American Mink

Neovison vison

One of the things I hear the volunteers say they get asked the most is (well, besides if a Nutria was a beaver or muskrat) the difference between a mink and a weasel. American Mink, which have been seen by a lucky few on our Refuge, have soft, thick, waterproof fur that is dark brown to almost black- with white patches on their neck and belly. Weasels, such as the Long-tailed Weasel featured below, are usually a much lighter color, with variants of brown to yellowish-brown fur, which is paler on the chin, neck, and underside. Mink are generally larger, longer and heavier than North American weasels, though that can be hard to judge when you are seeing only one or the other. Mostly the coloring is your biggest indicator.

Mink are mostly aquatic, usually seen swimming in the sloughs at our Refuge, or with mostly wet fur moving along the road. They aren’t picky about den sites, as long as they are near a water source. They usually create long burrows in river banks, holes under logs, tree stumps, or roots and hollow trees, though dens located in rock crevices, drains, and nooks under stone piles and bridges have been observed.

Their mating and reproduction habits are exceptionally interesting. Mink have a three week mating season during which, any time a male is near a female, she begins ovulating. We won’t go into the violence of mustelid mating, but for mink, it can last anywhere from 10 minutes to four hours. Females can mate with multiple males and produce litters of up to 11 kits with multiple sires. The American Mink, along with the striped skunk, is one of the only mammals to mate in spring and have a short delay before implantation. Delayed implantation allows pregnant mink to choose the ideal time to gestate based on environmental conditions. This delayed gestation can last anywhere from 8 to 45 days!

Mink are aggressive in many aspects on their lives. Males often fight during mating season, forming gangs that control access to females. They are also fierce predators, killing prey with a bite to the back of the neck. Their diet includes rodents, eggs, birds, frogs, fish, and crayfish. After killing prey, minks carry food to solitary dens to eat or save for later. Mink stalk shorelines, riverbanks, and wetlands, hunting whenever prey is available. They swim fast and can dive 15 feet underwater to catch muskrats, their favorite food. This is not that dissimilar from weasels, though weasels will more often be observed going for prey much larger than themselves.

American Mink need access to reliable sources of water for drinking and hunting, and shoreline vegetation for camouflage during frequent food-finding forays. Minks travel along miles of stream habitat and over acres of wetlands, where they find abandoned dens to burrow in, especially during harsh winter weather. Weasels live in a variety of habitats, usually including woodlands, brush, and fields. They do not swim or seek prey in the water like mink do though, and their range is less extensive. Weasels find homes in dry protected places that they line with grass, feathers, and fur.

-Samantha Zeiner, Friends Administrative Assistant