Species of the family Mustelidae
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The wolverine ( , ; Gulo gulo), also called the carcajou or quickhatch (from East Cree, "kwiihkwahaacheew"), is the largest land-dwelling member of the family Mustelidae. It is a muscular carnivore and a solitary animal. The wolverine has a reputation for ferocity and strength out of proportion to its size, with the documented ability to kill prey many times larger than itself.
The wolverine is found primarily in remote reaches of the Northern boreal forests and subarctic and alpine tundra of the Northern Hemisphere, with the greatest numbers in Northern Canada, the U.S. state of Alaska, the mainland Nordic countries of Europe, and throughout western Russia and Siberia. Its population has steadily declined since the 19th century owing to trapping, range reduction and habitat fragmentation. The wolverine is now essentially absent from the southern end of its range in both Europe and North America.
Naming.
The wolverine's questionable reputation as an insatiable glutton (reflected in its Latin genus name "Gulo", meaning "glutton") may be in part due to a false etymology. The less common name for the animal in Norwegian, "fjellfross", meaning "mountain cat", is thought to have worked its way into German as "Vielfraß", which means "glutton" (literally "devours much"). Its name in other West Germanic languages is similar (e.g. ).
The Finnish name is "ahma", derived from "ahmatti," which is translated as "glutton". Similarly, the Estonian name is "ahm", with the equivalent meaning to the Finnish name. In Lithuanian, it is "ernis"; in Latvian, "tinis" or "āmrija".
The Eastern Slavic росомаха ("rosomakha") and the Polish and Czech name "rosomák" seem to be borrowed from the Finnish "rasva-maha" (fat belly). Similarly, the Hungarian name is "rozsomák" or "torkosborz" which means "gluttonous badger".
In French-speaking parts of Canada, the wolverine is referred to as "carcajou", borrowed from the Innu-aimun or Montagnais "kuàkuàtsheu". However, in France, the wolverine's name is "glouton" (glutton).
Purported gluttony is reflected neither in the English name "wolverine" nor in the names used in North Germanic languages. The English word wolverine (alteration of the earlier form, wolvering, of uncertain origin) probably implies "a little wolf". The name in Proto-Norse, "erafaz" and Old Norse, "jarfr", lives on in the regular Icelandic name "jarfi", regular Norwegian name "jerv", regular Swedish name "järv" and regular Danish name "jærv".
Taxonomy and evolutionary history.
Classification.
Genetic evidence suggests that the wolverine is most closely related to the tayra and martens, all of which shared a Eurasian ancestor.
There are two subspecies: the Old World form, "Gulo gulo gulo", and the New World form, "G. g. luscus". Some authors had described as many as four additional North American subspecies, including ones limited to Vancouver Island ("G. g. vancouverensis") and the Kenai Peninsula in Alaska ("G. g. katschemakensis"). However, the most currently accepted taxonomy recognizes either the two continental subspecies or "G. gulo" as a single Holarctic taxon.
Evolution.
Recently compiled genetic evidence suggests most of North America's wolverines are descended from a single source, likely originating from Beringia during the last glaciation and rapidly expanding thereafter, though considerable uncertainty to this conclusion is due to the difficulty of collecting samples in the extremely depleted southern extent of the range.
Physical characteristics.
Anatomically, the wolverine is an elongated animal that is low to the ground. With strong limbs, broad and rounded head, small eyes and short rounded ears, it most closely resembles a large fisher. Though its legs are short, its large, five-toed paws with crampon-like claws and plantigrade posture enable it to climb up and over steep cliffs, trees and snow-covered peaks with relative ease.
The adult wolverine is about the size of a medium dog, with a body length ranging from ; standing at the shoulder; and a tail length of . Weight is usually in males, and in females . Exceptionally large males of as much as are referenced in Soviet literature, though such weights are deemed in "Mammals of the Soviet Union" to be improbable. The males are often 10–15% larger than the females in linear measurements and can be 30–40% greater in weight. According to some sources, Eurasian wolverines are claimed to be larger and heavier than those in North America, with weights reaching up to . However, this may refer more specifically to areas such as Siberia, as data from Fennoscandian wolverines shows they are typically around the same size as their American counterparts. It is the largest of terrestrial mustelids; only the marine-dwelling sea otter, the giant otter of the Amazon basin and the semi-aquatic African clawless otter are larger—while the European badger may reach a similar body mass, especially in autumn.
Wolverines have thick, dark, oily fur which is highly hydrophobic, making it resistant to frost. This has led to its traditional popularity among hunters and trappers as a lining in jackets and parkas in Arctic conditions. A light-silvery facial mask is distinct in some individuals, and a pale buff stripe runs laterally from the shoulders along the side and crossing the rump just above a bushy tail. Some individuals display prominent white hair patches on their throats or chests.
Like many other mustelids, it has potent anal scent glands used for marking territory and sexual signaling. The pungent odor has given rise to the nicknames "skunk bear" and "nasty cat." The anal gland secretion for the samples obtained from six animal's secretion was complex and variable: 123 compounds were detected in total, with the number per animal ranging from 45 to 71 compounds. Only six compounds were common to all extracts: 3-methylbutanoic acid, 2-methylbutanoic acid, phenylacetic acid, alpha-tocopherol, cholesterol, and a compound tentatively identified as 2-methyldecanoic acid. The highly odoriferous thietanes and dithiolanes found in anal gland secretions of some members of the Mustelinae [ferrets, mink, stoats, and weasels (Mustela spp.) and zorillas (Ictonyx spp.)] were not observed. The composition of the wolverine's anal gland secretion is similar to that of two other members of the Mustelinae, the pine and beech marten (Martes spp.)
