The wolverine (/ˈwʊlvəriːn/), Gulo gulo (Gulo is Latin for "glutton"), also referred to as
the glutton, carcajou, skunk bear, or quickhatch, is the largest land-dwelling species of the family Mustelidae. It is a stocky and muscular
carnivore, more closely resembling a small bear than other mustelids. The
wolverine, a solitary animal, 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 US 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 European range.
Anatomically, the wolverine is a stocky and muscular animal. With
short legs, broad and rounded head, small eyes and short rounded ears, it more
closely resembles a bear than it does other mustelids. Though its legs are
short, its large, five-toed paws with crampon-like claws and plantigrade posture enable them 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 length usually ranging from 65–107 cm (26–42 in), a tail of
17–26 cm (6.7–10.2 in), and a weight of 9–25 kg (20–55 lb),
though exceptionally large males can weigh up to 32 kg
(71 lb). The males are as much as 30% larger than the females and can
be twice the females' weight. Shoulder height is reported from 30 to 45 cm
(12 to 18 in). 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 hog badger may reach a similar size.
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 25–35 cm
(9.8–13.8 in) 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."
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.
Behavior
Diet and hunting
Wolverines are considered to be primarily scavengers. A
majority of the wolverine's sustenance is derived from carrion, on which they depend almost exclusively in winter and early spring.
Wolverines may find carrion themselves, feed on it after the predator is done
feeding (especially wolf packs) or simply take it from another predator.
Wolverines are also known to follow wolf and lynx trails, purportedly with the
intent of scavenging 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.
Prey mainly consists of small to medium-sized mammals, but the wolverine has
been recorded killing prey such as adult deer that are many times larger than
itself. 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, and coyote and wolf pups.
Wolverines have also been known to kill Canadian lynx in the Yukon of Canada.[15]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.
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 not as 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 frequently 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.
Natural enemies
Wolves are thought to be the wolverine's most important
natural predator, with the arrival of wolves to a wolverine's territory
presumably leading the latter to abandon the area. Armed with powerful jaws,
sharp claws, and a thick hide, wolverines, like most mustelids, are
remarkably strong for their size. They may defend kills against larger or more
numerous predators such as wolves or bears. At least one account
reported a wolverine's apparent attempt to steal a kill from a black bear, although the bear won what was ultimately a fatal
contest for the wolverine. In another account, a wolverine killed a polar bear.
Mating and reproduction
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.
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. In 2008 and 2009,
wolverines were sighted as far south as the Sierra Nevada, near Lake Tahoe, for the first time since 1922. They are also found
in low numbers in the Rocky Mountains and northern Cascades of the United States, and have been sighted as far
south and east as Michigan. However, most New World wolverines live in Canada and Alaska.
Conservation
The
world's total wolverine population is not known. The animal exhibits a low
population density and requires a very large home range.The wolverine is listed
by the IUCN as Least Concern because of its "wide distribution, remaining
large populations, and the unlikelihood that it is in decline at a rate fast
enough to trigger even Near Threatened".
The
range of a male wolverine can be more than 620 km2 (240 mi2),
encompassing the ranges of several females which have smaller home ranges of
roughly 130–260 km2 (50–100 mi2). Adult wolverines try for the most part
to keep nonoverlapping ranges with adults of the same sex. Radio tracking
suggests an animal can range hundreds of miles in a few months.
Female wolverines burrow into snow in February to create
a den, which is used until weaning in mid-May. Areas inhabited nonseasonally by
wolverines are thus restricted to zones with late-spring snowmelts. This fact has led to concern that global warming will shrink the ranges of wolverine populations.
This requirement for large territories brings wolverines
into conflict with human development, and hunting and trapping further reduce
their numbers, causing them to disappear from large parts of their former
range; attempts to have them declared an endangered species have met with
little success. In February 2013, the United
States Fish and Wildlife Service proposed
giving Endangered Species
Act protections to the wolverine due to
its winter habitat in the northern Rockies diminishing. This was as a
result of a lawsuit brought by the Center for
Biological Diversity and Defenders of
Wildlife.
The Wildlife
Conservation Society reported in June 2009
that a wolverine researchers had been tracking for almost three months had
crossed into northern Colorado. Society officials had tagged the young male wolverine
in Wyoming near Grand Teton
National Park and it had traveled
southward for about 500 miles. It was the first wolverine seen in Colorado
since 1919, and its appearance was also confirmed by the Colorado
Division of Wildlife. In May 2016 the same
wolverine was killed by a cattle ranch-hand in North Dakota, ending a >800
mile trip by this lone male wolverine, dubbed M-56. This was the first verified
sighting of a Wolverine in North Dakota in 150 years. In February 2014, a
wolverine was seen in Utah, the first confirmed sighting in that state in 30
years.
In captivity
Around
a hundred wolverines are held in zoos across North America and Europe, and they
have been bred in captivity, but only with difficulty and high infant
mortality.
Name
The wolverine's questionable reputation as an
insatiable glutton (reflected in the Latin genus name Gulo) may be in part due to a false
etymology. The animal's name
in older Norwegian, fjeldfross, 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. Dutch: veelvraat).
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 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.
In culture
Many cities, teams, and organizations use the wolverine
as a mascot. For example, the US state of Michigan is, by tradition, known as "the Wolverine
State", and the University of
Michigan takes the animal as their mascot.
The association is well and long established: for example, many Detroiters
volunteered to fight during the American Civil War and George Armstrong
Custer, who led the Michigan Brigade, called them the "Wolverines". The origins of
this association are obscure; it may derive from a busy trade in wolverine furs
in Sault Ste.
Marie in the 18th century or may recall a
disparagement intended to compare early settlers in Michigan with the vicious
mammal. Wolverines are, however, extremely rare in Michigan. A sighting in
February 2004 near Ubly was the first confirmed sighting in Michigan in 200
years. The animal was found dead in 2010.
The wolverine figures prominently in the mythology of
the Innu people of eastern Québec and Labrador. In at least one Innu myth, it is the creator of the
world.