Back at the lab, they studied the x-rays to quantify bone mass and analyzed the blood for substances associated with bone turnover. Over a three year period, from 2005 to 2007, they took blood samples and x-rayed paws. To find out, Seger and a team of researchers from the University of Maine used radio collars to track 85 black bears, active and hibernating. Perhaps bear bones were broken down at a high rate due to inactivity, but were replaced at a high rate, too? Or maybe bears – in contrast to other hibernating mammals – suspended bone breakdown over the winter? Seger initially considered several possibilities for how bears emerge from hibernation with strong bones. Then new bone forms, so you always have new bone forming.” How much bone is added back depends on how much weight the skeleton bears less weight-bearing activity means less bone is reformed. “So the skeleton is constantly being broken down, especially where there is wear and tear, and that bone gets reabsorbed. It’s so dynamic that in adult humans a whopping tenth of a skeleton is replaced every year. “Skeleton is very dynamic tissue,” Seger explained. In particular, she has examined data related to the breakdown and formation of bear bone mass over time. Rita Seger, a medical doctor with a PhD in ecology and environmental science, has been working to unravel some of the mysteries of bear hibernation. So why are bears different? And what can we learn from their biochemical processes that may help us treat osteoporosis and other bone diseases? To consider what a feat this is, consider humans’ susceptibility to bone loss: astronauts who spend six months in the weightless environment of space can lose nearly ten percent of their bone mass, and people forced to spend several months in bed may experience similar declines. The mother bear’s bones, however, will be as strong and as thick as the day she lay down, and her young may even have added bone mass over the winter.īears are the only animals known to maintain their bone mass during prolonged periods of inactivity. In the spring, they will wake up in a near starvation condition, their fat reserves depleted. Deep in the winter-dark woods, beneath the roots of a fallen tree, a mother black bear hibernates with her two yearling cubs.

Bear vs skeleton