Occasionally, American Mink - a semi-aquatic member of the Mustelid family - can be seen along the river Wharfe (see Nature Notes, December 2020). Looking through my photographs for the last year, I’ve had four sightings.

Mink are a non-native, semi-aquatic mammal, that were introduced to Britain in 1929 and farmed for their fur. However, with escapes and releases, by the latter half of the 1950s wild populations had become established in some areas. In 2000 fur farming was banned - although this was immediately preceded by further releases. The end result is that Mink are now widely distributed in Britain, and only thought to be absent on some Scottish islands and the very northernmost part of the Scottish mainland. Mink have a strong preference for riparian environments where there is reasonable vegetative cover and available den sites, although they can also be found in some coastal and still-water locations.

The predatory abilities of Mink are such that there has been longstanding concern about the impact of this feral population on native fauna. They are relatively small, very agile, and have semi-webbed feet - attributes that enable them to take fish and crayfish from the water, but also to pursue prey (birds and mammals) on land, entering burrows and climbing trees. This versatility is thought to have played a key role in the dramatic decline of the UK Water Vole population over a number decades, and also to have had devastating effects on some sea bird colonies.

Consequently, it is argued that conservation benefits accrue from applying lethal control, to protect areas with vulnerable wildlife. This typically involves the use of baited traps, placed along watercourses. This is a resource-intensive method, as traps need to be checked at least daily, and any mink that have been caught despatched. Efforts were made, in the 1960s, by the Ministry of Agriculture, to eradicate Mink entirely. However, after approximately 5000 animals had been culled, it was concluded the goal wasn’t achievable.

Recently, following technological/scientific advances, and what appear to be successful outcomes in some parts of the country, the possibility has been raised again: https://www.bbc.co.uk/news/uk-england-norfolk-67941507. Traps can now be constructed that send an electronic alert when occupied, massively reducing the number of site visits that need to be made. Techniques such as testing water samples for DNA may provide more effective means of checking progress. So, could this spell the end of American Mink in Britain? The logistical requirements of a nationwide project would still be enormous, not to mentioned the complex ethical questions that should be addressed. How would harms, costs, and benefits be assessed and weighed for such a wide-ranging endeavour? After all, there are lives at stake!

wharfedale-nats.org.uk