THE GROUND SQUIRRELS OP CALIFORNIA. 



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of the lower levels; but the metropolis of the species is in the middle 

 region among the salt-bushes (Atriplex) which thickly dot these plains. 



This ground squirrel is soon driven out when fields come under 

 cultivation. It clings closely to the wild land and apparently rarely 

 if ever invades adjoining ground which may happen to be under culti- 

 vation. Thus in May, 1918, at the mouth of San Emigdio Creek, Kern 

 County, we found these squirrels quite abundant on three sides of an 

 extensive alfalfa field which was entirely surrounded by virgin tracts 

 of the salt-bush (Atriplex), yet during our stay of nearly two weeks, 

 not a single Nelson Squirrel was observed to enter this field or even to 

 touch a leaf of the alfalfa. 



As usually encountered, the Nelson Squirrels are seen scurrying 

 rapidly across open places between clumps of salt-bushes, or else, more 

 rarely, standing straight up to their full height in true "picket-pin" 

 fashion just before they disappear down their burrows. The normal 

 mode of travel is by a series of short rapid jumps of from 6 to 12 

 inches. When approaching a hole leisurely, or when foraging about, 

 the animals sometimes slow down into a walk. 



These squirrels are not early risers, being rarely found abroad until 

 well after sun-up. At the mouth of San Emigdio Creek, during the 

 second week in May, Nelson Squirrels began to appear at the entrances 

 to their burrows in the south-facing overhanging bank of a wash, 

 between 8 and 8 :15 in the morning. They appeared earlier in the day 

 at this point than elsewhere in the vicinity, doubtless because this bank 

 first received the full force of the early morning sun. Ten o'clock 

 marked the period of greatest activity. The squirrels under observation 

 disappeared each day between 11:30 and 12 o'clock and were rarely 

 seen again until 2 :30 in the afternoon, when they began to reappear in 

 the shade of certain dense-foliaged salt-bushes that grew on the brink 

 of the wash. Although they were frequently seen to bask in the rays of 

 the early morning sunshine, these squirrels shunned the direct sunlight 

 at noonday. As early even as 10 o'clock in the morning one female 

 was seen repeatedly to seek shelter in the shade of a fencepost (J. 

 Dixon, MS). 



The tail of the Nelson Antelope Squirrel, as with the Desert Antelope 

 Squirrel, is the most conspicuous feature about the animal. When 

 running, the tail is curved forward over the back, in which position the 

 creamy under surface is most effectively displayed so that at a distance 

 one receives the impression that merely a bit of thistledown is blowing 

 along over the sand. The body of the animal, with its ground-like tone 

 of color, practically disappears. This illusion is furthered by the 

 twitching of the tail and by the momentary pauses of the animal which 

 correspond closely with the usual interrupted flight of a tuft of thistle- 

 down. 



When the squirrel is foraging about on all four legs, or else sitting 

 up, the tail is held curved forward over the back; in fact, one rarely 

 sees the tail held in any other position (see fig. 28). At such times the 

 tip of the tail is often curved slightly upward or outward. When 

 excited or frightened the tail of the animal is twitched rapidly fore and 

 aft, but rarely or never sideways. One individual observed at a dis- 

 tance of ten feet was seen to vibrate its tail intermittently with exceeding 

 rapidity, there being half-minute intervals between the periods of 



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