Something more is necessary, however, if the animal is to fly properly. It must be able to steer itself in the air just as a boat has to be steered in the water. Otherwise it would never be able to fly in the right direction. So nature has given it a kind of air-rudder; for the skin which is stretched upon the wings is carried on round the end of the body, and is supported there, partly by the hind legs, and partly by the bones of the tail. And by turning this curious rudder to one side or the other, or tilting it just a little up or a little down, the bat is able to alter its course at will.
The Useful Claw
But you would notice something else on looking at a bat's skeleton. You would notice that the bones of the thumb are not long and slender, like those of the fingers, but that they are quite short and stout, with a sharp hooked claw at the tip. The bat uses this claw when it finds itself on the ground. It cannot walk, of course, as it has no front feet; so it hitches itself along by means of its thumbs, hooking first one claw into the ground and then the other, and so managing to drag itself slowly and awkwardly forward.
It is not at all fond of shuffling along in this way, however, and always takes to flight as soon as it possibly can. But as it cannot well rise from the ground it has to climb to a little height and let itself drop, so that as it falls it may spread its wings and fly away. And it always climbs in a very curious manner, with its tail upward and its head toward the ground, using first the claws of one little foot and then those of the other.
When a bat goes to sleep it always hangs itself up by the claws of its hind feet. In an old church tower, or a stable loft, you may often find bats suspended in this singular way. And there is a reason for it. The bat wants to be able, at the first sign of danger, to fly away. Now if it lay flat upon the ground to sleep, as most animals do, it would not be able to fly quickly; for it would have to clamber up a wall or a post to some little height before it could spread its wings. And this would take time. But if it should be alarmed while it is hanging by its hind feet, all that it has to do is to drop into the air and fly off at once.
Bats in the Dark
There is something else, too, that we must tell you about bats. They have the most wonderful power of flying about on the darkest night, without ever knocking up against the branches of trees, or any other obstacles which they may meet on their way. It used to be thought that this was because they had very keen eyes. But it has been found out that even a blind bat has this power, which seems really to be due to very sensitive nerves in the wings. You can feel a branch by touching it. But a bat is able to feel a branch without touching it, while it is eight or ten inches away, and so has time to swerve to one side without striking against it.
The Winter Sleep
Bats, like hedgehogs and squirrels, pass through the winter in a kind of deep sleep, which we call hibernation. It is more than ordinary sleep, for they do not require any food for months together, while they scarcely breathe once in twenty-four hours, and their hearts almost cease to beat. If the winter is cold throughout, they do not wake at all until the spring. But two or three hours' warm sunshine arouses them from their slumber. They wake up, feel hungry, go out to look for a little food, and then return to their retreats and pass into the same strange sleep again.
An Interesting Specimen