American mink were bred on British fur farms from 1929. Escapes were frequent, but it was nearly 30 years before they bred in the wild, initially in Devon.
Thereafter they were reported around much of Britain, though this might not represent a rapid spread – these individuals could just have been overlooked.
One thing is clear, however: mink became established as otter numbers crashed.
In 1964, the Ministry of Agriculture, Fisheries and Food set up a mink-eradication team comprising seven people, but the response was too late and the group was disbanded in 1970. By then, the species was well established across mainland Britain.
Mink have since declined as otters have recovered. Data collected by the Game & Wildlife Conservation Trust suggests that numbers increased until 1978, but have roughly halved since 1984, and the population trend continues downwards.
While there have been a number of successful attempts to eradicate mink from islands and parts of mainland Britain, final eradication is a long way off and dependent on volunteers. But prospects are improving.