Life History of the Kangaroo Rat | Page 2

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).
INVESTIGATIONAL METHODS.
Some 18 years ago (in 1903) a tract of land 49.2 square miles in area on the Coronado National Forest near the Santa Rita Mountains, Pima County, southern Arizona, was closed to grazing by arrangement between the Forest Service and the Agricultural Experiment Station of the University of Arizona. Since that time another small tract of nearly a section has been inclosed (Griffiths, 1910, 7[1]). This total area of approximately 50 square miles is known as the United States Range Reserve, and is being devoted to a study of grazing conditions in this section and to working out the best methods of administering the range (Pl. II, Fig. 1).
For some years an intensive study of the forage and other vegetative conditions of this area has been made, the permanent vegetation quadrat, as proposed by Dr. F. E. Clements (1905, 161-175), being largely utilized. During the autumn of 1917 representatives of the Carnegie Institution and the Arizona Agricultural Experiment Station visited the Reserve and were impressed with the evidence of rodent damage to the grass cover. The most conspicuous appearance of damage was noted about the habitations of the banner-tailed kangaroo rat (_Dipodomys spectabilis spectabilis_ Merriam), although it was observed also that jack rabbits of two species (Lepus californicus eremicus Allen and _L. alleni alleni_ Mearns), which were very abundant in some portions of the reserve, were apparently affecting adversely the forage conditions in particular localities. Accordingly, the Biological Survey, the Agricultural Experiment Station of the University of Arizona, the Carnegie Institution of Washington, and the U. S. Forest Service have undertaken a study of the relation of the more important rodents to the forage crop of the Range Reserve in Arizona.
The present paper is a first step in this larger investigation.[2] In this work the authors have made no attempt to deal with the taxonomic side of the kangaroo rat problem. It is not unlikely that intensive studies will show that the form now known as _Dipodomys spectabilis spectabilis_ is made up of a number of local variants, some of them perhaps worthy of recognition as additional subspecies. But it is felt that the conclusions here reached will be little, if at all, affected by such developments.
Color descriptions are based on Ridgway's Color Standards and Color Nomenclature published in 1912.
[Footnote 1: References in parentheses are to the Bibliography, p. 40 (the last figure being to the page of the publication). References to authorities where no citation of literature is appended relate for the most part to manuscript notes in the files of the Biological Survey or the University of Arizona Agricultural Experiment Station.]
[Footnote 2: In addition to assistance rendered by officials of the Biological Survey and the University of Arizona, which is hereby acknowledged, the authors are indebted to the following persons for helpful suggestions and assistance: G. S. Miller and J. W. Gidley, of the U. S. National Museum; Dr. Frederic E. Clements and Gorm Loftfield, of the Carnegie Institution; Morgan Hebard, of the Academy of Natural Sciences of Philadelphia; James T. Jardine and R. L. Hensel, both formerly connected with the U. S. Forest Service; and R. R. Hill, of the Forest Service. They are also indebted to William Nicholson, of Continental, Ariz., for many courtesies extended in connection with work on the Reserve.]

IDENTIFICATION.
There are only three groups of mammals in the Southwest having external cheek pouches. These are (a) the pocket gophers (Geomyid?), which have strong fore feet, relatively weak hind feet, and short tail, as compared with weak fore feet, relatively strong hind feet, and long tail in the other two; (b) the pocket mice (Perognathus), which are considerably smaller than the kangaroo rats and lack the conspicuous white hip stripe possessed by all the latter; and (c) the kangaroo rats (Dipodomys).
[Illustration: FIG. 1.--Range, east of the Colorado River, of _Dipodomys spectabilis spectabilis compared with that of Dipodomys merriami_. Cross hatching indicates area of overlapping of the two forms. The range of Dipodomys deserti, not shown on the map, is west of that of spectabilis, and so far as known the two do not overlap.]
Dipodomys spectabilis spectabilis Merriam requires comparison with three other forms of kangaroo rats in the same general region, namely, D. deserti Stephens, of approximately the same size, and D. merriami Mearns and D. ordii Woodhouse, the last two of decidedly smaller size. The range of deserti lies principally to the west of that of spectabilis, and the two do not, so far as known, overlap. On the other hand, merriami and ordii, and subspecies, occur over a large part of the range of spectabilis, living in very close proximity to its burrows; merriami is