Sciurus carolinensis hypophaeus Merriam, Science, vol. 7, p. 351, 1880.
      Type locality.--Elk River, Minn.
      General characters.--Larger and darker colored than the Carolina gray squirrel, with little or no white on the underparts. Color, generally dark gray, often becoming dusky or black. Tail, large and bushy. Average measurements of adult specimens: Total length, 496 millimeters; tail, 220; hind foot, 67. Weight of adult female, 14 ounces (Murie).
      Distribution and habitat.--The large Minnesota gray tree squirrels barely come into the southeastern part of North Dakota along some of the timbered stream valleys, although they are abundant throughout the oak region of Minnesota. At Wahpeton, in 1915, an old resident said that he had killed one there 18 years before, but had never seen one since. Later, some squirrels had been brought from Minnesota and placed in a grove on the Dakota side of the river, but they were not protected and all were killed. At Fargo and Moorhead, O. J. Murie remembers them as long ago as 1906, and thinks they have always been there. Since 1910, they have been increasing and in 1919 were common on both sides of the river, and especially in the extensive and beautiful parks just south and north of Fargo, where an abundance of old hollow trees, oak, basswood, elm, and ash, furnish safe homes and choice food. At Valley City, in 1912, Eastgate reported them as introduced in the city parks and slowly increasing. In Minnesota their northern limit seems to be in the vicinity of Crookston, and it would be strange if they did not occasionally extend into the Red River Valley in the neighborhood of Grand Forks. Records, however, are wanting north of Fargo.
      General habits.--Besides being good game animals, these large, handsome squirrels are one of the popular attractions of city parks and protected grounds, where they readily become familiar and, with a little care, very tame. Constant hunting keeps them extremely [p.46] shy and secretive in their wild state; but, for rodents, they show a high order of intelligence and quickly learn the protected areas, eagerly responding to friendly advances in the way of food, water, and nest boxes. In their native habitat their food consists very largely of acorns from the numerous species of oaks with which they are associated, but it also includes nuts and seeds of many other plants. For a successful introduction into parks or private grounds they must he supplied with acorns, nuts, or grain.
      Their winter homes are usually in the hollow trunks of trees, where in well-protected and warm nests of bark and plant fibers they pass the coldest winter weather in comfort. In summer they build large nests of leaves in the branches of the trees, covering them over to form comfortable, rain-proof houses, with nest cavities in the center, which they enter through half-concealed side doors. In some cases the houses are made large and warm for occupation throughout the winter, but usually a hollow trunk or warm box is preferred for a winter residence.
      The interest and delight of children in watching the squirrels, which in parks and private grounds become so tame that they will come to the hand and beg for nuts gives them a value far greater than that of game and fully repays the effort to provide them with comfortable quarters and to plant such trees as will insure their permanent food supply.

FIG. 1.--Records of three species of chipmunks in North Dakota: Squares, Gray chipmunk; triangles, little northern chipmunk; circles, pale chipmunk

FIG. 2.--Distribution of the thirteen-lined ground squirrel (1), and its pale western form (2), in North Dakota

