Zapping invasive plants – a trial on Exmoor

Holly Moser, Exmoor Non-Native Invasive Species Project Officer
September 2021

As many of you may be aware invasive non-native species (INNS) control can take many years and here at Exmoor National Park Authority we have been going at it for the last sixteen! A major part of our work, our knotweed control programme, has been running since 2005 and has resulted in a large reduction of the knotweed species, particularly Japanese and Himalayan knotweed across the National Park.

Each year we seek permission from landowners to treat knotweed using the conventional method of spraying glyphosate. Currently, thanks to the funding, we can offer this service free of charge. Our contractor completes the treatments between September and November when the herbicide is most effectively drawn down into the rhizome system.

Spraying Himalayan knotweed

This autumn we will be visiting 95% of the 850 plus knotweed sites we can treat using glyphosate, probably the highest percentage ever achieved on the programme! This may sound a lot but many of these sites are being monitored and may no longer need treatment because there is no visible growth showing. It is vital that we continue to monitor these sites because knotweed rhizomes can stay dormant underground for something like up to ten years, which means shoots can sneakily reappear!

On Exmoor there are several knotweed sites we cannot treat with herbicide because they fall on organically certified land and we have not found a suitable “organic” alternative to glyphosate treatment. This land provides a serious reservoir for invasive species to flourish, particularly where a plant is situated close to a watercourse allowing them to spread easily. There is also a lot of controversy surrounding the use of glyphosate as a herbicide and the future of its application is uncertain. So it is crucial that we expand our toolkit of methods to control INNS and find solutions for control on organic land.

In 2017, we began trialling Rootwave Pro which has proved to be very effective on annual weeds and was first trialled on Japanese knotweed in 2016 in Gloucester, by the Environment Agency. This technology forces an electric current of up to 5000 volts down through the plant, raising the temperature and boiling the plant cells. It’s very dramatic to watch – lots of steam and popping and banging! The plant is left to decompose, and you can see the effects of the treatment within a few weeks. I have to admit it is satisfying watching a plant which is causing so many problems and is so difficult to get rid of, turning yellow and wilting without the use of herbicides to treat it.

The Rootwave machine. You rub the electrode up each stem for approximately 30 seconds. It is a very dramatic treatment with lots of steam, popping and banging!

How are the trials going so far?

In 2017 and 2018 the National Park commissioned Ubiqutek, the manufacturers of Rootwave Pro, to carry out one treatment a year on five knotweed sites. It soon became clear that one treatment a year might not be enough because the knotweed continued to throw up lots of little shoots.

Left: 2017 – Japanese knotweed before any Rootwave treatments took place.
Right: 2018 – after a single treatment in 2017.

Luckily the project was able to use our new funding to purchase our own Rootwave Pro so that we could continue these trials and increase the frequency of treatments. We were also able to train up several local contractors to operate the machine. So we can now carry out up to three treatments a year on 28 different sites including other INNS: American skunk cabbage, giant hogweed and montbretia.

Although we have made great progress carrying out multiple treatments a year it has not been smooth sailing…

There are several factors to consider when using Rootwave Pro:

  • First the location. The machine needs to be transported to site on the back of a 4×4 or ATV due to its size and weight and you are also limited to a 27 metre long treatment cable from the vehicle. Although we would not expect to find knotweed on some of the most remote parts of Exmoor this has been a limiting factor for us. The technology is however adapting quickly and who knows how long it will be until Rootwave can be carried on your back…
  • Secondly, it cannot be operated if it is raining. On Exmoor this is a challenge, especially with the wetter summers we are now experiencing. However wetter ground is better for conducting electricity so if your operator is able to drop everything and fit in a couple of hours when the rain has stopped then rainy days don’t have to be a write off.  Having the flexibility to change plans and carry out a treatment when the time is right is definitely a bonus!

Of course, we have also had to deal with the elephant in the room which is affecting everyone. Busy schedules and short time windows impacted by the pandemic and combined with the British weather have not made it easy for our contractors. The result is that we have struggled to complete three treatments a year at all of our sites as we had first planned.

What results have you seen since you started the multiple treatments?

It’s important to point out that we are only in our second year of multiple treatments and the very early stages of this trial, but despite all the challenges things are looking quite promising.

It’s clear that every site has reacted differently to each treatment as you would expect when there are so many factors like competition from other species, ground substrate and moisture content in play. In our first year of multiple treatments, some of our knotweed sites continued to show vigorous growth. This is to be expected – invasive species, by their very nature, are tough to control.

Left: May 2020 – young Japanese knotweed appearing before Rootwave treatments took place.
Right: September 2020 – two months after the second treatment of the year.

Other sites looked more positive with less regrowth appearing. At this site (image below) our contractors reported only a handful of stems after its first ever treatment.

Left: August 2019 – before any Rootwave treatments.
Right: August 2020 – two months after its first ever treatment.

We have also seen similar results over the years at the sites that were first treated in 2017. Below you can see a comparison of two sites that received a single treatment in 2017, 2018 and 2019 and two treatments in 2020. These photos were taken in September. Both sites are yet to receive a treatment this year which makes a good comparison to September 2017 when the sites hadn’t been treated at all. Again, some sites have continued to show quite vigorous regrowth (top two images); while at others the difference is more obvious (bottom two images).

Two Japanese knotweed sites treated using Rootwave – single treatment in 2017, 2018 and 2019 and two treatments in 2020.
Top left: Site 1 before (Sept 2017), Top right – Site 1 after treatments (Sept 2021)
Bottom left – Site 2 before (Sept 2017), Bottom right – Site 2 after treatments (Sept 2021)

For our other species it is a similar story that multiple treatments for several years looks like it could be the way forward. We were however delighted to see that one of our skunk cabbage sites, where there was a single plant, does seem to have disappeared for the time being after its first year of multiple treatments.

Left: June 2020 – a single skunk cabbage plant before any Rootwave treatments.
Right: June 2021 – after two treatments in 2020.

So we are seeing some interesting results in the early stages and these trials are playing an important role in broadening our options for INNS control. Like any trial, there are always lessons learnt to be passed on and we have definitely had our fair share. Check our website for updates as our trials progress and please do get in touch if you have any questions.

Tel: 01398 322259

Email: ennis@exmoor-nationalpark.gov.uk

The Exmoor Non-Native Invasive Species (ENNIS) project is trialling innovative approaches to invasive species management and working with the local community to map and control invasive non-native species such as Himalayan balsam, American skunk cabbage and American signal crayfish. If you would like to find out more about the project please follow this link to our ENNIS website.

The ENNIS Project is funded by the European Agricultural Fund for Rural Development and Defra.

