Kangaroo rat

“ It should be recalled, however, that this is the largest and one of the handsomest of all its family, and that it is one of the most characteristic and interesting of all the desert fauna; where extensive grazing or agricultural operations are not undertaken, therefore, we feel that the kangaroo rat should be let alone, unless its presence threatens infestation of valuable agricultural or grazing lands.
SUMMARY.
(1) Kangaroo rats may be separated with ease from all other mammals; the long tail and short and weak fore feet separate them from the pocket gophers ”

“ From all these estimates it may fairly be concluded that two mounds, or two animals, per acre is a conservative estimate for the infestation of the entire Range Reserve, with the possible exception of small areas at its upper edges, where the altitude limit of spectabilis is passed. It is, however, impossible to estimate the area of the State infested with kangaroo rats, for some large stretches of fine grassland show no kangaroo rats whatever, while others have more than are present on the reserve ”

“ As a kangaroo rat emerges from the burrow a reason for the relatively large size of the opening is seen in the fact that, kangaroolike, the animal maintains a partially upright position. Its ordinary mode of progression is hopping along on the large hind legs, or, when in the open and going at speed, leaping. When moving slowly about over the mound, as if searching for food, it uses the fore legs in a kind of creeping movement. ”

“ Rarely have I been conscious of a stranger thrill than when I raised that singular creature from the stones, dry as a board, his innocent heart long quiet, and all warm with sunshine. His long hind legs were stiff, his tiny forepaws clutched upon his breast, as if to leap; his poor life cut short upon that mountain by some unknown accident. But the kangaroo rat, it proved, was no such unknown animal; and my discovery was nothing.
Crickets were not wanting. I thought I could make out exactly four of them, each with a corner of his own, who used to make night musical at Silverado. ”

“ Distribution of the Ord kangaroo rat, Dipodomys ordii columbianus, in Washington.
Description.—The kangaroo rat with a body about the size of that of a chipmunk has an exceptionally large head and large, black eyes. The forelegs and forefeet are tiny but the hind feet and legs are large and powerful. The hind foot is almost a third as long as the head and body. The tail is long, longer than the head and body. Kangaroo rats possess fur-lined, external cheek pouches, like those of [Pg 301] the pocket mice. The upper parts are soft buff in color. ”

“ They are very efficient water conservationists. Although water is essential to the kangaroo rat, they rarely drink, but produce their own water from insects and dry seeds they eat. They have no sweat glands, and excrete highly concentrated wastes to minimize water loss.
These rodents are not related to kangaroos at all! Their name refers to their hind legs which are highly developed for jumping.
Watch for their tracks—when a kangaroo rat is moving slowly, it drags its tail which leaves a trail in the sand in conjunction with its foot prints. When the rat moves quickly, its tail doesn’t drag. ”

“ With the first streak of dawn activity usually ceases completely and much more abruptly than it began with the coming of darkness, but on a recent occasion Vorhies observed that a kangaroo rat which did not appear until near morning remained above ground until quite light, but not fully daylight. On removal of the plug from the mouth of a kangaroo rat burrow, one may sometimes see a fresh mass of earth and refuse shoved into the opening from within. ”

“ It is doubtful whether any animals live in a truly commensal relationship with spectabilis, but of not unfriendly associates there are a great number. It is the experience of Bailey, corroborated by observations of Vorhies on living animals, that these kangaroo rats are active in defending their caches of food, and will even fight individuals of the same species savagely and to the death. One moonlight night a strange individual was liberated on a mound. ”

“ It seems not unlikely, therefore, that during seasons of drought the banner-tailed kangaroo rat, where it is abundant on the grazing ranges of the Southwest, may be a factor of critical importance in relation to forage production and carrying capacity. ”

