Issue link: http://digital.canadawide.com/i/170490
But like "true" hibernators, a bear's metabolic rate plummets as much as 75 percent during hibernation. How bears adapt to this plunge startled Tøien when he plotted breathing and heartbeat data. He compares bears with diving marine mammals: a bear takes a breath, the heart beats and suffuses body tissues with oxygen, the bear breathes out and the heart slows, 20 or 30 seconds later the bear breathes in again, the heart beats, oxygen flows. "That's a long period without a heartbeat," Tøien says. "We would lose consciousness if we didn't have a heartbeat for that amount of time." We would also die without food or water, or without the ability to urinate or defecate. Bears accomplish these feats by relying almost exclusively on fat as fuel for about five months on the coast and up to seven months in the Interior. Closer to spring they're still hibernating but they're restless. Tøien's bears would stand up, scratch, rearrange bedding, make licking noises, and swipe at the expensive monitoring equipment as they got ready to leave. In the wild, the hints that it's time to rise depend on geography. But even then it's not clear what exactly forces bears outside, although spring melt trickling into their cozy retreats would prompt an evacuation for sure. t john E. Marriott / wildernessprints.com British Columbia has more than 120,000 black bears—a quarter of the Canadian population. North America has close to one million black bears. To Mars and beyond B ears are like their own stasis chambers, biological "closed-loop systems" that are the envy of researchers who care about things like getting humans to Mars alive, with muscles and bones intact. Astronauts lose 1 to 1.5 percent of hip bone mass for each month spent in space, roughly the same annual bone loss of postmenopausal women with osteoporosis. Through disease or lack of exercise, human bones and muscles quickly deteriorate. Bears spend up to seven months not eating, drinking, urinating, or defecating, but emerge in spring with close to the same muscle and bone mass they had in fall. Their trick? Recycling. They recycle calcium and phosphorous to rebuild bone and recycle nitrogen in their urine into amino acids, the building blocks of protein needed for muscle repair. If scientists can figure out the mechanisms behind the recycling, it could lead to new medicines and help facilitate long-distance space travel for humans. B r itish C o lumbia M agazine • fal l 2 0 1 3 23