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Hibernation Information: Why not sleep through winter? 

Sleeping through the winter.

click to enlarge natural-worldhibernation-haley-zadow.jpg
The longer I live, the more I wish scientists would succeed with induced hibernation, especially for old duffers like me. I hate winter! Well, not really...I do enjoy going out with my family getting in the winter wood, something I've been doing almost all my life. When I was a kid, we had a huge wood-burning furnace in the basement of the New England farm house where I grew up.

Woodcutting started in October in Connecticut, with oak and elm being the dominant species we used for keeping warm in winter, and the old two-man cross-cut misery whip was the saw we used to buck up logs into firewood lengths. I can still hear my Uncle Harry on the other end of the cross-cut: "Catsfur (my nickname), I don't mind you ridin' that thing, but would you quit draggin' your feet!"

If I could have just hibernated, woodcutting wouldn't be necessary, and think of all the money we'd have saved.

Hibernation is a way that many mammals in these latitudes spend winter - and as it turns out, some birds. Poor-wills were discovered hibernating among the roots of willows along the cut banks of streams in the Sacramento area in the '60s. They go into a deep sleep during which breathing and heart rate slow down to a hairline between life and death.

Hibernation, it should be noted, is not to be confused with the torpid state hummingbirds and swifts can drop into for short periods of time to escape a cold snap. Both are dependent on insects for food, so when a cold snap hits, the birds hide in the shelter of deep foliage, turn down their breathing and heart rate and wait it out. If the cold snap goes on for over 72 hours, however, then they're in big trouble.

To hibernate, the animal going into that state must first have a suitable layer of fat beneath its skin. The fat is slowly metabolized to make food and water for the animal's slowly circulating blood.

Almost all of the burrowing rodents we see running around during the spring and summer in Central Oregon sleep through winter. The yellow-bellied marmot, in addition to California, Belding's, Merriam's, Columbia and Washington ground squirrels spend up to seven months sleeping.

They appear above ground in March and are back in bed by late July. During that short five months, they give birth to their young and then: eat, eat, eat and eat some more. While the Belding's ground squirrel's favorite food is dandelions, their cousins aren't that fussy, all that green is fat or their fire of life. That said, if they happen to come across insects, bird's eggs, worms - or even one of their dead brethren on the road - they will consume that as well.

A bear will eat huge amounts of juicy, sugar-laden berries and insect larvae to put on the fat necessary to make it through winter. In some areas of the West, hibernation food for grizzlies is becoming a life-threatening issue as they can't find enough pine seeds and army cutworm moth larva to build up the fat reserves.

Mammals need water to maintain healthy blood and during hibernation that's taken care of with the water metabolized out of the fat. But what about elimination of wastewater afterward: urine? Like most old men, I get up three times in the night and head for the bathroom to do just that, something a hibernating bear can't do.

Amazingly, in bears the urea is recycled and turned back into protein. The same goes for packrats, who do not hibernate, and rarely drink water. They can recycle water they get from plants so many times that it is probably painful for them to pee it out. There is so much urea in the urine that it coats the rocks near the packrat's den almost pure white, instead of the characteristic yellow.

From my experience, bats are the deepest hibernators of all. When I was studying and banding them in the lava caves near Bend, I would often remove them from their head-down perch on the cave ceiling, photograph, weigh and band the bat and it wouldn't wake up. Then, I'd carefully hook the bat's hind feet back into the same crevice it was holding onto and leave.

But you know, I did discover that Townsend's big-eared bats wake up at least three times while hibernating. I would often return to the caves where I had banded them and find them sleeping in a different location than where I left them last.

Turns out, they are so deep in sleep that the oxygen content in their blood drops to such a low level that lactic acid builds up, causing the bat to waken and start breathing faster. They take advantage of that physiological alarm clock and fly around to pump up themselves. After the oxygen content reaches the level necessary to keep the cells alive and healthy, they go back to a new location in the cave and drop back into the hibernation state.

One of the most interesting hibernators are butterflies and moths. While the monarchs (a tropical species) have migrated to Mexico and California, our native swallowtails, and a few moths are wintering over as either eggs, or wrapped in the silk of their chrysalides and cocoons, but mourning cloaks and California torstiseshells winter over as adults. They all posses an antifreeze-like substance in their "blood" that protects them from freezing, even at 31-below zero!


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