Bull (gopher) snake (Pituophis melanoleucus ssp. affinis)—a large, 4 to 8 feet,  tan snake with darker brown blotches on the back. This snake often suffers from mistaken identity by people anxious to see a rattlesnake in every snake. Frequents deserts, prairie, brushland, woodland, coniferous forests, and farmland. It is active chiefly by day except in hot weather.

Western Rattlesnake (Crotalus viridis)—a heavy-bodied, venomous snake with a slender neck and broad triangular head. Coloration varies but is generally light brown with brownish diamond-shaped blotches down the midline of the back, generally edged with dark brown or black. Adults range from 1 to 5 feet long. It is most commonly found in the monument in open desert country, rocky hillsides, and overgrazed shortgrass prairies.

The Lesser Earless Lizard (Holbrookia maculata) is a 4"-5" gray to brown lizard with the color depending upon the color of the earth it inhabits. It is diurnal and may have no external ears since it burrows headfirst into the soil.

The Plains Spadefoot (Scaphiopus bombifrons) is a stout toad with a sharp-edged spade on the inside os each hind foot. This is used to push soil aside as the toad burrows in the ground. These toads are nocturnal.