by Bethan Wood
As I stepped out of my car onto my drive, I stood on something that softly cracked and squelched. Looking down I saw the bottom half of a frog – its head and front legs were missing. A whole frog I could understand; our small loch produces thousands of them and sometimes they are accidentally run over by vehicles. Half a frog was something new.
I looked around and noticed many similarly discarded frogs in various stages of dismemberment. Heron? Fox? It was then that I sensed I was being watched. No more than 8 feet away, an American mink sat (yes, sat) watching me. It showed no fear, no alarm, but waited for me to move so it could continue with its meal. I was both horrified by the carnage around me but intrigued to see a mink in the flesh. A colleague who studies small mammals in southern Scotland had told me and my students in a presentation that if you ever accidentally catch a mink in your Longworth trap you MUST apologise profusely and release it on the other side of a wall if possible, as mink are known to attack if cornered. So I went into the house and ran upstairs to watch from a window.
A little bit daunted and excited I spent the next hour watching as the mink entered the water of the loch, caught its prey, brought it to the driveway, dismembered it and ate the parts it wanted. My excitement I confess did turn to anger. Despite its fluffy tail and pointed snout, this was undoubtedly an indiscriminate predator which certainly was born to kill. Our resident moorhen family was nowhere to be seen; blackbirds, chaffinches, and our tenant robin were all sounding continuous alarm calls. This one small mammal which is only a fifth the size of an otter had unbalanced the peace of this small ecosystem.
The American mink (Neovison vison) is not native to the UK and as such has no natural predators here. It was imported in the 1920s to satisfy the demand for fur – coats, muffs, collars, etc. In the 1950s there were estimated to be around 400 mink farms in the UK with thousands of animals at each. With that number of individuals, it was no surprise that many escaped (or were deliberately released) and went on to flourish in the wild. For me, the most incomprehensible wildlife crime involving these animals was executed in the name of ‘animal protection’ when animal activists deliberately released these animals from fur farms into the countryside. It is estimated that in the 1980s and 90s thousands of mink were released by these campaigners which added to the already significant population in the wild.
The carnivorous American mink feeds on small mammals (including rabbits), fish, birds (especially moorhens – hence my concern), crustaceans, as well as my frogs and other amphibians. However the most noteworthy UK species it has influenced over the last few decades is the Water Vole (aka ‘Ratty’, in the Wind in the Willows). In the 1900s it was estimated that there were around 8 million water voles in the UK; Scotland has a darker population which came from southern Europe around 10 000 years ago when there was a land bridge to Europe, while England and Wales have the lighter water vole which originated from the Balkans. Despite the longevity of these populations since the last Ice Age, ninety percent of water voles disappeared within a few decades of the release of mink from fur farms in the 20th Century. By 2002 it was declared extinct in South West England. In 2011, one of the biggest conservation schemes commenced in North East Scotland, to remove mink from the rivers in a bid to protect and increase the numbers of the native water vole.
I am fairly convinced that we have water voles on our land in southern Scotland. I have found a few latrines over the years and found evidence of the cropped grass around a burrow. The presence of this mink was therefore of concern. Mink cannot be released back into the wild if caught because they are a non-native, invasive species; our animal was humanely killed by a single shot as it sat feeding on yet another frog. As the body slowly cooled I took the opportunity to examine this compact, evolutionary-superb animal. I first ran my hand down its dark-chocolate back and the silky, velvety-smooth fur made me see why women in the early 20th Century had valued its pelt. Its sparkly black eyes were slowly dimming but still kept a remnant of its intelligence. The bright white markings on its chin and throat reminded me of the brilliance of newly fallen snow. The long slender body was muscular and solid, and the feet webbed. It was the size of a small domestic cat. I confess, I admired this little animal and its tenacity to seize a niche in a new country and thrive. Research has shown that the presence of otters can limit mink numbers as the otter outcompetes the mink. As our rivers become cleaner our native otters are slowly returning to their former habitats and this creates hope that the mink population will decline as a result. However, we must remember that humans caused this ecological conundrum – and sometimes to save many species we may have to control a single species which in this case is an alien in this ecosystem.
One day later, as I was leaving for work, I heard the familiar call of one of our moorhens and saw that all of them were present and correct – clever birds!
Bethan Wood is an ecologist who lives in Southern Scotland. She teaches ecology at undergraduate and postgraduate level.