GOPHER SNAKE 645 



The ability of a gopher snake, or, for that matter, of any other snake, 

 to swallow prey much larger than itself is consequent upon the peculiar 

 structure of the snake's mouth. Its lower jaw is loosely attached, there 

 being a flexible connection between the two halves at the chin, while at 

 the back on each side there is a bone (quadrate) w'hich can be swung out 

 so as to make the diameter of the mouth orifice much greater. Then, as 

 there is no breast bone attaching to the ribs, the digestive tract can stretch 

 to a much greater extent than is possible in birds and mammals. When 

 engaged in swallowing a rodent, one of these snakes is relatively helpless 

 and can easily be captured. Once the act of swallowing is commenced 

 (the prey is practically always taken in head first), the squirrel or gopher 

 cannot be quickly disgorged. 



Near Stage Station (on the Coulterville road), on June 14, 1915, a 

 rotten log, upon being broken apart in a search for a lizard, yielded a 

 small Valley Gopher Snake which had in it a nearly full-sized White-footed 

 Mouse (Peromyscus, probably calif ornicus). The girth of the mouse 

 was about twice that of the snake; consequently the snake's skin was so 

 stretched opposite the place where the mouse lay in the digestive tract 

 that the scales on the sides were widely separated, and the soft skin show^ed 

 between them. The strong digestive juices had already begun to act, and 

 the fore part of the mouse's skull was almost completely dissolved. 



In Yosemite Valley near Pohono Bridge an active young gopher snake 

 was seen at the roadside May 1, 1916. This happened to be our only 

 record for the Valley proper. 



During the winter, gopher snakes are practically never seen abroad. 

 They spend this part of the year somewhere underground, coming out if 

 at all only on the warmest days. At Snelling, on January 6, 1915, while 

 Mr. Camp was excavating the burrow of a kangaroo rat he found a snake 

 of this species in one of the rodent's tunnels. The snake was quite lively, 

 showing none of the torpidity ordinarily to be expected of a hibernating 

 animal. 



Pacific Rattlesnake. Crotalus oreganus Holbrook 



Field characters. — A segmented horny 'rattle' at end of tail (fig. 64). Body stout; 

 tail (vent to rattles) short, usually less than I/^q length of body (to vent). Head 

 bluntly triangular; a definite constriction at neck. (See pi. 59b.) Scales on back rela- 

 tively large, keeled, and in 23 to 27 rows. Total length (snout to end of rattles) up to 

 4 feet (possibly more) ; girth of body up to 5 inches. General coloration yellowish 

 brown or grayish brown, with a series of large saddle-marks of dark brown or black 

 along middle of back ; also two rows of smaller dark spots along each side of body, these 

 alternating in position with the large blotches. Track: Broad, much curved; on soft 

 roadways shows much earth pushed up at sides of curves (pi. 40&). 



Occurrence. — Eesident in numbers on west slope of Yosemite region where recorded 

 from Snelling eastward to altitude of 8100 feet near junction of Sunrise and Merced 

 Lake trails. Lives chiefly near rocks and in brushy places, but also in open country 

 of lowlands. 



