THE POCKET GOPHERS (Geomys bursarius and its relatives)

(For illustration, see page 515)

With the exception of the moles no other extensive group of American land mammals is so highly specialized for a peculiarly restricted mode of life as the pocket gophers. They form a strongly marked family, the Geomyidæ, which includes various genera and many species, all very similar in external form, but varying from the size of a large mouse to a massively formed animal equalling a large house rat in weight.

Without exception they are powerfully built for their size, the head and front half of the body being extraordinarily muscled to meet the demands of their mode of life. The broad blunt head is joined almost directly on the body. The eyes are small and have the restricted vision to be expected from animals living underground. The ears are reduced to little fleshy rims about the openings, and the short naked tail is provided with nerves, which render it useful as an organ of touch.

The front teeth are broad, cutting chisels, and on each side of the mouth is a large pocket in the skin used for gathering and carrying food. On the front feet are long claws, which, when not being used to dig or handle earth, are doubled under, against the soles of the feet, so that the gopher walks on the back of them much as the ant-eater walks on its folded claws.

Peculiar to North America, pocket gophers occupy a great area extending from Illinois, Florida, and the Gulf of Mexico to the Pacific coast, and from the plains of the Saskatchewan, in Canada, southward to Panama. Their vertical range within these limits extends from sea level to timber-line, at above 13,000 feet on some of the high volcanoes of Mexico. The family attains its greatest development in that wonderful region of plains and volcanoes lying about the southern end of the Mexican table-land.

In the United States these animals are best known as “gophers,” but in the range they occupy in the Southeastern States they are called “salamanders” and in Mexico are widely known as “tuzas.” As a rule they frequent treeless areas, but are found also in many types of forests from among the palms and other trees of the tropical lowlands to the oaks, pines, and firs on the mountain sides.

All members of the family live wholly underground, in many-branched horizontal tunnels, which they are continually extending in winding and erratic courses about their haunts. The tunnels are from two to about five inches in diameter, according to the size of the animal, and while usually less than six inches below the surface, the approaches to the nest and storage chambers sometimes drop abruptly two or three feet below the regular working tunnels to the level of the living quarters. At intervals along the tunnels short side branches are used as sanitary conveniences, thus enabling the occupant to keep the main passageways in a habitable condition.

The courses of the underground workings are roughly indicated on the surface by series of piles of loose earth brought up through short side passages as the tunnels are extended. These little miners’ dumps of earth vary with the size of the animal, sometimes containing more than two bushels. The outlets of the passages leading to the surface are kept plugged with loose earth. When these animals are numerous the ground is thickly dotted in all directions with earth piles, and the caving caused by the network of tunnels just below the surface renders walking difficult. The perpetual industry of these rodent miners outclasses that of the proverbial beaver.

Gophers are both diurnal and nocturnal, the gloom of their tunnels scarcely varying except when one of the outlets is temporarily opened. They are averse to light, and if the plug to a freshly made opening is removed the observer may soon catch a glimpse of the owner as he suddenly thrusts his head into view for a moment before again plugging the door with earth.

Gophers dig their tunnels by using their teeth and the strong claws on the front feet. The loose earth is pushed along the tunnel by the head, the palms of the front feet, and the breast in little jerky movements until it is ejected on the surface dump.

Owing to their poor sight, heavy bodies, and short legs, gophers are clumsy and deliberate in their movements and peculiarly helpless in the open. Apparently appreciating this, they rarely venture from their underground shelter by day except when in grain fields or similar sheltering vegetation. Here they sometimes run out two or three feet to cut down a succulent stalk and drag it hastily within the entrance of the tunnel, where it is cut into short sections and placed in the cheek pouches if to be used as food or left on the dump if the object of the cutting is finally to secure the seeds or head of ripening grain.

During the mating season in spring pocket gophers run about clumsily from one burrow to another and may often be seen on the surface by the light of the rising sun. Most of their short trips above ground are made at night, when they sometimes swarm out and wander over a limited territory. Their night wanderings are proved in California by the many bodies which the morning light often reveals in the sticky crude oil on newly oiled roads which the gophers have tried to cross.