Flying, Flinging and Floating – Seed dispersal by Giant hogweed and Himalayan balsam

Vicky Hilton, Volunteer & Communications Officer, Scottish Invasive Species Initiative
September 2021

Here at the Scottish Invasive Species Initiative our invasive plant control seasons for giant hogweed and Himalayan balsam have now drawn to a close and thousands of plants have been sprayed, cut or pulled – removing these pesky plants for another year and critically preventing seeding and spread.  However, that’s not the end of the story.  In the soil lie dormant seeds: snoozing silently but waiting their chance to germinate.  And beyond our control areas are plants which are now about to do what they do best – scatter their seeds for future germination.

When it comes to invasive plants seed production and dispersal is usually significant and impressive – the ability to reproduce quickly, and in numbers, is one trait that makes these invaders spread successfully and be worthy of the status of ‘invasive’.

Plants have limited mobility and rely upon a variety of dispersal methods to transport their seeds, and so reproduce, away from the parent plant.  Seeds are more likely to survive away from the parent plant – they can reach habitats favourable to survival and with less competition and larger distance seed dispersal can allow plants to colonize altogether new geographical areas.

Giant hogweed and Himalayan balsam are both highly mobile species – they are good at seed dispersal and spread readily to new areas.  While this makes good evolutionary sense for the plant in ensuring its survival and success as a species – for those of us working to stop the spread of these species it certainly brings challenges.   

Understanding how these species disperse their seeds and how long these seeds persist in the soil helps enormously with the planning of control work.  For example, both these species use flowing water as a dispersal mechanism – meaning that control work needs to start with the most upstream plants in a river catchment. Treating plants downstream first would be futile as seeds from those upstream plants will wash down and re-infect cleared areas. 

Giant hogweed

Giant hogweed plants flower only once after growing for 2-5 years (longer if conditions aren’t ideal).  After seeding the plant dies.  Although that might give hope of successful control, in reality if the plant sets and spreads seed then the damage has already been done. A single flowering plant will produce between 10,000 – 50,000 seeds, with 20,000 seeds per plant being typical – and each seed can remain viable for many years. 

The dry flattened oval seeds are produced at the end of August.  Each is approximately 1cm in length with brown lines extending about three quarters of the length.

As the seeds are shed from the towering 2m high seed heads their winglike membrane allows them to be caught by the wind and dispersed over short distances (2-10m).  As they drift away from the parent plant they often fall into a river or burn where the water can carry them long distances to new areas.  Studies have shown that giant hogweed seeds can float for up to three days – in that time seeds could be moved huge distances in normal flows and even further in flood events.

Humans can also give a helping hand and be responsible for spreading giant hogweed seeds.  This can be accidental e.g. when seeds are caught and transported on vehicles or in shoe treads – or via transportation of seed contaminated soil.  

If seeds land on a suitable area of ground (there is usually plenty along a riverbank) they will settle into the soil and overwinter to allow maturation and breaking of dormancy.  Germination occurs from January to March with approximately 90% of seeds successfully germinating. Those seeds that don’t grow in the first year can lay dormant in the soil – the seed bank – for many years.

The consequence of this seedbank means that control works will need to be repeated on the same site for several years until the seedbank is depleted and the site truly clear of hogweed. Viable hogweed seeds have been recorded up to seven years after seeding occurs.  This reflects what we witness in the field – we have sites new to the Scottish Invasive Species Initiative where after control for four consecutive years, we still see significant regrowth of seedlings each year.   However, at sites where control has taken place for six or seven years (by previous and the current project) we see significant decreases in annual seedling reoccurrence giving hope that we are closer to achieving hogweed eradication in some locations.

Himalayan balsam

Himalayan balsam is an annual plant with a cycle of growing, flowering, seeding and dying all in one year. As such its survival from one year to the next depends entirely on successful seed production – so prevent the seed production and you remove the plant. 

Balsam seeds are produced in a seed pod, or capsule, which hangs on a long stalk alongside the flowers. The kite-shaped green pod is 2-3cm long and 8mm wide and contains on average 6 seeds per pod (between 4-16 seeds can be present).  The small round seeds are initially white, turning black as they dry.  On average 700-800 seeds per plant are produced.

When it comes to seed dispersal – balsam is the master.  It uses ballistic seed dispersal – exploding seeds pods – to forcefully fire the seeds up to 7m from the plant.  The seed pods are dehiscent – meaning that when mature they will spontaneously explode at the slightest disturbance. The capsule splits along the longitudinal edges – which are built in lines of weakness in the pod – firing out the seeds as the sections curl back.

These expelled seeds are often carried by humans – unintentionally caught on clothes and picked up in shoe treads – and there have also been observations of seeds being transported locally (up to 10m) by small rodents.  But mostly the spread of balsam seeds is aided by flowing water – fresh seeds can be transported within the sediment of riverbeds – particularly during the high flows present during flooding.  The dry seeds are buoyant and can float over large distances in the water currents – before being dropped into new areas to successfully colonise and continue their spread.

Himalayan balsam seeds also have a high germination rate – approx. 80% – but the good news is that balsam does not have a persistent seed bank.  Seeds only survive in the soil for around 18 months.  This means two to three years of control work at a site can be all that is required for successful balsam removal – as long as new seeds are not being brought into the site to replenish stocks!

A note on Japanese knotweed

Japanese knotweed (one of our target species in the project) is not of concern when it comes to seeding – it spreads solely by root and stem fragments.  While it does produce tiny white flowers each year it doesn’t set seed.  In Britain Japanese knotweed plants are all female with male sterile flowers. Its vigorous powers of vegetative reproduction mean that it has been able to spread to all parts of the British Isles without the aid of sexual reproduction – therefore it is classed as a single, exceptionally widespread clone.

Stopping the Spread

Everyone can help in stopping the spread of giant hogweed and Himalayan balsam seeds by practising good biosecurity – checking boots, equipment and vehicles for seeds and carrying out regular cleaning of these items between visits to different countryside sites.  You can find more information on good biosecurity practice on our website.

Autumn is the season

Of course, although we’ve covered giant hogweed and Himalayan balsam specifically here as problem and target species of the Scottish Invasive Species Initiative, do remember that not all plants are invasive.  Autumn is the main season for the setting and dispersal of seed of the majority of plants in Britain so now is a great time to see plant reproduction in action. 

As you’re out and about in the coming weeks take a second to appreciate the evolutionary genius of our plants as they spread seeds by wind, water, explosion, adhesion, using hooks to attach to passing animal traffic and as part of enticing fruits and berries for animal helpers to enjoy and transport.  You’ll be amazed at how many different tactics and methods there are – tell us how many you see.  

