Part 19

Several litters of young containing from three to seven each are born, the first usually appearing in spring and the last in fall. The young are blind and helpless at birth, and in this condition cling so tenaciously to the mother’s teats that when she is frightened from the nest they are often carried off attached to her.

Some individuals at least of the white-footed mice, like others of the genus Peromyscus, are known to have a prolonged and musical song. It is a fine warbling ditty, a little like the song of a canary. A number of good observers have recorded these performances, but they appear to be so infrequent that most people with woodland experience have never heard them.

The lives of these mice are passed in constant fear of a host of enemies. Hawks and owls, bluejays, and shrikes in the bird world are ever on the alert to capture them, while skunks, weasels, minks, foxes, and snakes persistently seek them in their retreats.

=THE BEACH MOUSE= (=Peromyscus polionotus niveiventris= and its relatives)

(_For illustration, see page 530_)

The beach mouse is a beautiful, velvety-furred little creature about the size of a house mouse and one of the smallest species of the genus Peromyscus. Its back is colored with delicate shades of pale vinaceous-buffy and its underparts, including the feet, are snowy white.

The species _Peromyscus polionotus_, of which the beach mouse is one of several geographic races, or subspecies, occupies a comparatively restricted range in the lowland region of Alabama and Georgia and thence through a large part of Florida.

It presents an unusually convincing illustration of the influence of changing environment upon the physical characters of animals. Among the cotton fields of Alabama and Georgia _Peromyscus polionotus_ is rather dark grayish brown, but on the lighter-colored soil of Florida the color responds and becomes paler in perfect correspondence with the change in soil until the white sand-dunes and beaches of the coast are reached. There, in strong contrast with the color of the northern members of the species, it is so modified that the pale representatives of this area are recognized under the name _niveiventris_, as a geographic race, or subspecies.

Changes in environment affect both great and small mammals in a variety of ways, sometimes in shades of color, sometimes in relative size, and sometimes in proportions. Exceptions to the rule are to be found, however, and some species of mammals have a wide range under a great variety of conditions, with scarcely an appreciable sign of variation.

The beach mouse is abundant on the sand-dunes and beaches of peninsular Florida, especially from Palm Beach to Mosquito Inlet, wherever there is a growth of sea oats (_Uniola_), which appears to be its principal food plant. It is a nocturnal animal and its nightly activities may be read, early in the morning, from the multitude of tiny tracks which lead in all directions and often form a network on the sand. A single track sometimes extends for a hundred yards or more from a burrow, and with all its windings may aggregate several hundred yards of travel, showing the activity of this small worker during many hours.

Tracks are most plentiful immediately about growths of sea oats, patches of saw palmetto, or scrubby bushes. The homes of these mice are usually in short burrows sheltered by growing vegetation or under fallen palm fronds.

As in the case of many of our mammals, we have scanty information concerning the life of these attractive little animals, and it is suggested that here lies a pleasant subject for investigation by some nature lover wintering in Florida.

=THE BIG-EARED ROCK MOUSE= (=Peromyscus truei= and its relatives)

(_For illustration, see page 531_)

The numerous species of mice of the genus Peromyscus in North America include a great variety of little beasts, many of which are distinguished by beauty of form and color. One of the most striking and picturesque individualities among these is found in the big-eared rock mouse, which is characterized by its great ears, a thick, soft coat of buffy brown fur, and a long, well-haired tail. In size it exceeds the common house mouse and even the white-footed mice which share its haunts.

This rock mouse is indigenous to the mountainous regions of the West, from Colorado and New Mexico to the Pacific and south to the Cape Region of Lower California, and down the Sierra Madre of Mexico to Oaxaca. Within this area it divides into several not very strongly marked geographic races.

As implied by its common name, it is a characteristic dweller among cliffs and ledges along the mountain slopes or rocky canyon walls, where it occupies the many crevices and little caves. In California it ranges from near sea-level up on the mountains to above 10,000 feet altitude. Although showing a distinct preference for rocky places, when available, some races of this mouse adapt themselves to other conditions and may be found on brush-grown flats, where they live in brush heaps, old wood-rat nests, and similar shelter.

That they make their homes in places other than cliffs in New Mexico was evidenced by a thick, soft nest made almost entirely of wool, found in a hollow juniper. They have several litters of from two to six young each year, the breeding period extending from spring to fall.

In Arizona and New Mexico I found the rock mouse most numerous in the belt of junipers and pinyons and in the adjacent yellow-pine forest. The crevices of cliffs about the Moki and Zuni Indian pueblos and in all the rocky wilderness of that region, including the Grand Canyon, are abundantly populated with them.

