There are a approximately 47 reptile species in Grand Canyon National Park. Ten are considered common along the river corridor and include lizards and snakes. Reptiles use both upland desert and riparian sites, but higher densities are supported in riparian areas due to the rich invertebrate food source and vegetation. Lizard density tends to be highest along the stretch of land between the water's edge and the beginning of the upland desert community. Within this zone, exotic saltcedar (tamarisk) is abundant, which is excellent lizard habitat. One can also find gila monsters and chuckwallas here, the two largest lizards in the Canyon.
Many snake species, which are not directly dependent on surface water, may be found both within the inner gorge and the Colorado River corridor. Since many snakes feed on lizards, higher prey densities along the river probably result in higher snake densities as well. Six rattlesnake species have been recorded in the park. Two are species rarely encountered, the South-western speckled rattlesnake and the Northern black-tailed rattlesnake. The other four rattlesnakes are subspecies of the Western Diamondback rattlesnake complex: the Grand Canyon pink rattlesnake, Great Basin rattlesnake, Mojave "green" rattlesnake, and Hopi rattlesnake. Of these, the Grand Canyon pink rattlesnake is the most common.
As the demand for reptiles in the pet trade increases and collectors seek new sources of supply, many national parks are having problems with illegal reptile collection, especially rattlesnakes. Approaching and feeding wildlife in the park is illegal and poaching is a punishable crime.
Desert Scrub: The arid conditions of the desert scrub uplands favor a fauna comprised chiefly of reptiles and desert-adapted rodents. Except for the desert banded gecko, which seems to be distributed only near water along the Colorado River, all of the reptiles found near the river also appear in the uplands, but in lower densities. The desert gopher tortoise, a threatened species, inhabits the desert scrublands in the western end of the park.
Coniferous Forest: Reptiles can also be found in Grand Canyon's rim forests. There are a variety of snakes and lizards here, but one species of reptile, the mountain short-horned lizard, is a particularly abundant inhabitant of the piñon-juniper and ponderosa pine forests.