VALLEY GOPHER SNAKE. Pituophis catenifer heermanni (Hallowell)

Field characters.—Size variable, often large; body always relatively stout, but tail tapering slenderly to a point. Scales on back ridged or keeled, and in 29 or more rows. Ground color of body ocher yellow, marked along back with many 'saddle-marks' of dark brown, and with smaller dark spots along sides. (See pl. 59a.) When first approached often lies motionless on ground; then glides off to nearest safety refuge; if cornered, is likely to 'show fight' by hissing and striking.

Occurrence.—Fairly common in the Lower and Upper Sonoran zones and lower part of Transition Zone on west side of Sierra Nevada. Recorded from Snelling and Pleasant Valley eastward to floor of Yosemite Valley. Lives in grasslands and along road margins; rarely or never goes into water or up into bushes or trees. Usually solitary.

The Valley Gopher Snake, sometimes called "bull snake," is fairly common in the western foothill district of the Yosemite region, and is likely to be seen in any of the grasslands or along any of the dusty road ways up to 4000 feet altitude.

The general run of gopher snakes to be found in the Yosemite region will probably exceed in average size the rattlesnakes now found there. This is due in part to the fact that the gopher snake tends to grow to a large size and also to the fact that the rattlers are killed whenever found, while some at least of the gopher snakes are protected by the farmers of the country and so reach greater age. Gopher snakes elsewhere often grow to a length of 5 feet or even more and have a normal body girth in the neighborhood of 6 inches; but the largest individual which we chanced to encounter within the Yosemite region was 1025 millimeters (40-1/2 inches) long. The average length of all those handled by us was 32 inches.

The Valley Gopher Snake is a distinctive species as regards its coloration (pl. 59a), being approached as to pattern only by the rattlesnake and by very young racers. The ground color is ocher yellow. Down the middle of the back there is a row of hexagonal or squarish blotches of dark brown which toward the end of the tail become black. Along each side of the body are rows of smaller spots usually blackish in color. The rattlesnake's pattern consists usually of very large blotches, each with a light margin, and it does not have so many side spots. The young racers are more spotted than the gopher snakes and of course they may be told from young gopher snakes at once by their smooth scales, those of the latter species, no matter what the age, always being ridged or keeled.

Generally speaking, the gopher snake is a rather quiet, even a lethargic species. When come upon on the ground in a field it will often lie perfectly quiet and thereby escape detection; there is no movement to catch the eye. Its usual color pattern is very close to that of the dry grassland in which it lives so much of the time. If aroused it can, and if unhindered will, make off with fair rapidity. But if cornered a gopher snake will show fight, coiling its body up and drawing back and spreading its head until the latter has the triangular outline often considered (though erroneously so) the mark of a poisonous species. Then it will usually fill its lungs with air, swell its body out considerably and suddenly lunge at its enemy, expelling the air with a hissing sound as it does so. This 'bluff' is often effective and gives the snake a chance to make good its escape. A curious habit of some individual gopher snakes is to vibrate rapidly the slender tip of the tail, whereby if the animal happens to be in dry grass or weeds a rattling sound is produced, suggestive of the rattle of a rattlesnake. This might, on occasion, serve the purpose of warning a potential enemy. But, of course, the Gopher Snake is not at all venomous.

Gopher snakes may often be seen around the burrows of earth-dwelling rodents such as the ground squirrels and pocket gophers, and the snakes subsist to a considerable extent upon these animals. The snakes are able to pursue the rodents underground and thus have an advantage over the large carnivorous mammals and birds which must either catch the squirrels and gophers above ground or else, as do most of the mammals except the weasel, dig them out.

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) which 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 californicus). 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 showed 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.