Wyoming Snakes: Identification Guide With Pictures

Last checked November 3, 2026 against official sources.

On this page

Venomous snakes
The other 14 snakes
Lookalikes
When they are active
If you are bitten or stung
How to report
What official sources say
About this list
Sources

This page lists 16 snakes: all from Wyoming Game and Fish Department's Reptiles in Wyoming. 2 are venomous by official accounts: Midget Faded Rattlesnake and Prairie Rattlesnake.

Venomous snakes in Wyoming

Official sources label these snakes venomous in Wyoming. Venomous snakes in Wyoming has more on each one.

Midget Faded Rattlesnake

Crotalus oreganus concolor

Venomous per Wyoming Game and Fish Department

Where in Wyoming: Range is restricted to the lower Green River Valley from the cities of Green River and Rock Springs south to the Utah-Wyoming state line. Wyoming Game and Fish Department, Nongame Section
Conservation: Wyoming Species of Greatest Conservation Need (NSS1, Tier I)

What the sources say

Venom: “Venom of this species is considered more potent than other closely related species (Baxter and Stone 1985).” (Wyoming Game and Fish Department)

Habitat: Rock outcrops in sagebrush desert communities. (Wyoming Game and Fish Department, Nongame Section)

Prairie Rattlesnake

Crotalus viridis

Venomous per National Park Service

Danger to people

“Only dangerously venomous snake in the park.” National Park Service

Size

Usually about 3 to 4 feet; Montana gives 15 to 60 inches and NPS says up to 5 feet. Arizona gives a maximum of 28 to 64 inches (excluding rattle) depending on subspecies; in Colorado it is rarely over 39 inches.

How to recognize it

Rattle (or a button in newborns) at the tail tip
Head much broader than the neck, many small scales on top of the head, heat-sensing pit between eye and nostril
Vertical (cat-like) pupils

Where in Wyoming

In Wyoming, Prairie Rattlesnakes occur in all counties east of the Continental Divide and in Carbon County west of the Divide. Wyoming Game and Fish Department

Conservation

Wyoming Species of Greatest Conservation Need (NSS4, Tier III)

What the sources say

Venom: “The only venomous snake found at the park is the prairie rattlesnake.” (National Park Service)

Habitat: Plains, foothills, and scarp woodlands, especially near granite or limestone outcrops. (Wyoming Game and Fish Department, Nongame Section)

Full Prairie Rattlesnake guide

The other 14 snakes

From A to Z. "Not stated" means no official source we use gives a venom status, not that the snake is harmless. Some harmless snakes mimic venomous ones: leave every snake alone.

Bullsnake

Pituophis catenifer sayi

Non-venomous per National Park Service

What the sources say

Venom: “Although bullsnakes can mimic rattlesnakes - flattening their head, coiling their body and hissing - they are not venomous.” (National Park Service)

Habitat: Plains grasslands, sagebrush-grasslands, sandhills, riparian shrub, marshes, rocky canyons, mountain-foothills shrub, agricultural areas, urban areas. (Wyoming Game and Fish Department, Nongame Section)

Desert Striped Whipsnake

Coluber taeniatus taeniatus

Not stated

Venom: No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier II)

What the sources say

Habitat: Prefers semi-desert shrublands. (Wyoming Game and Fish Department, Nongame Section)

Eastern Yellow-bellied Racer

Coluber constrictor flaviventris

Non-venomous per National Park Service

What the sources say

Venom: “Only one venomous species is present: the prairie rattlesnake.” (National Park Service)

Habitat: Woodlands and scarp woodlands within the plains and foothills zones, often near water. (Wyoming Game and Fish Department, Nongame Section)

Great Basin Gophersnake

Pituophis catenifer deserticola

Non-venomous per Wyoming Game and Fish Department, Nongame Section

Where in Wyoming: Found in southwest Wyoming. Wyoming Game and Fish Department, Nongame Section
Conservation: Wyoming Species of Greatest Conservation Need (NSS2, Tier II)

What the sources say

Venom: “Mimics rattlesnakes when threatened but harmless to humans.” (Wyoming Game and Fish Department, Nongame Section)

Habitat: Sagebrush communities and desert habitats. (Wyoming Game and Fish Department, Nongame Section)

Northern Rubber Boa

Charina bottae

Non-venomous per National Park Service

Size

In the Northwest it rarely exceeds about two feet (WDFW). Montana: 14 to 28 inches total length; Yellowstone gives a maximum of 28 inches; Colorado gives a maximum of about 33 inches.

