A grizzly–polar
bear hybrid (also pizzly bear, polizzly, prizzly
bear, pizzly-grizzly, nanulak, Polar-Grizzly, or grolar bear is
a rare ursid hybrid that has occurred both in captivity and in the
wild. In 2006, the occurrence of this hybrid in nature was confirmed by testing
the DNA of a unique-looking bear that had been shot near Sachs
Harbour, Northwest Territories on Banks Island in
the Canadian Arctic.
Possible
wild-bred polar bear-grizzly bear hybrids have been reported and shot
in the past, but DNA tests were not available to verify the bears' ancestry.
Analyses
of DNA sequences of bears have recovered multiple instances
of introgressive hybridization between various bear
species, including introgression of polar bear DNA into brown bears during
the Pleistocene.
Occurrences in the
wild
With many suspected
sightings and three confirmed cases, theories of how such hybrids might
naturally occur have become more than hypothetical. Although these two
species are genetically similar and often found in the same territories, they
tend to avoid each other in the wild. They also fill different ecological
niches.
Grizzlies (and
also Kodiak bears and "Alaskan brown bears", which are all
subspecies of the brown bear, Ursus arctos), tend to live and breed
on land. Polar bears prefer the water and ice, usually breeding on the ice.
The
yellowish-white MacFarlane's bear, a mysterious animal known only from one
specimen acquired in 1864, seems to attest that grizzly-polar bear hybrids may
have always occurred from time to time. Another theory suggests that the polar
bears have been driven southward by the melting of the ice cap, bringing them
into closer contact with grizzly bears.
2006
discovery Jim Martell, a hunter from Idaho, found and shot a
grizzly–polar bear hybrid near Sachs Harbour on Banks
Island, Northwest Territories reportedly on 16 April
2006. Martell had been hunting for polar bears with an official license
and a guide, at a cost of $45,450, and killed the animal believing it to
be a normal polar bear. Officials took interest in the creature after noticing
that while it had thick, creamy white fur typical of polar bears, it also
had long claws, a humped back, a shallow face, and brown patches around its eyes,
nose, back, and foot, which are all traits of grizzly bears. If the bear
had been adjudicated to be a grizzly, the hunter would have faced a
possible CAN$1,000 fine and up to a year in jail.
A
DNA test conducted by Wildlife Genetics International in British
Columbia confirmed it was a hybrid, with a polar bear mother and a grizzly
bear father. It is the first documented case in the wild, though it
was known that this hybrid was biologically possible and other ursid hybrids
have been bred in zoos in the past.
Amidst
much controversy, the bear has since been returned to Martell.
2010
discovery
On
8 April 2010, David Kuptana, an Inuvialuit hunter from the nearby
community of Ulukhaktok on Victoria Island shot what he
thought was a polar bear. After inspecting the bear and having its DNA tested,
it was discovered that the bear's mother was a grizzly-polar hybrid and the
father was a grizzly bear. The Department of Environment and Natural Resources
for the NWT said that it "...may be the first recorded second-generation
polar-grizzly bear hybrid found in the wild". The bear possesses
physical characteristics intermediate between grizzlies and polar bears, such
as brown fur on its paws, long claws, and a grizzly-like head.
2010
report
Biologists
affiliated with the American Museum of Natural History and City
College of the City University of New York have prepared a new report
published in Canadian Field Naturalist that offers the first
documented evidence that grizzlies are migrating into polar bear territory.
Researchers found that seven grizzlies had been spotted in Wapusk National
Park south of Churchill, Manitoba, between 2003 and 2008.
Naming
Possible
hybridisation between different species of bear Since the 2006 discovery placed
the hybrid into the spotlight, the media have referred to this animal with
several portmanteau names, such as pizzly, grolar
bear, and polizzly, but there is no consensus on the use of any one
of these terms. Canadian wildlife officials have suggested calling the hybrid
"nanulak", taken from the Inuit names for polar bear(nanuk) and
grizzly bear (aklak).