Wolverines, like other mustelids, possess a special upper molar in the back of the mouth that is rotated 90 degrees, towards the inside of the mouth. This special characteristic allows wolverines to tear off meat from prey or carrion that has been frozen solid.
Distribution.
Wolverines live primarily in isolated arctic, boreal, and alpine regions of northern Canada, Alaska, Siberia, and Fennoscandia; they are also native to European Russia, the Baltic countries, the Russian Far East, northeast China and Mongolia.
Wolverine remains have been found in Ukraine, but they are extirpated there today and it is unclear whether the wolverines would have formed sustainable populations.
Unique records of encounters with wolverines have been noted in Latvia, the most recent one being in late July 2022 (although it can be disputed because of the unclear footage); the population was widespread in the 16th and 17th centuries, but nowadays it is not native to the area.
Most New World wolverines live in Canada and Alaska. However, wolverines were once recorded as also being present in Colorado, areas of the southwestern United States (Arizona and New Mexico), the Midwest (Indiana, Nebraska, North and South Dakota, Ohio, Minnesota, and Wisconsin), New England (Maine, New Hampshire, Vermont, and Massachusetts) and in New York and Pennsylvania.
In the Sierra Nevada, wolverines were sighted near Winnemucca Lake in spring 1995 and at Toe Jam Lake north of the Yosemite border in 1996; and later photographed by baited cameras, including in 2008 and 2009, near Lake Tahoe. According to a 2014 U.S. Fish and Wildlife Service publication, "wolverines are found in the North Cascades in Washington and the Northern Rocky Mountains in Idaho, Montana, Oregon (Wallowa Range), and Wyoming. Individual wolverines have also moved into historic range in the Sierra Nevada Mountains of California and the Southern Rocky Mountains of Colorado, but have not established breeding populations in these areas". In 2022, Colorado Parks and Wildlife considered plans to reintroduce the wolverine to the state.
Wolverines are also found in Utah but are very rarely seen, with only six confirmed sightings since the first confirmed sighting in 1979. Three of these six confirmed Utah sightings have been caught on video. A wolverine, a male, was finally captured and tagged in Utah in 2022 before being released back into the wild to better understand the animal's range.
In August 2020, the National Park Service reported that wolverines had been sighted at Mount Rainier, Washington, for the first time in more than a century. The sighting was of a reproductive female and her two offspring.
In 2004, the first confirmed sighting of a wolverine in Michigan since the early 19th century took place, when a Michigan Department of Natural Resources wildlife biologist photographed a wolverine in Ubly, Michigan. The specimen was found dead at the Minden City State Game Area in Sanilac County, Michigan in 2010.
Behavior and ecology.
Diet and hunting.
Wolverines are primarily scavengers. Most of their food is carrion, especially in winter and early spring. They may find carrion themselves, feed on it after the predator (often, a wolf pack) has finished, or simply take it from another predator. Wolverines are known to follow wolf and lynx trails to scavenge the remains of their kills. Whether eating live prey or carrion, the wolverine's feeding style appears voracious, leading to the nickname of "glutton" (also the basis of the scientific name). However, this feeding style is believed to be an adaptation to food scarcity, especially in winter.
The wolverine is also a powerful and versatile predator. Its prey mainly consists of small to medium-sized mammals, but wolverines have been recorded killing prey many times larger than itself, such as adult deer. Prey species include porcupines, squirrels, chipmunks, beavers, marmots, moles, gophers, rabbits, voles, mice, rats, shrews, lemmings, caribou, roe deer, white-tailed deer, mule deer, sheep, goats, cattle, bison, moose, and elk. Smaller predators are occasionally preyed on, including martens, mink, foxes, Eurasian lynx, weasels, coyote, and wolf pups. Wolverines have also been known to kill Canada lynx in the Yukon of Canada. Wolverines often pursue live prey that are relatively easy to obtain, including animals caught in traps, newborn mammals, and deer (including adult moose and elk) when they are weakened by winter or immobilized by heavy snow. Their diets are sometimes supplemented by birds' eggs, birds (especially geese), roots, seeds, insect larvae, and berries. Adult wolverines appear to be one of the few conspecific mammal carnivores to actively pose a threat to golden eagles. Wolverines were observed to prey on nestling golden eagles in Denali National Park. During incubation in Northern Sweden, an incubating adult golden eagle was killed on its nest by a wolverine.
Wolverines inhabiting the Old World (specifically, Fennoscandia) hunt more actively than their North American relatives. This may be because competing predator populations in Eurasia are less dense, making it more practical for the wolverine to hunt for itself than to wait for another animal to make a kill and then try to snatch it. They often feed on carrion left by wolves, so changes in wolf populations may affect the population of wolverines. They are also known on occasion to eat plant material.
Wolverines often cache their food during times of plenty. This is of particular importance to lactating females in the winter and early spring, a time when food is scarce.
Reproduction.
Wolverines are induced ovulators. Successful males will form lifetime relationships with two or three females, which they will visit occasionally, while other males are left without a mate. Mating season is in the summer, but the actual implantation of the embryo (blastocyst) in the uterus is stayed until early winter, delaying the development of the fetus. Females will often not produce young if food is scarce. The gestation period is 30–50 days, and litters of typically two or three young ("kits") are born in the spring. Kits develop rapidly, reaching adult size within the first year. The typical longevity of a wolverine in captivity is around 15 to 17 years, but in the wild the average lifespan is more likely between 8 and 10 years. Fathers make visits to their offspring until they are weaned at 10 weeks of age; also, once the young are about six months old, some reconnect with their fathers and travel together for a time.
Interspecies interactions.
Wolves, American black bears, brown bears, cougars, and golden eagles are capable of killing wolverines, particularly young and inexperienced individuals. Wolves are thought to be the wolverine's most important natural predator, with the arrival of wolves