How to recognize it

Thick body, small eyes, tiny scales, and a blunt tail that looks like the head
Loose, wrinkled skin gives a rubbery look and feel
Small, smooth scales, almost velvety to the touch

Conservation

Wyoming Species of Greatest Conservation Need (NSS3, Tier II)

What the sources say

Venom: “There are no species of venomous snakes in the park.” (National Park Service)

Habitat: Near water and beneath logs, flat rocks, and other surface objects in forested foothills and lower montane zones. (Wyoming Game and Fish Department, Nongame Section)

Full Northern Rubber Boa guide

No confirmed photo of Plains Black-headed Snake

Plains Black-headed Snake

Tantilla nigriceps

Not stated

Venom: No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Where in Wyoming: Has been found in Platte County. Wyoming Game and Fish Department, Nongame Section
Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier III)

What the sources say

Habitat: Plains, grasslands, scrub brush, and woodlands. (Wyoming Game and Fish Department, Nongame Section)

Plains Gartersnake

Thamnophis radix

Not stated

Venom: No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier III)

What the sources say

Habitat: Near small streams, sloughs, marshes, ponds. May be found in urban areas, dry grasslands, sandhills. (Wyoming Game and Fish Department, Nongame Section)

Plains Hog-nosed Snake

Heterodon nasicus

Not stated

Venom: No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier II)

What the sources say

Habitat: Burrows in soft soil or sand in plains grasslands and sandhills. (Wyoming Game and Fish Department, Nongame Section)

Red-bellied Snake

Storeria occipitomaculata

Not stated

Venom

No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.

Size

Usually 8 to 10 inches; state figures run from about 4 to 16 inches, with a Florida record of 16.6 inches.

How to recognize it

Plain, unmarked red or orange belly.
Three light spots just behind the head, which may fuse into a collar.
Keeled (ridged) scales in 15 rows at midbody and round pupils.

Conservation

Wyoming Species of Greatest Conservation Need (NSSU, Tier II)

What the sources say

Habitat: Near water under flat rocks, logs, and other surface objects in moist woodland communities. (Wyoming Game and Fish Department, Nongame Section)

Full Red-bellied Snake guide

Red-sided Gartersnake

Thamnophis sirtalis parietalis

Non-venomous per National Park Service

Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier III)

What the sources say

Venom: “Only one venomous species is present: the prairie rattlesnake.” (National Park Service)

Habitat: Plains, foothills, montane zones, near permanent water sources. (Wyoming Game and Fish Department, Nongame Section)

Smooth Greensnake

Opheodrys vernalis

Not stated

Venom: No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Conservation: Wyoming Species of Greatest Conservation Need (NSS3, Tier II)

What the sources say

Habitat: Occurs under rocks, logs, or other surface objects in forests within the foothills and montane zones. (Wyoming Game and Fish Department, Nongame Section)

Valley Gartersnake

Thamnophis sirtalis fitchi

Non-venomous per National Park Service

Conservation: Wyoming Species of Greatest Conservation Need (NSSU, Tier III)

What the sources say

Venom: “There are no species of venomous snakes in the park.” (National Park Service)

Habitat: Plains, foothills, montane zones, usually near permanent water sources. (Wyoming Game and Fish Department, Nongame Section)

Wandering Gartersnake

Thamnophis elegans vagrans

Non-venomous per National Park Service

What the sources say

Venom: “There are no species of venomous snakes in the park.” (National Park Service)

Habitat: Found in all habitat zones except alpine, usually near water. (Wyoming Game and Fish Department, Nongame Section)

Western Milksnake

Lampropeltis gentilis

Non-venomous per National Park Service

Conservation: Wyoming Species of Greatest Conservation Need (NSS3, Tier II)

What the sources say

Venom: “Only one venomous species is present: the prairie rattlesnake.” (National Park Service)

Habitat: Grasslands, sandhills, scarp woodlands, usually below 6,000 feet. (Wyoming Game and Fish Department, Nongame Section)

Snakes people confuse

Prairie Rattlesnake or Western hognose snake?

Prairie Rattlesnake Venomous

Western hognose snake Not stated

The Montana Field Guide names the western hog-nosed snake as a lookalike and says that in Montana no other snake has rattles: a hognose has no rattle.

Photos show typical adults; individuals vary. Never get close to compare.

When snakes are active in Wyoming

Records of snakes in Wyoming peak in June to August. They show when people record snakes, not how many there are (about month bars).

150 records of snakes in Wyoming by month (GBIF, CC0 and CC BY records).

Prairie rattlesnakes overwinter in large groups underground and usually emerge in April or May (WGFD). Wyoming Game and Fish Department
Midget faded rattlesnakes are typically active late April through September (WGFD). Wyoming Game and Fish Department
Rattlesnakes are often active at night in summer (WGFD). Wyoming Game and Fish Department

If you are bitten or stung

Call 911 or Poison Help at 1-800-222-1222 right away. Poison Help connects you to your local poison center, any time of day.

