European minks are an endangered species in the Old World because of the introduction of their relative, the American mink.
A trend in recent years has been the release of farmed minks into the wild by animal rights activists. The result of the introduction of the American Mink into the wild in Europe has been disastrous for the European Mink, who occupies almost the same ecological niche but is out-competed by the larger and better-swimming American species. Attempts are now under way to introduce the European Mink to islands too far from the continent for American Mink to swim to, in an attempt to prevent the species from becoming extinct. The endangered populations of European Mink Mustela lutreola have shown a large decline over 80% of their natural range and the species may be regarded as one of the most endangered mammals in the world. Although natural hybridization events between two native species is regarded as an exceptional event, Thierry Lodé found some hybrids, emphasizing that European Mink and European Polecats are able to hybridize and their hybrids were fertile.
The European mink is one of the most endangered mammals in the world. The endangered western population of European mink Mustela lutreola has shown a large decline over its natural range, though in Iceland the breed has grown rampant and is an ever growing problem, especially to river owners leasing it for fishing. The species has been extinct in central Europe since the beginning of the century and the mink's range is actually fragmented into two population units: an eastern population unit ranging from the Urals and Estonia to the Black sea, a population which is already subdivided into small units, and a western population. Inhabiting mainly forest brooks, the European mink occupies an intermediate semi-aquatic niche between the European polecat Mustela putorius and the otter Lutra lutra.