In the Castoridae, together with the squirrels, the beaver family constitute the group termed Sciuromorpha, a group distinguished by its members having a special type of lower jaw structure, and also the same type of skull structure. The powerful incisor teeth of the beaver are admirably suited to the cutting through of small tree stems, of branches and twigs, whilst its flat and scaly tail serves as a rudder to a creature that always makes its home beside or in the midst of water.
The beaver is as much noted for its sagacity, and for what nowadays we call "faculty," as it is prized for its fur. One of the largest of the rodents, its body measures nearly three and a half feet in length, not taking the tail into consideration, which is eleven to twelve inches in length.
An attempt has been made to acclimatise the beaver in England again. That it once bred in our country is proved by the fact that some fossil remains of the animal have been obtained from the crag deposits in Norfolk and Suffolk. These were, however, declared by Professor Owen to have belonged to a much larger species of beaver than is now known. Sir Edmund Loder has a number of the common species established in a little valley stream in his estate, Leonard's Lea, near Horsham, carefully protected, which are said to be thriving, and Lord Bute had a still larger number established in Scotland; but it is not likely that they will ever be at home in our country again. Whilst badgers and others have had so much difficulty in holding their own, it is not likely that the beaver could breed and thrive unmolested. Whilst writing the present article, I have heard from Lord Bute that the last of his beavers died some time ago.
In other parts of Europe it is found now only in small numbers, on the banks of the Danube, the Rhone, and the Weser. In the northern districts of Canada it is very numerous. Its range in America is from the confluence of the Ohio and the Mississippi to the banks of the Mackenzie River. At one time the demand for the fur—greatly in vogue in those days for men's hats—was so large that it was feared this clever little creature might become extinct, and the noted furriers of the Hudson Bay Company took measures, in concert with certain Indian tribes, for its protection, whilst still procuring large quantities of its fur.
The most interesting feature in the natural history of the beaver is their amazing skill in the construction of their dams and the dwellings they make for themselves—"lodges," these are called. They are often constructed in small rivers and creeks where the water is apt to be drained off, when the supplies are dried up by winter frost. I spent some time in Colorado near to a part of the Rockies where beavers abounded, and where they were a never-failing source of interest to the young folks in my friend's family. In Montana also they abound in vast numbers. One of its counties is named Beaver Head.
What we—in our ignorance of the inner life of those creatures who have always shared the rich heritage of this world with ourselves—term instinct, has taught the beavers to provide against drought, and to keep up a certain necessary depth of water, by making a dam right across these smaller rivers just at what they know to be a convenient distance from their houses. The manner in which they construct this depends on the locality where they live. If the current is not strong—if there is only a slight motion of the water—the dam is made almost straight; but in proportion as the stream is a rapid one, the dam must be more curved, presenting its convex side towards the current. Where beavers have been allowed to build for a long period undisturbed, their dams become in time, through the persistent industry with which they repair them, a bank so solid that it resists quite a strong on-rush of water or even of ice. Vegetation plants itself on this—willows, birches, and poplar-trees take root. Sometimes so large a thicket is formed that birds build there, and the whole makes a charming colony of happy and busy life. The dams are built in some rivers of trees which are often five or six inches in diameter. These the beaver cuts down with his wonderful sharp incisor teeth.
In lakes and ponds also the beavers have their habitat. They like much the narrow creeks which so often connect the lakes of North America. The currents help them to convey the wood and other materials to their dwellings. A certain depth of water is, of course, necessary for their purpose. Driftwood is utilised by them in building, as well as the green boughs of willows, birches, and poplars. But mud and stones are used also, welded all firmly together, and the different parts of the dam must, of course, be of equal strength. In the same manner, that is, of the same materials, they construct their dwellings, but they are not built with equal care; their construction is rougher than that of the dams. The only thing essential in the work is that they should be made watertight, so that they may have dry sleeping-quarters. Sometimes a house is just big enough for one family, but larger dwellings are also made, such as will house a great number of animals. When this is the case, each family has its own apartment, with a separate door communicating only with the water, never with the home of any other family. The wood is laid crosswise, nearly horizontal, leaving a cavity in the centre. The smaller branches, that project uselessly, are cut off with the teeth, and they are thrown in with the rest to form a good safeguard against any falling in of the mud through the roof.
Once it was believed that the woodwork was first finished, and that then it was plastered, the tail being used as a trowel for this purpose. But this was a popular error. The tail is used as a rudder, and like that of a dog, is a vehicle for emotion. It is flapped even when a beaver has been tamed and domesticated, especially when the creature is startled. They have a very pretty way of carrying mud and stones in their little fore-paws, holding them close up under the throat. The wood naturally is dragged along, held in the teeth. All their work is done in the night-time, a charming sight for a lover of animals, if he can quietly remain concealed near enough for observation on a clear calm night.
A wonderful instinct, so-called, again prompts the beavers to cover their houses each autumn with fresh mud—as late in the season as they can manage it—so that it may freeze hard and keep them secure against their foe, the wolverine, a creature about the size of our common badger, which is much about during the winter. Wolverines are said to do more damage to the fur trade in smaller animals than all the other creatures of prey put together.
Their lodges are kept clean, their inhabitants always plunging into the water instead of polluting their sleeping quarters.