The great order Rodentia—rats, mice, rabbits, porcupines, squirrels, beavers, etc., derives its name from the Latin verb rodere, to gnaw, or eat away (something), and is characterized by the great development of the front (incisor) teeth, by means of which rodents get their living by biting off, or gnawing through, the plants and woody stems on which they feed, or which they use in constructing their dwellings. All are primarily vegetable eaters, yet none will refuse a meal of flesh when opportunity offers to get it, and some are decidedly carnivorous, especially as to fish. They are distributed all over the world, including the Australian region. They are chiefly terrestrial, and often burrow or live in ready-made burrows. Some are aquatic, such as the voles; others, like the squirrels, are arboreal. In perhaps a majority of the forms the hind legs are much longer and stronger than the forelegs, giving the animals great leaping power, while the forefeet, with their long and flexible fingers, are constantly used as hands. Many are beautifully marked in varied tints of gray, brown, red, and black, so that their pelts have value in the fur market; and their flesh is an important element in human food. On the other hand the activity of these animals, when numerous, causes serious damage to gardens, crops and orchards and one of them, the rat, is unquestionably the most dangerous animal to human health and prosperity in the whole animal kingdom. The fecundity of the smaller, murine species, is great, and from time to time they increase inordinately in favorable places, and swarm abroad in vast and destructive migrations. Were it not for the fact that the rodents furnish the principal part of the food of predatory mammals, reptiles, and birds, and are thus kept down, the globe would soon become so populous with this tribe that hardly anything else could maintain existence.

The distinguishing anatomical characteristic of the rodents is the dentition. The canines, so essential to carnivorous, predatory animals, are here completely absent, and a long empty space intervenes between the incisors and the molars, or cheek teeth, which vary greatly in number and form among the different families. The incisors consist of a single pair in each jaw, very large and strong, and composed of vasodentine, faced only with hard enamel, often yellow or red. As the softer substance behind the facing wears away more easily, the incisor takes a chisel shape, leaving the hard enamel in front projecting slightly as a cutting edge; thus these teeth always remain sharp. The rodents are traced back in their lineage to the order Tillodontia of Eocene time. The oldest family of modern type in the order is that of the squirrels.

Let us begin with the rabbits and hares (family LeporidÆ). The name properly applies to the Old World species Lepus cuniculus, the burrowing wild rabbit from which all our various domestic rabbits are descended, whose special characteristic is the fact that they live in holes in the ground of their own digging, and in large colonies called warrens. All the other species make their breeding beds and resting places on the surface of the ground, in the best concealment (outside of forests) that they can find. Such a home is called the animal's "form," and when it contains a litter of young the mother covers them with a blanket of hair which at that season she is shedding copiously. Strictly speaking, all the LeporidÆ, except the cuniculus, are "hares"; but the general term "rabbit" is now so common that the scientific distinction is of no consequence. Europe and Asia have two kinds of hares, and several exist in this country, such as the familiar "cottontail" or bush rabbit of the east, the southern swamp rabbit, and several species of large, long-eared, swift-footed hares of the western plains called "jack rabbits." The most important one, however, is the large northern one named "snowshoe rabbit," because in winter it receives a broad growth of hair on the feet, aiding it in traveling over the snow. This rabbit turns white in winter, the hairs losing their color with the advent of cold, as also does the big arctic hare which wanders as far north as land extends. These northern hares are the chief dependence for food in winter of all the Canadian fur-bearing animals, and indirectly of the native Indians. Consequently when, as happens at intervals of a few years, the rabbits of a district all but wholly die off by an epidemic, a famine and dreadful distress occurs—or used to when civilized aid was less available than now—in northern Canada, and the commercial outcome of furs is greatly diminished.

As the hares feed on herbage and bark, obtainable all the year round, they are abroad in winter; but they have a family of small cousins, the pikas (LagomyidÆ) that inhabit our western mountain tops above timber line and must hibernate. Other species abound in the Himalayas. They are little, short-eared, tailless creatures that make their homes in companies among loose rocks, and store in their deep crevices enough dried grass and flowering plants to keep themselves alive until the late spring of those cold heights. Western folks call them conies.

The porcupines are large, plantigrade rodents notable for the mixture of quill-like spines with the hair. This is most conspicuous in the European species, which bristles with spines reaching far beyond the hips and concealing the tail, forming an excellent defensive armor. Some smaller African and East Indian species are less well armed, and have longer tails, at the end of which are tufts of spines, making an effective weapon. All of these pass their time and get their food on the ground. Our American porcupines (family CercolabidÆ) differ somewhat anatomically and live for the most part in trees, although our common eastern porcupine wanders about a great deal in summer, especially at night, feeding on herbage, and rejoicing in a find of bones or other saline food here and there. It is defended by a coat of long black hair in which spines are plentifully mingled, and the short, flat tail, covered with thick spines, may give a sidewise stroke that makes man or beast cautious about attacking an animal that otherwise seems so lethargic and helpless. The porcupines of this family, however, really belong to trees, where they slowly consume the foliage and tender bark, and remain quietly through even Canadian winters. The Pacific side of the country has a similar species in the yellow-haired porcupine; and several smaller kinds exist in Central and South America with scanty spines and long prehensile tails.

