Hibernation: The Opposite of Sleep?

August 28, 1996

NEW YORK, N.Y., Aug. 23, 1996 -- You hear it every year: "I wish I could hibernate all winter." It's a cozy image--tucked under an earthen blanket, you snooze through the worst months of the year. The only problem with it, zoophysiologist Brian Barnes reports in the September/October issue of The Sciences (p.12), is that it is dead wrong. Instead of blissful slumber, what hibernating animals experience is more like a months-long bout of insomnia.

Barnes studies arctic ground squirrels, groundhog-like rodents that live in the Brooks Range of Alaska, 200 miles north of the Arctic Circle. During hibernation a ground squirrel lowers its body temperature below freezing and stays that way for weeks, virtually brain dead, with no detectable brain waves or signs of breathing. Once or twice a month, however, it stokes up its metabolic furnace and laboriously rewarms itself.

The cyclical rewarming, which costs more than 80 percent of the squirrel's stored body fat, has stumped scientists for more than a century. If hibernation is about conserving energy, why do animals waste crucial reserves bringing their body temperature back up to normal? Do they need to empty their kidneys? Restore their fluid balances? Recharge their memories?

Barnes has a different hypothesis: animals rewarm themselves so they can rest. "Cold brains cannot sleep. Although torpor may stave off the need to sleep for days or even weeks, eventually the animal will grow so tired and sleepy that it must rewarm itself for a snooze." To a ground squirrel, hibernation probably feels like long stretches of icy stupor punctuated with short, costly-naps--proof, Barnes says, that sleep is precious indeed.

New York Academy of Sciences

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