it emanates is difficult to fix; also the distance is hard to determine. It seems to be given as a warning by an individual, either located within the mouth of its burrow (Stephens, 1906, p. 70) or when 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 squaw-tea (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.
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