FIG. 3.--Records of the Franklin ground squirrel in North Dakota

      General habits.--Although occasionally seen up among the branches of low trees, the Franklin squirrels are strictly ground squirrels, living in burrows generally concealed in brush or weed patches, from which well-worn trails or runways radiate to other burrows or feeding grounds. They are shy and secretive, keeping much under cover of protecting vegetation, as they are too large and dark colored to be inconspicuous the open. When frightened they rush for their burrows, usually uttering a trill of alarm and warning to other members of the family. Their voice is much like that of the thirteen-lined ground squirrel but is as much heavier as they are larger. It is often heard in a long bubbling trill from a weed patch and is almost birdlike in musical quality.
      In the timber and brush patches along the Red River Valley, about Stump Lake, Devils Lake, the Sweetwater Lakes, and in the Turtle Mountains, the squirrels are especially numerous and in such situations they are generally the most abundant of the three species of ground squirrel occupying the general region. Throughout the Turtle Mountains they were found along the edges of meadows, fields, and clearings along roadsides, and in all the open places where woods and small brush served for cover. They gathered around camps or dwellings where there were no dogs or guns and even came into the writer's cabin and helped themselves from the grub box. They persisted in getting into traps set for others long after enough of them had been secured for specimens and most of the trails and runways attributed to other animals proved to belong to them.
[p.57] Their burrows were generally in groups of three or four, or more, not far apart and evidently connected below ground. They were in all sorts of situations, but a sloping bank, brush heap, old log, or stone pile usually provided the protection sought for their dens. A considerable quantity of earth is usually thrown out in front of one of the burrows but others open out with less conspicuous markings. Many old dens and burrows are located through the brush and woods and one seems always to be convenient when danger approaches. Often the animals will stop at the entrances of their burrows and straighten up in the picket-pin attitude, to make sure whether an enemy is pursuing. If approached too closely, they quickly dive into their burrows with a flirt of the tail and a parting chatter, but if all is quiet they soon reappear cautiously to reconnoiter.
      Franklin squirrels are easily tamed and make interesting, though rather mischievous, pets. H. V. Williams, at Grafton, had a tame one for which he made a den by burying a box underground. The squirrel carried about a half bushel of grain into this box, and in fall hibernated as usual. When examined in January it was unconscious, but before its awakening time in spring water ran into the box and it was drowned. While collecting specimens at Fish Lake in the Turtle Mountains, Williams fed one around his tent until it became so tame as to take food from his hand and come to the tent regularly at meal times. It finally became so bold that it would enter the tent and search through the baggage for food. After breaking and carrying off a lot of birds' eggs that had been collected for specimens it had to be killed to prevent further trouble.
      Hibernation.--With the first freezing weather in fall, usually in September, Franklin squirrels go to their nests deep underground and usually do not reappear until the following April. Before entering upon their hibernation they become very fat and depend upon this concentrated form of nutriment to carry them through the winter rather than upon the ample stores of food laid up in convenient chambers near their nests. Just when these stores are eaten is not well known, but probably before the squirrels have become entirely inactive in fall and again before the outside food supply is available in spring.
      Breeding habits.--Their half dozen young are usually born in May or June and by the last of July are half-grown squirrels, out of the burrows, and hunting for their food.
      Food habits.--Living largely upon nuts, seeds, and grain, these squirrels show an appetite for a wide range of food. The examination of a large number of stomachs and cheek pouches shows their food to consist not only of a great variety of grains and seeds, but also of berries, green vegetation, roots and bulbs, beetles, caterpillars, grasshoppers, crickets, ants, and eggs and pupae of insects. They also eat young birds, birds' eggs, and young mice, and are said to kill young chickens. When caught in traps or found dead they are even eaten by their own kind. They feed upon grain from the time the seed is planted until the last bundle is removed from the fields. Unlike the smaller ground squirrels, they do not cut the standing grain, but pull down the heads and in this way destroy the grain even more rapidly. In their capacious cheek pouches seeds of [p.58] grain are rapidly carried to their winter storehouses. Where a large number of the squirrels gather along the edge of a field they will often harvest considerable of the grain after having fed upon it during every stage of its growth through the summer.
      Economic status.--To a great extent the Franklin squirrels occupy the limited areas where the other two ground squirrels of the State, the thirteen-lined and the Richardson, are absent or less numerous. In extensive areas, therefore, they are the dominant species and levy their toll of destruction on the grainfields and gardens that otherwise would be comparatively safe. In some places, however, the three species occupy the same ground and in combined numbers cause enormous losses of crops. Although larger and according to their numbers possibly more destructive to grain than the Richardson squirrels, the Franklin ground squirrels are apparently less numerous in most of their habitat. They are easily poisoned and their abundance may be controlled at comparatively little expense, using the same methods as recommended for the Richardson, or flickertail.

FIG. 4.--Records of the Richardson ground squirrel in North Dakota

      General habits.--Originally the flickertails had a continuous distribution over the prairie in great numbers. On some favorite slopes they were so numerous as to suggest a colonial tendency, but apparently this only showed a preference for certain kinds of ground yielding an abundant food supply.
      In 1887, when much of the prairie was still unbroken, they were living in their primitive manner on such food as the prairie afforded and doing practically no harm except as grainfields and crops encroached [p.59] upon their original range. Their greatest numbers often appeared to be in the areas of the shortest grass and lowest vegetation, possibly because the grasshoppers and other insect life on which they fed to some extent were most easily obtained there. In places the prairie seemed alive with them and they could be seen scampering about together or standing up like picket-pins, while their shrill whistle was heard on all sides. With each call-note their short little tails are flipped up and down, a farewell twinkle being given as they disappear down the burrow, hence the popular name of "flickertail." In 1887 they were often seen also in the main streets of Devils Lake and Bottineau, which were then in their early stages of construction, and in 1916, it was most surprising to find them still occupying vacant lots on the edge of the city of Devils Lake. It was a striking illustration of their tenacity in holding to their original habitat through years of vigorous but sporadic efforts to destroy them.
      As soon as the grainfields spread over their range they quickly gathered along the edges to feast on this wonderful new and abundant food. They did not long confine themselves to the edges of the field, however, but went into the middle of large cultivated areas and made their burrows in the plowed ground or in the growing grain.
      No reliable estimate of their numbers can be obtained, but a general idea of their abundance may be gained from the statements of Elmer T. Judd, of Cando, in a letter of August 1, 18,90, in which he, says:

      An old gentleman here killed 1,500 'gophers' by actual count, before the first of June. From the first of June to the middle of July, he and a cotton broker from St. Louis, who spends the summer here on his farm, calculated that they killed over 2,500 more. One forenoon they killed 135, as shown by the tails they had captured.

