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Animal Hibernation
Nature Bulletin No. 44   December 8, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Supt. of Conservation

Many animals in this northern region go into a winter sleep, called "hibernation". They usually retire to some place where they do not actually freeze, or where they at least are protected from zero temperatures.

Birds do not hibernate but most species migrate to warmer regions Fish to not hibernate but withdraw to deeper waters and their body processes slow down to the point where tbeir food and oxygen requirements are a tiny fraction of the needs during summer months Aquatic insects do not hibernate. Most land insects die, leaving behind them their descendants in the egg, larva or pupa stages. Some insects, though, as for instance certain species of mosquito, hibernate in basements, cisterns and such protected places.

The honeybee has a thermostatic solution for existing through sub-zero temperatures. In moderately cold weather they remain quietly in the hives. But as the temperature drops each swarm suddenly begins to buzz and move around in the hive, which raises its temperature above the danger point -- just as a man thrashes his arms to keep warm.

Snakes, lizards, toads, frogs, salamanders and most kinds of turtles hibernate . A few turtles, such as the common painted turtle, are more or less active under the ice all winter. Earthworms burrow deep m the earth below the frost line.

The mammals, being warm-blooded, vary according to their ability to find winter food. The squirrels are out searching for food after each storm, The raccoons, opossums and skunks "hole up" and stay lethargic during prolonged cold snaps.

Certain species, notably bears, woodchucks (or groundhogs), gophers, chipmunks and bats, really hibernate. They instinctively prepare for their long sleep by eating heavily and accumulating fat, Then they retire to their dens. Some are light sleepers and, on mild winter days, may come out and indolently move about But some become completely dormant. Their body temperature falls as much as 50 degrees. The heart beats feebly, and breathing takes place only at long intervals and slowly. The excretions are slight. Their metabolism -- the body process -- is so lowered that the consumption of stored fat is very slow. They sleep.

We suggest that you do not hibernate, but get out and walk a lot, this winter!

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