The Beaver is usually about two feet and a half long, and is, therefore, one of the largest of the Rodentia, except the Capybara. The tail, which is flattened above and below, and of an elongated oval form, measures about ten inches. The muffle is naked; the ears scaly; the soles of all the feet are naked, and their upper surfaces clothed with hairs; and the second toe of the hind feet is usually furnished with a double claw, the additional one being placed beneath the other. The general colour of the fur is reddish-brown on the upper surface, lighter and greyish below. The colour varies a little in different individuals, and appears to become darker, or even blackish, in northern localities. White or pied individuals are not uncommon. The Beaver appears to increase in size for some years after it has attained maturity. Mr. Allen says that in America “two-year-old Beavers generally weigh about thirty-five to forty pounds, while very old ones occasionally attain a weight of upwards of sixty.” The size of the skull seems to increase throughout life; the thickness and density of the bones also increase, and the ridges for the attachment of the muscles become stronger in old individuals.
The Beaver is, or has been, distributed generally over all the northern parts of the Northern hemisphere, especially in the forest regions. Formerly it ranged over the whole of Europe, including the British islands, where there is historical evidence of its former existence, besides the skulls and bones which have been found in various places, but especially in the Fen lands. At present the animal appears to be completely exterminated in the southern parts of Europe from France southwards, with the exception of a small colony on the Rhone, which we believe is still in existence; and only a very few individuals survive in Germany, where they are found on a tributary of the Elbe, and in one or two other places. In some parts of Poland, Russia, and Austria, and in the Scandinavian peninsula, they still, to a greater or less extent, hold their ground; and in Asia they abound about the rivers of Siberia, and in the streams which flow into the Caspian Sea. In North America Beavers formerly abounded from Texas, and, according to manuscript evidence cited by Mr. Allen, even from Mexico, northward to the extreme limit of forest growth, and from the Atlantic to the Pacific coast. The constant pursuit to which the animals were subjected, in consequence of the demand for their skins, greatly diminished their numbers, and in many localities altogether exterminated them; but they still occur over a very large extent of the North American continent, especially in the western territories, where they are even abundant in some of the wilder parts.
In the preceding statements we have spoken of the Beaver as forming a single species; but it has long been a moot question with zoologists whether the Beavers of the Old and New Worlds were or were not specifically identical. The external differences are very slight, and those observed in the skull, upon which most stress has been laid, do not appear to be of sufficient importance for the separation of the animals as distinct species. They consist chiefly in the greater breadth of the anterior portion of the skull, including the inter-orbital space; the extension farther back of the nasal bones, the greater size and depth of the basilar cavity and the more anterior position of the auditory bullæ, in the European Beaver; but the examination of large series of specimens has proved that the skulls from both hemispheres present many exceptions, in which one or more of the peculiarities which they ought to exhibit do not occur: a circumstance which of necessity greatly invalidates the distinction founded upon such characters. Dr. Ely sums up the results of an extended investigation in the following words:—“The extremes of difference, in their aggregate, on the one side and on the other, are sufficiently striking to justify us in regarding them as varieties of one and the same species; while the want of constancy in these peculiarities suggests the inference that these variations are due to long separation of the races, and to accidental causes, rather than to original diversity of the stock.” The Beaver may thus be regarded as a species with two geographical forms (varieties or sub-species), viz., Castor fiber, var. europæus, and Castor fiber, var. canadensis.
So much has been written upon the habits of the Beaver, that the following short statement will suffice to give the leading facts in the natural history of the animal, the accounts of the marvellous sagacity of which, given by the older writers, have, perhaps, invested it with an exaggerated interest.
In populous countries the Beaver is contented, like the Otter, with a long burrow for his residence; but in the wilder regions of Siberia and North America his dwelling-place is a much more complicated affair. But even in these regions, according to some authorities, a certain number of Beavers—always males—show a lazy unwillingness to take part in the common labours of the colony, and these, as idlers, are expelled from the community, often with rather severe treatment, and then take up their abode by themselves in holes, which they dig out in the banks of rivers, whence they are called “terriers.” On the other hand, it would appear that the building instinct which is so remarkably manifested by the Beaver is not always extinct even in those which inhabit populous countries, for we have a most interesting account from M. Meyerinck of the construction of a lodge, and even of a dam, by the colony of Beavers on a tributary of the Elbe.
In North America, from which we have the fullest accounts of the habits of the Beavers, these animals select for their habitation some small stream running through a locality well covered with trees, especially willows, birches, and poplars, upon the bark of which they chiefly feed. These trees they cut down with their powerful incisor teeth, usually selecting those from the thickness of a man’s arm to that of his thigh, but sometimes even felling trunks eighteen inches in diameter. The operation, which at first sight would seem to be a rather difficult one for an animal like the Beaver to perform, is effected by gnawing all round the trunk for a certain distance, and gradually working deeper and deeper into its substance in the middle of the part attacked, until at length the tree stands upon quite a slender piece of wood, with the trunk both above and below this tapered off into the form of two cones, united by their apices. The work is done as sharply and neatly as if the wood had been cut away by a chisel; and the animals are said to have the sagacity to weaken the trunk more on the side that looks towards the water than on the opposite side, by which means, when it falls, it will generally do so in the direction of the water, which materially facilitates the further operations of the Beavers. The quantity of trees cut down by them in this way is very great, so that in the neighbourhood of a Beaver encampment the ground is everywhere full of the stumps which they have left.