FIG. 5.--Distribution of prairie-dog towns in North Dakota

      In 1915, U. S. Ebner, in charge of field operations in the rodent control work of the Biological Survey in cooperation with the North Dakota Agricultural College and Experiment Station, investigated the prairie-dog situation over a part of the range west of the Missouri River. He reported small prairie-dog towns covering 25 to 250 acres scattered along the Little Missouri River in Billings County, larger colonies of 60 to 640 acres in the northern part of Dunn County, a number of towns of 20 to 160 acres along Big Beaver Creek in the northern part of Golden Valley County, other towns of 25 to 500 acres in the eastern part of McKenzie County, and some large towns running as high as 600 acres on the Berthold Indian Reservation. In most of these prairie-dog towns he estimated 20 to 40 burrows to the acre.
      Although these records show only the colonies that have been located, they indicate a very general distribution of prairie dogs over this part of the State, and a careful survey would doubtless show a surprising number of inhabited prairie-dog towns in a region that is rapidly filling up with grainfields.
      As a general thing the colonies are located on the open level prairie and often on the best of the grain land. In the Badlands they are usually on the flat and level spaces where the best grass grows, always away from the brushy and barren areas.
      General habits.--Prairie dogs are highly social in disposition, almost invariably living in colonies. On rare occasions a new location is chosen where family or a few prairie dogs have started a colony, but generally there is evidence of their long residence. The old burrows and mounds remain for many years and the sites of ancient prairie-dog towns are marked by little swells of grassy turf scattered over the prairie.
      A well-populated prairie-dog town on a bright summer morning is as animated as any busy village could well be. At the first appearance of the sun the animals come out of their burrows and begin their breakfasts of grass and roots, most of them busily digging up grass and little plants for food, nibbling off the grass blades and [p.65] plant leaves like rabbits, or sitting up holding them in their hands like squirrels. There are always, however, a few on sentinel duty, usually sitting straight up on the highest mounds, or stretching up occasionally to full height from the grass where they are feeding. Some are always scampering from one point to another, and when the young are out there is much playing and scuffling among them.
A populous town of prairie dogs, all busy and many of them calling back and forth, with a few on sentinel duty, barking in steady little yap-yap-yap-yaps at some real or imaginary enemy, makes an interesting picture. If an enemy really approaches, the barking becomes frantic and is taken up by other members along the line, and there is a general scamper for the nearest burrows. If one walks toward them to within rifle range the panic increases and the nearest animals rapidly disappear down the burrows with a farewell twinkle of their tails. The barking passes along farther and farther through the town, usually beyond where the enemy can be seen, every prairie dog taking notice and most of the them joining in the alarm. Occasionally one of the guards will stretch up to its utmost height and throwing its head back utter a long Chu-r-r-r-r-r-r-r-r-r-r, as if a dozen barks were crowded into one. This seems to be their only note besides the regular yap-yap, and a chuckling, scolding Chu-r-r-r-r-r, after entering their burrows, as if they were grumbling at having been disturbed.
      The burrows are deep and go down at steep angles, sometimes almost straight down, for 2 or 3 feet and then slope off gradually. A pebble dropped into one can be heard rolling and bounding down, often for 5 or 6 feet, and a prairie dog with a string tied to its hind foot will sometimes take down 12 or 15 feet of string before reaching the end of the tunnel. The burrows are simple and almost never lead out to a second opening.
      The nest, instead of being at the lowest point, is usually in a chamber well protected from any rain water that may run down the burrow. As a further protection the earth thrown out is carefully placed around the entrance to form a craterlike rim that serves the double purpose of a watch tower and a dike to prevent the entrance of water from heavy rains.
