Wolverine

Quick Take

• The wolverine is famous for its ferocious bite, yet another small animal you'd never expect actually outranks it significantly in bite force. See the bite force facts →
• Michigan calls itself the Wolverine State, yet the real reason behind that nickname has nothing to do with the animal actually living there. Discover the Michigan nickname origin →
• A wolverine can drive off a bear twice its size from a fresh kill, and the way it pulls this off is stranger than you'd expect. Explore wolverine behavior →
• The wolverine's scientific name hints at a personality trait that defines almost everything about how it survives, and that trait is not aggression. Unpack the scientific name →

Despite its small size, the wolverine has earned a ferocious reputation as a top predator. This animal looks like a small bear, but evidence suggests it is closely related to the weasel, another small but aggressive creature. Alternative names for this species include the skunk bear, the Indian devil, and the carcajou. It has adapted to thrive in the colder parts of the Northern Hemisphere over millions of years of evolution.

An Incredible Animal: 4 Wolverine Facts

• The wolverine is often depicted as a trickster or conniving character in the various mythologies of the Algonquians and other native tribes.
• The wolverine is the traditional symbol of Michigan, widely regarded as the state animal and serving as the mascot for the University of Michigan sports teams, but evidence suggests the species was never historically present there in large numbers. The nickname probably came from the fact that Detroit was a major center for fur trading in colonial France and Britain.
• There are two distinct subspecies of the wolverine: the American and the Eurasian. Despite their geographical differences, both subspecies are similar in appearance and behavior.
• Despite its ferocious reputation, the wolverine actually has a rather average bite force compared to body size. According to one study, the palm civet, weasel, and Tasmanian devil all ranked well ahead of it in bite power. So the wolverine tends to use a combination of bite power and claws as its means of attack and defense.

Evolution and Origins

Wolverines belong to the Mustelid family, which is believed to have appeared on the evolutionary scene roughly 40 million years ago, with modern mustelids’ ancestors diversifying during the Oligocene epoch. The Corumictis genus is the oldest known mustelid from North America. Consisting of a single species, Corumictis wolsani, it appeared in Oregon during the early and late Oligocene (early and late Arikareean).

This mustelid, which was named for its genus and location (corum means northwest and mictis means weasel in Latin), is believed to have been equal in size to Mustela nivalis, the smallest member of the Mustela genus, also known as the least weasel.

Additional fossils which belong to the Miocene era have also been discovered, and it is believed wolverines, like other mustelids, simply crossed the Bering land bridge to reach America.

Classification and Scientific Name

The scientific name of the wolverine is Gulo gulo. This comes from the Latin gula, meaning glutton, perhaps due to its voracious appetite. This is the origin of the English word glutton. The wolverine is the only living member of the genus Gulo, but several extinct members are known from the fossil record dating as far back as the Early Pliocene, approximately 4.5 to 5 million years ago. More broadly, it belongs to the Mustelidae family along with badgers, weasels, otters, and minks.

Types

There are two subspecies of wolverine:

• The Eurasian wolverine (Gulo gulo gulo): The Eurasian variety can be found in Finland, Norway, Russia, and Sweden.
• The American wolverine (Gulo gulo luscus): This subspecies lives in Alaska, Idaho, Oregon, Montana, Washington, and Wyoming.

Appearance

The wolverine has a stocky, muscular build that has drawn obvious comparisons to a miniature bear. Other important features include short but powerful limbs, five toes on each paw, sharp semi-retractable claws, and a moderately powerful bite to help them hunt for prey. The fur color is brown or black with a yellow or gold stripe extending from the head to the rump. The patterns on the face, neck, and chest are unique to the individual.

The wolverine’s body measures some 26 to 41 inches, plus an additional 5 to 10 inches with the tail. The moderately sized body, weighing about 18 to 66 pounds, makes it about the same size as some dog breeds like the miniature Aussie Shepherd. Females tend to be around 10% smaller in length and 30% smaller in weight compared with the males.

Behavior

The wolverine is a highly independent species that prefers a life of solitude. They rarely get along with members of the same sex, and the breeding season is the only time they tolerate members of the same species. The den, which is the center of the wolverine’s life, usually consists of a small cave, rock crevice, fallen tree, or pre-existing burrow in which it can create a rough bed of grass and leaves.

A single wolverine requires a massive amount of territory to roam: some 200 to 400 square miles for a typical male and no more than 135 square miles for a female. The wolverine can travel 15 miles per day in search of food, and up to six to nine miles without stopping to rest. The facts suggest that this species is active throughout the entire day, but in areas with long periods of light, it can alternate between activity and sleep in spurts of three to four hours at a time.

