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.]