From one to seven young are born in a litter, but whether there is more than one litter in a season or not is unknown. The young when about half grown migrate to unoccupied ground sometimes one or two hundred yards from the home location and make tunnels of their own.

The food of pocket gophers consists mainly of tubers, bulbs, and other roots, including many of a more woody fiber. Whole rows of potatoes or other root crops are cleaned up by the extension of tunnels along them. Sometimes the animals follow a row of fruit trees, cutting the roots and killing tree after tree. In grain and alfalfa fields they are great pests, and in irrigated country their burrows in ditch banks often cause disastrous breaks.

The big tropical species sometimes exist in such numbers as to render successful agriculture very difficult. Sugar-cane planters in many parts of Mexico and Central America are compelled to wage unremitting war on them to avoid ruin. I know of an instance on a plantation in Vera Cruz in which thousands were killed during a single season without stopping the damage from these pests, which swarmed in from the adjacent area.

The large external cheek pouches of pocket gophers are used solely for gathering such food supplies as seeds, small bulbs, and sections of edible roots or plant stems and transporting them to storage chambers located along the sides of the tunnels. Food is placed in the pouches by deft sidewise movements of the front feet used like hands, and so quick are they that the motions of the feet can scarcely be detected. The pockets are emptied by placing the front feet on the back ends of the pouches and pushing forward, thus forcing out the contents. In their tunnels gophers run backward and forward with almost equal facility, the sensitive naked tail serving to guide their backward movements.

Pocket gophers are stupid solitary little beasts, with surly dispositions, and fight viciously when captured or brought to bay. This attitude toward the world is justified by the host of enemies ever ready to destroy them. Among their more active foes are snakes and weasels, which pursue them into their tunnels; and badgers, which dig them out of their runways.

They are also persistently hunted day and night by foxes and coyotes. Moreover, by day various kinds of hawks watch for them to appear at the entrances of their dens, and by night the owls, ever alert, capture many.

When one gopher intrudes into the tunnel of another the owner at once fiercely attacks it. In some places I have seen Mexicans take advantage of this characteristic pugnacity by fastening the end of a long string about the body of a captured gopher and then turning it into an occupied tunnel, through a recently made opening. The owner, scenting the intruder, would immediately attack him, the combatants locking their great incisors in a bulldog grip.

The movements of the string would give notice of the encounter, and by pulling it out steadily both animals could be drawn forth and the enraged owner of the burrow dispatched. In this manner I have known an Indian to catch more than a dozen gophers in a few hours.

Pocket gophers are active throughout the winter even in the coldest parts of their range, but in many places must rely largely on food accumulated in their storage chambers.

Melting snow in the mountains and in the North reveals the remains of many tunnels made through it along the surface of the ground. These snow tunnels are often filled for long distances with loose earth brought up from underground, and after the snow disappears in spring the curious branching earth forms left, winding snakelike through the meadows, are a great puzzle to those who do not know their origin.

In a state of nature pocket gophers are constantly bringing the subsoil to the surface and burying humus. Over an enormous area they exist in such countless thousands that their work, like that of angleworms, is often of the most beneficial character. On bare slopes, however, their work is highly injurious, as it greatly increases erosion of the fertile surface soil and thus has its direct influence in changing world contours.

When civilized man arrives in their haunts and upsets natural conditions with cultivated crops the new food supply stimulates an increase in the gopher population and their activities immediately become excessively destructive and necessitate unremitting warfare against them.

THE KANGAROO RATS (Dipodomys spectabilis and its relatives)

(For illustration, see page 518)

The desert regions of western North America have developed several peculiar types of mammals, and among them are none handsomer or more interesting than the kangaroo rats. These rodents, despite their name, are neither kangaroos nor rats, but are near relatives of the pocket mice, which share their desert haunts.

All are characterized by a kangaroo-like form, including small fore legs and feet, long hind legs and feet for jumping, and a tail longer than the body to serve as a balance. In addition, they have large, prominent eyes and are provided with skin pouches on each side of the mouth for use in holding food to be carried to their store chambers.

The color pattern, like the form, of the kangaroo rats is practically uniform throughout the group. Both are well shown in the accompanying plate of Dipodomys spectabilis, the largest and most strongly marked species. Its total length is from 12 to 14 inches; most of the other species are much smaller.

