Kip.TtSL.} LIFE HISTOEY OF THE KAXGAROO EAT. 39 



i7iemami and D. ordii. The darker color and vividly contrasted 

 black-and-Tvhite tail of spectahilis distinguish it from desertl. 



(2) Dipodoimjs s. spectabilis occurs in the open arid country of 

 portions of the Lower and Upper Sonoran Zones of Arizona, Xew 

 Mexico, Texas. Sonora. and Chihuahua. It lives in harder soil than 

 does deserfi, and builds more conspicuous mounds. 



(3) There is no evidence of intergradation or hybridization be- 

 tween spectabilis and deserti. 



(4) Dipodomys s. spectabilis is nocturnal; it is gentle, and does 

 not oit'er 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 spectabilis 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. spectabilis 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 ^ ounce) to 5,750 grams (12. 6T 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 spectaMlis 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. 