For more information about the work of the Scottish Invasive Species Initiative please visit our website – www.invasivespecies.scot

Top tips for getting started with Tracks, Trails and Signs.

James Symonds, Project Officer, Scottish Invasive Species Initiative
July 2021

Being able to recognise animal footprints is essential in our American mink monitoring work. As the monitoring rafts we use record the prints of visiting animals on a clay pad being able to correctly distinguish a mink from an otter print can be the difference between a successful mink capture and wasting our time. But, for me, animal tracking is so much more than that – it’s a glimpse into the secret world of the animals around us.

Having a basic understanding of animal tracks and signs can transform time spent in the outdoors from catching a simple breath of fresh air into a fascinating adventure of intrigue and mystery.  But be warned – it’s addictive!  I have lost count of the number of hours spent investigating some a patch of sand on a riverbank or examining around a tree stump looking for clues.

An otter walked here before you!

Most wildlife is cautious of humans, often with good reason, so the likelihood of seeing animals out and about is often low. The time of day, the time of year and the type of weather can also affect what you are likely to see.  But, by looking out for animal tracks and signs, you can build a picture of what animals live in the area, and what they’ve been up to. You might not see a pine marten or a tawny owl by day but the print or pellet you find can confirm their presence and inform a suitable place for an evening spotting session or trail camera placement. At the end of the day though, I get a buzz just knowing that these animals are out there.

Tracks and trails

Animals move about constantly within their habitats – particularly in the daily search for food – and when they do, they leave behind tracks (footprints) or trails (paths). A good clear track can give an instant animal identification or provide a good idea of the size and type of the animal in the neighbourhood.

Trails can also give a good idea of an animal or its size but can be misleading – popular routes are often used by many different species. However, they are always worth following in search of tracks and other signs en route.

Top tips for identifying that track

  • Use a field guide
    It takes experience and practise to know what it is you are seeing – so take out (and use!) a field guide.  If you forget take a photo of the track and have a look at the guide when you get home.
  • Look for the features in the print
    How many toes? Do you see claws? What shape is the pad?  These type of track features in combination help to eliminate species from your enquiries and guide you to the likely suspect.
    Look at the top row of images below; Left – four toes with claws, Centre – five toes with claws, Right – four toes no claws
  • Note the size of the print
    Size is important.  If you don’t have a ruler with you, take a photo with something in for scale e.g. a key or coin and work out the size later.
    Bottom row; Left – less than a 1p piece, tiny! Centre – several £1 coins wide with distinctive claw marks.
  • Are you seeing front or rear feet?
    Often a mammal’s fore and hind feet are shaped differently and leave different prints. For example, a rodent may have a different number of toes on the fore and hind feet.  Perhaps you are seeing two types of prints but these can be from the same animal – so take a note of each print features and size.
    Bottom row: Right – one animal but hind feet larger and appear in front of the fore feet

Top row (L to R): Dog, Otter, Cat. Bottom row: Water vole, Badger, Squirrel

Remember – when looking at prints you should take ground conditions into account.  A soft substrate e.g. sand, silt, clay or snow is more likely to give a nice clear full print with all features visible – just like in the books!  However, a hard substrate e.g. firm mud may result in a partial print – perhaps only showing some of the toes or omitting claw marks and so lead you to a false identification.  So, take what you see with a pinch of salt – the print itself might be misleading!

Tracks tell a story

Usually where there is one print there’ll be more, so have a look at the arrangement of the prints.  Animals move with different gaits – walking, trotting, running, bounding – each method of travel leaves a specific ‘print pattern’.  This tells us how the animal was moving, but often the fore and hind prints overlap each other so recognising gaits comes with practice and experience!

There may be more than one species of animal or bird track present – this can be where the detective work really starts.  Which animal was there first? Is one set of prints on top of the other?  Are you seeing a predator and prey?  And it’s always worth following multiple tracks to see if they tell a story – they might end in a pile of feathers and make it easy to deduce what went on at the scene!  

Looks like there was a party here! How many different prints can you spot?

Feeding signs

I was once told that tree stumps are either a table or a toilet! This couldn’t be more true.

Tree stumps are great places to look for feeding signs. There are a myriad of common feeding signs but have a look for some of these –

  • Stripped pine cones
    Most likely a squirrel or mouse if on a ‘table’ – but don’t discount birds like woodpecker or crossbill.
  • Nibbled nuts
    Mice and voles make a fairly neat hole edged with teeth marks, whereas a ragged hole with rougher edges and peck marks around is more likely to be a bird like great tit or woodpecker. A nut split in half is the work of a squirrel – look for the little hole at the top which it gnaws first.
  • Damaged bark
    The biggest clue here is in the height of the barking.  If it’s a few feet up the tree it’s a fair bet it’s the result of deer (or sheep).  If nearer ground level then think smaller mammals and rodents – rabbits, voles or beaver.
  • Nibbled trees
    The nutritious and juicy shoots and tips of small trees are often preferentially nibbled by grazers.  This is usually the work of roe deer – but don’t discount other herbivores like hares.
  • Bird remains and feathers
    If you find the remains of a bird with practise you’ll soon learn the differences between the kill of a predatory mammal (head bitten off and eaten, feathers bitten off in clumps, crushed bones) and of a bird of prey (beak and skull lying around, feathers plucked and scattered, breast meat eaten).
  • Pellets
    Many birds cough up pellets after feeding containing the undigested and indigestible bits of their prey such as fur, feathers, bones and insect cases.  As well as owls, all birds of prey, gulls and crows all produce pellets.  Dissecting a pellet is easy and provides a great insight into what the bird has eaten eating to a whole other world of mini skull and jawbone identification.

Feeding signs of predatory mammals are rarely found as small prey is generally eaten whole at the kill location and larger prey is usually taken back to a den or sheltered feeding site for more leisurely and safer consumption.

Poo!

Cause and effect and all that.  Animals that leave feeding signs will inevitably also leave droppings, or more accurately – scat!  Droppings consist of the indigestible parts of food, such as fur, feathers, bone, chitin, plant matter, mucous and lots of bacteria.

