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.