212 



AXIMAL LIFE IS THE YOSEMITE 



The body of the Flying Squirrel is somewhat flattened and along each 

 side there is a fur-covered double layer of skin extending between the fore 

 and hind legs and out to the 'wrist' and 'ankle.' (See fig. 32.) This sort 

 of membrane, when extended, about doubles the area of the lower surface 

 of the animal and thus contributes to the success of the squirrel's passage 

 through the air. The tail is broad, due to a thick, close covering of long 

 hairs at the sides, and is remarkably thin, reminding one, in toto, of a 

 single tail feather of a bird. The fur everywhere is dense, of even length, 

 and of a silky texture. The under surface of the body, which is of course 

 exposed during 'flight,' has a proportionately heavier covering of fur than 

 is present on other squirrels. Indeed, this heavy furring covers even the 

 feet, save for the sole pads. This type of pelage, besides serving to keep 

 the animal warm during the cold Sierran nights when it is abroad, also 

 makes for passage quietly through the air, a necessary precaution in a 

 region where owls are abundant. 



Fig. 112. Sierra Flying Squirrel. Photographed I'loin fresh sinciiiion Irujuicil in 

 Yosemite Valley, December 24, 1914; about % natural size. 



The head of the Flying Squirrel, and particularly the eyes, are pro- 

 portionately large as compared with the head and eyes of other members 

 of the squirrel tribe. Indeed the combination of large head and eyes and 

 soft body covering reminds one strongly of the condition found in such 

 nocturnal birds as the poor-wills and nighthawks. 



Information concerning the Flying Squirrel is much more difficult 

 to obtain than concerning the species of scpiirrels which are abroad in 

 the daytime. Our own knowledge of it wjis gained partly by sleeping out 

 at night under the trees, where the animals might be expected to occur, 

 and partly by trapping. A large number of traps was set at likely places, 



