GBAY SQUIEBEL 197 



The California Gray Squirrel population in the tree-clothed parts of 

 the foothills is perhaps not more than one animal to every 10 acres ; in the 

 yellow pine belt there is perhaps one to every 3 or 4 acres. On the floor 

 of Yosemite Valley, in certain years at least, the density of population 

 reaches one an acre. In October of 1914 the numbers were at their 

 maximum; more than 4000 were computed to be on the Valley floor and 

 the lower slopes adjacent. But the squirrel population is subject to 

 fluctuations from time to time and place to place. In the spring of 1916 

 the number of these animals on the floor of Yosemite Valley was very 

 much less than in the fall of 1914. 



The California Gray Squirrel is the largest of the local squirrels (save 

 the marmot), being somewhat heavier than the California Ground Squirrel 

 and very much bigger than any of the other species. The Gray Squirrel 

 shows specialization for life in trees in several obvious ways. Its body 

 and legs are long and slender and very strongly muscled so that it can 

 leap considerable distances between branches. The toes are all provided 

 with sharp curved claws which serve well in enabling the animal to cling 

 to the irregularities of the bark of trees and to sprays of foliage. The tail 

 is long and broadly haired to serve as rudder and counterbalance in the 

 various movements of the animal. (See pis. 83&, 34.) 



On the ground a Gray Squirrel moves by a series of jumps. The front 

 and hind legs act in pairs, the front ones being held close together while 

 the hind ones spread out widely and are carried forward beyond the body. 

 When traveling at full speed one of these squirrels has been found to have 

 covered as much as 4 feet in a single bound over snow. When ascending 

 a tree its movement is similar; the squirrel 'gallops' up the trunk, often 

 with all four feet off the bark at the same instant. The fine curved claws 

 on the toes of each foot catch readily in the bark and hence the squirrel 

 often has an even firmer hold when in a tree than when on the ground. 

 In descending a tree, which the squirrel does head first, the hind feet are 

 turned outward so that the claws of the hind toes will catch on the bark; 

 and the feet are moved alternately. 



Where trees are so close that the branches overlap or nearly touch, a 

 Gray Squirrel may travel aloft for long distances without once coming to 

 the ground ; if occasion demands, the animal can run through the tree tops 

 at a relatively high rate of speed. 



California Gray Squirrels are active throughout the year, showing no 

 tendency to hibernate as do the ground squirrels. On stormy days they 

 usually remain in their nests, but they promptly fare forth as soon as 

 the weather clears. Their ability to be abroad during the winter is prob- 

 ably due to the fact that their food, consisting of fruits, nuts, and fungi, 

 is practically all aboveground, and that it persists nearly or quite through 



