When a hibernating bat is sunk under water of the same temperature as that of its body, it does not even attempt to breathe. A similar experiment was tried with a hedgehog, and after it had been under water for twenty-one minutes, one tiny bubble of air rose to the surface. I need scarcely say that if the animal had been awake, it would have been drowned in less than a fourth of the time.
For the bat, no food can be found until the warm weather returns, and so the hibernation is unbroken for at least five months. But, though food be almost entirely withdrawn from the hedgehog, some nutriment remains, and therefore the animal is so constituted that it can discover and consume the food which has been provided for it.
This food chiefly consists of snails, which are themselves hibernators, and which during the winter months conceal themselves so effectually that they are seldom detected except by their two great wintry foes, the thrush and the hedgehog.
The hedgehog, not possessing so wide a range of hibernating temperature as the bat, which actually “hibernates” daily for a short time even during the hottest summers, is roused by an hour or two of warm sunshine such as we often experience about February. Awakened by the warmth, the hedgehog unrolls itself, creeps out of its refuge, and trundles (I know no better word to describe its peculiar pace) away in search of food. Taught by instinct, it is sure to come upon one of the strongholds of the snail, eats as many as it needs, returns to its home, and sleeps until awakened in a similar manner.
Then we have the vegetable-eating squirrel, which is a partial hibernator.
During the later weeks of autumn, the squirrel may be seen in the act of making provision for the winter. In the first place it collects a vast store of fallen leaves, moss, twigs, and similar materials, and with them constructs its winter nest.
Squirrels have two distinct kinds of nest, one for the winter and the other for the summer. Both nests are of considerable size, and both are so well concealed that to detect them is a very difficult task. The summer nest is comparatively light in texture, and is placed near the ends of lofty boughs, where it is hidden by the leaves. Moreover, its position renders it almost unassailable, as the branch on which it is built would not even endure the weight of a small boy. In the winter, when the leaves are off the trees, the nests are very conspicuous, and in the New Forest, where I gave some time to watching the habits of the squirrel, they are exceedingly numerous.
In fact, the squirrels of the New Forest swarm in such numbers, and do so much damage to the young twigs of the trees, that many hundreds must be shot annually, just as is the case with rabbits. They are always shot just before hibernating, because, as they put on new robes for the winter, their skins fetch the best prices. Moreover, the animals become fat, as is the case with all hibernators, and so their flesh is in good condition for the table. Squirrel-pie is a well-known luxury in some parts of England, and is far superior to rabbit-pie, as it is free from the peculiar flavor which attaches itself to the rabbit, and to many persons is exceedingly repulsive.
The winter nest is a very large one, containing at least four or five times as much material as would serve for a summer’s nest. Instead of being placed at the end of a bough, it is always set in the hollow caused by the junction of several large branches with the trunk. The exterior is so skilfully formed, that when the tree is viewed from below, even the most practised eyes will often fail to detect the nest, large as it is.
The amount of material which a squirrel employs in this nest is really wonderful. I have taken out of a single nest armful after armful of leaves, until quite a large mound was raised at the foot of the tree, and I should think that there was enough material to fill two large wheelbarrows, even if it were pressed down closely.