“ Its eyes and ears were closed, and its soft, naked skin was distinctly marked with the pattern of the adult, the colors being as given for the other two. This juvenile lived only a week. Young less than half grown were not trapped or noted in our poisoning operations outside the dens.
Kangaroo rats, if spectabilis be representative, reproduce at a slow rate as compared with many other small rodents. We have records of 67 females with embryos or scars showing the number produced, and of the two litters of young described above. ”

“ Examination of the runways and of the denuded area about a mound discloses an abundance of almost indecipherable tracks. The dust or sand is ordinarily much too dry and shifting to record clear footprints, and there are no opportunities to see footprints of this species recorded in good impressionable soil. Very characteristic traces of kangaroo rats may be readily observed in the dust about the mounds, however, and these are long, narrow, sometimes curving, furrows made by the long tails as the animals whisk about their work or play. ”

“ This helps them stay safe from predators, like coyotes, owls, kit foxes, and snakes. If a predator does approach, the kangaroo rat can use its back legs to kick sand into the eyes of its enemy, bound away, and return safely to its burrow. ”

“ Probably no instinct is of greater importance to the kangaroo rat than that of storing food supplies. When a crop of desirable seeds [16] is maturing the animal's activities appear to be concentrated on this work. During September, 1919, when a good crop of grass seed was ripening following the summer rains, a kangaroo rat under observation made repeated round trips to the harvest field of grass heads. Each outward trip occupied from 1 to 1-1/2 minutes, while the unloading trip into the burrow took only 15 to 20 seconds. ”

“ On the United States Range Reserve the food material appropriated by the kangaroo rat during good years is inappreciable. There is such an excess of forage grass produced that all the rodents together make very little difference. But with the periodic recurrence of lean years, when drought conditions are such that little or no grass grows, the effects of rodent damage not only become apparent, but may be a critical factor determining whether a given number of domestic animals can be grazed on the area (Pl. VIII, Fig. 2) . ”

“ Natural barriers to kangaroo rats, such as the Cedar Mountains to the west, high plateau country to the south, the Paunsaugunt Plateau to the east and the narrow canyons of the Sevier River to the north prevent these animals from extending their range or from coming into physical contact with any adjacent geographic races. ”

“ Another animal with which the bush swarms is the kangaroo rat, or, I should perhaps rather say the "boody," though there is but a very slight difference between the two creatures, except that the "boody" is a burrower and makes its habitation underground, while the kangaroo rat usually forms its nest in an old hollow tree. There is also a distinction between them in the colour of the tail. ”

“ That, plus whatever water is in the seeds themselves, is enough to sustain the kangaroo rat. The ability to live with very limited water and burrow in shifting sands, makes kangaroo rats very well adapted to life here at White Sands National Park. ”

“ Animals from 16 miles northwest of Moab, Utah, and from three localities in Colorado, even though intergrades with D. o. nexilis, are all referable to D. o. sanrafaeli. It appears that the Green River does not act as a complete barrier in this area since in the winter it occasionally freezes over, thus allowing the animals to cross. It is thought that kangaroo rats do not hibernate but remain more or less active throughout the winter. Man-made conveniences, such as bridges, might also serve as means of dispersal, permitting these animals to cross otherwise prohibitive barriers. ”

“ Observations on other rats thus driven from the home mound indicate that they are very familiar with the runways of the vicinity of the mound and the various subsidiary burrows, and it is a question whether they need to see clearly to follow these runs. Apparently they never attempt to escape by forsaking their well-traveled runways. Tests of the maze-running ability of these animals by animal-behavior experts would be of extraordinary interest, in view of the character of the homes which they always inhabit and the network of runs on the outside. ”

“ If the work is to be prosecuted intelligently and the fullest measure of success achieved, it is essential that the consideration largely of groups as a whole be supplemented by more exhaustive treatment of the life histories of individual species and of their place in the biological complex. The present report is based upon investigations, chiefly in Arizona, of the life history, habits, and economic status of the banner-tailed kangaroo rat, Dipodomys spectabilis spectabilis Merriam (Pl. I) . ”