They search every nook about their haunts and often visit cabins or temporary camps for food, but do not usually take up their abode in them as do the white-footed mice. When foraging their movements are quick, and when startled they make surprisingly long leaps. Like others of their kind, they eat a great variety of seeds and small nuts, quantities of which they lay up in winter stores. Pinyon nuts, and especially juniper seeds, are their favorite food.

While of nocturnal habits, rock mice at times wander forth in sheltered spots by day, and on the few occasions I have seen them I have been delighted with their grace and beauty, their great ears and prominent shining black eyes lending them an attractive air of alert intelligence.

Throughout their lives they are in deadly peril from predatory foes. Hawks and owls glide shadowlike along the faces of their rocky homes ready to pick them up whenever they venture into open view, while bobcats, skunks, and weasels prowl about by night hunting their furry victims.

=THE BROWN RAT= (=Rattus norvegicus= and its relatives)

(_For illustration, see page 531_)

It is safe to assume that few readers need an introduction to that world-wide pest variously known as the brown rat, house rat, wharf rat, or Norway rat. Two European relatives, the black rat and the roof rat, preceded the brown rat to the New World and became widely distributed. They resemble the brown rat, but are much smaller and are soon killed, driven away, or reduced to a secondary status by their larger and fiercer cousin, which averages about sixteen inches in length, although large individuals attain a length of more than twenty inches and a weight of more than two pounds. The black rat has nearly disappeared from most of its former haunts in the United States and the roof rat is mainly restricted to southern localities with a mild climate.

Neither the brown, black, nor roof rat has any near relatives among native rats of America, and all may be distinguished from our native animals by their coarser hair and long, naked tails.

The brown rat is believed to have first invaded Europe from Asia in 1727, when hordes of them swam the Volga River, and about the same year it arrived in England on ships from the Orient. Since then, traveling by ships and by inland commercial routes, it has spread to nearly all parts of the globe. In America it is now established in human abodes throughout the length and breadth of the continents from Greenland to Patagonia.

Wherever it goes the fierce and aggressive spirit with which it is endowed qualifies the brown rat more than to hold its own against all rivals, while its mental adroitness and its fecundity have largely nullified the constant warfare being waged against it by all mankind. Not content with infesting ships, dwellings, stores, warehouses, and even the refrigerating rooms of cold-storage plants in many areas, it has established itself as an extremely destructive pest in the open fields.

In towns it hides among stored merchandise, in the hollow walls of buildings, in sewers and other underground passages, or, as in the fields, in burrows which it digs in the ground. Its nests are soft, warm masses of fibrous material which is secured by raids on any available supply of cotton, wool, or fabrics, which they cut into shreds for the purpose.

In these retreats it has several litters a year, averaging about ten young, but exceptional cases of more than twenty young have been recorded. The young begin to breed when less than six months old. The size and number of litters increase with the food supply, and under favorable conditions rats soon become intolerable pests.

In Jamaica and the Hawaiian Islands rats became so numerous that sugar-cane and other plantations were at one time threatened with complete destruction. To save the crops the mongoose was introduced, but after checking the rats in Jamaica these curious little mammals in turn became a pest which it appears hopeless to control.

In the Hawaiian Islands the mongoose reduced the number of rats, but the survivors promptly took up their abodes in the tree tops, where they now live as completely arboreal lives as squirrels, safe from their ground-inhabiting enemy.

During a two weeks’ campaign against rats in the sewers of Paris 600,000 were killed, and on a rice plantation of about 1,200 acres in Georgia 30,000 were destroyed in one season. In Illinois 3,435 were killed on a farm in one month.

One of the most curious chapters in the life of this hardy beast is now developing in the far island of South Georgia, on the border of the Antarctic, east of Cape Horn. On this island, which has a cold and stormy summer and nine months of rigorous winter, several whaling stations have been established. For years great numbers of whale carcasses have drifted ashore each season and, half rotting, half refrigerated, have furnished a never-failing food supply for brown rats that have landed from the ships. With such abundant food they are reported to have increased until they now exist there literally in millions. They make their nests in the tussocks of grass and peat and swarm along well-marked trails they have made on the mountain sides.

In the trenches along the battle front in France they have become extremely abundant and troublesome, and in England have multiplied until the Board of Agriculture is recommending efforts to destroy them as a menace to the public welfare through their waste of food supplies.