      Originally the mound is built of the earth brought out of the burrow, but later fresh earth is scraped up from outside and brought back and added to the sides, and when the ground is moist after a rain the mound is carefully formed and patted and pushed with the end of the nose until externally it has the most approved slopes and internally the correct funnel form. A well-kept mound shows numerous dents and dimples where pushed and poked with the pudgy noses of the prairie dogs. Many old burrows with neglected and broken mounds are used, but the main nest burrows are always kept in good condition. Nest material of dried grass and soft plant fibers is carried into the burrows and the old material is occasionally brought out and scattered about the entrance. The cheek pouches of the prairie dogs are small and little used, and apparently no food is stored.
      Breeding.--The 4 to 6 or 8 young are born early in May, but usually do not appear out of the burrows until the first or middle of June. They are then seen in family groups around the entrance to [p.66] their homes and always under their mother's watchful eye. At a signal from her they quickly rush to the burrow and disappear. As their experience increases they are left more to their own discretion, but even when half grown if danger appears the mother insists on their all getting down the burrow before she will enter. Small young are often seen later in the year, but in the northern part of their range it is doubtful if more than one litter is raised in a season, the late young probably being the first litter of females of last year's brood.
      Hibernation.--In fall the adults become very fat and the young moderately so. They are always ready to hibernate in case of very cold or stormy weather or deep snow, but do not enter their dens to remain unless cold weather comes. In mild seasons they are sometimes active until midwinter and may be seen foraging on warm days when there is no snow. In severe winters, however, they disappear for a long period and evidently pass completely into the state of hibernation. They are out with the first warm days of spring and in March, when a few sagebrush tops were the only visible vegetation, the writer has seen them sitting on top of 2 feet of snow through which they had burrowed to the surface. As soon as the snow is off in spring they find plenty of food in the dry grasses and roots, and their store of fat helps to carry them through the mating season.
      Food habits.--The food of the prairie dogs consists principally of grass, including seeds, leaves, stems, and roots, but it includes also everything that grows over the surface of the ground to a considerable distance around their burrows. The short blades of grasses are not only eaten off to the ground, but the roots also are dug up and the tender bottoms of many species are eagerly eaten. Other little plants are eaten to the ground and those with edible roots or bulbs are dug up and exterminated. Often tall plants, grasses, and weeds that have sprung up in the prairie-dog town are cut down, if not for food, to keep the ground clear and the view unobstructed. An old and well-populated prairie-dog town is often so completely cleared of vegetation that parts of it have to be abandoned, the animals moving on toward the best grass on the margins. In this way parts of the prairie are progressively denuded of vegetation.
      The stomachs of prairie dogs are relatively large, as in all grazing animals, and at any time of the day except early morning they are found well filled with finely masticated vegetation, usually showing a good combination of green and white pulp from the foliage, stems, and roots of plants, often with streaks of color from various kinds of flowers and seeds. Many ripening seeds are included in their food, and fields of grain tempt them to extend their colonies into this unusual food supply. When the dog towns are plowed up and seeded to grain the occupants cling to the old burrows with great tenacity, opening them up and if left undisturbed living in the midst of wide grainfields.
      Depredations.--An area occupied by a colony of prairie dogs may usually be considered stocked to its carrying capacity and of little or no value for grazing or agricultural purposes. It may also be considered that the area thus occupied is just so much withheld from [p.67] other use, and it is only a matter of determining the area of land given over to these animals to know the extent of the loss in grazing. If a well-populated prairie-dog town is plowed and seeded, prairie dogs will be the ones to harvest the grain unless they are first destroyed.
      Destruction of prairie dogs.--Fortunately prairie dogs are easily poisoned by the use of oats or other grains coated with strychnine, as described for the Richardson ground squirrel, and a farm suffering severe losses may be reclaimed at comparatively small expense. Full directions for preparing and using the poisons will be furnished by the Biological Survey on request.