“ Not infrequently a season of severe drought precludes the possibility of any storage. The summer and fall of 1918 was such a season on the Range Reserve (Pl. II, Fig. 2) . If food stores are inadequate at such a time the kangaroo rats must perish in considerable numbers. Fisher found many deserted mounds in the vicinity of Dos Cabezos, Ariz., in June, 1894, which may be accounted for in this way. In 1921 Vorhies found all mounds within 4 or 5 miles of Albuquerque, N. Mex., deserted by spectabilis, resulting probably from overgrazing by sheep and goats during a succession of dry years. ”

“ Here is to be found the principal grass growth supporting the grazing industry, and the presence of a more luxuriant grass flora is probably an important factor in the greater abundance of kangaroo rats, both spectabilis and merriami. In this generally preferred environment the desert hackberry (Celtis pallida) is one of the most conspicuous shrubs; clumps of this species are commonly accompanied by kangaroo rat mounds. ”

“ The kangaroo rat, an animal nearly as large as a wild rabbit, is tolerably abundant, and very good eating, when cooked in the same manner. The natives take them by driving a spear into the nest, sometimes transfixing two at once, or by jumping upon the nest, which is formed of leaves and grass upon the ground. ”

“ They even pack the entrances to their burrows closed with sand to keep the burrows cool and humid. At night, kangaroo rats emerge to forage for seeds, storing them in their cheek pockets until they return to their burrows. These seeds comprise most of the kangaroo rat’s diet, but they may eat insects or other vegetation if necessary. Because kangaroo rats typically build their burrows beneath shrubs, they don’t even have to go far to find seeds during these foraging expeditions. ”

“ The burrow system, or den, in which spectabilis stores its caches of food materials, has its nest, and remains throughout the hours of daylight is a complicated labyrinth of tunnels. Ejection of refuse and soil from this retreat builds up the mound frequently referred to. These mounds are, as Bailey says, characteristic of the species, and are as unmistakable as muskrat houses or beaver dams, and as carefully planned and built for as definite a purpose—home and shelter. They are, furthermore, the most notable of all kangaroo rat dwelling places (Nelson, 1918, 400) . ”

“ Thus, when comparisons were made, the size and certain shapes were the criteria used in assigning the animals under consideration to a given subspecies.
Subspeciation in Dipodomys ordii seems to have been influenced [Pg 504] by water barriers. It is known (Grinnell, 1922:28) that kangaroo rats lack the ability to swim. Large stable rivers such as the Colorado, Snake and Columbia serve as effective barriers to further dispersal of kangaroo rats. Streams that freeze over in the winter months, however, are not efficient barriers. ”

“ If, for instance, anyone walking through the bush happens to pick up a young kangaroo rat, and carries it in his pocket for an hour or two, the rat, when set down upon the ground again, will come hopping after the man, or rather perhaps alter the coat-pocket which has no doubt brought back to the little creature's mind its reminiscences of the maternal pouch. ”

“ It is fairly evident that in seasons of scanty forage for stock the appropriation of such quantities of grass seeds and crowns and other grazing materials by numerous kangaroo rats may appreciably reduce the carrying capacity of the range. Studies of cheek-pouch contents and food stores taken from dens show that the natural food of spectabilis consists principally of various seeds and fruits, particularly the seeds of certain grasses. The study of burrow contents has been especially illuminating and valuable. ”

“ More striking extremes of this are shown by D. o. compactus of Padre and Mustang islands, Texas, which is pale-colored as is the sand on which it lives, and D. o. medius from east-central New Mexico and western Texas, which is reddish as is the soil there, which is derived from Permian rocks. In localities where alkaline soils are present, kangaroo rats may be found with a roseaceous cast to the pelage as a result of the action of the alkaline salts on the pigment of the hair. The roseaceous color is lost when the animal sheds the old pelage. ”