Wolverine

• 1. Introduction

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  The wolverine known as M-56 began his famous journey as a young male, tagged by Wildlife Conservation Society officials in Wyoming near Grand Teton National Park. Researchers tracked him south for almost three months. In June 2009 the Society reported that he had crossed into northern Colorado, roughly 500 miles from where he was tagged. Colorado wildlife officials confirmed the sighting. It was the first wolverine seen in that state since 1919.

  Seven years later, in May 2016, a cattle ranch-hand killed the same animal in North Dakota. His full trip had stretched beyond 800 miles. It was the first verified wolverine sighting in North Dakota in 150 years.

  How does an animal about the size of a medium dog manage such distances? Why does a creature of remote northern forests and mountains carry a name that means glutton in so many languages, and is the label fair? And what does this solitary animal need from the land and the snow to survive as people press into its range?

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• 2. A Glutton by Many Names

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  In Finnish the wolverine is called ahma, a word derived from ahmatti, which translates as glutton. Estonian has ahm, with the same meaning. The scientific genus name Gulo also means glutton, and that reputation may rest partly on a false etymology.

  The German word Vielfraß, literally "devours much," is thought to descend from the Norwegian fjellfross, which actually means "mountain cat." Other West Germanic languages have similar forms, such as the Dutch-style veelvraat. Hungarian goes further with torkosborz, meaning gluttonous badger.

  The Eastern Slavic word rosomakha and the Polish and Czech rosomák appear to be borrowed from the Finnish rasva-maha, meaning fat belly. In France the animal is the glouton. In French-speaking parts of Canada it is the carcajou, borrowed from the Innu-aimun kuàkuàtsheu. English also knows it as quickhatch, from the East Cree kwiihkwahaacheew.

  Not every language blames the animal for greed. The Norse names descend from Proto-Norse erafaz and Old Norse jarfr, and they live on as the Icelandic jarfi, Norwegian jerv, Swedish järv and Danish jærv. The English word wolverine is an alteration of an earlier form, wolvering, whose origin is uncertain. It probably implies a little wolf.

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• 3. Built for Frozen Ground

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  An adult male wolverine usually weighs 11-18 kg, and a female 8-12 kg. Body length runs from 65 to 109 cm, and the animal stands 36-45 cm at the shoulder. Males are often 10-15% larger than females in linear measurements and can be 30-40% heavier. Soviet literature mentions males of up to 32 kg, but Mammals of the Soviet Union deems such weights improbable.

  This makes the wolverine the largest land-dwelling mustelid. Only the sea otter, the giant otter of the Amazon basin and the semi-aquatic African clawless otter are larger. The European badger may match its mass, especially in autumn.

  Its body is elongated and low to the ground, with a broad rounded head, small eyes and short rounded ears. It most closely resembles a large fisher. The five-toed paws carry crampon-like claws, and the flat-footed posture lets it climb steep cliffs, trees and snow-covered peaks with relative ease.

  The coat is thick, dark and oily, and it is highly hydrophobic, so it resists frost. Hunters and trappers have long prized it as a lining for jackets and parkas in Arctic conditions. Some animals show a light silvery facial mask, a pale buff stripe along the flanks, or white patches on the throat or chest.

  Inside the mouth, a special upper molar at the back is rotated 90 degrees toward the inside. This lets the animal tear meat from prey or carrion that has frozen solid. In one comparison of bone strength at the jaw joint, the wolverine scored 940.8 Newtons, the highest of any carnivore tested. The cheetah came second at 784.4.

  The nicknames "skunk bear" and "nasty cat" come from potent anal scent glands, used to mark territory and signal to mates. Samples from six animals contained 123 compounds in total, with 45 to 71 per animal. Only six compounds appeared in every sample. The chemistry resembled that of the pine and beech marten rather than that of ferrets or weasels.

  Urine is also used for marking. Analysis of its vapors found 19 potential chemical signals, including several monoterpenes that are unusual in mammals. The likely source is the conifer needles found in wolverine scat.

