The Slinky, Stinky Weasel Family — May - June 2003

Photo of two otters.

Minnesota Mustelids: The Slinky, Stinky Weasel Family

By Blane Klemek

Have you ever heard anyone call somebody a weasel? If you have, then you might think that being called a weasel is bad. But weasels are good hunters, and they are cunning, curious, strong, and fierce.

Weasels and their relatives are mammals. They belong to the order Carnivora (meat eaters) and the family Mustelidae, also known as the weasel family or mustelids. Mustela means weasel in Latin.

With 65 species, mustelids are the largest family of carnivores in the world. Eight mustelid species currently make their homes in Minnesota: short-tailed weasel, long-tailed weasel, least weasel, mink, American marten, fisher, river otter, and American badger.

Flexible Mammals

You can recognize most mustelids by their tubelike bodies and their short legs. Some, such as badgers, are heavy and chunky. Some, such as minks, are long and sleek. All are very quick and flexible.

When traveling, fishers, weasels, minks, and otters flex their spine inchworm-style, thus appearing to have humped backs. Because of their shape and flexibility, mustelids can easily enter holes and tunnels, climb trees, and swim as they hunt prey to satisfy their big appetites.

Mustelids must hunt much of the time to survive. Their long bodies do not store heat well, so they need lots of food to fuel their internal "furnace." They are active in winter too: Mustelids do not go into a deep sleep or hibernate. They often kill more animals than they can eat at one time and cache, or store, the carcasses for later.

Mustelids are adapted to hunt in different environments. Fishers and martens are expert tree climbers. Badgers have strong front legs and long digging claws for underground hunting. Otters and minks are excellent swimmers that hunt in or near lakes, rivers, and wetlands.

Most female mustelids have a special way to ensure their young are born when food is available. Called "delayed implantation," this adaptation allows fertilized eggs to remain undeveloped for many months. When food is plentiful, usually when days are warm and long, the eggs develop and the young are born.

All mustelids have two large scent glands under the tail. These glands produce a very strong liquid scent, called musk, for marking territories and food caches, attracting mates, and deterring predators.

Weasels

Short-tailed weasels (Mustela erminea), long-tailed weasels (M. frenata), and least weasels (M. nivalis) live throughout Minnesota. In their northern range, including Minnesota, weasels turn white in winter. In autumn, white hairs begin to replace their brown summer coat. By winter the least weasel is mostly white, and the other two weasel species are white except for black tips on the tail. Owls and other predators sometimes focus on the black tip when attacking, which occasionally causes them to miss capturing the weasel all together.

With its long, tube-shaped body and short legs, the weasel can slip into just about any hole or burrow as it searches for food such as chipmunks, pocket gophers, rabbits, moles, rats, voles, mice, shrews, and sometimes birds, snakes, frogs, insects, and berries. It hunts almost constantly. Using its keen senses of smell and hearing, it checks out every nook and cranny. It might disappear into a hole in a log and pop out seconds later somewhere else.

Foxes, coyotes, bobcats, domestic cats and dogs, hawks, owls, martens, fishers, minks, and occasionally snakes hunt and eat weasels.

Weasels are solitary except during the breeding season. Baby weasels are born blind and almost furless in the spring. In just three months, they are full-grown and ready to live on their own.

Mink

Mink (Mustela vison) are good swimmers and spend plenty of time in and near water. They live on all kinds of land throughout Minnesota but always near water.

The mink eats a wide variety of foods. Favorite prey animals include fish, muskrats, rabbits, frogs, salamanders, diving beetles, and crayfish. Mink have also been known to eat waterfowl and chickens.

Full of curiosity, mink often sit straight up to better see whatever has captured their attention. They have to look out for owls, foxes, coyotes, dogs, and other predators.

In the spring a female mink gives birth to a litter of up to 10 kits. Mother mink might make her den under a rock pile or in an abandoned muskrat house, burrow, hollow log, or tree cavity. Her kits are born blind and helpless. By autumn the youngsters are fending for themselves.

American Marten and Fisher

With its foxlike face and attractive fur coat, the American marten (Martes americana) is a beautiful animal. At one time martens nearly disappeared from their north woods home because of logging and overtrapping for their valuable fur. Today martens range throughout the forests of northern Minnesota.

These exceptional tree climbers are also called pine martens because they prefer to live in old pine forests. Martens prey mostly on small rodents such as voles and mice, but eat whatever is available. They also hunt for squirrels, chipmunks, snowshoe hares, birds, eggs, and insects.

The fisher (Martes pennanti) is also common throughout the north woods. Unlike martens, fishers live in a variety of forests.

It's not entirely clear how the fisher got its name, because fishers rarely catch fish, though they do eat them. The fisher's favorite food is the snowshoe hare. It also eats small rodents such as mice and voles and larger prey such as raccoons, as well as nuts and berries. The fisher is one of the few predators to successfully prey on porcupines. It repeatedly attacks the porcupine's face while avoiding its quills. When the porcupine is tired and dazed, the fisher flips the animal and attacks its unprotected throat or belly.

