Can American mink be eradicated in the UK?

The University of Cambridge’s Bill Amos has been involved in a project that aims to eradicate mink from the UK's waterways. American mink began to spread through the UK after they escaped or were released from mink farms, which were banned here almost a quarter of a century ago. To find out more, Chris Smith caught up with Bill on the banks of the River Cam at Queens’ College, Cambridge…

Bill - So the American mink was brought over as a source of fur and they were farmed extensively throughout the UK. And when fur farming became less of a nice thing to do, many of them were just released or escaped. And so around the 1920s, 1930s, an awful lot of mink entered the English countryside where they found themselves very nice places to live.

Chris - What do we think the population of them is then?

Bill - Very difficult to tell. There are probably fewer than we think. We've basically looked to eradicate them from East Anglia as a start of tackling the problem. And in East Anglia we've probably caught 300-400 and we now think that there are none left. So it's not seething with them, but they do an awful lot of damage.

Chris - So you don't need many to have quite a devastating impact on the ecosystem.

Bill - Absolutely. They really are voracious hunters and they will hunt anything that they can catch. There are pictures of them attacking animals as large as a heron, which, considering the mink itself is only about a foot and a half long, that's impressive.

Chris - How are you trying to get rid of them then?

Bill - People have tried before, but the problem is that you have to be humane. You can't just allow them to starve to death in empty traps. So earlier trapping efforts really suffered from the fact that you need to inspect every trap every day to see whether it's triggered. The modern traps we have are fantastic because they're fitted with a little telephone device, which means that they signal whenever they trigger. And so you can run a hundred traps and the one that actually catches something you can go and visit. And so you can actually be extremely humane in getting rid of the mink and that's transformed the number of traps that you can have out in a given area. The other thing is that we've discovered that mink are incredibly inquisitive anyway, but if you've got the smell of another mink <laugh>, then they really go to town. So now all the traps we use, they're baited with the smell of mink, which is extracted from some of the dead mink we've culled as part of this process.

Chris - What smell in particular?

Bill - It comes from the anal glands at the back end. And the scientific name for the mink is a mustelid and must is the name that we use to describe some intense smells and mink are very smelly animals and this is where the smell comes from.

Chris - Are they attracted because they want a mate or are they attracted because they think this is a potential rival or is it both?

Bill - Probably both. We get males and females coming to the smell of mink. We have had traps before which have caught nothing caught, nothing caught nothing. There's a camera trap nearby, there's a mink around. You put the lure in, within 24 hours it's caught the mink and then you see nothing on the camera traps. So it's incredibly potent at mopping up the last few.

Chris - This is then presumably your strategy going forward that we use both digital traps that can be put at scale so that you can monitor very big flotillas of traps as it were, but equally you bait them up with this smell of mink, which enormously improves the efficiency of the whole operation.

Bill - Absolutely. It's completely transformed. I would say over a period of something like two to four years you can clear a really large area. And this is transformative. Previously people were putting out traps, they were having to visit them every day. You couldn't get enough traps and mink reproduce quite fast so they were just replenishing and you'd never get to elimination. And many people thought that it was actually impossible to eradicate mink from the UK.

Chris - Is eradication possible? Because elimination means we've cleared them from a geographical area. Eradication means we've cleared them totally. Do you think the latter is feasible? Because if they have a lot of babies it doesn't take very many mink to quite quickly repopulate.

Bill - No, we really do think this is possible. So I think the main part of using smart traps and lures started in about 2020, and already basically there are no mink in East Anglia. So I mean really <laugh> a huge chunk. Loads and loads of traps, not a single catch last year and no evidence of reproduction for two and a half years. And that's a large piece of the country. So all those traps or many of those traps are now being redeployed further out and we're trying to spread out across the UK. And yeah, as soon as the trapping goes, you start off catching loads and within a very short period of time, trap numbers plummet <laugh>, the number that you are catching plummets, and yes eradication or clearing of an area follows quite quickly.