Forest Preserve District of Cook County, Illinois
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Spring Awakening
Nature Bulletin No. 107   March 15, 1947
Forest Preserve District of Cook County
William N. Erickson, President
Roberts Mann, Supt. of Conservation

The hibernating animals are awakening from their long winter sleep. Reptiles, amphibians, land snails, numerous insects, and some of the mammals pass the long northern winter months in a strange torpid condition known as hibernation.

Some snakes may be found tightly coiled beneath logs or piles of rocks; others in burrows and caves. Frogs and most turtles bury themselves in the mud and vegetation at the bottom of a pond or stream, emerging when the ice breaks up in early spring. Toads bury themselves in the ground, digging their way backward with their horny heels. Some butterflies migrate; others pass the winter in hollow logs or in buildings, emerging to fly about on the first warm spring days. Some mosquitoes hibernate. Most insects, however, go through winter in the egg, larva, or pupa stage.

Few mammals migrate seasonally. Some species of bats do but others hibernate in caves. Rabbits, squirrels, foxes, muskrats, mink, weasels, field mice and deer mice are present and active all winter. The bears, skunks, raccoons, possums and chipmunks store up thick layers of fat and go to sleep in their dens when the severe cold comes. But they are light sleepers and on mild winter days are likely to awaken, come out, and move about.

Other mammals, however, truly hibernate. The woodchuck or groundhog, the gopher, the 13-striped ground squirrel, the long- tailed jumping mouse, and some of the bats, eat and eat until a third or more of the animal's weight is fat, and then retreat to an underground chamber where they enter a death-like sleep which may last from October until late March. All but the bats curl up in a tight ball. Breathing is faint, at long intervals. Heart beat is slow, circulation sluggish: if the toe of a mouse or a bat is cut off during hibernation, very little bleeding occurs. Body temperature drops to near that of the surroundings, sometimes close to freezing. Most of the stored fat is slowly used up. No one known just what awakens them. Temperature changes perhaps.

Why does sap rise in the trees? Why do birdies sing? Why do boys play hooky.

Because it' s spring!

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