Kangaroo rats of many species are distributed over most of the arid and semiarid regions of the United States and Mexico, from Nebraska, Oklahoma, and the Gulf Coast of Texas west to the Pacific coast, and from Montana and Washington southward to the Valley of Mexico and throughout Lower California. They are especially numerous in the southwestern deserts, where they are the oddest and most picturesque of animals.

Although they have no near relatives in the Old World, some of the African and Asiatic jerboas are externally almost perfect replicas of the kangaroo rats in every detail of form, color, and color pattern, even to the tail markings. This extraordinary likeness in appearance of two widely separated and unrelated animals is made doubly significant by the fact that both live in deserts and have similar habits.

Peculiarly desert animals, kangaroo rats live like the pocket mice, without drinking, but obtain the necessary water through their digestive processes. They are most numerous in sandy areas, and there the earth is sometimes so riddled by their burrows as to render horseback riding difficult.

Kangaroo rats are nocturnal and always live in burrows dug by themselves. As a rule they prefer soft or sandy ground, but some species occupy areas where the earth is hard and rocky. The burrows of some species have only one or two entrances with a small amount of earth thrown out, but others make little mounds with several openings, entering usually nearly on a level or at a slight incline. These openings are nearly always conspicuous, and while frequently near bushes, no effort appears ever to be made to conceal them, and a little trail often leads away through the soft earth.

The large Dipodomys spectabilis, which lives mainly in New Mexico and Arizona, constructs the most notable of all the dwelling places of these animals. From its underground workings it throws up large mounds of earth, which gradually increase in size with the length of time they are occupied until they are sometimes more than 3 feet high and 15 feet or more in diameter. From three to a dozen burrows enter these mounds, usually at the surface level of the ground, but some are on the slopes of the mound. The mounds, usually located in open ground, with their round entrance holes from four to five inches in diameter, are extremely conspicuous.

Although generally scattered at varying distances from one another, the mounds are sometimes grouped in colonies. Well-worn trails three or four inches broad lead away from the entrances, some to other mounds showing neighborly intercourse and others far away to the feeding grounds, sometimes 200 or 300 yards distant. One of the openings at the side of the mound is usually the main entrance, and by day this is ordinarily kept stopped with fresh earth. Within the mound and farther under ground are dug a series of ramifying passages, among which are located roomy nest chambers and store-rooms for food.

Kangaroo rats are not known to hibernate in any part of their range. They lay up food for temporary purposes at least and do not go abroad in stormy or cold weather. The northern species and those on the colder mountain slopes must make large store against the winter needs. Their food consists mainly of seeds, leaves of several plants, and of little plants just appearing above ground. Tiny cactus plants and the saline fleshy leaves of Sarcobatus are often among the kinds gathered for food.

The big Dipodomys spectabilis appears to be more social than most of its kind, as several may be caught in a single mound, and, as already said, well-worn trails lead from mound to mound. A little noise made just outside one of these mounds usually brings a reply or challenge in the form of a low drumming or thudding noise, no doubt made by the animal rapidly striking the ground with its hind feet like a rabbit or wood rat.

When caught they at first struggle to escape, but, like a rabbit, do not offer to bite, and soon become quiet. They have from two to six young, which may be born at any season. Nothing appears to be known concerning the number of litters in a year.

When in camp at San Ignacio, in the middle of the desert peninsula of Lower California, I had an unusual opportunity to learn something of the habits of one of the smaller species of kangaroo rat abundant there. The moon was at its full, and in the clear desert air its radiance rendered objects near at hand almost as distinct as by day. Scattered grains of rice and fragments of food on the ground about the cook tent attracted many kangaroo rats and pocket mice.

During several nights I passed hours watching at close range the habits of these curious animals. As I sat quietly on a mess box in their midst both the kangaroo rats and the mice would forage all about with swift gliding movements, repeatedly running across my bare feet. Any sudden movement startled them and all would dart away for a moment, but quickly return.

