Learn More About: Wolverines
Wolverines are the largest member of the weasel family.
Classification:
Kingdom: Animalia
Phyllum: Chordata
Subphyllum: Vertebrata
Class: Mammalia
Subclass/Infraclass:
Theria/Eutheria
Order: Carnivora
Suborder:
Fissipedia
Family: Mustelidae
Subfamily:
Mustelinae (or Guloninae)
Genus:
Gulo
Species:
gulo
Subspecies:
gulo (Old World)
luscus (New World)
vancourerensis?
Related species:
Weasels
Minks
Martins & Fishers
Otters
Skunks

Common names: Carcajou, Omeedatsees, skunk bear, devil bear.
Origins and Taxonomy

The wolverine is the largest member of the weasel family, Mustelidae, and the only representative of its genus, Gulo.

The mustelids (weasel family) probably originated in the late Eocene, and were established and recognizable by the late Miocene. In the Quarternary Period, representatives of the family spread to habitats ranging from the tropical to the temperate.

Our New World wolverine is probably decended from a large, marten-like animal called the Plesiogulo, which in turn decended from other marten-like antecedents. Plesiogulo migrated from Asia somewhere around 6-7 million years ago.

Physical Characteristics

Wolverines look somewhat like Tasmanian Devils (which are marsupials, and not related), and badgers (also not closely related). Like bears (and humans), they walk "plantigrade", or with the soles of their feet flat on the ground (but they are not related to bears, either). This characteristic may facilitate over-snow travel, giving them a "snowshoe"-like foot which distributes their weight. They are set low to the ground and have a slightly rolling, scurrying gait.

Generally, the fur is dark brown, often with a pale yellowish throat patch and/or mask. Wolverines may also have paler patches of fur on the front legs and feet, and a buff-colored line reaching from the shoulders to the rump along the sides is visible in some individuals.

The wolverine has long, powerful claws, which can be partially retracted. Males are typically much larger than females, weighing up to 35 pounds, while females weigh up to about 25 pounds.

Geographic Range: Historic, recent past, and current

Currently, subspecies of wolverine can be found in the northern United States, Canada, Alaska, Siberia, and northern Europe. All subspecies belong to the same species (Gulo). It is considered vulnerable by the International Union of Conservation and Nature, and Sensitive Species by the US Forest Service and Bureau of Land Management, although not threatened or endangered.

Historically, the wolverine probably ranged over much more of the U.S., including all of the northern states from Maine to Washington, and as far south as the southern Sierras and Arizona and New Mexico via the Rocky Mountains. Their habitat was diminished by human settlement over time, and they now are not known east of the Rocky Mountains. Their range has also diminished in Canada, where they once probably ranged over most of the country. They occur in Alaska, as well.

Populations of the Old World wolverine exist in Scandanavia, Siberia, and Asia in northern tundra and taiga-type locations.

Behavior

The wolverine is extremely strong for its size, and may kill and drag off prey much larger than itself. Strong, solid teeth and a powerful jaw can break up bones. It is a solitary hunter, joining with other wolverines only in the breeding season (although some evidence indicates that males may help raise the young). Wolverines are active day and night, although they may primarily hunt in low-light conditions.

Wolverines have musk scent glands, like most members of the weasel family. However, they generally use urine and abdominal scent rubbing to mark their territories. A wolverine will often use stumps, trees, and other permanent objects as marking posts, which it will repeatedly spray over time. If frightened, it may exhibit a skunklike posture with tail raised in anticipation of spraying with the musk glands as a defense.

Wolverines produce loud vocalizations, some of which sound like a combination of a snarl and a growl. They also vocalize to communicate with kits and other wolverines.

Although wolverines have been reported taking deer and other large ungulates, they probably rely mostly on scavenging and small rodents as food sources. They may occasionally eat vegetation such as berries but probably do so only incidentally.

Wolverines do not hibernate, and are active all year. Wolverine breed in the spring and early summer, from May to August. They exhibit delayed implantation, meaning that the fertilized eggs are retained without further development until about November, when they begin to develop again. The kits (one to five) are born in early winter (January through March). Kits have fur, but no teeth, and are not weaned for 9-10 weeks. They grow quickly and are often full-grown before the next fall. Sexual maturity occurs between 1 1/2 - 2 years of age. The males may participate in the rearing of juvenile-aged young (young of adult size, but less than sexual maturity).

Dens appear to be made by tunneling through deep snow to reach talus slopes and rock piles. The kits may be bedded on bare ground, snow, or possibly on branches and vegetation. Females may utilize several dens.

Wolverines may live 8 - 10 years in the wild, with starvation, predation, and human hunting as the major causes of death.
Research

Ongoing population density research is being conducted in the U.S., as well as in other countries. Due to their relative scarcity and the inhospitable environment in which they tend to live, relatively little is known about behavior, populations, and ranges in the wild. Most research into wolverines in the wild has only been conducted in the last 20 - 25 years.
Photo courtesy of C. Holland
A researcher prepares to anesthetize a wolverine in a trap using a jab stick.
After the wolverine is anesthetized, it is removed from the trap, weighed, measured, and prepared for release. The cuff protects its eyes. This male weighed 26 pounds
The wolverine has large teeth for its body size. These worn teeth indicate that this male is about five years old.
Although he weighs only 26 pounds, this wolverine's paw is half the size of a man's hand.
Photo courtesy of C. Holland
The wolverine is fitted with a transmitting collar and the receiving frequency is checked.
The wolverine is returned to the trap to recover from the anesthesia. He'll be monitored until he is awake enough to be safely released.
Photo courtesy of C. Holland
He's ready to leave in a hurry when the trap is cranked open later.
Photo courtesy of C. Holland
The inside of a wolverine trap takes a beating from the animal's strong teeth. That's why it's made of full-sized pine logs.
Photo courtesy of C. Holland
The Wolverine Foundation