Airdate: Dec 03, 1998
Scientist: Brian Barnes
Arctic Ground Squirrel-Supercool
Arctic ground squirrel hibernation is about the closest thing we’ve seen to turning into a zombie.
This winter, temperatures in the Arctic will drop to as low as minus forty degrees, forcing many of the animals that live there into a state of suspended animation, or hibernation. I'm Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History. We're listening to the calls of a record breaking hibernator -- the arctic ground squirrel.
"We've been able to show that, curled in a ball, eyes shut tight, that these arctic ground squirrels adopt the lowest body temperature ever measured in a mammal. It's actually below freezing; it'll drop to minus two, minus three degrees Celsius. Temperatures in which their blood freezes, if you take it that low in a test tube, but inside the animal, it stays unfrozen."
Brian Barnes is an Associate Professor of Zophysiology with the Institute of Arctic Biology at the University of Alaska in Fairbanks.
"As the animal supercools, a condition that simply means a fluid that's below freezing point, the temperature should freeze, but it doesn't. Sometimes you'll see this in your own freezer, if you put a cup of water with a thermometer, you'll see it drop below freezing, yet ice won't form until you either hit it, or, better yet, drop a little piece of ice to seed the crystallization of the water into ice in which case, it happens just like that, as the supercool liquid crystallizes into ice. That'll happen in the Arctic ground squirrel if their skin gets penetrated by an icicle or something frozen, which'll kick off the freezing process. But this typically doesn't happen. It's well known that lots of insects and some amphibia supercool, but the arctic ground squirrel on the tundra of Alaska is the first mammal ever to be shown to supercool like that."
Pulse of the Planet is presented by the American Museum of Natural History. Additional funding for this series has been provided by the National Science Foundation. I'm Jim Metzner.