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Reptiles of Yellowstone National Park

Reptile General Information

Cool, dry conditions limit Yellowstone's reptile to six species. Population numbers for these species are not known.

Yellowstone is home for a small variety of reptiles. Glacial activity and current cool and dry conditions are likely responsible for their relatively low numbers in Yellowstone. In 1991 park staff began cooperating with researchers from Idaho State University to sample additional park habitats for reptiles and amphibians. This led to establishment of long-term monitoring sites in the park. The relatively undisturbed nature of the park and the baseline data may prove useful in testing hypotheses concerning the apparent declines of several species of toads and frogs in the western United States. Reptile and amphibian population declines may be caused by such factors as drought, pollution, disease, predation, habitat loss and fragmentation, introduced fish and other non-native species.

Although no Yellowstone reptile or amphibian species are currently listed as threatened or endangered, several including the boreal toad are thought to be declining in the West. Surveys and monitoring are underway to try to determine if amphibian populations are declining in Yellowstone National Park.


Yellowstone National Park Reptiles
Bull Snake Prairie Rattlesnake Rubber Boa
Sagebrush Lizard Valley Garter Snake Wandering Garter Snake

Bull Snake

Bull Snake
Bull Snake - BLM Photo
Pitiophis catenifer sayi

Bull Snake - Pituophis catenifer sayi


Bullet A subspecies of the gopher snake, is Yellowstone's largest reptile, ranging from 50 to 72 inches long.

Bullet Yellowish with a series of black, brown, or reddish-brown blotches down the back; the darkest, most contrasting colors are near the head and tail; blotches are shaped as rings around the tail.

Bullet Head resembles a turtle's in shape, with a protruding scale at the tip of the snout and a dark band extending from the top of the head through the eye to the lower jaw.


Bullet In Yellowstone, found at lower elevations; drier, warmer climates; and open areas such as near Mammoth.


Bullet Lives in burrows and eats small rodents-behavior that gave the gopher snake its name.

Bullet Often mistaken for a rattlesnake because of its appearance and its defensive behavior: when disturbed, it will coil up, hiss loudly, and vibrate its tail against the ground, producing a rattling sound.

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Prairie Rattlesnake

Prairie Rattlesnake
Prairie Rattlesnake Snake - NPS Photo
Crotalis viridis viridis

Prairie Rattlesnake - Crotalis viridis viridis


Bullet More than 48 inches in length.

Bullet Greenish gray to olive green, greenish brown, light brown, or yellowish with dark brown splotches down its back that are bordered in white.


Bullet Only dangerously venomous snake in the park.

Bullet Lives in the lower Yellowstone River areas of the park, including Reese Creek, Stephens Creek, and Rattlesnake Butte, where the habitat is drier and warmer than elsewhere in the park.


Bullet Usually defensive rather than aggressive.

Bullet Only two snake bites are known during the history of the park.

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Yellowstone Rubber Boa

Rubber Boa
Rubber Boa Snake - NPS Photo
Charina bottae

Rubber Boa - Charina bottae


Bullet Infrequently encountered in Yellowstone, perhaps due to its nocturnal and burrowing habits.

Bullet One of two species of snakes in the United States related to tropical boa constrictors and pythons.

Bullet Maximum length of 24 inches.

Bullet Back is gray or greenish-brown, belly is lemon yellow; scales are small and smooth, making it almost velvety to the touch.

Habitat and Behavior

Bullet Eats rodents.

Bullet May spend great deal of time partially buried under leaves and soil, and in rodent burrows.

Bullet Usually found in rocky areas near streams or rivers, with shrubs or trees nearby.

Bullet Recent sightings have occurred in the Bechler region and Gibbon Meadows.

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Yellowstone Sagebrush Lizard

Sagebrush Lizard
Sagebrush Lizard - NPS Photo
Sceloporus graciosus graciosus

Sagebrush Lizard - Sceloporus graciosus graciosus


Bullet Only lizard in Yellowstone.

Bullet Maximum size of five inches from snout to tip of the tail; males have longer tails and may grow slightly larger than females.

Bullet Gray or light brown with darker brown stripes on the back set inside lighter stripes on the sides, running the length of the body; stripes not always prominent and may appear as a pattern of checks down the back; underside usually cream or white.

Bullet Males have bright blue patches on the belly and on each side, with blue mottling on the throat.


Bullet Usually found below 6,000 feet but in Yellowstone lives up to 8,300 feet.

Bullet Populations living in thermally influenced areas are possibly isolated from others.

Bullet Most common along the lower portions of the Yellowstone River near Gardiner, Montana and upstream to the mouth of Bear Creek; also occurs in Norris Geyser Basin, Shoshone and Heart Lake geyser basins, and other hydrothermal areas.


Bullet Come out of hibernation about mid May and active through mid September.

Bullet Diurnal, generally observed during warm, sunny weather in dry rocky habitats.

Bullet During the breeding season males do push-ups on elevated perches to display their bright blue side patches to warn off other males.

Bullet Feed on various insects and arthropods.

Bullet Eaten by bull snakes, wandering garter snakes, rattlesnakes and some birds.

Bullet May shed tail when threatened or grabbed.

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Valley Garter Snake

Valley Garter Snake
Valley Garter Snake - BLM Photo
Thamnophis sirtalis fitchi

Valley Garter Snake - Thamnophis sirtalis fitchi


Bullet Subspecies of the common garter snake.

Bullet Medium sized snake reaching total length of up to 34 inches.

Bullet Nearly black background color with three bright longitudinal stripes running the length of the body, underside is pale yellow or bluish gray.

Bullet Most distinguishing characteristics of this subspecies in our region are the irregular red spots along the sides.


Bullet Thought to be common in the past, now in decline for no apparent reason.

Bullet Closely associated with permanent surface water.

Bullet In Yellowstone observed only in the Falls River drainage in the Bechler region and three miles south of the south entrance along the Snake River.


Bullet Generally active during the day.

Bullet In the Yellowstone area it eats mostly toads, chorus frogs, fish remains, and earthworms; can eat relatively poisonous species.

Bullet Predators include fish, birds, and carnivorous mammals.

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Wandering Garter Snake

Wandering Garter Snake
Wandering Garter Snake - NPS Photo
Thamnophis elegans vagrans

Wandering Garter Snake
Wandering Garter Snake near Mammoth Hot Springs by John William Uhler © Copyright Page Makers, LLC
Thamnophis elegans vagrans

Wandering Garter Snake - Thamnophis elegans vagrans


Bullet Most common reptile in the park.

Bullet 6 to 30 inches in length.

Bullet Brown, brownish green, or gray with three light stripes-one running the length of the back and a stripe on each side.


Bullet Usually found near water in all areas of the park.

Bullet Eats small rodents, fish, frogs, tadpoles, salamanders, earthworms, slugs, snails, and leeches.


Bullet May discharge musk from glands at the base of the tail when threatened.

Bullet Gives birth to as many as 20 live young in late summer or fall.

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Information provided by the NPS and "Amphibians & Reptiles of Yellowstone and Grand Teton National Parks" by Edward D. Koch and Charles R. Peterson.

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