Wednesday, May 2, 2012

Polar-grizzly hybrids

Polar bears (Ursus arctos horribilis) and grizzly bears (Ursus maritimus) are now mating. The hybrids are said to be more aggressive than their parents, despite their feeble nicknames “grolars” and “pizzlies.” Multiple bear species have been crossbred in zoos. and the occasional mating between the closely-related species of polar bears and grizzlies in the wild goes back 50-some-odd years, but a couple of firsts have now been confirmed by DNA testing:

2006: The 1st documented case of a polar-grizzly hybrid in the wild 
This hybrid bear (1st image, more photos here, here, and here) was shot and killed by Jim Martell of Glenns Ferry, Idaho, on a licensed and guided hunting trip. The bear's father was determined to be a grizzly and his mother was a polar bear. The resulting offspring had thick, creamy white fur like a polar bear, except for brown patches around its eyes, nose, back, and foot, plus the long claws, humped back; and shallow face of a grizzly. David Paetkau, president of Wildlife Genetics International, says, "This is the first confirmed natural occurrence of something we know to be biologically possible, physiologically possible, and evolutionarily quite reasonable."

2010: The 1st documented case of a 2nd-generation polar-grizzly hybrid in the wild
This 2nd-generation hybrid (2nd image, slideshow here) was shot and killed by David Kuptana, a native hunter from Victoria Island, Canada, and proves that the offspring of hybrids are fertile. The bear had characteristics intermediate between grizzlies and polar bears, with brown fur on its paws, long claws, and a grizzly-like head. The 8 1/2' bear had the white fur of a polar bear but a bigger head, brown paws and longer claws more typical of a grizzly bear.Testing revealed that the bear's mother was a grizzly-polar hybrid and the father was a grizzly bear. "And some hunters have told me that they think sometimes the grizzly bears actually hunt seals, which I'm quite sure they could do," said Ian Stirling, biologist with the Canadian Wildlife Service.

The intermixing of bears was not at first attributed to global warming, since the habitats and breeding seasons for the 2 species overlap. But the hybrids are the result of more than chance encounters, since successful mating requires spending time together over several days. Scientists now believe that the hybrid bears are a direct consequence of climate change and will become more common as the polar bears stranded on land in the absence of summer Arctic sea ice come into more contact with grizzly bears. University of Alaska marine biologist Brendan Kelly observes, “We’re taking this continent-sized barrier to animal movement, and in a few generations, it’s going to disappear, at least in summer months. That’s going to give a lot of organisms - a lot of marine mammals in particular - who’ve been separated for at least 10,000 years the opportunity to interbreed again, and we’re predicting we’re going to see a lot more of that.

At the University of Colorado on April 27th, wildlife officers tranquilized, 
removed, and relocated a 200lb black bear 
spotted up a tree on campus (video here). 
Unfortunately, this bear was later hit by a car.

Selected previous posts about bears:

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