With its thick coat of fur and large toes, the wolverine is well-adapted for life in the harsh northern climates. The creature’s strong body build and movement pattern allow it to walk surprisingly well across the snow (but much less well on the bare ground) at speeds up to 30 mph (or 48 kph). The wolverine is also a capable swimmer and climber, which sometimes helps it escape from predators.

Scent is the main means through which the wolverine communicates. With its anal gland, this species marks its territories and vital food caches with a rather pungent smell to discourage other creatures from approaching or stealing. It complements this with a very good sense of smell to scavenge for food. It also has good hearing but poor vision. The wolverine makes few vocalizations except for the occasional grunts and growls to express its irritation.

Some studies suggest that the wolverine is quite a canny and intelligent animal. It has been known to play with toys and objects. It can follow human roads that have minimal traffic to speed up its travel time. It has the ability to sneak baits out of traps that are set by scientists for the purpose of collaring the animal.

Habitat

The wolverine currently lives in cold, high latitude regions across vast stretches of Canada, Russia, and Scandinavia. It is no longer endemic to the United States except for Alaska and some sporadic and isolated sections of the Rocky Mountains and the Sierras of California. The huge, uninhabited boreal forests and tundra are most suitable for its lifestyle because they offer the most territory to roam.

Predators and Prey

The wolverine is an apex predator throughout most of its range. Besides occasionally falling prey to random predators, the greatest threat is humanity. The wolverine was once hunted and killed throughout North America and Europe for its fur. This practice is much less common today, but it has yet to recover in some parts of its former range, perhaps due to habitat loss. In the future, as the Arctic warms, climate change could alter some parts of its natural habitat in complex ways.

What eats the wolverine?

Despite its relatively small size, the wolverine has few natural predators. Its sharp claws and ferocious attitude deter most other animals from threatening it. The wolf is probably the closest thing it has to a regular predator because an entire pack has the ability to pin down a wolverine and prevent it from escaping. In fact, wolverines and wolves sometimes do not even share the same territory. Bears, eagles, and mountain lions may also target a young wolverine and kill it.

What does the wolverine eat?

The wolverine is best described as an omnivorous species that can opportunistically change its diet based on season and location. Berries and plants are the main fare in the summer season, while rabbits, rodents, and leftover carrion constitute the bulk of its diet for the rest of the year, particularly in the sparse winter months.

The wolverine is so tenacious that it can take on prey up to five times larger than itself, usually when the prey is wounded or stranded in deep snow. The wolverine kills its prey with a bite to the neck, which severs the tendons and crushes the throat.

The wolverine is a clever animal that will look for any way to steal a kill from other predators to avoid expending time and energy on the hunt. It has been known to drive away much larger animals such as bears and cougars and then take over and consume the carcass of the animal they killed.

Reproduction, Babies, and Lifespan

During its breeding season, the wolverine is a polygamous species that tends to pair up with any member of the opposite sex living inside or overlapping with its territory. This breeding strategy is highly asymmetrical, though. Some wolverines may mate multiple times, while others may mate barely at all.

The female is the first to initiate the mating process, starting with the breeding period between May and August. Once they pair up, the pair spends a few days alone to copulate and then goes their separate ways. The female has the ability to delay the implantation of the eggs until a more favorable moment in the late winter or early spring. The actual gestation period only lasts some 30 to 50 days.

Once safely hidden inside her den, the mother gives birth to three kits at a time. She raises them entirely on her own, while the father plays almost no role. Although completely dependent on the mother at birth, these kits soon begin to grow quickly. They are fully weaned off their mother’s milk at the three-month mark. The kits are then fully capable of foraging for themselves at around five to seven months.

It takes a year to reach full size but some two to three years to achieve sexual maturity. Because of the longer development times, the female only mates every other year. The wolverine has an average life expectancy of some seven to 12 years in the wild. However, females in captivity have lived for as long as 17 years.

Population

Exact population numbers have not been estimated, but the IUCN Red List currently classifies the wolverine as a species of least concern. It might not have always been in good health, because the wolverine was once heavily hunted in the southernmost parts of its range. Although it is currently protected, numbers do not appear to be recovering in these areas. Because of its large territorial needs, the wolverine has a low population density.

Animals in the Zoo: Where to find the Wolverine

The wolverine is a popular exhibit at many American zoos, including the Columbus Zoo, San Francisco Zoo, Zoo New York, Zoo Montana, the Minnesota Zoo, and the Detroit Zoo, many of which are involved with conservation and breeding programs. The Woodland Park Zoo in Seattle runs the Washington Wolverine Project in conjunction with the US Forest Service and the Washington Department of Fish and Wildlife in an effort to rehabilitate populations in the state.