The European mink is a small mustelid that originally populated almost all of Europe. Its range has severely declined since the mid-19th century and nowadays it can only be found in northern Spain and southern France, the Danube Delta, and in some areas of Ukraine and Russia - less than 10% of its former range. The IUCN Red List has ranked it as a Critically Endangered Species since 2011.

The decline of the European mink has been attributed to habitat loss/alteration and to over-exploitation. These main causes were supposedly aggravated by factors such as population fragmentation, loss of genetic variability, the Aleutian mink disease parvovirus (AMDV), and anthropic pressures. However, in the last decades it has become evident that the main cause is the invasive American mink. This alien pest species is in direct competition with the European mink for habitat and food resources, and their interaction usually ends in the displacement of the native species. Furthermore, the American mink is a transmitter of AMDV.

The American mink is also a mustelid species, but native to North America. Highly valued by the fur industry, it has been introduced in many countries via fur farms (from which they often escape) or simply released into the wild to establish populations to hunt from. Once naturalised, it becomes an extremely competitive predator which has had a huge impact on the populations of both its prey and competitor species.

Several traits of the American mink might give it the advantage over the European mink in any competition scenario, causing the decline of the latter. For instance, American minks are larger, both in length and weight, and can overcome the native species in physical confrontation and even prey on it. Furthermore, American minks are extremely adaptable, and seem able to utilize any body of water, including artificial ones, whereas the European mink is highly sensitive to pollution and habitat alteration. Regarding reproduction, American minks have larger litters than do European minks (mean 5.8 vs. 2.4 offspring per litter).