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The Three Bears Dance With Climate

Posted by | October 18, 2008

An unusually large grizzly sat on top of a deer carcass outside of Cooke City, Montana earlier this fall. Locals got pictures of the great grizzly, estimated at 900 lbs, which evidently was guarding the deer by sitting on it.

“It’s a bear in good fall condition, not an old behemoth,” said Kevin Frey based on the photos. Frey is a bear management specialist for Montana’s Fish, Wildlife and Parks Department, and his opinion was reported by the Billings Gazette.

People around Cooke City had other grizzly encounters this summer. A  bear bit a camper inside a tent in July. The next month, another bear entered a home.

Geologists doing fieldwork encounter grizzlies from time to time. One colleague of mine took a .45 revolver with him as bear-repellant when he headed to fieldwork in Alaska. Alas, he put the weapon in his carry-on luggage and took it to the airport, managing to get himself arrested. (Geologists are not necessarily the sharpest tacks in the box, a fact in which I take comfort when I cannot find my bifocals even though they rest on top my head exactly where I propped them.)

The grizzly activity in Montana this summer and fall is an indication that the great bears have staged a partial comeback since their low point in the early 1970s.

Bear researcher Charles Robbins of Washington State University is one scientist who has watched that comeback closely. Robbins and his graduate students study grizzlies in the wild using GPS collars. The collars record where the bears have been over time. Researchers on the ground then back-track the bears, looking for information about their behavior and feeding habits.

“Their scat tells us what the bears where eating,” Robbins said.

Robbins also studies grizzlies year-round at WSU’s bear research center where captive bears live and reproduce. Interacting with hibernating grizzlies in the winter at WSU is quite different from what the good folks in Montana experienced this past summer.

“The bear’s heart rate drops down to eight or nine beats per minute and two of the four chambers in the heart stop beating,” Robbins said. “Even so, the bears can stand and walk. All of that could help us develop medicines for people with high blood pressure and congestive heart failure. And despite lying around for months at a time, bears don’t lose muscle mass or bone density. That’s quite a trick we could learn from.”

Grizzlies still face a number of challenges.

“Many grizzlies depend on salmon as a food source,” Robbins said. “As ocean conditions change with global climate, there may be a real impact on bears.”

Grizzlies are already veterans of climate change. They are an offshoot of their close cousins the coastal brown bear that migrated across the Bering Strait during the Ice Age when global sea level was lower because so much water was frozen into glacial ice.

Modern brown bears are similar to the ancient, immigrant bears, while grizzlies are their inland cousins.  Polar bears are an offshoot of both the grizzlies and browns.

“Polar bears are extremely well adapted to life on the ice. Being white is just one small part of it,” Robbins said.

A polar bear once pursued a geologist colleague of mine in Greenland. The fellow had no gun, but he quickly took off his coat and dropped it as he ran along shore. As the animal paused to sniff and maul the coat, the geologist was able to reach his boat, and the bear didn’t pursue him into the water. (Occasionally even we geologists can think clearly.)

Robbins tells me that polar bears changed quite quickly during the Ice Age as they evolved from brown bears. And since coming onto the scene, they’ve proven themselves significantly adaptable to some climate change.

About 10,000 years ago, the bitter cold of the Ice Age gave way to warmth like the present. Polar bears survived, although their habitat must have decreased greatly. They also lived through the warmest part of current epoch, a point called the “Optimum” that occurred about 7,000 years ago.

But it’s unclear how polar bears may fare if climate warms above both recent temperatures and then potentially above even the Optimum.  That distinct possibility has a number of wildlife biologists highly concerned.

The tale of the three bears is still being written around us.