Stopping mink in their tracks – tips and tricks of the trade

Karen Muller, Project Officer, Scottish Invasive Species Initiative.
May 2021

Sleek, dark brown fur, flashes of white under the chin and a bounding gate or streamlined-shape cutting through water – the invasive non-native American mink. In the last 50 years they have become a more common sight along our Scottish watercourses and coastlines than we – and our native wildlife – would like. 

The devastating impacts of this adaptable and ferocious predator are clearly apparent – mink predation contributing to significant declines of native wildlife species, particularly water voles and ground nesting birds.

Over the last 15 years much mink control has taken place in Scotland.  However as these are wily creatures who think nothing of travelling 80km to find new breeding territories and craftily avoid entering traps their removal is not straightforward.  So, here are some tips and hints from the Scottish Invasive Species Initiative for successful mink trapping and how to out-trick these irreverent tricksters.

Please note – this article is not a guide to trapping.  Trapping should only be undertaken by trained people who understand their responsibilities regarding animal welfare, humane dispatch and relevant legislation.

American mink (photo credit – Liam Skinner)

Understand your foe

Mink are very adept semi-aquatic predators, active during the day and night and feeding opportunistically on a wide range of prey, such as fish, amphibians, birds (and their eggs), rabbits and other small mammals.

They are solitary and territorial animals – a female territory will cover around 1-3kms while male territories are usually larger (5kms) and can span across several female territories.  It’s worth noting that territories in good quality habitats will be quickly recolonised if the original occupant has died or been removed.

A good territory will be close to freshwater and often along a river in low altitude farmland, marshland or woodland edge with a plentiful supply of food e.g. rabbits.  Coastal areas are also popular – but mink still need a freshwater source nearby to clean their coats regularly.

To trap or not to trap – that is the question

As traps must be checked every 24hrs trapping can be time consuming, so it is worth monitoring for mink presence first and only starting trapping when you know mink are in the neighbourhood.

Mink monitoring is done by using a floating raft with a clay pad – to record footprints.  The raft is easily switched to trapping mode by adding a live capture trap when you know mink are present.  Read more about mink monitoring rafts on our website.

The mink monitoring raft – the clay pad sits inside the tunnel.

It’s also worth remembering to keep in touch with neighbouring monitoring rafts – our mink control is part of a large scale effort and so if you find mink signs let your neighbours know so trapping effort can be co-ordinated. The chances are that, due to their transient nature the mink you detected might have already carried on upstream and already be in your neighbour’s patch!

Alternatively, you can use a trail camera, or look for field signs if you don’t have a monitoring raft.   Check muddy or sandy banks for tell-tale footprints, bridge arches or prominent rocks for scat and look for flattened trails on riverbanks. 

Key trapping times

The best times for catching mink are pre- and post- breeding periods when mink are mobile and so there is a greater likelihood of catching them. Trapping success at these times will have a greater impact on the overall mink population.

Between January and March, many mink are transient and travel widely outside of their territories – males searching for a mate and young females searching for a breeding territory. Catching mink at this time will avoid successful breeding and prevent new mink being added into the population mix.

In summer family groups emerge from the den and by early autumn young mink are starting to leave their natal home territory but still congregate quite locally. These juvenile mink are extremely inquisitive and naïve making them easier to catch – so from July – October is the second critical trapping time.

Young female mink caught in trap.

The ‘how’

There are many native and domestic animals which can frequent the same habitats as mink – so we use live-capture traps and release non-target species unharmed.  Placing the trap on a floating raft on water further reduces the likelihood of catching non-target species as many of these are less likely to make the swim to the raft and trap.

Always cover your trap with a wooden tunnel for shelter and securely tie both the trap and tunnel to the raft.  This prevents the trap being dislodged by an angry mink or another animal and avoids the risk of accidental drowning.  Raft and traps units should be disabled or removed if the river is going to be in flood.

Live capture trap set on a mink raft, under the tunnel.

Location, location, location

Finding the right spot in the river for your mink raft and trap is the number one deciding factor in capture success – so here’s some handy hints to help you site your kit effectively on the water:

  • Look for confluences, where two water bodies join – you are doubling your chances that a mink will come across the trap by following either of the rivers or burns.
  • Find freshwater sources along coastlines – sooner or later mink are bound to search them out and use them.
  • Use pinch points – where mink are naturally forced through smaller gaps – as mink traffic can be funnelled towards your trap.  These can be:
    • under/near bridges or on bridge foundations/arches
    • culverts
    • weirs
    • in-stream islands
    • inflows and outflows on lochs
  • Select a sheltered spot out of the main flow – mink are good swimmers but they are not daft and will use the most efficient route to pass through their territories. Slow glides and slack water which make for easier swimming are ideal.