All this excrement is different, identifying features include:

  • Size
    Note the size of the dropping but be aware that this is not always a reliable indicator.  Size is dependent to some extent on the animal’s age and can also be affected by the composition of food in the diet.
  • Shape
    Smooth or crinkly, straight or twisted, blunt or tapering?  All helpful to note.  At first glance a rabbit dropping looks quite similar to a roe deer’s but look again. The rabbit dropping is round and the deer’s is ‘tic-tac’ shaped with a little pinch at the end.
  • Colour 
    This is very influenced by what the animal has eaten.  For example, it will be very obvious if a bird or mammal has been eating berries!
  • Smell
    Fresh mammal droppings in particular have a strong scent – often “enhanced” by the addition of scent from anal glands.  Scent is a helpful identifying feature, but having a good sniff can be a bit of a sensory risk!  It might be sweet and vaguely pleasant e.g. otter (jasmine tea / fishy) or badger (musky) or it could be pretty foul e.g. mink (sharp and repellent)  If you’re feeling brave – have a sniff!
  • Content
    The contents of the dropping won’t always help you identify the animal – but will tell you what the animal has eaten.  Remember, an animal’s diet may change seasonally with the availability of food.  Do you see bones, fur, fish scales, grass?
  • Position
    Some animals will deposit droppings in specific places – a badger digs a small hole, known as a latrine, and repeatedly uses it. Both otter and mink will mark a territory by leaving spraint on a prominent riverside rock.

Other signs

Every animal needs somewhere to live or lie up – so another often easily spotted sign of animal presence are their homes and holes. 

It’s always worth a glance into the trees to see if there are signs of nests or dreys or excavated holes in trunks.  Underfoot look out for holes or burrows dug into the ground.  Some residents can be easily deduced – a badger sett for example is large and quite distinctive.  But remember, holes may have had multiple different occupants over the years or may be abandoned so the animal who originally made the residence may not be the inhabitant now.  Sometimes, of course, there is no hole and nothing more than a patch of flattened grass reveals an otter resting spot.

There are many other indicators of animal presence – sounds, smells, scrapes, feathers and fur and hair are other great indicators.  A walk along a fence will often uncover fur snagged on wire where an animal has passed under, over or through. There are signs everywhere you look, believe me.

Give it a go

So why don’t you get outdoors and give it a go?  Move slowly and open your eyes, ears and nose to the whole environment around you – you’ll be surprised what you can find.  Your walks may take a little longer but that’s a good thing right?

I cannot emphasise enough the importance of a good field guide. I always carry ‘Animal Tracks and Signs’ by Bang and Dahlstrom – an excellent resource. The Field Studies Council also produce a huge range of excellent (and compact) fold out guides which I highly recommend.

Finally, another mantra passed on to me when it came to tracks and signs and which I always keep in mind is that ‘Common things happen most commonly’.  Your imagination and enthusiasm can run away with you at times so before declaring you are on the trail of a mythical beast from ancient folk lore just have another look, consider the context and you may come to conclude it is perhaps just a very large fox that has gone before you!

Now enough reading, get outside, start collecting chewed cones, smell some animal droppings and have some fun!

For more information about mink monitoring rafts and the work of the Scottish Invasive Species Initiative visit our website www.invasivespecies.scot

Coronavirus, community conservation and the green recovery

Can a community and volunteer based approach to conservation projects lead the green recovery after coronavirus?

Callum Sinclair, Project Manager, Scottish Invasive Species Initiative
May 2021

As we emerge from the 2021 lockdown, we reflect on the impact the coronavirus pandemic has had on the Scottish Invasive Species Initiative.   As a project we weathered the Covid storm surprisingly well.  Although activities were constrained, we kept invasive plant species in check and maintained our mink monitoring and trapping network.  We credit this to taking a community-based approach to invasive species management – and so we pondered what we have learnt and whether other projects could take a similar approach to help deliver a ‘green recovery’ after the pandemic.

Community volunteers in Nairn.

Community control vs Covid

At the heart of the Scottish Invasive Species Initiative are the local people who care for their local environment.  An initial and ongoing programme of awareness raising and education activities raised the profile of invasive species and their impacts. This generated significant buy in and enthusiasm to get involved from land managers, local groups and organisations, businesses, and individual volunteers.  Having recruited and enthused, we support and enable people to actively volunteer by providing training and helping them gain qualifications and experience.  This network of committed people is gaining the skills needed to make a difference to their local places – in this instance controlling invasive non-native species – both now and in the future.

When the spring 2020 lockdown occurred we weren’t, like everyone else, able to carry on as usual. It was unclear if we were about to lose a year and give up the gains made by the project since 2018.  Rather than regress, however, what we witnessed instead were the investments in embedding skills and training with local communities paying back. Farmers and land managers used their staff (trained by us) to carry on giant hogweed treatment when we couldn’t, and local people headed out to pull Himalayan balsam at sites we’d worked on together previously.  Mink raft monitoring volunteers used their daily exercise to visit and check their rafts – telling us that this small activity gave them a purpose and made them feel they were making a difference during an immensely difficult time.  The project didn’t grind to a halt – far from it – in fact we perhaps were able to snatch a glimpse of what might happen when the Scottish Invasive Species Initiative is no more.

We believe that this approach – investing in communities, training volunteers and engaging people locally can provide effective and sustainable benefits – as endorsed by the enthusiasm of our volunteers and partners to carry on invasive species control when we weren’t around. 

To date volunteers have contributed a total of 2,181 days to control invasive plants and 119 volunteers have been put through their pesticide application course.

Building community resilience

Taking a community and volunteer-based approach – rather than just employing contractors on an ongoing basis – also provides benefits to the people involved.  Volunteering, pretty much any volunteering, is much more than just the activity itself.  In our case people are making a real contribution to their local environment. But the benefits are much wider than that. Being involved within their community, meeting other people and socialising, being physically active and engaging with nature – these all contribute to improved physical and mental wellbeing.  We believe these benefits have helped give people greater personal resilience to the individual and collective stresses we have all felt during the coronavirus pandemic.

Our engagement work in communities is wide and varied.  It ranges from providing education resources for remote use and our direct education work in schools, to partnerships with farmers and universities to find alternative and innovative techniques for invasive species control.  Engaging and enabling land managers to be a central part in the  development of potentially more sustainable and affordable invasive control methods – such as sheep grazing to control giant hogweed – helps these businesses to see alternative control strategies and be more resilient to future change.

Our Macduff sheep grazing trial in partnership with a local farmer is investigating if and how managed sheep grazing can be used as a form of chemical-free, low intensity giant hogweed control.

Environmental benefits

This community-based approach, as well as empowering people, also has environmental benefits. 

Invasive non-native species require long term management and commitment.  They often produce large numbers of seeds or have persistent rhizomes and require treatment year on year. The American mink needs ongoing control to continue to depress population numbers and counter inward migration. These animals travel great distances to secure new breeding territories and can quickly repopulate previously managed areas. Having an upskilled, enthusiastic and committed local community group willing to, for example, ‘adopt’ a section of river to deliver annual plant control and/or mink control can be effective through their collective efforts – both  providing sustainable and economically effective approaches to management.

Thanks to the monitoring and trapping work of 360 volunteers maintaining 670 rafts and traps, 388 mink have been removed. This provides benefits to the local native wildlife populations, particularly water voles and ground nesting birds.