By
one convention, the name of the sire comes first in such combinations: the
offspring of a male polar bear and a female grizzly would be the
suggested nanulak or a "pizzly bear", while the offspring
of a male grizzly and a female polar bear would be a "grolar bear" or
possibly an aknuk, however the sports company Gola are currently trying to
secure naming rights on the animal to help with the re-launch of their football
boots. If the remains of MacFarlane's 1864 specimen—which was validly described
according to ICZN rules—were traced and confirmed to be such a hybrid
by ancient DNA techniques, the scientific name Ursus × inopinatus would
be available for these animals.
Characteristics
Two
grizzly–polar hybrid cubs (one female and one male) were born at Osnabrück
Zoo in Osnabrück, Germany, in 2004, and their physical traits are
generally an intermediate between the polar bear and the grizzly bear. For
example, their bodies are smaller than polar bears, but larger than grizzlies,
while their heads fall between the broader grizzly head and the leaner polar
bear head. They have long necks like polar bears, but small shoulder humps
like grizzlies. The soles of their feet are partially covered in hair;
polar bears have hair-covered soles, which act as insulation, and grizzlies
have hairless soles.
Similarly,
the hair of the hybrids exhibits a pattern of hollowness, which blends the
traits of both polar bears and grizzlies. In cross section, the hair of polar
bears is hollow, while the hair of grizzlies is either solid or has small
hollow regions. This varies according to which part of the grizzly the hair is
located. In the hybrid male, the paw hair was solid, but the dark back
hair was somewhat hollow, albeit with "smaller empty regions than found in
polar bear hair". The hair of the female hybrid, "contains a
range of hollow regions".
The
hybrids demonstrated behavior more similar to polar bears than grizzlies. They
stomped toys similar to how polar bears break ice, and hurled bags to the side
"as polar bears may hurl prey". Grizzlies given the same bags do
not demonstrate this hurling behavior. The hybrids were also observed
lying down similar to polar bears: on their bellies with rear legs splayed.
Standing
as tall as 2.5 m (8 ft) and weighing up to 360 kg (800 lbs.), the grizzly bear
is a subspecies of brown bear that inhabits western Canada and the northwestern
United States.
Grizzly bears are specially adapted to survive the changing seasons. During warmer months, they eat a massive amount of food so they can live off body fat during the winter, when food is scarce. They may intake 40 kg (90 lbs.) of food each day, gaining over 1 kg (2.2 lbs.) of body weight a day. As omnivores, grizzlies will eat anything nutritious they can find, gorging on nuts, fruit, leaves, roots, fungi, insects, and a variety of animals including salmon and other fish, rodents, sheep, and elk. Their diet varies depending on what foods are available for the season.
In the fall, as temperatures cool and food becomes scarcer, grizzlies dig dens in the sides of hills. They have long rounded claws (the size of human fingers) and a large mass of muscles on their backs that help them dig. These characteristics, along with small rounded ears and white-tipped (or “grizzled”) fur, distinguish grizzly bears from black bears.
The
bears settle in their dens to hibernate for the winter. This deep sleep allows
the grizzlies to conserve energy. Their heart rate slows down from 40 beats per
minute to 8, and they do not go to the bathroom at all during these months of
slumber.
Pregnant
grizzly bears even give birth in their sleep! Midwinter, grizzly bear cubs
(usually born in pairs) arrive into the world blind, hairless, and toothless.
They use what little strength they have to nestle into their mother and nurse.
For a month, the cubs feed on their mother’s milk and gain strength. By the
time spring comes, the cubs have opened their eyes and grown teeth and fur; the
new family is ready to venture outside the den.
The
cubs stay under their mother’s care for 2-3 years. While mother grizzlies are
fiercely protective of their cubs, nearly half the cubs do not survive past the
first year, falling to disease, starvation, and predators like wolves, mountain
lions, and adult male grizzlies.
Grizzly
bears have a multitude of strengths. They are highly intelligent and have
excellent memories. Detecting food from great distances away, grizzlies have an
astute sense of smell, even better than that of a hound dog. They are good
swimmers and fast runners, reaching speeds as high as 50 km/h (35 mph) over
land. Young grizzlies also have the ability to climb trees to evade danger, but
this skill fades as they become bigger.
Conservation
Status