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• 4. Scavenger and Killer

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  Behind many a wolf pack, a wolverine waits for what is left. Most of its food is carrion, especially in winter and early spring. It follows wolf and lynx trails to find the remains of their kills, and it will simply take a carcass from another predator.

  Its ravenous manner of eating gave rise to the glutton nickname. Yet this style is believed to be an adaptation to scarcity, particularly in winter.

  The wolverine is also a capable hunter. It has been recorded killing animals many times its own size, such as adult deer. The list of prey includes porcupines, squirrels, beavers, marmots, rabbits, lemmings, caribou, sheep, bison, moose and elk. It also takes smaller predators, among them martens, foxes, Eurasian lynx, coyotes and wolf pups. In the Yukon it has killed Canada lynx.

  Much of this hunting targets animals that are easy to get. Wolverines go after prey caught in traps, newborn mammals, and deer, moose or elk weakened by winter or stuck in heavy snow. Birds' eggs, geese, roots, seeds, insect larvae and berries fill out the diet.

  Golden eagles are one of the few animals that fear it. In Denali National Park, wolverines were seen preying on golden eagle nestlings. In northern Sweden, one killed an incubating adult eagle in its nest.

  The animals of Fennoscandia hunt more actively than those in North America. Fewer competing predators in Eurasia may make hunting for itself more practical than waiting to steal a kill.

  The wolverine has its own enemies. Wolves, American black bears, brown bears and cougars can kill adults. Golden eagles can kill the young and inexperienced. The grey wolf is by far the most serious threat, and the arrival of wolves in a territory presumably drives wolverines out. One account describes a wolverine trying to steal a kill from a black bear and losing the fatal contest. In Denali, wolverines seemed to avoid grizzly bears.

  In times of plenty the wolverine caches food. That store matters most to nursing females in winter and early spring.

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• 5. Late Starts and Lone Males

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  Among wolverines, a successful male forms lifelong bonds with two or three females and visits them only occasionally. Other males are left without a mate. Mating takes place in summer, but the embryo does not implant in the uterus until early winter. That delay holds back the fetus's development.

  Wolverines are induced ovulators. When food is scarce, females often do not produce young at all. Gestation lasts 30-50 days, and litters of typically two or three kits are born in spring. The kits grow quickly and reach adult size within their first year.

  Fathers keep visiting their offspring until the kits are weaned at 10 weeks old. Once the young are about six months old, some reconnect with their fathers and travel together for a time.

  In captivity a wolverine typically lives 15 to 17 years. In the wild the average is more likely 8-10 years. Around a hundred wolverines are held in zoos across North America and Europe. They have been bred, but only with difficulty and with high infant mortality.

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• 6. Ancestry and Range

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  Genetic evidence places the wolverine closest to the tayra and the martens, all descended from a shared Eurasian ancestor. Two subspecies are recognized: the Old World form, Gulo gulo gulo, and the New World form, G. g. luscus. Some authors once described as many as four more, including forms limited to Vancouver Island and to Alaska's Kenai Peninsula. The most accepted view now recognizes either the two continental subspecies or a single Holarctic taxon.

  Most North American wolverines appear to descend from one source, likely originating in Beringia during the last glaciation. They then expanded rapidly. Researchers admit considerable uncertainty, because samples are hard to collect in the extremely depleted southern part of the range.

  Today wolverines live mainly 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. Remains have been found in Ukraine, but it is unclear whether a sustainable population ever formed there. In Latvia the animal was widespread in the 16th and 17th centuries and is no longer native, though a disputed sighting from late July 2022 was reported.

  In the New World, records once placed wolverines in Colorado, Arizona, New Mexico, much of the Midwest, New England, New York and Pennsylvania. In the Sierra Nevada, sightings came near Winnemucca Lake in spring 1995 and at Toe Jam Lake in 1996. Baited cameras photographed one near Lake Tahoe in 2008 and 2009.

  A 2014 U.S. Fish and Wildlife Service publication places them in the North Cascades and the Northern Rocky Mountains. Individuals have moved into the Sierra Nevada and Southern Rockies but have not established breeding populations there. Utah has only six confirmed sightings since the first in 1979. A male was captured and tagged there in 2022 to learn more about the animal's range.