Reaping the rewards

Restored river habitats and, in turn, landscapes that are free from invasive species give so much back to us.  Our rivers are important for recreation and provide brilliant opportunities to exercise and have fun or places for quiet reflection to boost mental wellbeing.  The connection between people and nature – widely recognised as providing significant health benefits – is further enhanced when people have directly contributed to the care and conservation of the environment.

The importance of connecting with nature has been widely recognised throughout the pandemic.  Many of us discovered, or rediscovered, our local green spaces and enjoyed, and needed, the serenity these places and being outdoors brought.  

As we carefully step into what, we hope, will be our recovery from the pandemic, we have the opportunity as a society to reshape and rethink the way we do things.   We can find new and sustainable ways to work which provide long-term benefits both to people and the environment – the “green recovery”.  For us at the Scottish Invasive Species Initiative we’re not sure that is actually such a new thing – it’s the ethos by which we’ve worked since we started.

Our rivers are important places for recreation and reflection.

Is the model sustainable?

The approach we take – working locally with partners, communities and individuals – undoubtedly benefits both people and the environment and fosters strong connections between the two. 

Volunteer input to the project – 9,794 volunteer days contributed, equal to 46 full time equivalent staff from March 2018 to March 2021 – is incredible and encouraging.  The work completed through these contributions, given by 650 people, would simply not be affordable to the project otherwise.  Each and every contribution – large or small – is important to us but, perhaps more significantly, important to the person donating their time.

The Scottish Invasive Species Initiative continues to build this community network so the work we have started can be a self-sustaining after we have gone.  The work continued by our volunteers and community network during the 2020 coronavirus lockdown suggests this can be the case. But we recognise that to sustain, connect and coordinate a volunteer network to a common and shared purpose will need support and resources.  Maintaining enthusiasm, preventing ‘volunteer fatigue’, continually recruiting and supporting volunteers, training and providing local co-ordination are all essential to the success of this approach. However, the scale of return we find would suggest these investments are both extremely cost effective and environmentally beneficial.

The scale of achievement in 2020, despite working restrictions due to the pandemic.

So, while the coronavirus pandemic has reached every part of our society and touched so many of us personally, we believe there are lessons from the period that can help us in the future.  Investing in people and communities is always worth it to build support, capacity and commitment.  When investments are maintained the benefits continue.  If those investments cease, then the goodwill and benefits generated from all that has gone before are lost. 

As a project we have emerged relatively unscathed from the coronavirus lockdown – we know many have not been so fortunate. We believe the community-based approach we have adopted and the hard work and dedication of our many, many volunteers have been central to this.  We simply can’t thank these people enough.

To find out more about our work and how to get involved visit our website, follow us on social media or contact us on sisi@nature.scot

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.

A day in the life of a SISI Project Officer

James Symonds, Project Officer, Scottish Invasive Species Initiative
November 2020

James

We asked our very own James Symonds, what a typical day of a Scottish Invasive Species Initiative (SISI) Project Officer looks like.

As a Project Officer, I am responsible for the management and co-ordination of invasive species control across four rivers in Moray and Speyside; the Rivers Spey, Findhorn, Nairn and Lossie.  Our main species of concern are; American mink, Giant hogweed, Japanese knotweed and Himalayan balsam – although we also have an interest in White butterbur and American skunk cabbage.

But what does a day in the ‘office’ look like for a SISI Project Officer?

Well that changed significantly this year with the coronavirus pandemic, but following lockdown we managed to get back out in the field to continue our work – albeit with changes to our work practices to keep everyone safe and whilst balancing home working and home schooling challenges.

My typical workday starts the same as any other for a father of 2 small humans – unsocially early! After making my way to the coffee pot and feeding the rabble I can check my work phone. I am checking my “Mink Police” app for any mink traps activated overnight and to see if any volunteers have been in touch about their mink monitoring rafts or traps.  All clear!

The Mink Police units are great innovations. Live capture traps, by law, have to be checked at least once in a 24hr period to meet animal welfare protection requirements.  The Mink Police units, using a combination of technology and magic, send multiple daily updates for specific trap locations which negates the need to physically check each trap in person each day. They allow me to remotely check the traps wherever I have access to Wi-Fi or mobile signal and, most importantly, notify me instantly if an animal has been caught.  This means that traps can be deployed to areas where, for example, mink have been sighted in physically difficult access locations or where we don’t have an elusive local ‘trapping volunteer’ to do these daily checks.  Using Mink Police units I can monitor multiple traps across a wide geographical area myself.

Mink Police unit mounted on top of a live capture trap

After finally managing to get a shower and get breakfast, I double check the weather for todays planned activity – Giant hogweed spraying. The weather looks good so I drop a text to all of the volunteers who have offered their help to reconfirm the meeting time and place.

I visit the stores and pick up all equipment required for the day and make sure I stock up on the ever-essential tea and biscuits on the way to site.

After a quick meet and greet with today’s volunteers, I go through the essential risk assessment and tools talk.  Much of the time we work on uneven terrain alongside rivers and today we are working with Giant hogweed – a dangerous plant with photo-toxic sap.  We also have in place additional COVID-19 working adaptations which need to be explained.  Safety and volunteer welfare is our number one priority.

Volunteer spraying Giant hogweed

We kit ourselves out with protective clothing, fill our knapsacks and set to work.  Today we are spraying in about six acres of riparian woodland with frequent sizeable Giant hogweed stands.  One of my volunteers is new, so I work alongside them offering support and supervision.  Pre-coronavirus there would be a team of volunteers working with me – battle hardened and dedicated hogweed assassins who gained their pesticide application qualifications with us – but today it’s just three people to keep numbers low and allow for social distancing.  We work in a rough line moving in a zig-zag upstream hoping to catch all of the hogweed we see on the way.

We started at 10.00 am it’s now 12.30 pm – definitely time for a proper break.  We put our knapsacks down and set up camp on the riverbank.  On a normal volunteering day I would  pull out the Kelly kettle, tea and biscuits – chocolate hobnobs if they are lucky – offer a demonstration on how to light the kettle using a fire steel and natural tinder and the volunteers would have a go at fire lighting themselves.  This year we’ve had to ask volunteers to bring their own flasks which is a shame as we like to offer additional activities alongside the hard work of plant spraying.  We appreciate the time our volunteers give to us and want to keep each day varied and fun for them – that way they might come back again!  

Putting the kettle on!

I check my phone and whilst we were working a trapping volunteer has called – she has a mink in a trap on another river. I phone back and she confirms the trap was empty last night but a mink has been caught this morning.  I’ll visit as soon as I am finished on site.

