Then what _do_ they do with those tails? Well, for one thing, they sometimes use them to carry mud by curling them between their legs and holding the mud against their bodies. Perhaps they resort to this way of carrying mud where they have such a steep climb up the roof they need all four legs to climb with; or it may be just an individual fancy of some beavers. For, being really _thinkers_ and not mere machines, acting entirely on what is called instinct, different beavers have different ways of doing things. The beaver's tail is also very useful in swimming, and Mr. Beaver is a great swimmer. You should see him. He swims mostly with his hind feet and tail, holding his fore paws against his breast as a squirrel does when he's sitting up looking at you. His tail he uses as one uses an oar in sculling, turning it slightly on edge as he works it back and forth. But he has two other important uses for this big tail, as we shall now see; for the beavers of this colony we are watching, having put up their dam and built their big house, are now ready for the Fall harvest that is to provide for the long Winter. The beavers are strict vegetarians. Their diet consists of the tender bark of young trees and roots dug from the bottom and along the banks of the ponds in which they live. "But, for mercy's sake, where are they going to get the tender bark of trees in the dead of Winter, when all the trees are frozen solid and the beavers can't get from under the ice anyhow?" Well, Mr. Beaver has thought out just how to do it and we didn't. That's the beauty of being a beaver. What he does is to cut down small trees, trim them, divide them into lengths, and then heap them up in a great pile at his door, under the water. By the time they are three years old beavers feel grown-up; as, indeed, they are in size, although, like certain other young people I could name, they have a great deal yet to learn. At this age they choose their mates and either settle down in the home colony or go away somewhere else. School takes up with the beavers in September. All through September and October the harvest is gathered and preparations made for the long Winter. The baby beavers of the Spring, who by this time are four or five months old, take part in the harvesting; at least they play at it. They don't do much, but they learn a great deal. Now let's all be little beavers for a few minutes and see what we can learn. We are out in the harvest-field--the woods--with father, and he's going to cut down a tree for the Winter food-pile. Watch him.