Although the kangaroo rats did not become so fearless and friendly as the pocket mice, they were so intent on the food that at times I had no difficulty in reaching slowly down and closing my hand over their backs. I did this dozens of times, and after a slight struggle they always became quiet until again placed on the ground, when they at once renewed their search for food as though no interruption had occurred.

One night, to observe them better, I spilled a small heap of rice on the sand between my feet. Within two or three minutes half a dozen kangaroo rats had discovered it and were busily at work filling their cheek pouches with the grains and carrying them away to their store chambers.

While occupied in this rivalry for food they became surprisingly pugnacious. If one was working at the rice pile and another rat or a pocket mouse approached, it immediately darted at the intruder and drove it away. The mode of attack was to rush at an intruder and, leaping upon its back, give a vigorous downward kick with its strong hind feet. Once I saw a pocket mouse kicked in this way. It was knocked over and for a minute or more afterwards ran about in an erratic course, squeaking loudly as though in much pain.

Sometimes the pursuit of one kangaroo rat by another continued for twenty yards or more. By the time the pursuer returned another would be at the rice pile and it would immediately dash at the victor of the former fray and drive him away. In this way there was a constant succession of amusing skirmishes.

Sometimes an intruder, bolder than the others, would run only two or three yards and then suddenly turn and face the pursuer, sitting up on its hind feet like a little kangaroo. The pursuer at once assumed the same nearly upright position, with its fore feet close to its breast. Both would then begin to hop about watching for an opening. Suddenly one would leap at the other, striking with its hind feet exactly like a game cock. When the kick landed fairly on the opponent there was a distinct little thump and the victim rolled over on the ground. After receiving two or three kicks the weaker of the combatants would run away.

The thump made by the kick when they were fighting solved the mystery which had covered this sound heard repeatedly during my nights at this camp. The morning light revealed a multitude of little paired tracks made by the combatants in these battles. Such tracks in the sand have been referred to as the “fairy dances” of these beautiful little animals, but the truth revealed proves them to be really “war dances.”

THE BANDED LEMMING (Dicrostonyx nelsoni and its relatives)

(For illustration, see page 519)

Banded lemmings are unique among the mouse tribe in their change from the rufous brown, or gray summer coat to pure white in winter. With the assumption of the white winter fur a thick, horny, padlike growth develops on the underside of the two middle claws of the front feet, which is molted in spring when the winter coat is lost. For an animal living in the far North the usefulness of a white coat in winter is evident, but no good reason is apparent for these curious claw-pads.

The summer coat varies remarkably in color and color pattern, and many of the lemmings in their beautiful shades of chestnut, browns, or grays are very handsome. They are more heavily proportioned than field mice and the very long fluffy fur, which completely conceals the rudimentary ears and tail, tends to exaggerate their size.

The banded lemmings form a strongly marked group, containing a number of species inhabiting circumpolar regions. In North America they occur nearly everywhere in the arctic and subarctic parts, including Greenland, most of northern Canada, including the Arctic islands, and a large part of Alaska, including some of the Aleutian Islands.

They range as far northward as vegetation affords them a proper food supply and have been well known to many of the explorers of those stern northern wilds. To the southward they extend into the subarctic northern forests, where they usually keep to the open barren areas.

Not much is known of their life histories on this continent. They are mainly nocturnal and live in burrows from two to three feet long, ending with a nest chamber four or five inches in diameter, warmly lined with grass and moss. Near the nest there is usually a branch burrow a foot or more long which is used for sanitary purposes and as a place of refuge when the main burrow is invaded.

In the nests during early summer litters generally containing about three young are brought forth. Ordinarily the burrows open in unsheltered places, but in wooded regions may be under a log or beneath a bush or the roots of a tree. No runways lead out from the burrows as is customary with many of their relatives. They are active throughout the winter, making many tunnels along the surface of the ground under the snow, which are revealed when it melts in spring.

These surface tunnels are their foraging roads, safe from most of the fierce storms which rage overhead. At times, however, the snowy shelter is blown away or some other cause brings the lemmings to the surface, where they blunder aimlessly about, soon to be captured by some enemy or to perish from the cold. As their infrequent appearance on top of the snow is usually during storms, the Alaskan Eskimos have a legend that these white lemmings live in the land above the stars and descend in a spiral course to the earth during snowstorms.