We spray for another 70 minutes and manage to cover the whole woodland.  My volunteers (and myself) have worked hard today but it’s been good fun.  As a reward I let them all go home early, 2.45pm instead of 3pm!  I’m nothing if not generous….

After the plant control equipment is cleaned down and packed in the car I can make my way to the mink in the trap. It’s a large mink and I have the unhappy task of humanely dispatching the animal.  This is done quickly, quietly and discretely with a high-powered air pistol. I take some basic measurements and sex the animal – a male.  You can tell this by feeling for a small bone between the hind legs – the baculum – present only in males. You can work out what this identifying feature is I’m sure!

Non-native American mink caught in trap

Dispatching mink is not something I or the project enjoy – but it is essential.  The mink is a voracious predator and their presence has a devastating impact on native wildlife.  For example, since the introduction of mink, Water vole numbers have declined by over 94% across the UK – largely due to predation.  They also have a negative impact on populations of native ground nesting birds, amphibians and fish species as well as taking domestic fowl.

I get home, change a nappy, check my emails and follow up with volunteers planning on coming out tomorrow.  The weather is looking wet so instead of spraying Giant hogweed we will decapitate the flower heads using pole saws – always fun!  I am just about to email a few volunteers about later in the week when my 4-year old runs in and rugby tackles me – it’s time to finish work for today.

Using a pole say to remove flower heads from Giant hogweed

Invasive species control work is seasonal so once we are done with Giant hogweed, we move on to pulling or slashing Himalayan balsam – great for all the family to get involved in and then, as autumn looms on the horizon, we move on to spraying or stem injecting Japanese knotweed.

The specific threats these plants pose vary in one way or another but what they all share is the fact that they are so successful in our climate and our native flora cannot compete. If left unchecked we face a massive loss to biodiversity, destabilisation of our riverbanks and very different ecosystems to the native ones that should be present. 

Injecting herbicide directly into Japanese knotweed stems (L) and slashing Himalayan balsam (R)

It’s been a productive day and there is a tremendous sense of achievement seeing what a huge difference can be made in such a short space of time with so few people.  I have missed the larger volunteering groups this year, it’s always good to get a big crowd out, but we soldier on for now and hope to get everyone back together next season.  The volunteering opportunities we have been able to offer this year have never felt so important – as well as helping nature they provide valuable time outdoors and social opportunities just when we’ve all needed these the most.

Volunteer groups 2019

If you’d like to find out more about getting involved and volunteering with James and the Scottish Invasive Species Initiative read more on our website.

Adventures with Bonnie – training a mink detection dog

Mirella Toth, Project Officer, Scottish Invasive Species Initiative
October 2020

I started to volunteer for the Scottish Invasive Species Initiative in March 2019 and have loved being involved ever since. I am from Hungary, am a motivated practical conservationist and love being outdoors and feeling like I’m doing something that matters.  I learnt a lot being a volunteer and I was so pleased that I had the opportunity to join the Scottish Invasive Species Initiative team this summer as a Seasonal Project Officer and learn even more.  As well as controlling invasive plants, part of my job was to work on the American mink control project, finding and catching invasive mink in the Spey and Findhorn, Nairn and Lossie catchments.  As well as conservation I have another passion – dog handling and training which I was able to use this summer.

Bonnie, a Hungarian wirehaired Vizsla

I used to train dogs for hunting as well as having over 7 years’ experience training police and truffle dogs in Hungary.  When my boyfriend took a detection dog handler job with the Orkney Stoat Project, it opened my eyes to the possible use of dogs to help find American mink in the field.  Imagine how amazing it would be to walk along the riverbanks, have a dog indicate the presence of mink and so know where to place our traps.  I thought this could be my own project within the Scottish Invasive Species Initiative and so, when I had the opportunity to get a puppy my journey with Bonnie started.  

Bonnie at 3 months old

Bonnie is a Hungarian wirehaired Vizsla. I have previous experience with the breed – they are excellent hunting dogs and good trackers which are ideal characteristics for my planned mink detection role. She is now 1 year old and is amazing.  I started her obedience training when she was around 3 months old and moved on to search work a little later.  Because of her young age she can still be easily distracted – a butterfly fluttering by or even her own shadow are sometimes more interesting distractions which makes the training more fun from my point of view.  It is always a pleasure being around Vizsla’s – they are so charismatic.

I started her search training when she was 6 months old. Whenever I am working with her I put a harness on to show her that she is working – if she has a harness then we are working if not then the walks just for fun!   My priority was to get her to confidently detect any sign of mink in the field.  I started her training in my garden with a dead mink – which she was really interested in – and then later moving out and progressing to the banks of the River Spey where we could look to find some real-life mink tracks and signs.

Bonnie in training

Bonnie took to the job really well and during the summer she was a huge help to me when on the trail of the mink.  When our volunteers on the River Spey found mink signs on their monitoring rafts it was up to me to put out traps in the area to try and remove the culprit. Initially (pre-Bonnie!) I spent hours looking for mink tracks and signs on the ground and, using my experience and knowledge, set my trap in a suitable place. I then waited and checked the trap each day but didn’t catch anything – the mink can be an elusive quarry. Towards the end of the summer I felt Bonnie was ready for her first real mink mission on the River Spey.  I took her to the river and she soon indicated on a spot on the riverbank – so I moved the trap there.  The result? Success – I caught not just one, but to date, four mink from Bonnie’s trap!

Success! – a mink caught in Bonnie’s trap on the River Spey

But her success on the Spey was not just luck. On the River Nairn I had the same situation.  Volunteers reported mink sightings and although I had my traps out and set after weeks and weeks, nothing had been caught. We decided a change of plan was needed and that we should move the traps to a new location and so I put Bonnie in the car and we headed to the river. Again, she found a minky spot and I moved the trap there based on her advice!  A couple of days later we had caught a mink in it.

Mirella and Bonnie – in the car on the way to the River Nairn

I am very happy with the results from this summer and with Bonnie’s progress. There are so many factors to think about when locating a trap to try and increase the likelihood of catching the mink and, even for the experienced, there is still a good bit of luck required!  I think that even an experienced trapper would save so much time and effort with the help of a trained dog like mine.  Although I’m moving to a new job for the winter, I’m sure Bonnie will come back and find more American mink for the project in the future.  Watch this space!

Bonnie checking a trap is placed to her satisfaction!

If you’d like to find out more about the Mink Control Project or are interesting in volunteering and monitoring a mink raft or trap visit – www.invasivespecies.scot or contact us on sisi@nature.scot

Trail cameras – our secret agents in the field

Jack Farge, Project Officer, Scottish Invasive Species Initiative
September 2020

Trail cameras are handy gadgets that we’ve found increasingly useful here at the Scottish Invasive Species Initiative – so handy in fact that we thought we’d like to tell you a bit about how we use them and what they show us.

