Life History of the Kangaroo Rat | Page 2

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).
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 (Geomyidæ),
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