Although banded lemmings never become so extraordinarily numerous over great areas as the brown species, they become very abundant at times in the barren grounds of Canada and the Arctic islands and migrate from one part of their range to another. The best observation in regard to this was made by Rae in June at the mouth of the Coppermine River. On the west bank of the river north of the Arctic Circle he encountered thousands of them speeding northward.

The ice on some of the smaller streams had broken up and he was amused to see the little animals running back and forth along the banks looking for a smooth place in the stream, indicating a slow current, where they could swim across. Having found such a place, they at once jumped in and swam quickly to the opposite side, where they climbed out and, after shaking themselves like dogs, continued their journey as though nothing had happened.

During the years I lived in northern Alaska the advent of winter was marked by invasion of the storehouses by many brown lemmings and other mice, but banded lemmings rarely appeared. When occasionally captured alive, the old ones fought viciously, but the young were gentle and quickly became tame and interesting pets. Their skins were highly prized by the little Eskimo girls to make garments and robes for their walrus ivory dolls.

THE BROWN LEMMING (Lemmus alascensis and its relatives)

(For illustration, see page 579)

Few small mammals are so well known in far northern lands as the brown lemmings. They form a small group of species having a close general resemblance to some of the field mice, from which, however, they may at once be distinguished by their much heavier proportions, extremely short tails, and the remarkable length of the hair on their backs and rumps.

They inhabit most of the arctic and subarctic lands of both Old and New Worlds. In North America they are known from the northernmost lands, beyond 83° north latitude, to the southern end of Hudson Bay, and throughout most of northern Canada and all of Alaska, including the islands of Bering Sea.

The extraordinary migrations of these lemmings have attracted attention far back in the early history of northern Europe. At intervals, through favorable conditions, they become superabundant over a large area, and then a sudden resistless desire to migrate in a certain direction appears to seize the entire lemming population. The little beasts start in a swarming horde, sometimes containing millions, and traverse the country.

In their travels they appear indifferent to all obstacles and with dogged and unwavering persistence swim the streams and lakes encountered on their way. Similar migrations have been observed at various points in Arctic America, several of them in Alaska, where the lemmings abound on the open tundras.

These migrations sometimes continue for more than one season, the animals meanwhile being killed in countless numbers by disease, by accident in field and flood, and, in addition, through the heavy toll taken from their numbers by their winged and four-footed foes, which always gather in numbers to accompany them.

The migrations sometimes wear out through the diminution in numbers, and sometimes when they reach the sea, as in Norway, they are said to enter the water and swim offshore until they perish. When one of these swarms of rodents passes through a farming district it cleans up the crops and other surface vegetation like a visitation of locusts.

These lemmings do not hibernate, but, active throughout the severest winters, are abroad almost equally by day and by night. Their burrows consist of winding tunnels, often many-branched and with more than one opening. A dry bed of peat or a dense growth of moss is often pierced by a network of them. Well-defined runways often lead away from the burrows or from the entrance of one burrow to that of another.

Their tunnels run everywhere under the snow, with occasional passages leading to the surface. When fierce gales blow away the snow or a winter rain melts it, many lemmings lose touch with their burrows and wander about until they perish from cold or are caught by some enemy. They are sometimes found several miles from shore, where they have strayed out on the sea ice.

In winter in the fur countries, in company with field mice, they invade storehouses and habitations in search of food. Among their enemies are ravens and all northern hawks and owls, as well as foxes, weasels, lynxes, bears, and other beasts of prey of all degree.

Within their underground tunnels and often in dense vegetation on the surface lemmings make warmly lined nests of grass and moss in which their young, from two to eight in number, are born. The young appear at varying times, thus indicating several litters each year.

When taken alive, the old ones are fierce and courageous, growling and fighting savagely; but several half-grown young brought me during my residence in Alaska proved to be most amusing and inoffensive little creatures. From the first they permitted me to handle them without offering to bite and showed no signs of fear.

They were kept in a deep tin box, from which they made continual efforts to escape. When I extended one finger near the bottom of the box they would stand erect on their hind feet and reach up toward it, using their forepaws like little hands. If my finger was lowered sufficiently they would climb up into my hand and thence to my shoulder, showing no sign of haste, but much curiosity, continually sniffing with their noses and peering at everything with their bright beadlike eyes.