These tree trunks are then cut up into lengths of five or six feet, which, after their bark has been stripped off and eaten, are employed in the formation of a lodge, to serve as a shelter for the company of Beavers forming it. Access to the lodge is obtained by means of several subterranean passages, which always open under water, and lead up into the chamber occupying the interior of the lodge. The lodge is usually of an oven-like shape, and is built close to the edge of the water; its walls are very thick, and composed of the above-mentioned trunks of trees, plastered over with mud, clay, &c., mixed with grasses and moss, until the whole fabric measures from twelve to twenty feet in diameter, and forms a hill some six or eight feet high. The larger lodges are in the interior about seven feet in diameter, and between two and three feet high; and the floor of this spacious chamber is covered with fine chips of wood, grasses, and the soft bark of trees, which serve to form the beds of the occupants. Occasionally the lodges are said to contain store-rooms. In front of the lodge, according to Audubon, the Beavers scratch away the mud of the bottom until they make the water deep enough to enable them to float their pieces of timber to this point, even when the water is frozen; and, communicating with this, a ditch surrounds the lodge, which is also made so deep that it will not readily freeze to the bottom. Into this ditch, and the deep water in front of the lodge, the passages by which access to the water is obtained always open, and thus the inhabitants can at any time make their way out when their business requires them to do so. In the neighbourhood of the lodge the timber cut into lengths, as above described, is piled up, so as to furnish a supply of food as it is required; and the pieces of timber, after being stripped of their bark, are usually employed by the Beavers either in repairing their lodges or in constructing or strengthening the dams which they very frequently throw across the streams haunted by them. These dams, which are destined to keep the water of variable streams up to the necessary height for the convenience of the Beaver, are wonderful pieces of work, and almost justify the marvellous stories told of its intelligence and sagacity by the older writers. They are often of great length—sometimes 150 or 200 yards and more—and run across the course of the brook inhabited by the Beavers—sometimes in a straight line, sometimes in a curved form, according to peculiarities in the ground or the stream, and the exigencies of the engineers. They are composed, like the lodges, of lengths cut from the trunks and branches of trees, filled in with smaller sticks, roots, grasses, and moss, and all plastered with mud and clay in a most workmanlike manner, until the whole structure becomes quite water-tight. Their height is from six to ten feet, and their thickness at the bottom sometimes as much as double this, but diminishing upwards by the slope of the sides until the top is only from three to five feet wide. These dams convert even small rivulets into large pools of water, often many acres in extent; and in districts where Beavers abound these pools may occupy neatly the whole course of a stream, one above the other, almost to its source. Their use to the Beavers, as constantly furnishing them with a sufficiency of water in which to carry on their business, and especially to float to their lodges the tree trunks necessary for their subsistence, is easily understood; but it is a more remarkable circumstance that by this means the Beavers exercise a considerable influence upon the external appearance of the locality inhabited by them, which may persist even long after they have themselves disappeared. In and about the pools the constant attacks of the Beavers upon the trees produce clearings in the forest, often many acres in extent; at the margins of the pools the formation of peat commences, and under favourable circumstances proceeds until the greater part of the cleared space becomes converted into a peat-moss. These peaty clearings are known as Beaver-meadows, and they have been detected in various countries where the Beaver is now extinct.
As in the case of the majority of Rodents, the chief activity of the Beaver is nocturnal; and it is only when driven from its lodge by a high flood, or in the wildest and most sequestered localities, that it goes about during the day. It swims quickly, but entirely by the agency of the hind feet, the fore feet being used chiefly for carrying and building operations, and for conveying the food to the mouth. Before diving, it is said to slap the surface of the water with its tail, producing a sound that may be heard at a considerable distance. On land it sometimes travels a good way in the warm season, and is then stated to indulge in a change of diet, feeding upon roots and fruits, and sometimes upon corn. The roots of the water-lily (Nuphar) are also said to constitute part of its food. The Beaver is hunted—but less now than in former years—for the sake of its skin, the soft under fur of which was much used in the manufacture of hats. It is asserted that the flesh is very good, but according to some authorities, only certain parts of it are palatable; and Audubon declares that the tail, which is regarded as a peculiarly choice morsel, closely resembles marrow, and is so rich that only those whose stomachs are incapable of being upset by greasy food can eat more than a very little of it.
The Beaver has been hunted not only for its fur, but also, and from time immemorial, for the sake of a peculiar secretion produced by it, which, under the name of Castoreum, has been for many centuries a highly-esteemed medicament. This substance is secreted in a pair of glandular pouches, situated in the inguinal region of the male Beaver; and it would seem that it was almost entirely in order to procure these that the ancients hunted this animal. Even in connection with this they had wonderful tales to tell of its sagacity: as how that, when it was pursued and found itself unable to escape, it would throw itself upon its back, as if to invite the hunter to take what he wanted and spare its life. Nay, some ancient writers seem to have believed that the Beaver would go the length of biting off its own castoreum glands, and leaving them for the hunter to pick up! Castoreum contains some volatile oil and resin, and a peculiar crystallisable substance called castorine; it is used in medicine as a stimulant, and seems to act especially on the nervous system, but is not much employed nowadays. Its odour, which appears to spread over a considerable space, is described as being very attractive to other Beavers. Audubon states that it is used for this reason as a lure by the American trappers.