THE GROUND SQUIRRELS OP CALIFORNIA. 671 



it emanates is difficult to fix; also the distance is hard to determine. It 

 seems to be given as a Avarning by an individual, either located Avithiu 

 the mouth of its burrow (Stephens, 1906, p. 70) or Avhen standing 

 motionless under a bush. C. L. Camp (MS) records that he has seen 

 an individual, when its curiosity was aroused, stand high up on its hind 

 legs and utter its "sharp squeak" with the mouth wide open, at the 

 same time "giving the thorax a violent contraction." 



Facts in regard to the breeding of this squirrel are shown in the 

 following data. On March 15 (1914) near Barstow a male Round- 

 tailed Ground Squirrel was seen abroad which proved astonishingly 

 indifferent. "It came up to where we were digging out a kangaroo rat 

 colony, smelling into various burrows, evidently intently hunting for a 

 female. The testes of this animal were enormous, dragging on the 

 ground behind it as it waddled along" (Grinnell, MS). Two females 

 captured in the valley of the Colorado River opposite Cibola, April 3 

 and 4 (1910) , were found to contain six and four embryos, respectively ; 

 young about half grown were taken at Needles July 15 and 19 (1909) 

 (Grinnell, 1914, p. 224). Stephens (1906, p. 70) says that the breeding 

 season falls in March and April and that the number of young in a litter 

 is four to seven. In spite of the long hot period each year in the habitat 

 of this species, there is no evidence to show that more than one litter 

 is reared annually. 



There is a period of inactivity during midwinter, when these animals 

 are not seen abroad. Whether or not there is regular hibernation, as 

 with the species of colder regions, we do not definitely know; but this, 

 seems to be the case. 



"The food is seeds the greater part of the year; these are stored to 

 some extent. In the spring, during the few weeks when green vegetation 

 is obtainable, leaves and buds are eaten voraciously" (Stephens, 1906, 

 p. 70). In our experience, stems of the squRw-teai (Ephedra) and 

 leaves of the mesquite form an important element of the diet wherever 

 and whenever obtainable. 



In June, 1918, W. C. Jacobsen (MS) found several colonies of Yuma 

 Round-tailed Ground Squirrels in the Imperial Valley within five or 

 six miles south of Holtville. The interesting thing was that here the 

 animals were invading the cultivated fields and were finding alfalfa 

 suited to their tastes. Individuals were seen to eat the leaves of the 

 alfalfa with avidity, but left the stems uneaten. Many dry stems were 

 found lying about near the mouths of their burrows. At another 

 point, near Bond Corners, oat hulls were seen around burrows.' 



There is a possibility, therefore, that this strictly desert rodent might 

 come to have an economic bearing on the reclaimed sections of the 

 desert. Whether or not it will become a serious pest remains to be seen. 

 One note of interest in this connection is furnished by Stephens (MS), 

 who says that at Silsbee, while occasionally getting into the fields, the 

 Round-tails were easily drowned out. As far as known to us, this 

 species never drinks water even when within reach of it; In most parts 

 of its range and at most seasons of the year water is secured only 

 through chemical elaboration from its dry or nearly dry food materials. 

 It is currently reported by the farmers in Imperial Valley that the 

 native desert animal life quickly disappears when the land is brought 

 under cultivation and especially irrigation. 