Remember – the location is no good if you can’t safely reach it in both high and low flow conditions – double check this first.  Also ensure if placed near a structure like a bridge or culvert that your raft will not cause a blockage in a flood.

A perfect spot at the confluence of two water courses.

A raft set up won’t be suitable for all locations – sometimes you can set a ground trap.

In these cases, you need to think like a mink!  Consider the likely routes mink use to move around.  In coastal areas, on beaches, this could be along the bottom of cliffs or harbour walls or between rock outcrops or prominent rocks.  Inland look for trails through vegetation along the bank, along hedges or fence lines, or fallen logs and wood and rock piles – even better if you find a well-situated log or rock pile and can fit the trap amongst them.  A mink might go for a rummage there for their next meal.

Note – If using a ground trap ensure the location is not at risk of flooding or within the tidal area. If in doubt put your trap on a raft, tied with enough slack that the raft can move in the case of water levels rising unexpectedly.

Please keep in mind that, any spot, even if it ticks all the boxes above is likely to be of little use if it is in too public a place.  We have had equipment vandalised or removed in the past and, given that if you catch a mink it will need to be despatched this task is not one which should have an audience and you certainly do not want a member of the public approaching a trapped animal.  If in doubt – find another place.

Ground traps; under a rock (L) and in a well camouflaged tunnel (R)

So, you’ve found your spot; you’ve set up your trap – time to open the box of tricks! Read on.

Trapping Hacks

Mink are curious, and you may never need to reach deep into your bag of tricks.  But if after a few weeks you are not having success then it may be time to try something a little different.

Location and set up:

  • Move your raft slightly -Try swapping to the opposite bank or a move upstream or downstream by 200 metres. Mink are fickle and these moves can often make a difference!
  • Change the direction of the trap opening – Footprints on your clay pad may give a clue to the general direction of mink travel so switch things around to see if that helps.
  • Try a double ended trap – Set two rafts with two traps opening in opposite directions. Or if on land set two traps up back to back.
  • Use camouflage – Your mink might be shy, so blend the unit into the environment. Pile some vegetation on top of a floating raft and tunnel and weigh it down with rocks.  If on land, cover it with small logs, branches, or rocks.
  • Make it obvious – This is a bid of a reverse to the camouflage suggestion above but, in non-public areas, you could also play to the mink’s curiosity and have the raft/trap in plain sight.  Sometimes the animal can’t resist the urge to explore the new addition to its habitat.
  • Make the tunnel appealing – Stuff some dry grass or other vegetation between the trap and tunnel – it creates an appealing tunnel to explore and a trapped animal to make a cosy nest from material pulled through the cage.  Make sure vegetation won’t be a hindrance when it comes to animal dispatch.  There is an added bonus here – if you catch a mink this vegetation will be saturated with scent and might entice the next one to the trap too!
  • Make sure it’s stable – If trapping on land, make sure your trap is stable – use stones or wood if needed. A wobbly trap can dissuade a mink from entering it or worse, set the trap off when knocked from the outside.

Go mad with camouflage (L) or line the tunnel with dried grass (R)

Baiting is usually unnecessary but if you do feel you need a little bit of extra help, you can try baiting with food, visual attractants or scent:

  • Food – Stab a cat food pouch a few times and hang it in the back of the trap or season your raft with a bit of oil from a tin of sardines or something else debatably “delicious” smelling. Don’t use actual food – you’ll attract every animal in the neighbourhood!
  • Visual attractants – Hang a bit of tin foil or a budgie mirror in your trap to grab the mink’s attention – get creative!
  • Scent – A scent lure holds the biggest potential, because mustelids use scent marking to communicate with each other. So, use of scent can be effective in enticing territorial animals to investigate a trap more closely – even the wily ones that turn their noses up at anything else.  There are options of how to do this but whatever you do – wear gloves!