  In August 2020, the National Park Service reported wolverines at Mount Rainier in Washington for the first time in more than a century. The sighting was a reproductive female and her two offspring.

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• 7. Shrinking Snow

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  The International Union for Conservation of Nature, known as the IUCN, lists the wolverine as Least Concern. It cites the animal's "wide distribution, remaining large populations, and the unlikelihood that it is in decline at a rate fast enough to trigger even Near Threatened." Yet the world total is unknown. Wolverines live at low density and need very large home ranges.

  A male's range can exceed 620 square kilometers and take in the ranges of several females. Female ranges are smaller, roughly 130-260 square kilometers. Adults mostly avoid overlapping with others of the same sex. Radio tracking suggests one animal can range hundreds of miles in a few months.

  Snow shapes where they can live. Females burrow into snow in February to build a den, and they use it until weaning in mid-May. Areas that wolverines inhabit year-round are therefore limited to zones where spring snowmelt comes late. That fact has raised concern that global warming will shrink their ranges.

  The need for space also brings wolverines into conflict with development. Hunting and trapping reduce their numbers further. The species has disappeared from large parts of its former range, and attempts to have it declared endangered have met with little success.

  In February 2013, the United States Fish and Wildlife Service proposed Endangered Species Act protections because the winter habitat in the northern Rockies was diminishing. The proposal followed a lawsuit by the Center for Biological Diversity and Defenders of Wildlife. In November 2023 the agency announced that it was adding the wolverine in the Lower 48 states to the threatened list.

  Surveys paint a mixed picture. Canada holds an estimated 15,000-19,000 wolverines, a stable figure. Norway and Sweden together held about 1065 by 2012, an increase. Finland had 165-175. European Russia counted 1500 and was declining. A count in the Rocky Mountains of Montana, Idaho and Wyoming between 1989 and 2020 found 28-52.

  In 2022, Colorado Parks and Wildlife considered plans to reintroduce the wolverine to the state, and in 2024 Colorado's government passed a bill authorizing it. As of February 2026, the plan is to release 15 wolverines each year for three years. It would be the first attempt to reintroduce wolverines to a region where they have been extirpated.

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• 8. Trickster and Mascot

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  Kuekuatsheu, the wolverine of Innu mythology in eastern Quebec and Labrador, is a conniving trickster who created the world. In the tale he builds a big boat, similar to Noah's Ark, and loads it with every animal species. Heavy rain floods the land. He sends a mink diving for mud and rocks, then mixes them into an island, which becomes the inhabited world.

  Many Kuekuatsheu stories are humorous and irreverent, with crude references to bodily functions. Among the Mi'kmaq and Passamaquoddy, the wolverine is called Lox, a trickster and thief who is generally more dangerous than his Innu counterpart and is often shown as a companion to the wolf. The Dené of northwestern Canada tell of the wolverine as a trickster and cultural transformer, much like the coyote in Navajo tradition or the raven on the Northwest Coast.

  In the Marvel Comics universe, James "Logan" Howlett earned the nickname "Wolverine" while cage fighting. The name fit his skill, short stature, keen animal senses and ferocity. It fit most of all his claws, which retract from both sets of knuckles.

  Many North American cities, sports teams and organizations use the animal as a mascot. Michigan is traditionally known as the Wolverine State, and the University of Michigan takes the animal as its mascot. Professional baseball and football clubs have also carried the name. During the American Civil War, many Detroiters volunteered to fight, and George Armstrong Custer, who led the Michigan Brigade, called them the "Wolverines."

  The origin of the association is obscure. It may come from a busy fur trade in wolverine pelts at Sault Ste. Marie in the 18th century. It may instead recall an insult comparing early Michigan settlers with the vicious animal. Real wolverines are extremely rare there. A sighting in February 2004 near Ubly was the first confirmed in Michigan in 200 years, and the animal was found dead in 2010.

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