On farms, in addition to destroying growing and stored crops, they kill great numbers of young chickens, turkeys, and other poultry, and create havoc with such ground-frequenting game as pheasants. At all times brown rats are more or less carnivorous, and when several are confined in a cage the stronger will soon kill and devour the weaker.

In city department stores and large hotels they often cause thousands of dollars damage yearly in single establishments. An English organization for their destruction estimated in 1908 that, outside the towns and shipping, in Great Britain and Ireland they caused annual losses of about $73,000,000.

When there is a sudden diminution in the food supply, an abundance of which has caused a great increase in the rat population, the rats migrate into other districts, sometimes in enormous numbers. These migrations usually occur at night, and many are matters of history in Europe and in the United States.

A witness of one of these migrations in Illinois in 1903 reported that one moonlight night as he was passing along the roads he heard a rustling in a field near by and soon saw crossing the road in front of him a multitude of rats extending as far as he could see. The following year the invaders became a plague in that district. At times of food scarcity rats become extremely bold and aggressive. Without hesitation they swim streams encountered in their wanderings and at times will even attack man.

Owing to their great numbers, universal distribution, and destructiveness, brown rats are the worst mammal pest known to mankind. Through their habit of living in sewers, among the offal of slaughter-houses, and in garbage heaps, from which they invade dwellings and storehouses, they pollute and spoil even more foodstuffs than they eat.

In addition, they are known carriers of some of the worst and most dreaded diseases, as bubonic plague, trichinosis, and septic pneumonia; while there is little doubt that they spread scarlet fever, typhoid, diphtheria, and other contagious maladies. Bubonic plague is mainly dependent upon rats for its dissemination and has been carried by them to more than fifty countries, including the United States. In India more than two million people have died in one year from this rat-conveyed disease.

Although rats are abhorred by man, yet they have been for ages so closely associated with most of his activities that they have long had their place in Old World literature. Among other instances, many readers will recall Victor Hugo’s gruesome account of Jean Valjean’s fight with the rats in the sewers of Paris. In England and on the continent rat catching has been a regular trade and dogs have been specially bred for use in their pursuit.

Rats are loathsome vermin which civilized man should eliminate with the other evils of his semi-barbaric days which he is leaving behind. One might still wish that in many places a modern “Pied Piper of Hamelin” would appear and rid the people of these pests. This is not necessary, however, if the public will cease to take their presence as a matter of course. Their exclusion from buildings and destruction are merely matters of good housekeeping, both personal and communal.

Rats can be banished by removing or destroying trash heaps and similar harboring places and by the simple expedient of rat-proofing buildings, especially dwellings, granaries, warehouses, and other places where food supplies are stored.

These precautionary measures should be supplemented by trapping or poisoning in open places. Campaigns of this kind can be fully successful only when engaged in by the community at large. The returns from the investment for such a purpose will be large, not only in the vast money values of property saved, but in the reduction of the death rate and in the great improvement of the public health.

THE HOUSE MOUSE (Mus musculus)

(_For illustration, see page 531_)

The familiar house mouse is of Old World origin and may be distinguished from most of our native mice by its proportionately slenderer body, long hairless tail, and the nearly uniform color on the upper and under parts of the body. Like the house rat, wandering an alien from its original home in Asia, and transported by ship and by inland commerce, it has gained permanent foothold and thrives in lands of the most diverse climatic conditions, except those of the frigid polar regions.

For centuries the house mouse has been parasitic about the habitations of man, and in many places in America has spread into the surrounding country, where it holds its own in the struggle for existence with many of our native species. It is probable that its ability to live in houses also infested by the fierce brown rat is due wholly to its agility, and to the small size, which enables it to retreat through crevices too small for the rat.

In buildings it hides its warm nests in obscure nooks and crannies, making them of scraps of wool, cotton, or other soft fibrous material, often cut from fabrics. Out in the fields, like any other hardy vagabond, it adapts itself to whatever cover may be available on the surface or in crevices and the deserted burrows of other mammals.

It has several litters of from four to nine young each year. The young are born blind, naked, and helpless, but are soon able to run about, often following the mother on her foraging expeditions. When a little more than half grown they usually scatter from the home nest and seek locations of their own.

Throughout most of its world-wide range the house mouse has the same general appearance, but in some localities the effect of changed environment is developing appreciable differences, which appear destined to result in marked geographic races. The representatives of these mice I caught in weedy fields on the coast of Chiapas, near the border of Guatemala, have an appreciable rusty shade on the back in place of the ordinary dull gray.

The success of both the house mouse and the house rat in establishing themselves so successfully in all parts of the world, in the face of the antagonism of mankind, affords marvelous examples of physical and mental adaptability not equaled elsewhere among mammals.

