There is another kind of sleep into which some animals go. It is a very long sleep. It lasts all winter. Great numbers of such animals as frogs, bats, flies, and spiders, go into by-places in the fall to sleep till spring comes. Many of the birds do this.
It is a deeper sleep than that which animals go into at night. It is a different kind of sleep. In the sleep at night the blood keeps moving, and the animal breathes; but in this winter sleep there is no breathing, and the blood stops circulating. All is as still as death. But there is life there, just as I told you, in Part First, there is life in the seed, and in the trees that look so dead in winter. It is life asleep. The warmth of spring wakes up again the life in these animals, as it does the life in the trees. The blood then begins to circulate in them, as the sap does in the trees, and they come out from their hiding-places.
The long sleep of a toad.
I have said that this sleep which some animals go into lasts through the winter. It may be made to last longer than this. Some frogs were once kept in this winter sleep for over three years in an ice-house; and then, on being brought out into the warm air, revived and hopped about as lively as ever. We do not know how much longer they might have been kept in this sleep. You remember that in Part First, Chapter XV., I told you about some seeds in which the life was asleep many hundred years. And it may be that the life might be kept asleep in frogs and other animals as long as this by steady cold. A toad was found lately in the middle of a tree fast asleep. How he came there was not known, but the wood had kept growing year after year, and as there were 67 rings outside of the toad, it was clear that he had been there 67 years. A long sleep it was, but he soon woke up and hopped about like other toads.
The winter sleep of some animals not perfectly sound.
There are some kinds of animals that crawl into winter quarters in whom life is not wholly asleep. The blood moves a little, and they once in a while take a breath; and, besides, they now and then, when the weather is quite warm, wake up enough to eat a little. Now it is curious that such animals always lay up something to eat right alongside of them when they go into their winter sleeping-places. But those who do not wake up at all do not lay up any food, for it would not be used if they did lay it up. They are governed by instinct in this matter.
The field-mouse lays up at its side nuts and grain when it goes into its winter quarters, and when it is partly waked up by a warm day, eats a little of his store. The bat does not lay up any thing, although he wakes up when it is warm. He does not need to lay up any thing, because the warmth that wakes him up wakes up also gnats and insects on which he lives. He catches some of these, and then, as he finds himself going to sleep again, he hangs himself up by his hooks as before. The marmot or woodchuck does not wake up at all, but he always lays up some dried grass in his hole. What is this for? He feeds on it when he first wakes up in the spring, to get a little strength before he comes out from his hole.
How much life is asleep in the winter.
How much life, then, is asleep in the winter in animals as well as in plants! And how busy is life in its waking in the spring! While the roots and seeds in the ground send up their shoots, and the sap again circulates in the trees and shrubs, and the buds swell, multitudes of animals are crawling out of their winter hiding-places into the warm, balmy air. And when the leaves are fully out, and the flowers abound, the earth swarms with the busy insects, and birds, and creeping things, of which we saw none during the winter.
Flight of birds south in winter.