FIG. 6.--Localities where woodchucks are known in North Dakota

      General habits.--These largest and least squirrel-like of the squirrel family have generally the burrowing habits of the ground squirrels and prairie dogs. They are mainly burrowing and grazing animals, occupying the region of rich plant growth rather than the short-grass prairie, and depending to a great extent on cover and concealment for protection. They are not colonial in habits, except as mother and young remain together during the season, but if undisturbed they often multiply so rapidly as to be seriously destructive to crops and forage.
      Their burrows are extensive, and instead of being one simple tunnel, usually open out in two or more directions from the central den. Near Larimore Kellogg dug out a den where an old female and her half-grown young were living. There were four entrances and three nests in different chambers. The nests were made of dry grass and leaves and one contained some fresh-cut plants, including nettles. The branches of the den were respectively 6, 7, and 9 feet long, but apparently there were other branches not discovered, as the old woodchuck and her young had been seen to enter the burrow, but could not be found. When first seen, one of the young was up in a basswood tree and when alarmed ran down into the burrow. These woodchucks are good climbers and in places where there are no fences or rocks to serve as watch towers, they are often found up in trees where a good view can be had. They also take refuge in trees to escape from dogs and other enemies. A family of seven young is reported from Manvel, by Kellogg, and this seems to be about the average number for the species.
      Food habits.--The food of woodchucks consists largely of green vegetation, with which their large stomachs fire usually filled. They are particularly fond of clover, alfalfa, or any of the native leguminous plants, but will eat grass and growing grain and vegetables with great relish. In fall, flowers, seeds, and grain furnish a richer food from which more rapidly to accumulate their winter fat. Apparently they do not lay up stores of food, but depend on finding an ample supply until time to hibernate, and in spring live on their store of fat until green vegetation is available. They usually come [p.69] out in spring while the ground is still covered with melting snow. Doctor Bell took a specimen at Fargo on April 29, 1906.
      Economic status.--The fondness of woodchucks for almost every kind of garden or field crop renders them serious pests wherever they are numerous. Here on the border of their range they may never become troublesome, but they should be watched and their numbers kept down wherever an undue increase is noticeable.
      It is unfortunate that the habits of so many of our native animals conflict with the interests of man, as their presence would otherwise add much to the interest of life. A few woodchucks in the meadow and along the fences, where their loud, shrill whistle is occasionally heard and where they are seen sitting up in the grass or on the fence watching for danger, or with flopping tails scampering to their burrows, would add a touch of life and interest to any landscape. Their depredations, however, are too serious to be taken lightly, and it is often necessary to destroy them. Usually they may be shot or trapped, or killed with carbon disulphide placed in their burrows, but they are not easily poisoned, as there is usually an ample supply of their favorite food within reach.
      Woodchucks as food.--Woodchucks have some value as food animals; their meat is like that of squirrels, but coarser. Many persons are fond of them, and in the markets they sometimes bring as much as a dollar each. There could be no cleaner or more exemplary animal in food habits and their underground dens are as clean and fresh as the abode of any burrowing animal. When necessary to destroy them their use as food should be encouraged.

[Glis] canadensis Erxleben, Syst. Regni Anim., p. 363, 1777.
      Type locality.--Quebec, Quebec, Canada.
      General characters.--In size somewhat smaller than rufescens. Color, strongly rufescent. Average measurements: Total length, 513 millimeters; tail, 108; hind foot, 76.
      Distribution and habitat.--From a range extending across Canada from Nova Scotia on the east to Fort Simpson on the Mackenzie, the small northern form of the monax group of woodchucks barely enters the extreme northeastern corner of North Dakota. One specimen collected at Pembina in 1887 was identified by Howell as belonging to this form. It was taken on the North Dakota side of the river, but after it had been seen to swim across from the Minnesota side. In 1915, Kellogg reported a few woodchucks at Pembina, but did not obtain any specimens. The river at this point has considerable timber along both sides, and woodchucks are likely to pass back and forth freely, if not during the summer, they certainly would early in spring before the river breaks up. At Walhalla they are fairly common, but by October 1, 1919, they had all denned up for winter. One found in the bank and later mounted was evidently the little dark-colored canadensis.
      General habits.--The only difference in habits between this form and the more southern rufescens may be attributed to climate and environment. With a longer winter, more snow, and a somewhat different set of plants from which to draw their food supply, these [p.70] rodents readily adapt themselves to local conditions. In the shorter season they are still able to lay up sufficient fat to carry them through the long, cold winters, and in spring they come out of hibernation even while the snow is still deep. As early as March 18, in northern Minnesota, they sometimes come out on 4 feet of snow, making tracks in the soft, melting surface or on the frozen crust and visiting back and forth from one burrow to another, opened out through snow tunnels. This is the mating season, and, according to Seton (1909, vol. 1, p. 426), the four or five young are born about the end of April. Over this great northern country they are generally harmless, except where locally they come in contact with fields and gardens.

