THE GROUND SQUIRRELS OF CALIFORNIA. 



655 



The average weight of six adult female Oregon Ground Squirrels 

 was found to be 302 grams (about 10£ ounces). The full stomachs of 

 these six squirrels were found to give an average weight of 18.5 grams. 

 Subtracting the ascertained weight of the stomach itself (3.5 grams), 

 gives the weight of the contents, alone, representing doubtless one full 

 meal, as 15 grams, or one-twentieth the entire weight of the animal. 

 The stomach contents was in all cases a closely packed, slightly moist 

 (not watery) mass of finely chewed green stuff. This could not be 

 analyzed as to kinds of plants represented, but the squirrels were seen 

 to be feeding upon all sorts of vegetation, practically everything going 

 to make up the usual forage grazed from such lands by live stock. 



Our observations led us to believe that, at the very least, two full 

 stomach-loads of greens were eaten by each squirrel each day, or 30 

 grams of forage. Of course this does not account for wastage, evidence 

 of which, in the way of cut stems and grass blades, was plentiful. 

 Figuring from the average number of adult squirrels per square mile, 

 70,000, and counting on two meals per day, we find a minimum of 

 2,100,000 grams, or somewhat more than two tons, of green forage 

 devoured by the squirrels each day on a square mile of pasture. 

 Granted that a grazing steer eats fifty pounds of pasture forage each 

 day, we conclude that the squirrels on a square mile of pasture 

 appropriate each day the forage which might support ninety head of 

 cattle. 



Expressing it in other ways, 750 Oregon Ground Squirrels during the 

 growing season of pasture grass eat as much as one steer, and the 

 squirrels on every seven acres of pasture thickly inhabited by them 

 eat as much as one steer! 



The burrows of the Oregon Ground Squirrel where the animals are 

 at all numerous fairly riddle the ground. Most of the openings come 

 to the surface at a rather steep angle and without any earth at their 

 mouths. Now and then there is an opening which slants to the surface 

 and has a good-sized mound, and such as these seem to mark the 

 nesting burrows as distinguished from the short, temporary, refuge 

 burrows, or those occupied by males. We spent the entire day of 

 May 16 excavating one nesting burrow, with results shown in figure 19. 



The mound at the main entrance to this burrow system was rather 

 large in extent, though shallow. It consisted of this year 's loosely piled 

 earth, covering up the grass on an area of nearly two square yards and 

 thus marking the place conspicuously. The system of burrows, in part 

 at least, probably represented two seasons' work and maybe more. 

 While there were only two openings to this system, there were several 

 points at which underground branches came nearly to the surface so 

 that a hard-pressed squirrel, pursued by some underground enemy, 

 could have quickly dug clear out and escaped overland. 



As usual with ground squirrels, the runways were everywhere smooth 

 and free from excrement, the nest chamber in use being unexpectedly 

 clean. The feces of the young are evidently collected by the mother and 

 carried to the places where her own are deposited, in the special 

 branches or defecatoria. Here the earth is tamped over the mass in 

 such a way that the pellets are kept separated by the soil particles, with 

 no chance to fester. The fecal pellets are dryish, anyway. Some 

 saved for examination, probably from the adult squirrel, prove to be 



63 



