Invasive species (II): the American mink

The American mink has become one of the invasive species in Europe. It has spread in recent decades to Spain and other European countries, displacing and endangering native species, such as the European mink.

The American mink ( Neovison vison ) is a small carnivore belonging to the mustelidae family. Its natural habitat includes the USA and Canada. P iel of minks is considered valuable for making coats, why are ranched since the nineteenth century. The American mink fur farming business later expanded to Europe, where the mink began to escape, resulting in stable populations in the new habitat.

In Spain there have been several releases of mink in this type of farms because groups of animal activists (it would be a mistake to call them ecologists, since their motivations were the welfare of the animals , not the conservation of an ecosystem) attacked the facilities and released to animals with a great impact on the environment.

The problem of the American mink as an invasive species

The impact of the American mink is very negative in Europe, either due to predation or displacement of native species. It is an opportunistic carnivore, capable of feeding on birds, fish, invertebrates, reptiles or other small mammals. In coastal areas its presence affects populations of seabirds by predation on eggs, chickens and even adult specimens.

For example, in the Laguna de la Nava (Palencia) the loss of 60% of the imperial heron chickens by the American mink was verified. In other European countries there has been a decline in the populations of the gopher rat ( Arvicola amphibius ) due to the invasive species, and it is suspected that it may have affected the scarce populations of Iberian desman ( Galemys pyrenaicus ) in Spain due to the fact that both species they share habitat, although there is no confirmation of the latter. The desman is one of the most threatened species in Spain and it is an endemism, so its disappearance would mean the extinction of the species.

Another problem with the American mink in Europe is that it displaces native mustelid species. This phenomenon occurs when two species occupy the same ecological niche, that is, they live in the same habitat and feed on the same prey. The most competitive species will end up displacing the other, which will disappear from the ecosystem. This especially affects the European mink ( Mustela lutreola ), a threatened species of which there are barely 500 specimens left in Spain . In northwestern Europe their populations are not in immediate danger, but the progressive expansion of the American mink may destroy them.

As if this were not enough, the American mink is also a carrier of plasmacytosis or Aleutian mink disease (ADV), a virus that causes a fatal immune deficiency for these animals. The disease can be transmitted between the American and European species, adding another negative impact to the indigenous species.

Control mechanisms of the American mink

In Spain, attempts are being made to reduce the existing populations of American mink by means of nocturnal cage-traps. These are cages with a bait, which trap the animals without damaging them. This is important, since a negative impact on other species is avoided. If an American mink is caught in these traps, it is anesthetized and euthanized avoiding its suffering. If it is another species, the captured individual is simply released.

In the last decade , several thousand individuals of American mink have been captured throughout the Iberian Peninsula, including 1,900 minks in central Spain and 1,165 in Catalonia since 2002. Another notable case is that of the Parque Nacional das Illas Atlánticas in Galicia. , where the existing population has been reduced considerably, eliminating 200 individuals.

The islands are ecosystems especially vulnerable to the introduction of carnivorous mammals, a sad example being the extinction of the dodo ( Raphus cucullatus ) on the island of Mauritius (located east of Madagascar) in the 17th century. This extinction was not due to man, but to predation by rats, cats and dogs that were accidentally introduced to the island when the Europeans discovered it.

In some European countries, American mink populations are considered to have been satisfactorily controlled through the use of trap cages. The Cairngorns National Park, in Scotland, or the Hebrides Islands, in the United Kingdom, are a good example of this. The seabirds of these islands, as well as the water rat in Scotland, are recovering after the negative impact of the mink. Another satisfactory case can be found in Finland, where the capture of mink during the last 15 years has reduced the populations of this species at the same time as seabirds and voles are recovering.

Let’s hope that in the coming years the American mink populations in Spain will decline, allowing the European mink to regain its natural habitat.