Beavers are capital swimmers, for the toes of their hinder feet are joined together with webbing, and make excellent oars, while the broad, flat tail is very useful as a rudder. They are very much hunted, for their fur is valuable, while they also secrete a curious substance known as castor, or castoreum, which is used in medicine. So in some parts of North America these animals are strictly preserved, and only a certain number may be killed every third year. [Illustration: TYPES OF RODENTS 1. European Hamster. 2. East Indian Striped Squirrel. 3. Woodchuck; Marmot. 4. South American Capybara. 5. South American Vizcacha. 6. Beaver.] THE DORMOUSE Everybody knows what a sleepy little creature the dormouse is. Very often it may actually be picked up and handled without waking! It sleeps all day long, and hibernates from the middle of October till the beginning of April as well, so that it fully deserves its name of dormouse, or sleep-mouse. It is found in Europe and Asia, and sometimes in Africa. In Germany it is called the Haselmaus, or hazel-mouse, because it is so fond of hazelnuts. It eats these just as the squirrel does, holding them in its fore paws as it sits upright on its hind quarters. But it also feeds upon acorns, beechnuts, hips and haws, and corn when it can get it. Dormice always make two nests during the year, one being used during the summer, and the other during the winter. They are very warm and cosy little retreats, about six inches in diameter, and are made of grass, leaves, and moss. Sometimes numbers of the summer's nests are found in thick bushes, or among the low herbage at the bottom of a hedge, perhaps with the dormice fast asleep in them. But the winter nests are generally more carefully hidden, so that it is not very easy to find them even when the leaves are off the bushes. Before it goes into hibernation in the autumn, the dormouse becomes very fat. But it does not sleep right through the winter without taking any food, for on very mild days it wakes up for an hour or two, and eats one of the nuts or acorns which it has carefully stored away in its nest. JERBOAS The jerboa is an extremely curious animal, and if you were to see it in the sandy deserts of the Old World, where it is found, you would be very likely to mistake it for a small bird. For it has very short fore legs, which it tucks up against its breast in such a way that they can hardly be seen, and very long hind ones, on which it hops about in a very bird-like manner. But you would soon notice that it has a long tail, rather like that of a mouse, but which has a tuft of hairs at the tip. When it is leaping about it stretches this tail out behind it, and seems to find it of very great use in keeping its balance.