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.