They were curiously expert in walking on their hind feet, holding the body in an upright position and taking short steps. If anything was held just out of reach above their heads, as the point of my finger, they would continue in an erect position for a considerable time. At such times they would reach up with their front paws and often spring up on their hind feet for half an inch above the floor trying to touch it. When eating they sat upright on their haunches, like little marmots, and held the food in their front paws.

THE COMMON FIELD MOUSE, OR MEADOW MOUSE (Microtus pennsylvanicus and its relatives)

(For illustration, see page 522)

The Pennsylvania meadow mouse is a small species about as long in body as the house mouse, but much more heavily proportioned. Its head is rounded, the eyes small and beadlike, the legs and tail are short, and the comparatively coarse fur is so long that it almost conceals the short, rounded ears.

It is a typical representative of a group of small mammals commonly known as field mice, or “bear mice,” which includes a great number of species closely similar in general appearance, but varying much in size. In England they are termed voles, and large species living about the water in England and northern Europe are known as “water rats.”

Field mice are circumpolar in distribution and abound from the Arctic barrens, beyond the limit of trees, to southern Europe and the Himalayas, in the Old World, and to the southern United States and along high mountains through Mexico and Guatemala, in Central America. They occur in most parts of the United States except in some of the hotter and more arid sections.

As a rule field mice prefer low-lying fertile land, as grassy meadows, but the banks of streams, the rank growths of swamps and marshes, the borders of damp woodlands, the grassy places on Arctic tundras, or the dwarfed vegetation of glacial slopes and valleys above timber-line on high mountains furnish homes for one species or another.

Two, and even three, species of field mice are sometimes found in the same locality, but each kind usually occupies a situation differing in some way from that chosen by the others. Some occupy comparatively dry ground and others, like the European water rat, live in marshes and are almost as aquatic as the muskrat. Most species living about the water are expert in diving and in swimming, even under water. In streams inhabited by large trout they are often caught and eaten by the fish.

The presence of field mice is nearly always indicated by smoothly worn little roads or runways about an inch in width, which form a network among the vegetation in their haunts. These runways lead away from the entrances of their burrows and wind through the vegetation to their feeding grounds. They are kept clean and free from straws and other small obstructions, so that the owners when alarmed may run swiftly to the shelter of their burrows. Fully conscious of their helplessness, meadow mice are as cautious as the necessities of existence will permit.

Their burrows are often in the midst of grassy meadows, as well as under the shelter of logs, rocks, tussocks of grass, or roots of trees, and lead to underground chambers filled with large nests of dry grass, which shelter the owner in winter and often in summer. The summer nests in many places, especially in damp meadows or marshes, are made in little hollows in the surface or in tussocks of grass. In these nests several litters containing from four to eleven young are born each year.

It is rarely that an observer is located where he can study the every-day lives of little animals like the meadow mice and at the same time go on with his regular occupation. At one of my mountain camps in Mexico I fortunately pitched my tent on a patch of lawn-like grass in front of the ruins of an abandoned hut. Runways of field mice formed a network everywhere in the surrounding growth of grass and weeds.

For hours at a time as I worked quietly in the tent the many mice, unconscious of my presence, came silently along their little roads through the tall vegetation to the border of the short grass. Just within the shelter of the tall growth they would each time stop and remain watchfully immovable for a half minute, and then, if everything was quiet, make a swift run two or three feet into the open, bite off a tender little grass blade and dash back to the sheltered road. There they would sit up squirrel-like, holding the grass blades in their forepaws and eating them rapidly, or would sometimes carry the food back to the burrows.

Occasionally as the mice darted into the open I made a slight squeaking noise and perhaps two or three in sight at the time would instantly turn and dash back into the sheltered road, sometimes not reappearing for a long time. Again and again I saw them come into the open for food, and before securing it suddenly scamper back in a panic without apparent cause for alarm.

