Arizona \ 
Kxp. Sta. / 
LIFE HISTORY OF THE KANGAROO RAT. 
39 
merriami and D. ordii The darker color and vividly contrasted 
black-and-white tail of speetdbilis distinguish it from deserti. 
(2) Dipodomys s. speetdbilis 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 be- 
tween speetdbilis and deserti. 
(4) Dipodomys s. speetdbilis is nocturnal; it is gentle, and does 
not otter 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 speetdbilis begins in January and con- 
tinues 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. speetdbilis 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 J 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 dif- 
ferent plants have much to do with the kinds of storage found. 
(7) The dens of speetdbilis 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 in- 
teresting of all the rodents peculiar to our Southwestern deserts, and 
should not be molested except where it is destructive. 
