the cute little weasel-like creature that roams our waterways but how many of you realise how severe a threat they are to our wildlife??

American mink are, as the name suggests, native to North America and in their natural habitat live in harmony with the local creatures; they have both prey and predators.  The mink were introduced to Britain during the 20th Century as a farming stock for the clothing industry.  Escapes and intentional releases by animal rights activists led to the mink quickly becoming feral and establishing a presence in our countryside.  Due to lack of predation and an ample food supply, the mink has flourished here.  Mink will wantonly kill more prey than is necessary for them to survive which has led to declining numbers in many of our native birds and mammals, most notably the water vole. 

The UK water vole population has declined rapidly from pre-1960 levels of around 8 million to around 354,000 (other source: 750,000) in 1998 and in the past decade the numbers of water vole have declined by a further estimated 90%. This decline is due to both habitat loss and mink predation.  Oxford University’s Wildlife Conservation Research Unit (the WildCRU) reported in 2008 that keeping water vole and mink populations apart is vital if efforts to reintroduce water voles, one of Britain’s most endangered mammals, are to be successful.

Ian Mitchell and Norman Ratcliffe in 2007 presented data on the impact of American Mink on puffin populations on 605 islands on the coastline of the UK.  Their data showed that there are significantly fewer breeding pairs on islands that are currently inhabited by the invasive mammals.  Their work extrapolated that if all the islands were colonised by mink then the number of breeding pairs would drop from 428,000 to 19,000.  Conversely, if all islands were free from invasive mammals, the breeding pairs would increase to 1.75 million.  

Closer to home, the effect of mink predation on sea birds in Western Scotland was observed by Clive Craik from the Scottish Association for Marine Science, on the island of Eilean Inshaig.  This rich colony was first known to have been attacked in 1987, when the mink, a female with young in a den on the island, was caught. Severe mink predation did not recur until 1992 when the 311 pairs of black-headed gulls, 85 pairs of common gulls and smaller numbers of other species all raised no young. Whole-island breeding failure caused by mink occurred again in 1993 and 1994. In 1995-1998 few or no birds attempted to breed. The island colony had become virtually extinct after repeated mink predation, mainly of eggs and young. Mink control at this site began in 1996. A few dozen pairs of black-headed and common gulls returned to breed successfully in 1999. During 2000-2007 the numbers and productivity of most species on the island had recovered almost to pre-1987 levels. 

These examples show not only the devastating effect mink predation has on our wildlife but also how effective mink eradication projects can be.  The mink is considered such a threat to UK native species that as per the Wildlife and Countryside Act of 1981 it is illegal to release or to allow escape captive American mink into the wild.  Several large scale mink eradication projects are in place in the Scottish Islands and Northern Scotland, which have had great success in the protection of endangered native species.

That our native species are at risk is clear, the only question is what we can do about it.  I have been looking into the feasibility of a mink control project in the Falkirk area and would welcome any input you feel you could offer.

If you want to know more about this or if you have any project ideas you want to discuss, please get in touch.

Further Reading

Tackling the Problem of invasive alien mammals on seabird colonies - Strategic approaches and practical experience -

Scottish Mink Initiative -

State of Britain’s Mammals 2011 -