You can collect your own scent – though this often isn’t for the faint hearted.  You can –

  • Relocate scent doused vegetation, tunnels, or traps after a mink dispatch to a different raft – though that may be impractical on a day to day basis.
  • Harvest your own scent – This is perhaps not for the squeamish or faint nosed – but I have experimented with scent harvesting from dispatched mink. A biodegradable cigarette filter, held in forceps, is saturated with “Eau de mink” from their anal scent gland. This can be done by just bringing the filter contact with their anus or, if we take it a step further to harvest even more scent, can be brought into contact with a scent gland after it has been extracted from the mink.  Not for everyone this!

Wire is threaded through the filter which is then hung from the cage grid above the trap treadle to entice the mink to enter as it takes a closer sniff.  These “scent bombs” can be stored in sealed plastic bags and added to traps as needed. This method has been used in other mink eradication programmes in preference to baiting with food.  An advantage of scent is it is more likely to specifically attract mink compared to food aromas which may also attract non-target species such as rats, otters or the odd adventurous cat.

Finally, a tip that makes your life easier – especially if your trap is located on a small island, or in a difficult to reach areas.   Attach a flag to your trap door as a visual aid to check on the status of your trap – some trap designs are better suited to this than others, and some are not suited at all but it can be really helpful. When the trap door is open the flag is up, when the trap door closes the flag goes down and is no longer visible – time to check on the trap!  You may even be able to check on your flag with binoculars from a distance. Watch a video of Karen demonstrating the signal flag.

All of the above should give a good starting point.   But of course, sometimes you may still catch nothing – remember you are pursuing a wild animal which won’t always behave as we hope or expect it to.  Be flexible and try something new now and again.

A bit of patience and luck results in a capture.

Sometimes, of course, it’s not you or the trap itself.  Perhaps the mink was transient (just moving through) and won’t come back, maybe it found itself in a different trap in the area or met its demise in a natural way, or possibly there is too much disturbance at your location and the mink doesn’t take time to investigate.  Or maybe you have a wily and cautious animal which simply won’t enter the trap pretty much whatever you do!

Despite our best efforts, there is always a little bit of luck and patience involved in mink trapping. Remember no signs of mink is a good sign – but please remain vigilant so we are ready when an animal heads your way, don’t get disheartened and don’t give up.  And while you’re there,  remember to take a moment to enjoy the native plants and animals living and thriving around you, breathe some fresh air, listen to the birds and relish the opportunity to get to know parts of your local river better you’ve never explored before.  Nature is good for you!

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Read more about the Scottish Invasive Species Initiative Mink Control Project on our website (www.invasivespecies.scot). Most of our rafts and traps are looked after by volunteers, if you’d like to find out more about getting involved read more about volunteering or contact us on sisi@nature.scot

Please note – our mink project only operates in Northern Scotland – specifically Highland/Eastern Perthshire, Angus, Aberdeenshire, Moray, Inverness-shire, Ross-shire and West Sutherland.

Restoring Ratty – Bringing the water vole back to Kielder

Graham Holyoak – Restoring Ratty Project Officer, Northumberland Wildlife Trust
July 2020

I am writing this having just completed our 7th release of water voles, with over 1700 animals released in total so far.  The eighth release is just a couple of weeks away so we are preparing for this now.  It seems a long time ago when I sat down to start the first phase of the project back in 2013!

Graham with a water vole

The idea for reintroductions actually started long before this with Forestry Commission (now Forestry England) surveying the rivers in Kielder Forest back in 2008, and the then Forest Management Director Graham Gill suggesting that a reintroduction would be a good fit in an operational Forest.  On the back of this idea , a lottery bid was submitted in 2009 which unfortunately failed, and it wasn’t until 2013 that a partnership of Tyne Rivers Trust, Forestry Commission and Northumberland Wildlife Trust received funding from the National Lottery Heritage Fund for a two year Water Vole Heritage Project.  This aim of this project was to show that there was a suitable mink free habitat for water voles and that the local community was supportive.

On the successful completion of this project with no confirmed mink found we applied for further funding from the National Lottery Heritage Fund to begin bringing water voles back… and so the Restoring Ratty project was born! 

Water vole

Kielder Forest is the largest man-made forest in England and lies in Northumberland on the Scottish border.  It produces 20% of all the timber in England.  Over the last 30 years, changes in forest management practices have changed the dark stream sides with conifers down to the edges, to an area of excellent riparian habitat for water voles as planting of new trees is now done further back from the banks..  This process is ongoing so the amount of habitat for voles carries on increasing.  Forestry England’s Wildlife rangers had been controlling mink since the 1990s meaning that there was very few left in the forest.