[Mus] norvegicus Erxleben, Syst. Regni Anim., p. 381, 1777.
      Type locality.--Norway, where introduced in 1762.
      General characters.--Size, variable; ears, small; nose, long and pointed; tail, long, nearly naked, and minutely scaly; color, dull brownish-gray above, light or whitish below, occasionally bluish black. Measurements of average adults: Total length, 415 millimeters; tail, 192; hind foot, 43; measurements of a large individual, 468, 212, and 44, respectively. Weight of large individuals, about 1 pound.12
      Distribution and habitat.--The familiar house rats are not native to America, but came over on ships about 1775, and since then have spread over most of this country, except some of the arid interior. They follow railroads and settlements into every part of the country where they can find food and cover, preferring the buildings and habitations of man. It is safe to say that they first entered North Dakota with the early steamboat traffic up the Missouri River.
      In 1833, Maximilian (Wied, 1839-1841, Bd. 2, pp. 72, 251, 256-257, 1841) found them a great pest among the grain stores of the Indians at Fort Clark. He says that in the loft of the stores of the fort were 600 to 800 bushels of maize that a great number of Norway rats assiduously labored to reduce. They were so numerous and troublesome that no kind of provision was safe from their voracity, but their favorite food was the maize, among which they created much havoc, and it was calculated that they devoured 5 bushels, or 250 pounds, daily. The rats were brought thither by American ships, but as yet had not reached the Minnetaree villages. The following winter, in the house which had been built for him among the Mandan Indians, Maximilian says: "We were molested during the night by numerous rats and put my little prairie fox in the loft above us, where some maize was kept and here he did excellent service."
      In 1887, these large rats were abundant at Fort Buford, which was then the terminus of the Great Northern Railway. The old buildings about the fort were filled with them and they were very destructive. Even in the little adobe hotel they were racing about the room every night until caught in traps. At Grand Forks they were said to have only recently arrived and they were not known [p.71] at Pembina, Devils Lake, or Bottineau. In 1909 they were common at Bismarck and Mandan and were said to be at Devils Lake and Rugby Junction, but at Bottineau none had been found. In 1912 they were abundant and troublesome about Fargo, Hankinson, Valley City, Lisbon, Stump Lake, and Grafton. At this time a dead rat was seen at a ranch near Marstonmoor, Stutsman County; Williams reported them at Walhalla, in Pembina County; and within a few years they had begun to infest the country along the eastern edge of the Turtle Mountains. In 1915 Sheldon found them at Fairmount, where they were a great pest around barns and granaries. He says that the farmers who tried to raise poultry had considerable trouble with them, as they took the little chickens at every opportunity. During his visit at the Hoffman farm, two of the farmhands, while transferring a quantity of hay from one section of the barn to another, killed about 100 rats in a few hours. Most of these were about half-grown, only 1 adult being killed. At Lidgerwood, in Richland County, Sheldon found them less common than at Fairmount. On a trip west across the rest of the southern part of the State, however, he did not find any further trace of them.
      In 1915 Kellogg found them at Wahpeton, at Grafton, and a few at Oakes, in Dickey County; at Towner, McKenzie County, he reported them as not very common. In 1913 Jewett reported that no trace of them could be found at Sentinel Butte and old settlers living there had never seen them. At Medora, also, none were found. It is probable that the rats will not find their way to the scattered farms over considerable portions of the western and more arid parts of the State for some years to come, but eventually they will undoubtedly cover practically the whole State.
      General habits.--So closely have rats been associated with man and his works and for so long a time, that they have become largely parasitic in habits, seeking the cover and protection of buildings and preying upon the food supplies produced and gathered by man. Their sly, filthy habits, mean appearance, and vicious dispositions have not only won the enmity of mankind, but have done much to instill a dislike for other harmless and more attractive native animals with which their name has become associated. To their destruction of property is added the even more serious menace of conveying disease to man. They are by far the most destructive and dangerous of rodent pests and warfare against them should be relentless.
      Breeding habits.--A large female rat was sent to the Biological Survey from Fargo by K. F. Bascom, who reported that it had contained 12 well-developed fetuses. This is not an unusual number of young at a birth, and the rats breed so rapidly that under favorable conditions of food supply and protection the rate of increase is enormous. Litters of young are said to be produced sometimes at intervals of 25 days and the breeding season lasts for a large part of the year (Lantz, 1909, p. 16).
      Food habits.--Probably no rodents are more omnivorous than rats. They accept anything of an edible nature from fresh or stale meat to young chickens, eggs, fruit and vegetables, grain, nuts, seeds, and even green vegetation. They revel in garbage of all sorts and will often find an abundance of food in city dumps, manure piles, and in the refuse about stables. In a grain-producing region their fondness [p.72] for grain leads to enormous losses, as where an abundant supply is available they merely take the germ and ruin far more than they require for food.
      Control measures.--The depredations of these animals are so serious that it is generally found to be good economy to make buildings rat-proof, or as nearly so as possible, by means of concrete, brick, stone, and wire mesh. Where grain and other food can be kept away from them their numbers can easily be controlled, but they are so skilful in burrowing under walls and gnawing through wood that special methods are necessary to exclude them. So adept are they in avoiding traps and poison that a combination of rat-proofing, poison, and traps is often necessary to prevent serious losses from them. The most successful methods of combating them are given in Biological Survey bulletins and circulars, which are available for free distribution.