The cameras are fixed in place and are triggered by motion sensors which makes them useful for collecting footage of elusive animals such as American mink – a non-native invasive species that we are trying to locate and trap – which we otherwise wouldn’t see.  Day or night, rain or shine, our trail cameras are on the job!

Mink mysteries
Our first step in mink monitoring uses a simple, low tech method which can be widely rolled out – the mink raft – this relies on an extensive network of dedicated volunteers to confirm the presence or absence of mink across our project area using these floating rafts. Our fabulous volunteers look after these rafts which consist of a tunnel, with a clay pad inside, to collect the footprints of mink, or any animal, that walks through the tunnel (left image below).  Where the presence of mink is confirmed we place live-capture traps onto the raft (right image below) and see if we can catch the mink – which are then humanely dispatched. Mink are naturally curious and usually check out the tunnels on their own accord but they are also sneaky and wily and occasionally they taunt and deceive us – which is where trail cameras come in.

Capturing video footage of mink can provide an insight into their behaviour and help us identify why – even though we know mink are present – they are not venturing into our traps. The raft/trap unit could be positioned on the wrong riverbank or pointing downstream when it would be better pointing upstream – whatever the issue sometimes the trail camera can help us solve the mystery. 

Click video to watch (on YouTube) or scroll to bottom of article


We also have had to solve the case of the disappearing bait!  We couldn’t work out how bait kept disappearing from inside the trap without the trap being triggered and the door closing! Trail camera to the rescue – it turned out that an otter was sneaking in and having a nice snack on the bait while it held the trap open with its large back!

Click video to watch (on YouTube) or scroll to bottom of article

Snapping Sheep
Trail cameras are also proving really useful at our sheep trial site at Macduff where we are working with a local farmer and the University of Aberdeen to see how best sheep can be used to control Giant hogweed through a managed grazing regime. We’ve installed several cameras around the site which allow us to monitor the sheep’s behaviour, without human influence, by capturing videos of the sheep in grazing action. We are also using trail cameras to gather a visual record of the impact of the sheep by capturing time lapse footage of their grazing progress each day.

Click video to watch (on YouTube) or scroll to bottom of article

What else is out there?
Sometimes it isn’t just mink we find.  One of our mink raft volunteers recently asked to borrow a trail camera after suspecting water voles were in the area. Water voles are one of our most threatened native mammals, largely due to mink predation, so it is great to see if they are making a comeback in areas where we are controlling mink.  We were happy to lend a camera as gaining familiarity with these gadgets is  a great skill for volunteers to learn as well as providing great images for the project.  She didn’t get water voles on film but instead found something even rarer, this amazing footage of a family of Scottish wildcats! (N.B. Later confirmed as hybrid wildcats).

Click video to watch (on YouTube) or scroll to bottom of article

Such footage of our native wildlife is really useful and valuable; it can be important for other conservation projects, we can use it on social media to help raise awareness of our native wildlife and it can help engage people with their local environment.  We’ve also found that when working in schools showing a class of children video footage of an American mink and an otter is not only helpful in explaining the difference between the two species, but also great at grabbing and focussing their attention!

You can watch more wildlife clips on the Wildlife Watcher page on our website or on our YouTube channel.

Give it a go!
If you’ve got your own trail camera or can borrow one and would like to learn more about how and where to set it, check out our helpful hints in the Alien Detectives ‘Caught on Camera’ activity.  If you get some animal footage you’d like us to see and share then get in touch with us at the email address below – we’d love to see what you find!

If you’d like to find out more about our mink control project or are interested in monitoring a mink raft find out more at www.invasivespecies.scot or contact us on sisi@nature.scot

I like to think this mink knew that is was on camera!
This cheeky otter was stealing all the bait out of the mink trap!
When they get stuck in these ravenous ruminants make short work of giant hogweed.
This footage was really useful for the Scottish Wildcat Action project.

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.

The ins and sprouts of Giant hogweed control

Karen Muller, SISI Project Officer
June 2020

If you have ever come face to stem with a Giant hogweed plant or witnessed a dense infestation, you know it to be a truly impressive plant.  Not purely because of its size – but because it makes the very most of itself in everything it does to ensure success.  Huge leaves on a tall stem shading out other vegetation, an average of 20-50,000 seeds per plant which are viable for about 3 years (some studies say up to 7 years!), a taproot that stores energy and seeds that can float in water for up to 3 days on their voyage downstream to new realms.  Easy come, easy grow.

Giant hogweed in flower

It can be overwhelming to think about how best to tackle this towering hazard, but plant yourself here for a while and let’s talk about Giant hogweed control: methods, tried and tested by us, and the (mostly) weird and wonderful approaches that the internet spat out.

Before we dive in, safety first!  Giant hogweed sap contains furanocoumarins, which enhance the sensitivity of skin to Ultra Violet (UV) light. Simply put, when the sap comes in contact with skin it reacts with direct sunlight causing photodermatitis (skin burns) and you’re often left with long-term sunlight sensitivity in that area.  So, the first step is to get suited and booted and gloved to protect yourself.  A face shield or safety glasses are also advised where there is risk of getting splattered with sap e.g. when digging or cutting the plant.

The second basic rule when tackling Giant hogweed is that you need to have a plan.  Always start from the uppermost hogweed infestation along a water course, so that when you clear an area you don’t have to worry about any more seeds floating down and re-infesting your treated area.

Safety first; get suited, booted and gloved

Green and gone

At any point, while the plant is green and actively growing, a systemic herbicide with aquatic approval e.g. Glyphosate is perhaps the most straight forward answer for dealing with hogweed near water.  Note that you require the relevant training and qualifications before you can use pesticides, particularly near water.

Using a knapsack sprayer to apply the herbicide is the most efficient option for dense infestations and extensive populations.  For less dense areas or sites with occasional plants, you could consider wiping neat herbicide on the leaves with a weed wiper or directly injecting it into the hollow stem.  However, these methods do involve getting closer to the plant – something you should generally look to avoid.

Hogweed can be resilient and so a second ‘mop up’ visit a couple of weeks later can be warranted in the worst infected areas to catch any plants missed and to make your control effective.

Herbicide application by knapsack spraying, weed wiping and stem injecting

The taproot of the matter

Young Giant hogweed plants with their turnip-like taproot lend themselves well to digging up.  This is more labour intensive but it reduces the use of herbicide, requires only basic training and can be done by anyone.  Stick your spade through the root, cutting it approximately 15 cm below ground, then dig up the taproot and leave it above ground to dry out.