Restoring Ratty is unusual in water vole reintroductions, as the donor animals for our captive breeding programme come  from wild populations rather than the usual method of removing water voles from building development sites.  Voles were captured from sites in the North Pennines, North Yorkshire Moors and the Trossachs in order to create a wide genetic pool to breed from – with genetics similar to the water voles that would originally have been in Kielder.   In order to not harm the donor population we only captured voles in later summer that were smaller than 160g and would be unlikely to survive the winter.  The voles were transported down to Derek Gow Consultancy (DGC) in Devon for breeding.

Water voles ready for release

The first 317 voles were ready in June of 2017 for our big first release!  Along with a team from DGC it was the chance for our amazing volunteers to see voles back in Kielder after close to 4 years of monitoring for mink!  This was followed by a further release in August 2017 and then every June and August to the present day!

We employ a soft release method where voles are put into a straw filled pen on the edge of a stream at the release site.  They are then fed with apple and carrot for several days to allow them to acclimatise to their new surroundings, and in the case of paired voles – hopefully breed.  A wooden plate with two holes is then placed over one end of the pen and this allows the voles to come and go as they please, but prevents most predators getting in.  Some voles are eager to go and head off into the wilds as soon as the plate is put on whilst others are more tentative.  By the time we remove the pens a few days later a handful of times have we had to evict a water vole!

Water vole release pen on site – nearly free!

The criteria we use to choose our water vole reintroduction sites have changed over time as well.  Prior to the project, a feasibility study was conducted looking at habitat suitability from the water vole handbook.  Well it is safe to say that some of our water voles haven’t read the handbook!  We initially put them in streams with lovely earth banks and widths of between 1-3 metres with a mix of grass and herb vegetation.  Where they seem to thrive in Kielder are very small ditches often around 30cm width.  As per best practice, we have also often conducted surveys along burns looking at the banks and the 2m zone on each side and found little. Feeling despondent on the walk back, further away from the burn we have stumbled across some feeding signs or a latrine tucked away in some rushes or a burrow under a tussock or the scampering of a water vole through the vegetation over 10m away from the streams.  These small streams and ditches are now our release sites of choice – you have to listen to the voles!

Local school helping with water vole release

We have continued the mink monitoring from the first phase throughout the project mainly using mink rafts. We have around 60 rafts that are checked on fortnightly basis by volunteers, land owners and project staff.  Mink rafts are essentially a floating platform containing a tunnel with a clay and sand tracking pad inside with floral foam to keep the clay moist.  We have been trying to make the rafts more environmentally friendly and reduce plastic loss to the environment.  We use recycled plastic rafts and wrap the polystyrene that provides the buoyancy to ensure that this does not wash away.  We have also been trialling substitutes to the floral foam using coir (coconut husk) and that has worked well in some situations.  We have also increased our use of camera traps and have tried baiting them further away from water vole locations.  It seems that mice are very fond of tinned sardines as surprisingly are red squirrels!  We have found that mink numbers are low although we have had a couple of incursions that we have had to deal with so vigilance and continued mink monitoring is paramount.

Volunteers checking mink monitoring raft

We only have a year left of Restoring Ratty – but this cannot be the end.  We have a commitment to carry on the mink monitoring to ensure that this reintroduced population is safe.  That is not the extent of our ambitions though.  Our ultimate aim is to link up the new population with the nearest donor population some 40 miles away in the North Pennines.  We are looking at a phase 3 of the project to continue this progress with further releases to boost the natural recolonisation of the water voles as well working to improve habitat and remove mink.  We have recently had some good news on this front with a partnership of Durham Wildlife Trust, Tees Valley Wildlife Trust and Northumberland Wildlife Trust receiving funding from National Lottery Heritage Fund for a three year mink control project in the Tyne, Wear and Tees catchments.

A final note on the 2020 releases – they have been very strange as we haven’t been able to have our volunteers with us due to COVID19 restrictions.  The volunteers have been integral to every part of the project from helping with events, mink monitoring, water vole monitoring and the releases.  It is not an exaggeration to say that we could not have done this project without them and so although the water voles may be the stars our volunteers are not far behind!

L to R; The pringles tube, perfect for vole handling. Ratty Ale, innovative fundraising! One of the first water voles released.

Follow the work of the Restoring Ratty project on their Facebook page.