Water Voles and Mink

American minkAmerican mink, copyright Mike Read

Enter the villain of the piece...

American mink were originally introduced for fur farming in the 1920s, with a peak of around 700 mink farms in the UK in the 1960s. Increasingly stringent legislation gradually saw the end of the mink farming business, but the damage had already been done. Mink were first confirmed breeding in the wild in 1957, with a combination of escapes and deliberate releases during the 1960s and 70s increasing their numbers such that mink have now spread throughout the country. Estimates suggest that the mink population in Britain may now number as many as 110,000 animals.

Mink are generalist predators of the water’s edge, feeding on fish and frogs, moorhens and ducks, rabbits and rats. However, as they hunt along the narrow fringe of vegetation along the river bank, mink will inevitably hunt water voles; and they are very good at it.
 

No escape

The water vole has two main defences from its predators: to escape from a fox or a kestrel, it will leap into the water. To escape from a pike or a heron, the water vole takes refuge in its burrow. American mink are good swimmers, so can follow in the water, and a female mink is just the right size to slip in to the water vole’s burrow. With water voles already restricted to a narrow fringe of vegetation along the river banks, a single female mink with several hungry mouths to feed can easily find and eat every water vole in their home territory, wiping out the water vole population in a single season.

Mink take more water voles during the early part of the year than at other times. The removal of adult voles that have survived the winter before they have had a chance to breed can threaten the future of whole colonies, increasing fragmentation and putting neighbouring colonies at risk. High numbers of water voles may also be taken during early summer when female mink are nursing young.