Eternal vigilance is the only defense such animals have, and despite their watchfulness myriads of them are devoured daily by a large number of rapacious birds and mammals, including even such huge beasts as the great Alaskan brown and grizzly bears, which dig them from their burrows on grassy northern mountain sides.

Despite their numerous natural enemies field mice are so prolific they continue among the most destructive of agricultural pests. They are so obscure and the damage by a single mouse appears so insignificant, that it requires a knowledge of their habits, their wide distribution, and their enormous numbers to appreciate what a serious drain they are on the farmer’s income, even when in their normal numbers.

In summer they feed on growing grass, clover, alfalfa, and grain, seeds, bulbs, root crops, and garden vegetables. In fall they congregate under shocks to feed on the grain, and in winter often do enormous injury to young or even well-grown fruit and other trees by gnawing off the bark on the base of the trunk and roots, sometimes in this way destroying entire orchards and nurseries.

One species in California destroys large quantities of raisins drying in the field by carrying them off to some shelter, where they cut out the seeds and leave the rest of the fruit. I have seen half a pound of raisins under a piece of board, the result of the night’s work of a single mouse.

While field mice are always destructive, at intervals they have sudden and mysterious accelerations of increase and become so excessively abundant that they are a veritable plague. Many instances of this are on record in the Old World, where they have become so numerous as to call forth governmental intervention.

The most notable recent outbreak of this kind in the United States took place in the Humboldt Valley, Nevada, where, during the winters from 1906 to 1908, they swarmed over the cultivated parts of the valley and completely destroyed 18,000 acres of alfalfa, even devouring the roots of the plants. During this outbreak the mice in the alfalfa fields were estimated to number as high as 12,000 to the acre.

Whenever field mice become over-abundant notice appears to go out among their natural enemies, and in extraordinary numbers hawks, owls, crows, ravens, sea gulls, coyotes, foxes, bobcats, weasels, and other animals appear to prey upon them.

At no season of the year are they free from their foes, for they remain active throughout the winter, and most species apparently lay up no winter store of food. They travel to winter feeding places through series of tunnels under the snow, and it is mainly at this season that they do the most serious damage to orchards and shrubbery.

In the far North at the beginning of winter they gather in large numbers about the fur-trading stations and other habitations, where they persistently invade the food supplies.

Some of the northern mice, however, gather stores of food for winter. A species living along the coast of the Bering Sea and elsewhere on the Arctic tundra of Alaska accumulates a quart or more of little bulbous grass roots, which are delicious when boiled. They are hidden in nests of grass and moss among the surface vegetation, and before the first snowfall I have seen the Eskimo women searching for them by prodding likely places with a long stick. The roots thus taken from the mice are kept to be served as a delicacy to guests during winter festivals.

THE PINE MOUSE (Pitymys pinetorum and its relatives)

(For illustration, see page 522)

The pine mice form a small group of species peculiar to North America and closely related to the field mice. They are similar in form to the common field mice of the Eastern States, but are usually smaller, with much shorter tails and shorter, finer, and more glossy fur.

Most of the pine mice are limited to the wooded region of the States between the Atlantic coast and the eastern border of the Great Plains, and from the Hudson River valley and the border of the Great Lakes south to the Gulf coast. Strangely enough, one species lives in a restricted belt covered with tropical forest along the middle eastern slope of the Cordillera, which forms the eastern wall of the Mexican tableland, on the border between the States of Vera Cruz and Puebla.

Pine mice occupy the borders of thin forests and brushy areas, from which they work out into the open borderlands, especially in orchards or other places where there are scattered trees amid a rank growth of weeds. Instead of making their runways among growing vegetation on the surface of the ground like field mice, they live in little underground tunnels or burrows which extend in all directions through their haunts. These tunnels are closely like those of the common mole except that they are smaller and have frequent openings to the surface, through which the owners make short excursions for food. They often utilize the tunnels of moles when conveniently located for their purposes.

The tunnels are often so near the surface that the ground is slightly uplifted or broken as by a mole, or they are made under the fallen leaves and other small decaying vegetable matter covering the ground under the trees. Occasionally, when the surface soil becomes dry and hard, the burrows are deeper, so that no surface indications can be discovered. On account of the similarity of their burrows the depredations of pine mice are commonly attributed to moles.

