Radio Script
1998

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Southeast Alaska's Unique Brown Bears
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STORY: Thousands of years ago, scientists say brown bears migrated from Asia across a land bridge to what is now Alaska. Some of these brown bears ended up in Southeast Alaska. Scientists at the University of Alaska Fairbanks say these bears evolved into a genetically distinct species. UAF professor of zoology and geneticist Gerald Shields explains.

SHIELDS: "There is a group of bears on the islands of Southeast Alaska. And these are the so-called ABC Islands--Admiralty, Baranof and Chichagof Islands. Those bears are decidedly different genetically from any other bears worldwide. And we've been able to put these ABC bears in the context of their relationship to every other population worldwide. We believe they are remnants of the first brown bear population which crossed the Bering Strait and moved into Alaska, probably about three times as long ago as any other populations in Alaska."

To make the discovery, Gerald Shields and other scientists collected blood and tissue samples from more than 200 bears in Alaska and Asia. They examined the mitochondrial DNA--a kind of DNA that mutates during the evolutionary process. By tracing the mutations--the more mutations a species undergoes the more unique it is--the scientists were able to conclude that Southeast Alaska's brown bears were a distinct species.

But that was just the first amazing discovery. The scientists also used DNA to figure out what the closest relative to these bears are. Gerald Shields.

SHIELDS: "There's another aspect about the ABC bear population which is really quite startling, and that is the sister group, if you will, of the ABC brown bears is not another population of brown bears but is a population of polar bears. All polar bears worldwide are the closest relatives to these ABC brown bears."

But the DNA didn't tell scientists everything. For example, Gerald Shields says it's not possible to determine when the bears became a unique species. It could have occurred before the bears migrated to Alaska, or they could have evolved into a new species during the last ice age. However, scientists know from fossil evidence that brown bears have lived in Southeast Alaska for at least the past 35,000 years. And now that scientists know the brown bears of Southeast Alaska are unique, wildlife managers must figure out how to balance human activities such as logging with the need to protect bear habitat.

SHIELDS: "It's important from a genetic standpoint in that they have an interesting evolutionary history. It's also interesting from a management standpoint because they are unique genetically. And of course if those populations are lost, they can't be restored."

OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.