Closely allied to the porcupines are the gregarious viscachas of the South American plains, that live in "villages" of burrows, and much resemble prairie dogs in appearance and habits; also the chinchillas of the high levels of the Andes, whose soft gray coat is one of the prizes of the furrier. Here, too, come the swift-footed, slender agoutis and pacas of South America, many species of which exist and are useful as food; and a neighboring family contains the little cavies, from one of which are derived our pet "guinea pigs," which are not pigs and do not come from Guinea; also their cousin, the almost aquatic capybara, which measures three feet long, and so is the biggest known rodent. This is much hunted for its flesh, and is the principal prey of the jaguar.

This brings us to the world-wide tribe of rats and mice formed by a group of eight families, of which the typical one (MuridÆ) alone contains a third of all Rodentia, and the other seven creatures differing greatly from these familiar models. Many are small, such as the house mouse (originally a native of southeastern Asia, as also were the rats that commerce has carried all over the civilized globe), and the even tinier harvest mice, gray or brown in plain color, and with long, slender and nearly hairless tails and legs fairly equal in size. Thence in size they grade up to the stature of the rat, and from that on to the South African "springhaas" which is as big as a rabbit, and to our muskrat, two feet long, counting in its tail. Although essentially alike in structure some have varied widely from the ordinary type. Thus the jerboas, several species of which inhabit the plains of Asia and Africa, have the hind legs so long that their bones are considerably longer than the distance from the root of the tail to the nose; and they progress in long rapid leaps, balancing themselves by long tails, often tufted at the end. The big "jumping hare" of South Africa has much the appearance of a kangaroo with a squirrellike tail; and a genus of exquisitely dressed mice in our sandy Southwest are called "kangaroo" mice. In fact one of our commonest reddish field mice, found all over the country, has similar proportions, and is remarkable for its long leaps when hurried.

A shortening of the tail is seen in the voles, to which the common meadow mice of various species belong, and still more in the lemmings, in the Old World mole rats, and in our pouched gophers. All these are not only ground-keeping kinds, but burrowers, and have no use for a long tail, save in the case of the muskrat, which is really a big vole that has taken to an aquatic life, and needs an oar to scull himself through the water; for muskrats swim more by means of their tails than by their feet. The foremost burrowers are the pouched gophers, whose long tunnels, and food-getting, do so much damage to crops in the central plains region of this country. They must be distinguished from the ground squirrels, also called "gophers."

An interesting diversity of habits may be met with here. Some rodents live in deeply excavated burrows, others in shallow diggings or holes in stumps and rock crevices; some, like the water voles, reside in holes in the banks of streams, or, like the muskrat, heap up "houses" in a marsh in which to pass the winter in security; while still others construct ball-like nests among the herbage, or in bushes and trees. Some truly hibernate in cold countries, like the famous dormice of Europe, and our equally sound sleeper, the American jumping mouse; but mostly they stay in snug habitations and live through the winter on collections of food, or, like field mice, gather seeds abroad even in the coldest weather, or poke about under the snow for food, as do the lemmings. From time to time certain species, especially of the short-tailed field mice and the lemmings, multiply excessively in some district, and then are forced to spread away from their birthplace in those migrations of myriads which form the "plagues" that devastate large tracts of country. They march on until an accumulation of enemies and an epidemic of illness combine to kill them off.

SQUIRRELS, WOODCHUCKS AND BEAVERS

Squirrels in form and activities are much alike all over the world, and are absent only from Australia and Madagascar. The long, bushy tail that makes so excellent a blanket as it is wrapped about their bodies when curled up asleep, is the badge and pride of the tribe. They inhabit hollows in the trees or sometimes holes among their roots, and in summer make globular nests of leaves and twigs in which the young are nursed and trained. Nuts form their staple food, but berries, fruits, roots, funguses, insect grubs, etc., offer changes in fare with the recurring seasons. Sometimes great ingenuity is displayed in getting at this food. Some species are arrant robbers of birds' nests, and now and then kill and eat small birds and mammals; and the older males are resolutely kept away from their babies by the mothers for fear of cannibalism. This catholic appetite, and their willingness to wander from place to place in search of things seasonable, enable squirrels to find food of some sort every month of the year, yet most species have the forethought to lay up in more or less secret places a winter supply of provender; consequently no species of Sciurus hibernates, strictly speaking.

This storing of winter provender is a matter that has been regarded with more general interest, perhaps, than any other feature of animal economy, and is mainly manifested among the rodents, although practiced in a limited way by some others, as for instance, by weasels and foxes. It looks like conscious foresight of the famine time to come, but it is no doubt in the main, if not wholly, instinctive, since the young, who have had no experience of the winter's scarcity or imprisonment ahead, make suitable preparations. It seems to me that this habit, so necessary to the existence of small, vegetarian creatures in cold climates, arose in some such way as this:

The little animals that store supplies designed to keep them alive through the winter are those whose food is for one reason or another unobtainable then. Remember, also, that they are feebly endowed with powers either for defense or for escape outside their homes, and when gathering their food must not loiter much to eat as they go, but must pick up what they can carry and hasten to the safety of their doorways. This is the reason why surviving species of such animals have acquired cheek pouches, in which they can transport a fair meal of their food to be eaten at home at leisure.

