Pictures: "Pizzly" to Be Joined by More Arctic Hybrids?

Polar Bear-Grizzly Hybrid
Photograph by Troy Maben, AP
A stuffed "grolar bear," or "pizzly"—grizzly-polar bear hybrid—looms over the living room of Jim Martell in Glenn Ferry, Idaho, in 2007. Martell shot the animal (picture), the first recorded grolar bear, in Canada's Northwest Territories in 2006.
As the Arctic thaws as a result of global warming, polar bears will increasingly be forced to stay onshore, where they're likely to bump into their grizzly cousins—some of which are moving north as temperatures rise. Arctic Ocean sea ice, which polar bears rely on to hunt marine mammals, is predicted to disappear in summer before the end of the century, experts say.
(See "Grizzly Bears Moving Into Canada's Polar Bear Capital.")
The two bear species are among the 22 Arctic marine mammal species most likely to interbreed, or hybridize, in a new Arctic "melting pot," according to a commentary published this week in the journal N ature.
For the paper, scientists combed through studies and museum collections to find evidence of hybridization already underway in some species, and concluded that as many as 34 hybrids may occur.
What's more, of the 22 types of animals, 14 are listed or may be listed as endangered, threatened, or of special concern by one or more nations. The polar bear and grizzly are currently on the U.S. endangered species list.
Hybridization "can be the final straw in loss of species," commentary lead author Brendan Kelly, a research biologist at the U.S. National Marine Mammal Laboratory in Juneau, Alaska, told National Geographic News.
Species in healthy numbers can interbreed naturally without disappearing, Kelly noted. But "when humans alter habitat particularly abruptly, they can greatly accelerate and make more likely these hybridizations and extinctions," he added.
As for the pizzly, a second-generation individual—with a grizzly bear father and a hybrid mother—was killed this year in Canada, according to the Nature paper.
—Christine Dell'Amore
Published December 15, 2010
Narwhal-Beluga Hybrid?
Photographs by Brian J. Skerry, National Geographic (left) and Paul Nicklen, National Geographic
Among the 22 marine mammal species deemed most likely to interbreed, beluga whales (left) and narwhals produced the first "hints of Arctic hybrids," Kelly and colleagues note in the new paper.
In the late 1980s a skull of a whale thought to be a narwhal-beluga mix was found in western Greenland (see map). Local hunters have also reported seeing whales that look like narwhal-beluga crosses.
So "biologists should not be surprised" that hybrids can occur in the Arctic, the paper said.
(See "Narwhal More at Risk From Warming Than Polar Bear?")
Published December 15, 2010
Hooded Seal-Harp Seal Hybrid?
Photographs from Photolibrary (left) and Bill Hickey, Getty Images
Both the hooded seal (left) and the harp seal breed on pack ice of the North Atlantic Ocean and migrate into the Arctic Ocean in summer.
Neither of the seals are considered rare or threatened, but hybrids may proliferate as the animals vie for space on the disappearing ice. Molecular analysis shows that that the two species—which are from different genera—have interbred in the past.
Of course, "not all cross-species matings will produce viable—or indeed any—offspring," the commentary points out.
But "the chance is enhanced in Arctic marine mammals, because their number of chromosomes [a type of DNA structure] has changed little over time." (Get a genetics overview.)
(See "Interspecies Sex: Evolution's Hidden Secret?")
Published December 15, 2010
Right Whale-Bowhead Hybrid?
Photographs by Brian Skerry, National Geographic (top) and Paul Nicklen, National Geographic
The Atlantic bowhead whale (bottom) inhabits the Arctic Ocean and adjacent seas. Right whales dwell in the North Pacific and North Atlantic.
Both rare species will likely travel north as the Arctic melts, according to the Nature paper. And as diminishing ice causes the animals' ranges to overlap, the two species may begin interbreeding themselves out of existence.
In fact, the hybridization may have already begun—a possible bowhead whale-North Pacific right whale hybrid was photographed in the Bering Sea in May 2009, according to the paper.
(See "Endangered Whales Get Protected Area off Alaska.")
Published December 15, 2010
Spotted Seal-Harbor Seal Hybrid?
Photograph from Alaska Stock Images/National Geographic (top) and Photolibrary
Harbor seals (bottom) are found across temperate and sub-Arctic waters. But as the Arctic warms, the mammals will likely will move north and run into spotted seals (top), according to the new paper.
That newfound proximity may result in a new, hybrid species, if it hasn't already. Kelly and colleagues found a possible spotted seal-harbor seal hybrid specimen at the University of Alaska Fairbanks.
Published December 15, 2010
Dall's Porpoise-Harbor Porpoise
Photograph by Emily Frederick, My Shot (top) and Bill Curtsinger, National Geographic
The harbor porpoise (bottom), native to the North Atlantic and North Pacific, will increasingly move north into the North Pacific habitat of the Dall's porpoise (top) as Arctic ice melts. (Read more about harbor porpoises in National Geographic magazine.)
Scientists have already documented extensive hybridization between the two porpoise species off the coast of British Columbia, Canada, according to the paper.
Similar events will likely occur as the species mingle in newly colonized Arctic habitats, where there are likely to be low numbers of each species—and fewer candidates for mating—the authors note.
(See "Porpoises Starving in Europe Due to Ocean Warming.")
Published December 15, 2010
Ribbon Seal-Spotted Seal Hybrid?
Photographs from Photolibrary
The ribbon seal (bottom) and spotted seal both rely on Arctic sea ice to breed in winter and spring—possibly with each other. A museum specimen at the University of Alaska Fairbanks provided Kelly and his team with evidence of a probable hybrid offspring of the two species.
Overall, the hybrid phenomenon is "just another example of some of the not obvious or intuitive ways that warming the climate is going to vastly alter the organisms that inhabit it," Kelly added.
(See "Bald Eagles May Have to Eat Toxic Seals, Study Says.")
Published December 15, 2010