636 ANIMAL LIFE IX THE YOSEMITE 



we have ever seen. "When fully relaxed this example .measured 645 milli- 

 meters (251/2 inches) from tip of nose to tip of tail, and its greatest girth 

 was 65 millimeters (21^^ inches). Most of the representatives of this species 

 which we have seen have been less than 20 inches long. 



The one individual noted by us in the Yosemite region was found 

 October 7, 1914, in a road near Sentinel Bridge. It had been killed by 

 some workmen who had passed along just previously. It is deplorable 

 that people should persist in destroying non-poisonous snakes. The deep- 

 rooted tendency in some human beings for this kind of reaction toward 

 all snakes seems to operate entirely without reason. The Rubber Snake is 

 not only harmless, but, for a reptile, it makes an admirable pet. We have 

 never known of a snake of this species attempting to bite or to resent 

 handling in any way. 



Garter Snakes. Genus Thamnophis*^ 



Field characters. — Body long, slender and tapering; tail pointed; scales of back all 

 ridged (keeled), never in more than 23 rows. (See fig. 62b.) Coloration of upper sur- 

 face black or grayish, with a light line along each side of body and another line down 

 middle of back, or else many small light spots on back; pattern never in large blotches 

 or cross-bands; under surface bluish green. Emit a foul-smelling liquid when handled. 



Occurrence. — Common along streams, about margins of ponds, and in wet meadows 

 throughout the Yosemite region up at least to 8600 feet altitude.42 Live on damp ground 

 and in water. Several individuals often found together. 



42 The identification of the species and subspecies of Garter Snakes is often a diflScult 

 matter even for a trained herpetologist. There is much variation among individuals, 

 especially in the numbers of scales; consequently series of specimens are usually required 

 to properly identify the snakes from any one locality. Difficulty may be experienced 

 in attempting to name certain individual specimens. The latest comprehensive study 

 of the Garter Snakes of western North America is that by Van Denburgh and Slevin 

 (Proc. Calif. Acad. Sci., ser. 4, vol. 8, 1918, pp. 181-270, pis. 7-17) who have identified 

 our specimens from the Yosemite region as belonging to tw^o species, one of which is 

 represented by three subspecies. These forms, with their principal characters (as 

 exhibited by the most typical specimens), and the localities at which they were found, 

 are as follows: 



Pacific Garter Snake, Thamnophis sirtalis infernalis (Blainville), has (usually) 

 7 scales on upper lip (supralabials), not more than 19 lengthwise rows of scales on back, 

 and upper surface black with three distinct light stripes, one down middle of back and 

 another low on each side of body. It is a lowland species, common at Snelling and 

 Lagrange and ranging eastward as far as floor of Yosemite Valley. 



Giant Garter Snake, Thamnophis ordvwides couchii (Kennicott), has usually 8 

 scales on upper lip, usually 21 rows of scales on forepart of body, and upper surface 

 of body black but with no light line down middle of back, the upper surface being 

 marked with small scattered light spots. (See fig. 62&.) It is a central California race, 

 found on meadows in Yosemite Valley. 



Mountain Garter Snake, Thamnophis ordinoides elegans (Baird and Girard), has 

 (usually) 8 scales on upper lip, not often more than 19 rows of scales on back, and a 

 dark body coloration with 3 distinct light stripes, one down middle of back and one 

 on each side of body. It is a high mountain subspecies, reported from floor of Yosemite 

 Valley, but more common in the higher altitudes as at Merced Lake (7500 feet) and 

 Tuolumne Meadows (8600 feet). 



Wandering Garter Snake, Thamnophis ordinoides vagrans (Baird and Girard), has 

 (usually) 8 scales on upper lip, 21 rows of scales on forepart of body, and a dull (often 

 grayish or greenish) liody coloration, l)ut with a distinct line down middle of hack; large 

 scales on under surface often with black markings. This snake is a Great Basin form, 

 taken at Walker Lake and near Mono Lake. 



