American Mink

Skye and Lochalsh Mink Monitoring Programme

Introduction

Mink are members of the weasel family (Mustelidae). The American mink Neovison vison (syn. Mustela vison) was introduced into the UK in the first part of the twentieth century for the production of pelts for the fur trade. Scotland introduced mink fur farming by 1937 and many farms developed throughout the country. In the 1960s regulation of the fur farms and the keeping of wild animals in captivity became a less attractive proposition. Although escapes had occurred from the earliest introduction of mink more releases and escapes into the wild has lead to a colonisation of much of Scotland. Although at the moment Caithness and Sutherland have submitted no reports.

In the wild mink are adaptive predators, eating small mammals, frogs and toads, fish, crustaceans and ground nesting birds. In various areas the mink have caused significant damage to wildlife populations. On the mainland the water-vole is particularly sensitive to mink predation, whilst in the Outer Hebrides ground nesting birds have shown an increase on reproductive success at the same time as a mink eradication programme has been in place. In total over the five trapping cycles so far, 13183 mink had been caught in Harris, Lewis and the Uists by September 2010. Domestic poultry are often a target for mink predation.

Although mink are widespread throughout the UK they are semi-aquatic, keeping to waterways and coastal habitats. In general mink are solitary animals that hunt and feed in long narrow territories (Reynolds et al., 2006), along stream and riverbanks, and on the coastal fringes. The territories tend to be between 3 and 7 kilometres long, the males holding larger areas than the females. On the Hebrides research suggests (Bodey et al., 2010) that the preferred habitat is coastal, as animals are trapped on the coast the land based animals move to replace them. This is probably due to the ease of finding food in the coastal areas. Steep rocky coasts in isolated areas in the Outer Hebrides tend to have a lower mink population, whilst on the East Coast of Scotland mink have been found throughout the catchments of the main rivers, such as the Dee, Don and Spey. This illustrates one of the main attributes of the animal, plasticity in the types of prey taken and an ability to colonise over long distances.

The life cycle of the mink includes several key points in the year when activity is greater. In the early months of the year - February to March - mating takes place. Kits are born in late April and May and are reared in dens by the female. The male plays no part in their nurture. The juveniles then disperse covering as far as one hundred kilometres from their den. Males will not tolerate other males within their territories but sometimes female territories overlap with male territories.

The Skye and Lochalsh Project

Skye and Lochalsh Environment Forum succeeded in obtaining funding from Leader, Highland Council and Scottish Natural Heritage for a monitoring programme in the Skye and Lochalsh area starting in July 2010. The aim of the project is to find the distribution of mink throughout the area and to assess the scale of the impact on the local wildlife and domestic stock.

In order to achieve these ends over eighty volunteers have become enthusiastic participants. Approximately fifty of these were able to monitor clay pads situated in tunnels and rafts spread throughout the area (mink's view of tunnel/raft interior, with clay pad between mink and exit). Volunteers were recruited by an advertising campaign including, posters, press, radio and television. Community councils were invited to become involved, as were the Grazing clerks and landowners throughout the area.

The monitoring programme has lead to 55 tunnels and rafts being deployed throughout the area between August and November 2010. The impressions of animals passing across the pads (there are no mink prints in this picture - here are mink paws) have been recorded either weekly or fortnightly and null reports have also been recorded. The tunnels and rafts were initially anointed with a musk lure (on floor and pillar bases at entrance) containing extracts from anal glands of captured mink and sourced from the USA. This was renewed after six weeks.

Volunteers have been issued with record sheets (both paper and electronic versions) as well as time sheets, mileage claim sheets and volunteer profile questionnaires supplied by 'Leader'.

In addition reports of sightings and damage to poultry and livestock are being collated so as to provide a more complete picture of the distribution of the mink.

The monitoring programme is divided into two parts to coincide with the main activity periods of the mink. The first of these periods was from August 2010 until November, the time of kit disperal (TABLE of results). Tunnels and rafts were distributed from Point of Sleat in the south of the area to Staffin in the north, and from Arnisdale, Shiel Bridge and Stromeferry in the east to Roag in the west.

Initial results have indicated a widespread presence of mink in Skye and Lochalsh, including Island populations on the Crowlins and Rona. The Mink Monitoring Group has been delighted with the positive responses and help it has received, from participants, statutory bodies and the general public.

Discussion

From the data gathered so far, sightings and fatality results have outnumbered the pad marks found in tunnels and rafts. This may be due to a variety of factors including specific site positioning of the equipment, inappropriate moisture content and/or 'setting' of the pad clay and, possibly, problems associated with the use of mink musk as a lure (Reynolds et al., 2006).

Many volunteers at this point (November 2010) have yet to submit their records. Nonetheless, most sightings and pad markings that have been obtained are close to the coast or on rivers and burns. It is notable that inland sites such as Loch Fada in Braes (Skye) have no records at all whereas close by, on the River Varragill at the head of Inner Loch Portree, mink have been trapped, recorded as pad marks and sighted. This broadly coincides with the findings from Bodey et al. (2010) which indicate a preference for coastal territories over inland ones should they become vacant after trapping.

The overall distribution of records of mink throughout Skye and Lochalsh suggests that mink are utilising the vast majority of the coastal fringe in Skye and Lochalsh. Certain areas have a more numerous return visits to the tunnels by mink, particularly Kyle of Lochalsh, Eilean Ban, Kyleakin, Erbusaig area, Strome Ferry, Glenelg to Duisdale, Loch Bracadale and the North Trotternish area of Skye. On islands in the Sound of Raasay mink sightings have been common, although no records so far have been returned for Raasay or Scalpay.

Notable gaps in mink records include the Waternish peninsula, although the area was well supplied with tunnels and rafts (road kill has been recorded at Edinbane). In Skye, gaps in recording have arisen between Skeabost and Uig, Glen Brittle, Loch Scavaig and the more precipitous and remote coastal cliffs around Talisker Bay, Neist Point, and between Staffin and Beareraig Bay on the East of Skye. Loch Duich records have yet to be submitted and will require inclusion as soon as they are available.

Further recording in tunnels and rafts is being carried out by Elaine Fraser of Aberdeen University in the Lochalsh/Shiel Bridge area with whom SLEF is liasing and close contact is maintained between staff of NTS from Morvich.

So far the overall pattern of returns suggests a healthy mink population in the Skye and Lochalsh area.

References & further reading

• Reynolds, J.C., Short, M.I. & Leigh, R.J. (2006). Development of Population control Strategies for Mustela vison using floating rafts. Biology Conservation Vol 120, issue 4.
• Bodey T.W., Bearhop S., Sugoto R. et al (2010). Behavioural responses of invasive American mink Neovison vison to an eradication campaign, revealed by stable isotope analysis. Journal of Applied Ecology, 47.
• MacLeod, I. (2010). Hebridean Mink Project Phase II. SNH Bulletin.
• Horrill, C. et al (2010). North of Scotland mink Project. RAFT Newsletter No. 7.