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Grizzly–polar bear hybrid facts for kids

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Grizzly–polar bear hybrid
Polar/brown bear hybrid at Osnabrück Zoo
Polar/brown bear hybrid at Osnabrück Zoo
Scientific classification
Species: U. maritimus × U. arctos
Polarbrown-1
Polar/brown bear hybrid, Natural History Museum at Tring, Tring

A grizzly–polar bear hybrid (also named grolar bear, polar grizz, polizzle, pizzly bear, grizzlar or nanulak) 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. The number of confirmed hybrids has since risen to eight, all of them descending from the same female polar bear.

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.

Genetic analysis has revealed multiple instances of introgressive hybridization between bear species, including introgression of polar bear DNA into brown bears during the Pleistocene ("grizzly bear" is a local common name for Ursus arctos whereas "brown bear" is used internationally and in science to refer to the species as a whole).

Occurrences in the wild

With several suspected sightings and eight confirmed cases, theories of how such hybrids might naturally occur have become more than hypothetical. Although these sister species often occupy adjacent regions, direct contact has not been the norm because polar bears hunt, breed and sometimes even make maternity dens on sea ice, where brown bears have an overwhelmingly terrestrial lifestyle.

2006 discovery

Jim Martell, a hunter from Idaho, reportedly shot a grizzly–polar bear hybrid near Sachs Harbour on Banks Island, Northwest Territories on April 16, 2006. Martell, with his local guide, Roger Kuptana, had been hunting for polar bears, 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.

On May 8, 2006, the discovery of the grizzly-polar bear hybrid received increased attention when, soon after the story was announced, the comedy television show The Colbert Report light-heartedly named the new species as the number one threat to American Security.

Amidst much controversy, the bear has since been returned to Mr. Martell.

Subsequent discoveries

On April 8, 2010, David Kuptana, an Inuvialuit hunter from the 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 bear possesses physical characteristics intermediate between grizzlies and polar bears, such as brown fur on its paws, long claws, and a grizzly-like head.

Between 2012 and 2014 another six hybrid bears were either killed by hunters or live-captured by biologists.

Range expansion of brown bears as a possible contributing factor

Although a grizzly bear was killed on Banks Island in 1951, it has until recently been rare for this species to stray far north of the coast of mainland Canada. In 1991 one or more grizzly bears were documented hunting seals and polar bears on the sea ice near Melville island, over 500 km from the mainland coast. In 2003 and 2004 a geological team working on Melville Island obtained photographic and DNA evidence of a grizzly bear in the area. Their report also collated information on several other sightings in the Canadian Arctic Archipelago.

Grizzly bears have apparently also been extending their range east across the Barren Grounds towards Hudson Bay, and south towards northern Saskatchewan and Manitoba. Between 2003 and 2008 seven individuals were spotted in Wapusk National Park south of Churchill, Manitoba, an area used by polar bears for maternity dens and as a refuge during the ice-free season on Hudson Bay.

Naming

Ursidae hybridisation
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 bear, 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.

Characteristics

Two grizzly–polar hybrid cubs (one female and one male) were born at Osnabrück Zoo in Osnabrück in 2004, and their physical traits are generally 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 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 taken from. 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 in a manner reminiscent of how polar bears break the 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 as polar bears do: on their bellies with rear legs splayed.

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