From early days the domestic mouse has been a familiar member of the household with people of all degree, and the housewife has had to match her wits against the cunning persistence of this small marauder in order to safeguard the family supplies of food and clothing.

Despite the antagonism excited by its destructive habits the mouse is so small and often so amusing in its ways that it has commonly been regarded with a half hostile, half friendly, interest. This is apparent by frequent references to it in proverbs, nursery rhymes, fables, and folklore, as well as in more serious literature.

Many cases of singing house mice have been recorded, their notes being a series of continuous musical chirps, trills, and warblings, rising and falling about an octave and slightly resembling the song of a canary. It has been claimed that this singing is due to an affection of the songster’s breathing organs, but this can scarcely account for its being uttered at definite times and places and ceasing at the volition of the performer.

In one instance the song had been heard in a china closet and an observer sat by the open door to locate the singer. After patient waiting “a mouse peered out from behind the plates, climbed up a little way on the brackets, and after looking around several times, began to sing.” This mouse continued to sing in the same place at intervals for several weeks and became accustomed to the presence of people during its performances; then it suddenly disappeared, probably a victim to one of the dangers which constantly beset its kind.

=THE MOUNTAIN-BEAVER= (=Aplodontia rufa phaea= and its relatives)

(_For illustration, see page 534_)

The first adventurous fur traders who penetrated the Oregon wilds found the Chinook Indians provided with robes made of skins of the mountain-beaver. From that time until recently but little accurate information has been available concerning the habits of this curious animal. Locally it is known by several other names, including “Sewellel,” “mountain boomer,” “boomer,” and, in the Olympic mountains, “chehalis.”

The genus of mountain-beavers contains only a single species with several subspecies, all having a close superficial likeness in size and form to a tailless muskrat, except for their coarse, harsh fur. It is an exclusively North American type and, aside from a remote relationship to the squirrel family, has no kin among living mammals. It appears to be a sole survivor from some former age. As with the pocket gophers, its mode of life has developed powerful muscles about the head, front legs, and forepart of the body.

The distribution of the mountain-beaver in Tertiary times extended through the Great Basin to North Dakota, but at present is closely restricted to the humid region between the crests of the Cascades and the Sierra Nevada and the Pacific coast, and from the lower Fraser River, British Columbia, south to the latitude of San Francisco Bay, California.

Within this superbly forested region this animal delights in locations that are cool and oozing with water, where, under the dense shade of an almost tropical undergrowth of shrubs, ferns, and other herbage, it constructs numberless tunnels and trails. These are sometimes in flats, but much more often along canyons and mountain slopes, among willow, alder, aspen, or other thickets, or even in the heavy coniferous forest.

Veritable colonies inhabit certain areas and the ground is honeycombed with burrows six to eight inches in diameter and covered with a network of surface trails. The irregular branching tunnels are sometimes two or three hundred feet in length and have at frequent intervals side passages through which the earth mined in extending the burrow may be ejected in small dumps. The tunnels appear in a large measure built for the safety of the owner in traveling, since they repeatedly come to the surface at the end of a log, where an open, neatly kept trail extends under its shelter the entire length, the tunnel being resumed at the far end of the log.

All surface runways connecting tunnel entrances or leading through the thick surface vegetation are well kept and free of all obstructions. The ground in these haunts is commonly so saturated with water that the tunnels form drainage channels down which run little streams.

Nest chambers discovered by T. H. Scheffer in the Olympic Mountains were located in tunnels two feet underground. They were oval in form and one measured eighteen inches in horizontal diameter and seventeen in height. Here three storage chambers opened directly from the nest chamber, one of which contained two quarts or more of sections of fern roots, which had been kept so long they were spoiled, and another was partly filled with freshly cut leaves of nettles and twigs of cedar and fir. At the far end an opening dropped six inches into a small drainage basin partly filled with water, out of which led two passages. The roofs of the chambers were lined with a thin layer of clay, which appeared to have been packed in place by the owner.

In the upper and drier part of the nest, which was made of dried fronds of ferns, grasses, and small twigs, were found three young less than a week old, with coats of fine fur, but with eyes still closed. Like burrowing animals generally, the mountain-beaver is cleanly in its housekeeping, and offal, loose dirt, and debris of all kinds are pushed out by the forefeet and head to the dumps at the less-used openings.

In winter much of the mountain-beaver country is buried under several feet of snow, but this does not stop the activities of this hardy animal. Between the entrances to its burrows and out along the surface of the ground it tunnels through the snow in various directions in search of forage.