18 BULLETIX 1091, U. S. DEPAETMEXT OE AGEICULTUKE. {buIi's^o^I, 



MeasuremeDts (in miUiineters). 



Weight 



<in 



grams). Total TaU Hind 



length, vertebrae. foot. 



No.l 13.3 90 38 24 



No.2 12.6 1 93 .38 24 



1 



At thi.- .-tage the Toiing ^ve^e partially clothed with a coat of fine 

 velvety fur. more especially on the bodies, the tails being still nearly 

 naked. The body color vras dark plumbeous, just the color of the 

 dark underfur of the adult, or a shade darker, while the character- 

 istic "wliite markings of the adult stoo'i out sharply as pinkish- 

 white areas against the dark background (see PL IX. Fig. 2, at 

 p. oil ) . The proportions were mucli as in the adult, except that 

 the tails were relatively much shorter and the feet relatively longer. 



Only one other record of young is at hand, that by Bailey, who 

 secured tlie young after capture of a suckling female at Santa Kosa, 

 X. ]Mex. In this case the litter contained only one. This was squeak- 

 ing when found, but was not large enough to crawl away. Its eyes 

 and ears were closed, and its soft, naked skin was distinctly marked 

 with the pattern of the adult, the colors being as given for the other 

 two. This juvenile lived only a week. Young less than half grown were 

 not trapped or noted in our poisoning operations outside the dens. 



Kangaroo rats, if spectahilis be representative, reproduce at a 

 slow rate as compared with many other small rodents. We have 

 records of 67 females with embryos- or scars showing the number 

 l^roduced. and of the two litters of young described above. Of the 

 69 females thus recorded. 15. or 21.7 jDer cent, had but one offspring 

 each: 52. or 75.3 per cent, but two each; while only 2 individuals, 

 or 2.0 per cent, had three. Three young is the maximum litter re- 

 corded. This, taken in connection with the protracted breeding sea- 

 son and lack of sure evidence of the production of two broods a year, 

 gives a surprisingly low rate of reproduction, indicating relative 

 freedom from inimical factors. 



Our breeding records for merriano. are fewer than for spectaJAlis^ 

 but are very similar in every way so far as they go. both as to the 

 time of year and number of young. 



FOOD AND STORAGE. 



Drpodomys s. spectahUls does not hibernate, so must prepare for 

 unfavorable seasons by extensive storage of food materials. There 

 are two .seasons of the year, in southeastern Arizona at least, when 

 storage of food takes place, namely, in spring, during April or May. 

 and in fall, from September to Xovember. the latter being the more 

 imi:»ortant. For the periods betAveen. the animal must rely largely 



