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. It must be remembered, moreover, that the stored material consists largely of seeds, so that this loss is of greater importance than would be the case were it ordinary forage. Some of the range grasses of this region found in greatest quantity in the stored material depend in large part, under certain conditions, upon seed reproduction. Rehabilitation of a depleted range after severe drought and consequent close grazing and trampling is retarded by the heavy toll of seed taken by the kangaroo rats.
Kangaroo rats may be easily eradicated by the use of the poisoned grain used for prairie-dog control by the Biological Survey and the University of Arizona Extension Service. This can be obtained by application to the State representative of the Biological Survey or to the local county agricultural agent, or may be mixed as follows:
Formula for poisoned bait.—Dissolve 1 ounce of strychnine sulphate in 1-1/2 pints of boiling water. Add 1 heaping tablespoonful of gloss starch, previously mixed with a little cold water, and boil until a clear paste is formed. Add 1 ounce of baking soda and stir to a creamy mass. Add 1/2 ounce of glycerine and 1/4 pint of corn sirup and stir thoroughly. Pour over 16 quarts of rolled barley and mix well until every grain is evenly coated. Allow to dry before using.
In bushel quantities use as above directed, 2 ounces of strychnine, 2 ounces of soda, 1 ounce of glycerin, 1-1/4 ounces of starch, 1-1/2 quarts of boiling water, and 5/8 pint of corn sirup.
Scatter poison, when the natural food of the kangaroo rat is scarce, on clean hard places near the holes, 1 quart to 50 holes.
If powdered strychnine alkaloid is used, prepare the hot starch paste first. Then sift strychnine and baking soda, previously thoroughly mixed, into the hot starch paste and stir to a creamy mass. Proceed as in the above directions with sirup, glycerin, etc.
Use this poison within five days after mixing or retain in air-tight containers.
Caution.—All poison containers and all utensils used in the preparation of poison should be kept plainly labeled and out of reach of children, irresponsible persons, and live stock.
A spoonful of the poisoned grain scattered about the used entrances of a mound is sufficient, and prebaiting is not necessary, as with prairie dogs.
A word of caution should perhaps be offered in connection with control measures. As man has come to occupy a greater portion of the earth's surface, and as he has become more and more the master of his environment, he has inevitably disturbed the relationships of the birds and mammals about him, has upset the balance of nature. If he kills the carnivorous species because of their depredations on game and live stock he must be prepared to cope with the increased hordes of rodents which feed on vegetation and on which the carnivorous animals act as a check. If he destroys the rodents, he may remove the checks on certain noxious plants or insects. One control measure often necessitates the adoption of another.
This is not to argue against control measures, for if our harmful species were not controlled, agriculture in many sections would be impossible. Control measures, however, should be scientifically founded and applied. The indiscriminate slaughter of supposedly harmful species of birds and mammals in the guise of benefiting agriculture may do far more harm than good. Many of the species which do some harm do far more good. The exact status of each suspected species should be carefully determined through an adequate scientific investigation. If the species is condemned, sound control measures should be thoroughly applied.
In grazing districts or in areas devoted to intensive agriculture the death sentence should probably be passed on the banner-tailed 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.
(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; the white hip-stripe distinguishes them from the pocket mice. The decidedly larger size and the white-tipped tail separate Dipodomys spectabilis spectabilis and D. deserti from D. merriami and D. ordii. The darker color and vividly contrasted black-and-white tail of spectabilis distinguish it from deserti.
(2) Dipodomys s. spectabilis occurs in the open arid country of portions of the Lower and Upper Sonoran Zones of Arizona, New Mexico, Texas, Sonora, and Chihuahua. It lives in harder soil than does deserti, and builds more conspicuous mounds.
(3) There is no evidence of intergradation or hybridization between spectabilis and deserti.
(4) Dipodomys s. spectabilis is nocturnal; it is gentle, and does not offer to bite when taken in the hand; is silent for the most part; active; somewhat sociable with its fellows, but fights in defense of its food stores; progresses chiefly by leaping; signals by a drumming or tapping on the ground with its hind feet.
(5) The breeding season of spectabilis begins in January and continues into August. Whether more than one litter is raised in a single season is unknown. The number of young in each litter varies from 1 to 3, averaging 2.
(6) Dipodomys s. spectabilis does not hibernate, but provides food stores, mostly seeds, for use during seasons when food would be otherwise unavailable. Storage in each den varies in quantity from 5 grams (about 1/6 ounce) to 5,750 grams (12.67 pounds). Materials stored include several important forage plants; for example, various species of Bouteloua and Aristida, with B. rothrockii (crowfoot grama) the most important. Accessibility and abundance of different plants have much to do with the kinds of storage found.
(7) The dens of spectabilis are the most notable of all kangaroo rat dwelling places. They range from 6 inches to 4 feet in vertical height, and from 5 to 15 feet in diameter. Here the kangaroo rat has its home, shelter, and food-storage chambers. Within the den is found a tortuous network of burrows, with many storage and some nest chambers, the whole arranged so as to be two to four stories high.
(8) Dipodomys s. spectabilis is not of great economic significance, except locally, in ordinary seasons. During periods of extreme drought it may be of critical importance on grazing areas from the standpoint of the carrying capacity of the range.
(9) Kangaroo rats are easy to poison by following the same formula as that used by the Biological Survey for destroying prairie dogs.
(10) In many places unsuited to extensive grazing or agriculture spectabilis does no appreciable damage. It is one of the most interesting of all the rodents peculiar to our Southwestern deserts, and should not be molested except where it is destructive.
ALLEN, J. A.
1895. On a collection of mammals from Arizona and Mexico, made by Mr. W. W. Price, with field notes by the collector. Bull. Amer. Mus. Nat. Hist., vol. 7, art. 6, pp. 193-258. 17 figs. in text.
BABCOCK, S. M.
1912. Metabolic water: Its production and role in vital phenomena. Research Bull. No. 22, Univ. Wisconsin Agr. Exp. Station, pp. 159 and 170, March.
1905. Biological survey of Texas. North Amer. Fauna No. 25, Biol. Surv., U. S. Dept. Agr., pp. 222, 16 pls., 24 figs. in text.
CLEMENTS, F. E.
1905. Research methods in ecology. Lincoln, Univ. Pub. Co., pp. xvii, 334, 85 figs. in text.
1910. A protected stock range in Arizona. Bull. No. 177, Bur. Plant Ind., U. S. Dept. Agr., pp. 28, 6 pls., 1 fig. in text.
1921. Revised list of the species in the genus Dipodomys. Journal of Mammalogy, vol. 2, No. 2, pp. 94-97, May 2.
MCATEE, W. L.
1921. Farm help from the birds. In Yearbook of the U. S. Dept. Agr. for 1920, pp. 253-270; unnumbered figs. in text.
MERRIAM, C. H.
1890. Description of three new kangaroo rats, with remarks on the identity of Dipodomys ordii of Woodhouse. In North Amer. Fauna No. 4, Div. Ornith. and Mamm. (Biol. Surv.), U. S. Dept. Agr., 41-49.
NELSON, E. W.
1918. Smaller mammals of North America. Nat. Geog. Mag., vol. 33, No. 5, pp. 371-493; numerous unnumbered figs. and colored pls. in text.
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