colonial burrow that was dug out, three nests were found, of which two were new. The nests were always placed well back in the burrows (see figs. 6, 7), where they would have maximum protection from digging enemies such as coyotes and badgers. The cavities in which the nests were placed were short globular chambers and were usually situated slightly above and to one side of the main run, so that the drainage was away from rather than into the nest. The cavity in which a nest containing a female and four small young was found measured 10 inches in length, 9 inches wide and 7 inches high. The nest cavity used by a male squirrel was 12 × 10 × 7 inches (in the same dimensional order), while the two nest cavities in the colonial burrow measured 12 × 10 × 8 and 12 × 12 × 7 inches, respectively.
All of the nests found were of similar composition and construction. Finely shredded dry grass blades and roots, and fine stems of foxtail and needlegrass, formed the bulk of the constituent material. The nests were spherical in shape and deeply cupped. The walls were from
Fig. 10. Nest and female of "digger" squirrel as uncovered after the burrow had been gassed. Excavated on the University of California Campus, Berkeley, April 6, 1918.
two to two and one-half inches thick. The walls of the nest which contained the young squirrels were arched over and met at the top, forming a sort of a canopy. Entrance to this nest was gained through a hole near the top. The material in the walls had been compressed or felted into a thick, warm fabric. The outside dimensions of this nest were 10 × 9 × 7 inches, while the inside cavity measured 6 × 4 × 5 inches. Compared with that of the female just described, the nests of male squirrels were smaller, had lower walls and were more loosely constructed (see fig. 9). The nests of the males did not completely fill the cavities in which they were placed, as did the nest of the female. A nest occupied by a male measured 8 × 10 × 7 inches outside and 4 × 5 × 4 inches inside. The three nests in a colony burrow excavated
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