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Melting Arctic ice heralds new polar hybrids: Pizzlies and more

A pizzlie is a cross between a polar bear and a grizzly bear, and this new hybrid animal may foreshadow as many as 34 hybrids to come as Arctic ice melts, say scientists.

By Janelle WeaverLiveScience contributor / December 16, 2010

An activist disguised as a polar bear holds up a sign at the United Nations Climate Change Conference in Cancun, Mexico, on Dec. 9.

Israel Leal/AP


An odd-looking white bear with patches of brown fur was shot by hunters in 2006 and found to be a cross between a polar bear and a grizzly bear. Apparently, grizzlies were moving north into polar bear territory. Since then, several hybrid animals have appeared in and around the Arctic, including narwhal-beluga whales and mixed porpoises.

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The culprit may be melting Arctic sea ice, which is causing barriers that once separated marine mammals to disappear, while the warming planet is making habitats once too cold for some animals just right. The resulting hybrid creatures are threatening the survival of rare polar animals, according to a comment published Wednesday (Dec. 15) in the journal Nature. [Real of Fake? 8 Bizarre Hybrid Animals]

A team led by ecologist Brendan Kelly of the National Marine Mammal Laboratory counted 34 possible hybridizations between distinct populations or species of Arctic marine mammals, many of which are endangered or threatened.

IN PICTURES: Hybrid animals

"The greatest concern is species that are already imperiled," said Kelly, first author of the Nature comment. "Interbreeding might be the final straw."

Pizzlies and Narlugas

When hunters encountered a hybrid of a polar bear and a grizzly in 2006, Kelly's colleagues remarked that the incident was just a fluke. But as Kelly delved into the issue, he found more evidence of similar anomalies. In 2009, a cross between a bowhead and a right whale was spotted in the Bering Sea, between Alaska and Russia. And a museum specimen in Alaska attests to breeding between spotted seals (Phoca largha) and ribbon seals (Histriophoca fasciata), which belong to different genera, a scientific classification of organisms that is broader than the species level.

Evidence suggests at least five other types of hybrids that may arise from animals of distinct genera, Kelly's team reported. These include:

  • Narwhal (Monodon monoceros) and beluga whale (Delphinapterus leucas)
  • Ringed seal (Phoca hispida) and ribbon seal (Histriophoca fasciata)
  • Bowhead whale (Balaena mysticetus) and right whale (Eubalaena spp.)
  • Harp seal (Phoca groenandica) and hooded seal (Cystophora cristata)
  • Harbour porpoise (Phocoena phocoena) and Dall's porpoise (Phocoenoides dalli)

Breedings between these marine mammals near the North Pole are likely to result in fertile offspring, because many of these animals have the same number of chromosomes, said comment co-author Andrew Whiteley, a conservation geneticist at the University of Massachusetts, Amherst.

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