[Mus] musculus Linnaeus, Syst. Nat., ed. 10, t. 1, p. 62, 1758.
      Type locality.--Sweden.
      General characters.--Size small, with slender, tapering tail, pointed nose, and rather small ears. Color, brownish-gray above, buffy-gray below, usually without any clear white. Measurements of average adults: Total length, 160 millimeters; tail, 81; hind foot, 19. Weight of adult female, 23.5 grams.
      Distribution and habitat.--Troublesome little Old-World mice have become well established over almost every part of North Dakota, in fact through most inhabited parts of North America. So thoroughly have they become dependent on the habitations of man that little is known of their origin and distribution. They followed quickly on the heels of the first settlement of the country and generally appeared within a few years after the establishment of a ranch or farm, even at a considerable distance from other habitations. At almost every place over North Dakota where field work has been done by the Biological Survey, these mice have been reported as common or abundant and troublesome about buildings, and in many cases they have been caught in the fields in traps set for native species.
      At Fargo, in 1912, these little mice were so numerous along the edges of fields and roads that it was difficult to catch other species until enough trapping had been done to reduce the numbers of the house mice. Near Williston, in 1913, they were abundant at the ranches and very destructive of grain in the bins and sacks. In the bunk house at one of the ranches the mice kept up a racket all night, and in the morning there were little piles of oat shells on the floor where grain had been brought in and eaten. Their musky odor was very evident in the room, leaving no doubt as to the identity of the species, and one was shot as it ran across the floor. At Kenmare, in the northwestern part of the State, they were abundant both in town and in the weedy bottomland, where many were caught in traps. At Mandan, in 1913, Jewett found them abundant in town and also on rough slopes in the surrounding fields to a distance of 2 miles from town. At Glen Ullin he caught them on the sides of buttes a mile from town, and also in the tall grass along the creek [p.73] bottoms. At Sentinel Butte they were found at almost every ranch; also at Fort Clark, and around Oakdale in the Killdeer Mountains. Specimens were also taken at Buford, Bismarck, Cannon Ball, and many other localities over the State.
      General habits.--House mice are generally imported in boxes and loads of goods where they have made their nests, and are carried long distances on trains or in wagons. They prefer the protection of buildings, but when they have become numerous overflow into the surrounding fields and country wherever food and cover are to be obtained. They breed and increase with great rapidity and but for their natural enemies would soon overrun the fields and render agriculture unprofitable. Cats are generally used to keep down their increase, but serve as a very limited check. The native owls, hawks, and weasels, however, do much to control their abundance.
      In habits the mice are often filthy, running through the dirt of stables and cellars and then over the food in pantries or kitchens, in this way not only destroying food but distributing disease germs.
      They are so slender that they can slip through cracks and narrow openings into places supposed to be proof against their entry, and they will also gnaw through a considerable thickness of wood to get at food or grain that is stored. Concrete, plaster, and fine wire mesh are the best protection against their inroads, but in spite of all efforts it is often necessary to resort to poison and trap in order to destroy them. Inverted boxes covering poisoned grain, with small openings through which larger animals can not pass, may be kept in buildings where mice occasionally enter and many may be destroyed in this way. Directions for preparing poisoned bait, as well as for trapping these pests, will be furnished by the Biological Survey, United States Department of Agriculture, on request.

Mus bairdii Hoy and Kennicott, Rpt. Comr. Patents. [U. S.] 1856, p. 92, 1857.
      Type locality.--Bloomington, McLean County, 111.
      General characters.--About the size of osgoodi, but colors much darker, often dusky along the back, and less buffy or ochraceous; underparts, white. Measurements of an average specimen: Total length, 150 millimeters; tail, 60; hind foot, 19. Weight of adult male, from Fargo, 18.5 grams.
      Distribution and habitat.--From Ohio and Oklahoma the little dark-colored white-footed mice (bairdii) extend over the eastern half of North Dakota and into southern Manitoba. In their typical form they do not reach west of the Missouri River, but at about the one-hundredth meridian they grade insensibly into the paler, more buffy osgoodi. There are specimens from almost every locality where collecting has been done in eastern North Dakota, from Hankinson to Pembina and westward to Linton, Towner, and Kenmare. They are found on the tall-grass prairies in the area of humidity and ample cover, where their dark color is protective in the grassy and weedy shadows.
      General habits.--These little mice, like their western form, osgoodi, are the most abundant and generally distributed mammals of their region. They live in a great variety of situations, from brushy weedy bottoms in the woods, half-dried tule marshes, and dead-weed rows along the roadsides to the middle of grainfields and out over the wide, open, grassy prairie, making nests and homes in hollow logs or trees, in underground cavities which are found, or if necessary, excavated, or under any cover that will offer a dry bed. From osgoodi of the drier, more open plains farther west, they differ in habits only in adaptation to more abundant plant growth and more nearly continuous grainfields.
      Where food is plentiful they congregate in great numbers, but where it is scanty they become scarce. At Stump Lake, in a line [p.77] of traps set along the sandy beach, 16 of these mice were caught in one night where they were finding a choice food supply in the cockleburs which covered the sandy ground. At Crosby the writer found them feeding largely on little caterpillars. At Valley City many were caught in the rows of tumbleweeds or Russian thistles along the fences, where they were feeding on the seeds of these weeds under the cover of which they found ample protection. Eastgate reported 19 caught in his line of 41 traps the first morning after he camped near this place. They are often found in the haycocks and wheat shocks in the fields, and if these are left for a considerable time the mice are sure to make their nests in them and do more or less mischief.
      In breeding and food habits these mice are essentially the same as the western osgoodi. Their injury to crops is somewhat greater because of the more general cultivation of land over their range. Their enemies are practically the same and if only given a fair opportunity will keep down the too rapid increase of these interesting but destructive little rodents. At Fargo in the well-cleared city parks not a mouse could be caught, while in the uncleared woods near by, where weeds and bushes protected them from the little owls, these mice filled the traps the first night.

