In summer he has plenty to eat--leaves, twigs, and grass. But when the winter comes, and the leaves fall, and the ground is covered with snow, the poor elk would starve and die, if he did not have at least the bark of trees to eat. And very little bark he gets for many days at a time. Here I must tell you that some kinds of deer are among the most _hardy animals_; that means that at times they can live on very little. There is a kind of deer, called the _reindeer_, that lives in the frozen North, where there is snow and ice almost all the year round; and the reindeer has nothing more to eat for many days than a little bit of moss or seaweed. But there is another animal, not a deer, that is still more hardy: he can go a whole week without eating or drinking--and do work all the time! That seems very wonderful. But I shall tell you about that animal in another chapter. Now about the elk. His antlers are fine! You can see in the picture how huge they are. And yet, would you believe it, he grew them in only five months! I told you a little while ago that a deer throws off his antlers every year, and grows new ones. I shall now tell you how the elk does that. [Illustration: Elk Photograph of a group in the American Museum of Natural History, New York] In the middle of the winter, the elk's antlers break off bit by bit. In a few weeks they have all fallen off, leaving the elk's head bare, with just a ridge or rough stump on it. Then, early in the spring the new antlers start growing from the top of the stump. They grow very fast, and in five months are as huge as ever. But while the new antlers are growing, they are not hard. As yet they are soft and tender, and all that time they have an outside covering like hairy leather, to guard them from harm. But as soon as the elk feels that his antlers are quite grown, and are strong and hard, he strips off the outside covering by rubbing the antlers against trees. Of course, while his antlers are still growing, and are soft and tender, the elk cannot use them to fight another animal; so during that time he hides in the bushes. But as soon as his new antlers have become hard and strong, he is very brave again, and is ready to fight! Does the elk fight much? He does! He fights most awfully when he has his new antlers. What he fights about, and with whom he fights, I shall tell you in another book. There are a few other kinds of deer in America, but the funniest of them is called the _mule deer_, which lives along the Rocky Mountains. He is called the mule deer because he has very long ears, like a mule's ears. And perhaps you have seen a mule bucking--that is, jumping about while holding his legs quite stiff. Well, the mule deer can buck just like that. And while he is running at a gallop, he will often jump off the ground with stiff legs, and then hop on and on many times like that, with stiff legs, finishing up with another gallop.