They were wonderful teeth. After the babies were too old to live on milk, four curved teeth grew out in the front of each little mouth. Two were in the upper jaw and two in the lower jaw. It was the strangest thing! The more these teeth gnawed the sharper they became. The inner side of each tooth was softer than the outer side. In biting together, the inner edge wore down faster, and left the outer edge as sharp as a knife.
The beaver belongs to the Order of Gnawers. Squirrels and rabbits and rats and many other mammals belong to this order. They all have these chisel-shaped front teeth, which keep on growing all their lives long. If any one of them is too lazy to gnaw every day his teeth grow so long that he cannot bite anything at all. Beavers are the largest of the gnawing animals, except the water-hog of South America. They have stronger teeth than any of the others.
Not long after this stormy night the mother beaver decided to take the three babies out with her into the woods. She chose another rainy evening because then their enemies were not likely to be wandering under the dripping trees. Bears and foxes and wild-cats hate to get wet, but beavers enjoy feeling the cool water trickle over their fur and splash on their tails.
Except for their broad, flat tails, the three little beavers looked like rats covered with silky brown fur. The mother seemed like a giant rat, about three feet long from her round nose to the root of her tail. Instead of fur her tail was covered with thick skin. This skin was so creased and dented that it looked like scales.
What an exciting evening it was for the babies! One behind the other they trotted down the dark tunnel after their mother. At first the floor was dry and hard. After a few steps their feet touched something wet. Soft mud oozed between the fingers on their fore-paws. Their hind-feet were webbed up to the toe-nails, and so did not sink in so deep as their fore-paws. Beavers are the only mammals which have webs on one pair of feet, and not on the other pair. They are half land animals and half water animals.
This was not the first time that the three little beavers had ventured into the tunnel. More than once before they had crept down as far as the water and waded about at the edge. But now they kept right on, splashing in farther and farther. The water grew deeper and deeper. In the dark they felt it wash up to their knees, and then up to their chins, and finally away over their backs and their heads to the roof of the tunnel.
Away went the three babies swimming after the old mother. They held their breaths, and shut their ears tight. Their small fore-paws hung down by their sides. They paddled with their webbed hind-feet, and used their broad tails as rudders, to send them now this way, now that.
It seemed the longest time to the last little beaver before his head popped up into the fresh air above the pond. He blinked his light-brown eyes, and winked away the drops on his eyelashes. Now and then a flash of lightning glimmered on the trees around the pond. Of course he did not know yet that his food came from those tall, shadowy things at the edge of the water.