In 1931, the mink (Mustela Vison) was imported for fur farming.  Quite a few animals escaped, and the first den in the wild was discovered in 1937 in the capital area.  It took about 35 years for the mink to spread all over the country.  The average litter size is 6,6 (4-10) cubs.  Its habitats are mainly near the sea-shore and fresh water (rivers and lakes).  Littoral fish is the main food source in such areas, but birds and crustaceans are also eaten.  Inland the food is seasonal.

In winter it is small salmonides (4-15 cm) and sticklebacks.  In spring it is the avifauna and its eggs.  The mink eats field mice the whole year round, especially in autumn when their number is greatest, but it does not seem to be an important factor in the diet, which is mainly fresh water fish at this time of year.  The fox even eats invertebrates (bumble bees).

The mink has been hunted relentlessly to keep the population down or to exterminate it from the wild.  These attempts at keeping the population down have not proven so successful as expected and many are of the opinion, that the damage done by the mink is considerably less than people generally assume.