June, 2010 featured article

A Mysterious Animal Appears in the Far North

New DNA Evidence Shows Polar and Grizzly Bears Might be Interbreeding

by David Morel, age 15

For several years stories have spread of a strange-looking bear that roams remote coastal areas near the Arctic Ocean. Until recently most scientists considered these stories nothing more than legend. But now DNA evidence confirms that a bear shot in 2006 is a polar bear-grizzly bear hybrid.

Locals call this mysterious bear a “pizzly” or “grolar” bear.

This particular bear, shot in the Canadian Arctic, is the first bear to be confirmed as a hybrid. But reported sightings of large bears with unique blond or light brown coloring are becoming more common.

It’s not as strange as you might think.  Some 110,000 years ago these two animals actually belonged to the same species. A team that included molecular biologist Charlotte Lindqvist discovered an ancient polar bear fossil and conducted DNA research on it. Although the DNA was partially fragmented because of its age, an analysis could be conducted because it was preserved in a dry and cold region.

Analysis of ancient “grolar” bear fossils conducted by Lindqvist concludes that “morphologically and behaviorally it was a polar bear, but genetically, it was almost a brown bear.”

“This fossil is…at the exact point when polar bears split from brown bears,” says Lindqvist. She came to this conclusion through an analysis of stable isotopes of the canine teeth of these fossils. She compared them to isotopes from the teeth of modern grizzly and polar bears. Scientists think this hybrid indicates the two bear species might once again be converging.

This rare discovery raises questions about how such an incident could occur. The grizzly bear has a home range in the Rocky Mountains and the Brooks Range of Alaska. A home range is the area an animal uses in pursuit of its biological requirements. The home range of the polar bear includes the Canadian, Russian, and European arctic. The existence of a hybrid bear indicates that perhaps the bears are traveling outside of their home ranges.

When an animal travels outside of their home range, it can be attributed to a variety of factors, such as the environment. A warming climate may be playing a role in this migration. Scientists speculate that some grizzly bears may move outside of their home range as the environment around them warms, ice melts, and more resources become available to them farther north.

Whatever the reasons, evidence is mounting that polar bears and grizzly bears are encountering each other in the wild. Scientists do know that these two species are closely related enough genetically to interbreed. And the chances to do so are probably increasing because ice is melting and climate is changing in the far north. These changes may motivate grizzly bears to migrate, as regions where they once resided may now be too hot. Polar bears may be migrating because the ice on which they once resided is melting.

The role that humans play in this migration raises much speculation. Since the industrial revolution, humans have been releasing fossil fuels that trap heat in the atmosphere of the earth, and some say this is the primary reason behind global warming.

In addition, deforestation to sustain the human population’s thirst for timber and other resources eliminates trees, damages forests, and decreases habitat for wildlife. Trees absorb the greenhouse gases that contribute to climate change.

No matter what the cause of this interbreeding, the discovery of this hybrid bear is a monumental event. Both polar bears and grizzly bears require an extensive mating ritual for reproduction. Ian Sterling, a polar bear expert that works for the Canadian Wildlife Service said, “I don’t think anyone expected it to actually happen in the wild.”

 [Sources: National Geographic, Nature News, San Francisco State University of Geography, USA Today]

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