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Bear Bones Research focuses on the only mammals that don’t experience bone loss despite inactivity by Rich Hewitt | Photography by Darrold Dorr

Black bearRita Seger remembers her first encounter with a black bear. She was enrolled in a University of Maine undergraduate wildlife ecology course that included a January fieldtrip led by the Maine Department of Inland Fisheries and Wildlife bear biologist, and UMaine alumnus, Randy Cross.

As she watched Cross and his team handle the bear to gather health assessment data, and affix ear tags and radio collars as part of Maine’s long-term bear monitoring program, Seger began thinking about the wonders of hibernation physiology — how the American black bear manages to remain in its den for up to 6 months each year in Maine, not eating, drinking, urinating or defecating. During this time, mature females even give birth to and nurse their young.

Seger, a medical internist, found it fascinating that hibernating bears do not experience bone loss despite months of inactivity.

“I always thought I would like to study wildlife, and potentially combine medicine and wildlife studies in one way or another,” says Seger, who had been practicing internal medicine for 11 years in Missouri, Alaska and Maine when she starting taking courses at UMaine to explore an additional graduate degree. “That January 2004 fieldtrip is where it all came together for me.”

That fall, Seger began her Ph.D. research on bone metabolism in active and hibernating black bears. A year after seeing her first bruin, she was back in the field with Cross and his crew. Her goal was to begin to fathom the many unanswered questions as to how hibernating bears are the only mammals that do not experience bone loss due to inactivity.

“This is the most fascinating work I could hardly imagine doing,” says Seger, who earned her Ph.D. in 2008 and is now, in addition to practicing medicine, a researcher in the UMaine Department of Animal and Veterinary Sciences. “Being out of doors, up close — in the dens — with these beautiful animals, that have the most complex and fascinating physiology. To me, they’re captivating.”

Seger and a team of researchers, which included colleagues at UMaine as well as some of the top bone researchers in the country, may have found a clue as to what it is in the bear’s physiology that wards off the effects of long-term inactivity.

In most mammals — other hibernators and humans included — months of inactivity result in significant bone loss and a host of other complications. But, in bears, there is little or no deterioration of the bone during hibernation. Learning how they do it may shed new light on bone growth and ways to prevent and perhaps treat bone loss in humans.

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Winter 2012

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