A sharpened spade is about as specialised as it gets with this method – but we have dug out plenty without sharpening, too.  It just very much depends on the ground you are working on.

Small hogweed plants can be dug out

Bud intentions

If you find that time has grown legs and the hogweed plants are forming flower buds or are already fully flowering, it is best to slash their ambitions with a long handled pruning saw.  It should be an absolute priority to treat flowering plants – every time a plant sets seed you can add another three years to your treatment plan.  Seed ‘em and weep!

Giant hogweed flowers only once after growing for 2-5 years and then only if the conditions and its energy reserves allow for it.  So, if you are only seeing hogweed leaves for several years at your site, there will be flowers coming soon.  Although the hogweed plant will die after flowering a lot of later treatment work can be avoided by removing the flowering head before it sets and disperses seed.

Giant hogweed bud and flower

Long handled cutting equipment is advised – this allows you to keep a safe distance from the plant and any sap splatters as you cut it.  If cutting is the only form of control you are doing be ready to revisit the site regularly during the growing season to cut any new emerging flower spikes on the lower stem or regrowth at the crown.  Cut under the flower head first – removing it intact – then cut the stem in sections until you’re as close to the ground as possible.  If you can combine this with chemical control – treating the cut stem with herbicide – you’ll get better results.  Chemical application needs to occur relatively quickly after cutting to ensure the plant will take up the pesticide and transport it into the taproot before drying out.

Catch them early enough – while there is only a bud or white flower – and it appears safe to leave the flower head on site to degrade.  However, if the flower head has turned green the seeds might still ripen on the cut head and be viable when they drop off.  If the flower head is green, and if you can reach, carefully put a cotton bag or similar over the flower head and tie it off before cutting – then collect and burn.

Cutting flowering heads followed by herbicide application directly into cut stem

All dressed up and nowhere to grow

Suppressing new Giant hogweed growth by covering with mulch or membrane is an interesting method that does come up frequently when looking for hogweed control solutions – but we haven’t used in in the project due to the often large areas we work in.  It is most suitable for smaller areas, like a garden, and is likely to work best on areas where there are only seedlings coming through.  The idea is to cover the area with sturdy black plastic and or a generous layer of mulch and suppress seedling growth by blocking out light – a reasonably standard approach to weed suppression in gardening.  You do need to check back regularly to make sure nothing pokes through the covering.  Let us know how you get on if you give this a try.

Giant hogweed seedlings and field ploughing (image – Stanze)

In suitable locations, particularly in fields, ploughing can be a good solution.  It is most effective if combined with chemical or mechanical control – cutting the plant low to the ground first, or treating it with herbicide and waiting for it to take effect, followed by deep ploughing the area.  After that most seeds, or seedlings, will be far enough underground to not see the light of day again.  If, after initial treatment, more mature plants are being ploughed the large taproots should be removed as much as possible to prevent regrowth.  Like the covering, we haven’t tried this approach ourselves, but in the right location this could be well worth a whack.

Rooting for native species

Where possible, and particularly in areas of previous heavy infestation and a built-up seed bank, reseeding with native plants and trees can make control efforts more effective.  The aim is for native vegetation to outcompete new hogweed seedlings which emerge from treated areas – this sort of planting can also help stabilise bare riverbanks following treatment or winter die back.  Timing is everything here – long-established, dense hogweed infestations cannot be defeated by reseeding alone.  Manual or chemical control is necessary until mostly just new hogweed seedlings are appearing and their density is reduced to a degree that they will not easily overpower the native species you have seeded.

Flocking to the rescue

Situation permitting, grazing can be an effective approach in Giant hogweed control.  Sheep, goats and cattle will readily eat hogweed and pigs even go one step further by uprooting and feeding on the taproot as well.  However, there are a few things to consider before sending the four-legged cavalry into the field.

Woolly warriors brought in to battle Giant hogweed

Hogweed infestations in fields, woodlands, or at the very least a few meters removed from the riverbank, can be suitable locations for grazing control.  However, stock still need to be managed and so the costs of additional fencing, gates etc should be considered.

Hairy breeds of animals, with dark skin, are the best choice to prevent the sap having negative effects on them.  Black face sheep, for example, have successfully and without injury been used to graze hogweed. Since 2014, such a trial has been taking place in the Deveron catchment, with a second grazing trial site set up in 2019 by the Scottish Invasive Species Initiative (read about it here).

Livestock prefer to graze younger or smaller plants, so grazing should start early in the growing year as hogweed emerges.  The grazing of seedlings can be very effective due to the lack of energy stored in the taproot at that point in the plants multi-year life cycle.  On the other hand, grazing of more mature plants might not be to every animal’s taste – although we have witnessed sheep taking down flowering plants during our trials – and while it prevents plants from growing larger, grazing doesn’t kill mature hogweed as the already stored energy in the tap root allows the plant to make a come-back that same year or the following year.  In this instance, the grazers merely work from season to season to prevent regrowth and progressively deplete the energy store – preventing flowering and spread.

Like chemical or mechanical control grazing is required at a site for a number of years before you can call it a job well done and consider the plant eradicated.  Ongoing review and assessment of livestock density and grazing days is also important to prevent overgrazing of other vegetation – otherwise you might just be replacing hogweed and grasses with native recolonising species such as nettles and dock.

The sheep in the trial developed a taste for Giant hogweed and made short work of these plants

A word of caution

Household ammonia, salt, liquid nitrogen and heating oil, amongst other things, are at times suggested on the internet for use as alternative approaches to Giant hogweed control.  We haven’t tried any of these methods ourselves and neither have we found any robust evidence to suggest that any of these would be effective.  The potential negative impacts on soils, waterways and wildlife when other proven methods are available means we won’t be exploring these methods further.

Summing up

Tackling Giant hogweed isn’t for the faint-hearted and isn’t for everyone.  Wearing protective gear is essential and specialised training is required to use pesticides safely.  But, hopefully, there are control methods, such as cutting flower heads, digging of roots, mulching or use of barriers in your garden or grazing with animals in larger spaces that might work for you in your own hogweed situation and circumstances.  So, don’t be afraid to try this at home – but do be careful and do some thinking beforehand.   If you do decide to take hogweed on use a method that is suitable for you and your site, only proceed after proper planning and, if needed, training and absolutely always with the correct protective clothing!

Just remember, always check and clean yourself and your equipment before leaving a site to avoid further accidental spread, prioritise control strategically in a downstream direction and focus on plants about to flower.

If you are in the Scottish Invasive Species Initiative area and want to help our control work then get in touch (E: sisi@nature.scot) and we will see what opportunities are available in your patch. Read more on our website.