[Mus sylvaticus] noveboracensis Fischer, Synop. Mamm., p. 318 (p. 14, δ.), 1829.
      Type locality.--New York.
      General characters.--Largest of the white-footed mice of North Dakota, with relatively long tail and dark colors; upper parts of adults, dark buffy or tawny-gray, with more blackish or dusky about face and ankles than in aridulus; underparts and lower half of tail, pure white. Young and immature, bluish gray or plumbeous. Measurements of adult male from Fargo: Total length, 185 millimeters; tail, 78; hind foot, 22. Weight, 27.5 grams.
      Distribution and habitat.--The northern form of the white-footed mouse is the common deer mouse or woods mouse of the northeastern United States and southeastern Canada from Nova Scotia to eastern North Dakota. It is largely a forest species, rarely found far from forest or brushland and seems not to extend over the open prairie country. Specimens taken at Fargo, Moorhead, and at Manvel, just north of Grand Forks, are fairly typical of this eastern form and certainly referable to it rather than to the paler aridulus of the Missouri Valley. They probably have a continuous range along the timber of the Red River Valley, but seem not to be abundant.
      General habits.--Deer mice are largely forest dwellers, but have a wide range of adaptation and will go anywhere that safe cover and an attractive food supply lead them. From their original homes in hollow trees and logs or in the ground under old trees and stumps they readily follow the rail fences and brushy fence rows around the fields, taking up their quarters under grain shocks, haycocks, or haystacks, or entering new buildings erected in the clearings. They are great climbers and will run up the trunks and branches of tall trees or up vines and through bushes in search of [p.78] seeds or berries, or over walls and timbers of buildings, with ease and skill.
      They are strictly nocturnal and very timid, nervous little sprites, with long, sensitive whiskers and large, thin, delicate ears that are constantly changing form and expression, apparently catching the faintest sounds; their large, prominent black eyes are owl-like in their adaptation to the dark of night. Apparently they can see fairly well in the daytime, but are rarely natural or at ease in the light and lose much of their vivacity and beauty as usually seen when driven out of their diurnal beds or captured and held as unwilling prisoners. They are among the most beautiful and expressive of our small native rodents, to which the unfortunate name of "mouse" is generally applied, and but for their occasional mischief and nocturnal habits might be as interesting and popular as many of our song birds. In fact, they are not without voices, and certain individuals have a fine squeaking trill that might well be called a song. They have many little squeaks and low notes that doubtless mean much to them if little to us. A more common means of communication, however, consists of a rapid tapping with their finger tips on any hard surface or thin material, which produces a sound suggestive of the drumming of minute woodpeckers. These vibrations vary in length and tone and doubtless mean much to them in the way of communication.
      Breeding habits.--Nests containing young are frequently found under grain shocks or haycocks, or are plowed out of hollows below the surface of the ground. They are usually as soft, well built, and well lined as those of any bird; and the delicate, naked young are found resting on silk or cotton wool from various plants or on feathers or fur or other equally soft materials provided by the parents. Usually 4 to 6 young are born at a time and apparently several litters are raised each year. The mammae of adult females are six in number, arranged in two posterior or inguinal pairs and a single pair of anterior or pectoral. Often when suddenly disturbed the mother runs from the nest with 5 or 6 young, each clinging securely to a nipple, as she drags them rapidly to some safe cover.
      Food habits.--Although the greater part of their food consists of seeds, grain, and nutlets, deer mice also are fond of berries, fruit, and a great variety of such foods as the human species regards as its own and exclusive perquisite. This often leads to trouble, for the little moonlight people get into fields, gardens, granaries, and even cellars and pantries and help themselves, always to the best there is to be had. The fact that they consume large quantities of seeds of noxious weeds is generally overlooked and some easy method of lessening their abundance is sought. Unfortunately, this often takes the form of keeping cats, which may scare some of the mice away, while the cats live largely on song birds. If little owls could be kept instead, there would be no more trouble from the mice. In fact, there are usually enough little owls to keep down the abundance of the mice, where brush, weeds, and rubbish are removed so the mice will have no protecting cover.