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The Great Basin Gopher Snake is distributed from Canada into Washington and Idaho, south into California, Nevada, Utah, and Colorado, and reaches into the northern parts of Arizona and New Mexico. In Wyoming it resides in the arid sagebrush, greasewood, and shrub communities of the desert life zone in the Wyoming Basin of Sweetwater County. It is most commonly found associated with rock outcrops, within or near juniper woodlands, and the flats of broad valleys and basins. Its distribution does not overlap with the range of the closely related Bullsnake.
It is active from late April through September. It is primarily diurnal but may become crepuscular or nocturnal during hot weather. It kills by constriction and feeds on mice, chipmunks, pocket gophers, ground squirrels, rabbits, birds and eggs. It quickly assumes a defensive posture when alarmed and will coil, flatten its head into a triangular shape, emit a long drawn-out hiss during inhalation and exhalation, and will strike at the intruder. When handled they can and will bite quite hard but soon become docileŚwrapping coils around the arm and squeezing.
They are large and heavy-bodied snakes about 4-5 feet long (TL). Their scales are weakly keeled and the anal plate is entire. The background is tan or pale yellow with 60-80 large, dark brown or black rectangular blotches along the midline of the body; these become saddles and rings near the tail. A second row of smaller blotches is found along the sides and these alternate with the midline blotches. The belly is white, cream, or beige with dark spots on the lateral margins of every 2nd, 3rd, or 4th ventral scale. They have a distinct black line running across the top of the head, through the eye, and down on to the middle of the jaw. A second black slash extends from just behind the eye to the rear of the jaw. They are distinguished from the Bullsnake by having a triangular (equilateral) shaped rostral scale that is as high as it is wide.
Mating occurs after leaving the den in early spring. They are oviparous and in June and July they will lay a clutch of 5-23 eggs hidden in burrows, under rocks, or buried in loose soil. Females will often congregate and lay their eggs in a communal area. Incubation requires 64-79 days and hatchlings begin appearing in August and September. Males reach sexual maturity in their 2nd year and females in the 3rd or 4th year.