During the larger part of the year food is scant, and these rodents get into the way of picking up every bit they can find, and seem so restless and energetic that some of them, such as the viscachas and pack rats, accumulate about their burrows or nests quantities of inedible things, moved, apparently, by mere objectless acquisitiveness. The search for food, the foremost occupation and anxiety of these small wood-folk, would be increasingly stimulated as the ripening season of the seeds and nuts on which they depend advanced, and the impulse to incessant industry, so necessary in the poorer parts of the year, would now be overworked, and each animal, in his haste to be up and doing, would constantly bring home more food than would be consumed, so that it would pile up in the accustomed "dining room." The gradual failure of outdoor supplies, as winter came on, would lead to the eating, with increasing frequency, of those fragments casually saved in and about the burrow or house, which, from their nature, would not have decayed. The animal which had been most busy and clever in food gathering would own the largest amount of the leavings of these autumnal feasts. Having the most food he would be among those of the colony or neighborhood strongest and most likely to survive, and to give to his offspring the tendency to strength and industry which had been his salvation. This would be continued and shaped by the process of natural selection into a valuable, instinctive habit of gathering nonperishable food in large quantities every autumn, and thus providing themselves with stores to last through the coming winter; but it does not follow that the squirrels and mice are conscious of this wise forethought.

The striped, chattering, ever-busy chipmunks, of which America possesses several delightful species, although able to ascend into trees, and frequently doing so, are groundlings, and fond of rocky places into whose crevices they can quickly rush when an enemy is seen or heard; hence their fondness for the stone walls that in the East divide farm fields, and in general they are more inclined to associate with man and his works than are the tree squirrels, although the grays lend themselves readily to the semidomestication of residence in village streets and city parks, as the red never does. The chipmunks dig long underground tunnels, enlarged here and there into chambers serving as bedrooms, storerooms for food, and refuse bins; and the northwestern species are so numerous that between what they eat and waste in gardens and grainfields and the bad runways for water their galleries make, they are justly regarded as a pest.

These pretty but troublesome chipmunks are called "gophers" in some parts of the West, but that name is more generally given to the gray or brownish ground squirrels of the plains, classified as spermophiles by naturalists; and they are so varied, numerous and destructive wherever grain is grown, from the prairies of Kansas and Nebraska to the California valleys, and northward to the Saskatchewan, that extensive and costly poisoning operations are necessary to suppress them. Similar to them, but larger, are the prairie dogs, whose communities, or towns, of burrows and tunnels render useless large tracts of land in the southern half of the plains. Very similar animals to these abound in Russia and eastward throughout the open country of central Asia. They have undoubtedly increased much within late years through the killing off of the natural enemies that in the old days held their multiplication in check.

The prairie dogs used to be called "marmots," a term that applies more properly to some larger European burrowing rodents and to our woodchucks, which are so common all over the eastern half of the country, and, in another species, on the summits of the northern Rockies, where they are known as "whistlers." The most remarkable thing about them is the length and intensity of their dormancy in hibernation. There remains only the beaver, the largest of the rodents except the capybara, and altogether the most important one, measured by the value of its fur, and by the service its race has done through thousands of years in preparing, by its clearings and dams, valleys for man's cultivation.

Every beaver settlement is a true colony, the offspring of some previous settlement, which may be hundreds of years old. When such a settlement becomes too populous for the food supply, young males and their mates travel to some fresh spot by a small woodland stream, and begin life by digging a burrow in the bank with an underwater entrance, and at once dam up the stream by piling sticks, sod and mud across its current at some favorable spot below their home, the effect, if not the conscious purpose, of which is to maintain a depth of water in the stream at all seasons sufficient to cover the entrance to the burrow, and also to permit the storage of green wood under water (and ice) near the home for food (they eat the bark) during the next winter. The young beavers born that season will remain through the winter with the parents, and a domelike house is usually built in which the family lives. Next season the young set up a home for themselves near by, and so the colony grows. Beavers get most of their food by cutting down trees other than evergreens, and gnawing the bark. As the trees disappear near the bank, and the colony increases, the dam is enlarged so as to spread the set-back water over a wider territory; and later canals are cut deep into the woods, permitting far-away trees to be felled, and their pieces floated to the houses, especially in gathering the supply for winter. Old dams are sometimes 100 or more yards long, and are built with astonishing intelligence with reference to holding back a great breadth of water. These are diligently and skillfully repaired; and the houses become, in the course of years, big enough to accommodate three generations of beavers at once, and are so massive, especially when frozen in winter, which is the time of most danger from their enemies, that they are practically safe from attack. From such a mature colony others are continually formed, until in a level, swampy region the whole district is well occupied by beavers. This is possible now, of course, only in the remote Northwest; but a few beavers survive in the Rocky Mountain region of the United States, under protective laws, and they are still numerous in the more thinly settled parts of Canada, and furnish a large return to trappers.