Several inches below the surface pine mice excavate oval chambers to be used for nests or for storage purposes. The nest chambers have several entrances from ramifying tunnels and are filled with short fine pieces of grass, making a warm nest-ball. Here the several litters of young are born each year. Pine mice are less prolific than field mice, however, and the litters contain only from one to four young.

The food chambers are larger than the nest chambers, and when full of stores are kept closed with earth. In these are stored short sections of green or dry grasses, bulbous grass roots, and short sections of other edible roots. One such store contained about three quarts of the fleshy roots of a morning glory cut into short sections.

Pine mice obtain much of their food from the bark about the bases and roots of trees, including both coniferous and deciduous species. They kill many small trees and shrubs by girdling, or by cutting the roots below the surface, and in this way frequently inflict severe damage in orchards and nurseries. Owing to their underground habits they are much more dangerous to orchards than field mice. They also do much damage by burrowing along rows of potatoes and other root crops, upon which they feed.

Both pine mice and field mice are serious pests to agriculture and only by vigilant care can they be prevented from steadily reducing the returns from farm and orchard. A mouse appears so insignificant an enemy that the general inclination among farmers is to ignore it, but both field and pine mice exist in such enormous numbers and are so generally distributed that the aggregate annual losses from them are great.

Clean cultivation in orchards, especially for some distance immediately about the trees, is an excellent protective measure against both of these mice. The shrubbery and fruit trees of orchards, lawns, and gardens may be protected by the use of poisoned baits and traps as soon as signs of pine mice or field mice are observed.

THE RED-BACKED MOUSE (Evotomys gapperi and its relatives)

(For illustration, see page 523)

With the exception of the banded lemmings the red-backed mice are the most brightly colored of the smaller northern rodents. They are close relatives of the common field mice, which they about equal in size, but from which they are distinguished externally by rufous coloration, finer and more glossy pelage, larger ears, and proportionately longer tails.

The red-backed mice form a group containing a considerable number of species distributed throughout the northern circumpolar lands, except on the barren islands of the Arctic Sea. In North America they occur from the Arctic tundras north of the limit of trees southward throughout Alaska and Canada to the northern United States. With other northern species of mammals, birds, and plants they follow the high mountain ranges still farther southward to North Carolina, New Mexico, and middle California.

It is true that in the far North they are numerous on the moss-grown tundras, and in the South range above timber-line on high mountains. As a general rule, however, they are woodland animals, whether among the spruces, birches, and aspens of the North or farther south in the United States in the cool fir and aspen-clad slopes of mountains. They also frequent old, half-cleared fields, brush-grown or rocky areas, and similar places where cover is abundant.

Although so closely related to the field mice, the red-backed species are not known to become excessively abundant nor seriously to injure crops. One reason for their harmlessness in this respect may be their strong preference for forest haunts.

I once found them numerous in the grass-grown streets and yards of an abandoned mining camp in the forest at the head of Owens River, in the Sierra Nevada, of California. The mice were making free use of the congenial shelter afforded by the old log cabins, and their runways and entrances to burrows were all about under scattered boards and similar cover.

They are abroad equally by day and by night, and for this reason are better known to woodsmen than most of the small woodland animals. When foraging by day among the fallen leaves and deep green vegetation they present a most graceful and attractive sight, now moving about with quick and pretty ways, now pausing to sit up squirrel-like to eat some tid-bit held in the front paws and then on the alert to detect a suspected danger and poised in quivering readiness for instant flight.

Red-backed mice usually live in underground burrows similar to those of field mice, but generally located with more care in dry situations, the entrances sheltered by a stump, old log, root of a tree, rock, or other object. Ordinarily they do not make such well-defined runways as do many field mice, and sometimes no trace of a trail can be found leading away from their burrows. But where they travel about through small dense vegetation, under logs and about stumps and rocks they often make well-marked trails.

Their nests are bulky and formed of a mass of fine dry grass, moss, and other soft material, which is sometimes located in an underground chamber opening off the burrow and sometimes in hollow stumps and logs or under other surface shelters. But little is known about the home life of these mice except that they are prolific, and between April and October have several litters containing from three to eight young in each.