A female fisher prefers dens inside trees or logs for raising her family of one to four young. The youngsters go off on their own before their first birthday.

River Otter

River otters (Lontra canadensis) have a reputation for goofing off. They spend a large part of their day wrestling, sliding on their bellies, and playing chasing games. These critters have even been observed playing with and teasing turtles, fish, and other animals.

Otters spend a lot of time in groups, usually of four to six family members. River otters are smaller than their West Coast cousins, sea otters. While sea otters can weigh as much as 100 pounds, most river otters weigh 15 to 30 pounds.

River otters are semiaquatic (living both in water and on land) and are quite common around Minnesota lakes and rivers. Intelligent and nosy, an otter will often swim close to boaters for a better look. It might grunt and pop halfway out of the water to get a good look at you.

An otter easily catches fish. It floats on its back or carries its catch to shore to eat for its main meal.

Otter fur is very dense and does a good job of insulating otters underwater. Glands under the otter's skin release oil to waterproof its thick fur. Because oil and water don't mix, water rolls off the oily fur and the otter's skin stays dry.

A river otter can hold its breath as long as two minutes and dive more than 40 feet deep! Mother otters coax their young into the water to teach them to swim. Webbed feet, ears and nose that close underwater, powerful hind legs, a long tail, and a flexible body help them become expert swimmers.

American Badger

Built flat, wide, and low to the ground, the American badger (Taxidea taxus) has incredibly loose-fitting skin with a thick layer of fat under it. This skin helps the badger slip and slide in underground tunnels. The fat layer grows thicker in fall to keep the badger warm through the cold season.

Not many animals can dig better or faster than a badger can. Active at night, badgers use powerful front legs and long claws to dig many long, deep burrows - up to 60 feet long - and to hunt for ground squirrels, gophers, and other burrowing animals.

Badgers live throughout Minnesota in open, treeless areas where there is plenty of prey.

Two to seven baby badgers are born blind in underground dens. When they grow up, badgers are fierce and strong. Not many predators will attack an adult badger.

Wolverine

Wolverines (Gulo gulo) have large feet and long claws, and look like small bears. In fact, because of its strong odor and bearlike appearance, American Indians once called the wolverine "skunk bear."

In North America, wolverines range throughout the forests and tundra of Canada and Alaska. At one time wolverines inhabited Minnesota's wilderness, but we don't know how many lived there. Wolverines are hard to find because they roam very large, remote territories ranging up to 566 square miles. Perhaps they were never more common in Minnesota than they are today. The last record of this species in Minnesota was a specimen taken in 1899 in Itasca County.

The wolverine is a good tree climber and eats just about anything, from cranberries to carrion. Gulo is Latin for glutton: Like other weasel family members, the wolverine has a big appetite. It protects its food stores by marking the food with a musk odor to keep away other carnivores.

Although not much bigger than a medium-size dog, the wolverine is ferocious. Its natural enemy is the wolf.

Skunks: Mistaken Identity?

Until recently, skunks were included in the family Mustelidae because of their scent glands and other similarities. Now some scientists believe skunks might have evolved apart from mustelids. Among differences, skunks have bigger scent glands and stronger musk than mustelids do. Some mammalogists place skunks into a family of their own, Mephitidae.

Valuable Furbearers

Mustelids are important furbearers, animals that are hunted or trapped for fur. Humans have a long history of making useful and decorative items from animal furs. American Indian chiefs adorned their war bonnets with weasel skins. French voyageurs and pioneers wore clothing made from mustelid fur. In fact, many Europeans came here to trade furs. Even today people trap many mustelids for fur.

The highest-priced Minnesota fur today is otter. It is prized for its luster, durability, and water resistance. Mink fur is favored for its combination of shiny, long guard hairs and dense, downy fur. Most mink used for today's fashions are raised on farms.

Marten fur (also known as American sable) is very soft and thick. Sometimes it is found in a rare orange-yellow color. Fisher fur is coarser, and sometimes grizzled with white hairs.

The badger's silvery long hair was popular for baggy fur coats in the 1920s. It is still used for high-quality paintbrushes and shaving brushes.

Wolverine fur is used to trim the hoods of parkas because frost doesn't stick to the long, soft, silky hairs.

Fur trappers buy licenses and follow trapping laws, which help the Department of Natural Resources manage furbearer populations.

To learn more about using Minnesota Conservation Volunteer as a teaching tool, contact Meredith McNab, meredith.mcnab@state.mn.us or 651-259-5348.

Weasel Web Sites:

To learn more about mustelids, visit these web sites.

Minnesota DNR. Nature Snapshots. Learn about Minnesota's wildlife.
www.dnr.state.mn.us/snapshots/mammals

Minnesota Zoo. Animals, education, and conservation. www.mnzoo.com

National Trappers Association. Trapping facts, furbearing mammals, and Kid's Corner.
www.nationaltrappers.com

A complete copy of the article can be found in the May - June 2003 issue of Minnesota Conservation Volunteer, available at Minnesota public libraries.