IN November I set up a trail camera overnight at Otley Wetlands Nature Reserve, focussed on a waterside log used as a spraint point by otters to mark their territory.

The first creature to be picked up after dark, rather surprisingly was a robin, perched on the log and flirting its tail.

The second was an animal that, at first glance at the tiny camera screen I took to be an otter. Enlarged on the computer at home it was obvious that it was an American mink, its body all dark apart from a white throat spot and a possible white chin, its bushy tail not as pointed or as curved as an otter’s.

Having previously obtained trail camera photos of otters at the same spot a comparison also showed the mink to be much smaller. Its tail appeared bushy rather than wet – it had come along the bank, not out of the water as the otters usually did.

Mink are seen occasionally at OWNR and along the Wharfe although they are now reported much less frequently than otters with only three definite sightings this year in Wharfedale compared to about thirty for otters.

The last mink farm in this country closed in 1993 but in the preceding sixty years mink had escaped or been released by animal liberationists with devastating effects on our riverside wildlife, especially the now endangered water vole.

The first mink were seen in Wharfedale in 1988 with the water vole population disappearing soon after.

Mink numbers reached a peak of 110,000 in the 1980s with one theory for their expansion being the collapse in otter numbers in the 1950s and 60s due to poisoning by toxic pesticide residues in the food chain.

However, with otter numbers recovering it is thought that otters are displacing mink from their mainly waterside habitats. Mink numbers are now estimated to be as low as 40,000.

Mink swim well but in the water are no match for the bigger, faster otters and it is thought that, where they occur together, mink now concentrate on prey they find on land to avoid confrontation.

There are reports online of otters killing mink on rare occasions. One describes a mink and an otter facing up to one another with the smaller mink refusing to back down and being torn to pieces.

Otters are taking back control of their rivers!

wharfedale-nats.org.uk