THE GROUND SQUIRRELS OF CALIFORNIA. 



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It is quite likely that California Ground Squirrels construct new 

 burrows from time to time, or, what is more probable, that each young 

 individual as it approaches maturity leaves the parent burrow and 

 digs a home for itself. In any event, in places there are many more 

 burrows than individual squirrels present at any one time. Some of 

 these tunnels, especially in the plains and foothill country, are joined 

 together below ground to a greater or less degree and constitute the 

 colonial burrows already described. When hurriedly seeking safety 

 a squirrel will pitch down into the nearest one of a number of holes in 

 the vicinity of the one about which it was first seen. The commonly 

 uninhabited burrows may thus serve in extremity as temporary refuges. 



The burrows of the squirrels are often inhabited by species of animals 

 other than the rightful owners. Ground owls habitually make their 

 homes in squirrel holes, probably deserted ones; and, to a less extent, 



Fig. 9. Nest and male of "digger" squirrel as dug out after burrow was treated 

 with carbon-bisulphid. The spherical shape of the nest-cavity and the structure of 

 the nest itself is well shown. 



the holes are frequented by California toads, Western gopher snakes 

 and Pacific rattlesnakes. It is unlikely that the presence of the latter 

 two animals is congenial to the squirrels, as both of these snakes are 

 known to eat ground squirrels in numbers. Regularly communal occu- 

 pants of squirrel burrows are scorpions, centipedes and mole crickets. 

 Mole crickets were found to serve as reliable indicators of the efficiency 

 of the gas when squirrels were fumigated in their burrows. If the 

 gas had not killed the crickets it was found that the squirrels had not 

 succumbed. 



California Ground Squirrels are accustomed to furnish their under- 

 ground quarters comfortably. Special nests are constructed and main- 

 tained in good order, where the individual may sleep or rest in warmth, 

 free from contact with the damp earth. Each burrow occupied by 

 a single squirrel was found to contain at least one well-made nest. Id 

 some eases there w r ere two, one obviously older than the other. In the 



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