The status of the American mink (Neovison vison) in the Netherlands
The American mink (Neovison vison) is a north American mustelid that has been farmed for its fur in Europe since the 1920s. It has been feral in the Netherlands since 1958. This paper discusses its distribution, diet, the indications for reproduction, and whether feral animals are born in the wild or are escapees. The American mink mostly occurs in areas where many mink are kept in farms. The largest distance between an observation and the nearest farm was 45 km. Sixteen animals caught by muskrat control officers were dissected. The stomach content of the 16 animals revealed a diet of amphibians, birds and small mammals. The dissections gave no clues about reproduction: one of three males was sexually active, but none of the 13 females showed placental scars, a thickened uterus or signs of lactation. Only one observation of reproduction in the wild was received. Isotope analyses of teeth and nails indicate that the animals generally only stay feral for a short period of time before being caught. The ratios of carbon and nitrogen isotopes of the wild caught animals were very close to the isotope ratios of ten reference animals from a fur farm, except for one adult female, whose teeth isotope values were different from the farm animals and as such she seems to have remained in the wild for longer and was possibly born in the wild. In general however most animals are caught shortly after escaping and only remain in the wild for a short period of time. It seems that feral mink stem from constant escapes and that muskrat control removes these feral animals. Thus, the existence or development of a feral population in the Netherlands is unlikely, especially since it is planned to phase out mink farming by 2024.