Official advice from Wyoming Game and Fish Department:

If someone is bitten by a rattlesnake, call 911 immediately; carry a reliable way to call. Wyoming Game and Fish Department
If you come across a rattlesnake, do not try to move or kill it; back off quietly and let it retreat. Wyoming Game and Fish Department
In rattlesnake country wear sturdy boots and long pants, stay on trails, step on logs and rocks rather than over them, keep pets leashed, and use a flashlight at night. Wyoming Game and Fish Department

How to report

Report mountain lion sightings to Wyoming Game and Fish at 1-877-WGFD-TIP (or the non-emergency police line). Rare or interesting nongame birds, mammals, amphibians and reptiles can be reported to the WGFD Nongame Section through its "Report an Observation" form. Wyoming Game and Fish Department

What official sources say

Are there venomous snakes in Wyoming?

Yes. Two rattlesnakes are on the WGFD reptile list: the prairie rattlesnake (all counties east of the Continental Divide and Carbon County west of the Divide, per the WGFD SWAP account) and the midget faded rattlesnake (lower Green River Valley). Wyoming Game and Fish Department

“Rattlesnakes occur in many parts of Wyoming.”

Are there rattlesnakes in Wyoming?

Yes. WGFD: rattlesnakes occur in many parts of Wyoming; they like rocky areas, prairie dog colonies, river corridors and debris that gives cover. Wyoming Game and Fish Department

“Rattlesnakes occur in many parts of Wyoming.”

Are there venomous snakes in yellowstone?

Yes. NPS: the prairie rattlesnake is the only dangerously venomous snake in Yellowstone; it lives in the lower Yellowstone River areas. National Park Service

“Only dangerously venomous snake in the park.”

Are there venomous snakes in grand teton national park?

No. NPS: Grand Teton has three snakes (wandering and valley garter snakes, rubber boa) and no venomous snakes. National Park Service

“There are no species of venomous snakes in the park.”

About this list

The species list comes from Reptiles in Wyoming (WGFD species list, data from WYNDD Data Explorer) (Wyoming Game and Fish Department, Last modified 01-22-2023; data 01-19-2024).

Venom labels come only from official sources and link to them; "Not stated" never means harmless. How labels work.

Want a paper copy? Print the Wyoming snakes ID chart.

Sources

Nongame Wildlife. Wyoming Game and Fish Department. no page date shown; checked November 3, 2026.
Reptiles in Wyoming (species list). Wyoming Game and Fish Department. Last modified on 01-22-2023; checked November 3, 2026.
Reptiles - Devils Tower National Monument. National Park Service. updated April 24, 2025; checked November 3, 2026.
Quoted passages (3)
“Although bullsnakes can mimic rattlesnakes - flattening their head, coiling their body and hissing - they are not venomous.”
“Only one venomous species is present: the prairie rattlesnake.”
“The only venomous snake found at the park is the prairie rattlesnake.”
Atlas of Birds, Mammals, Amphibians, and Reptiles in Wyoming. Wyoming Game and Fish Department, Nongame Section. December 2021; checked November 3, 2026.
Quoted passages (1)
“Mimics rattlesnakes when threatened but harmless to humans.”
Midget Faded Rattlesnake - Crotalus oreganus concolor (SWAP 2017 species account). Wyoming Game and Fish Department. 2017 (document footer; checked November 3, 2026.
Quoted passages (2)
“Venom of this species is considered more potent than other closely related species (Baxter and Stone 1985).”
“The active period for this snake is typically from late April through September.”
Reptiles - Grand Teton National Park. National Park Service. updated October 18, 2022; checked November 3, 2026.
Quoted passages (1)
“There are no species of venomous snakes in the park.”
Prairie Rattlesnake - Yellowstone National Park. National Park Service. updated April 29, 2025; checked November 3, 2026.
Quoted passages (1)
“Only dangerously venomous snake in the park.”
Prairie Rattlesnake - Crotalus viridis (Wyoming SWAP 2017 species account). Wyoming Game and Fish Department. 2017; checked November 3, 2026.
Quoted passages (1)
“…prairie dog burrows, or other abandoned mammal burrows and usually emerge in April or May.”
Wendy, what should I do if I come across a rattlesnake? Wyoming Game and Fish Department. July 19, 2019; checked November 3, 2026.
Quoted passages (2)
“Have a reliable form of communication so you can call 911 immediately if you or someone you are with do get bitten by a rattlesnake.”
“If you come across a rattlesnake DO NOT try to move it or kill it.”
Hiking in rattlesnake country. Wyoming Game and Fish Department. undated page; checked November 3, 2026.
Quoted passages (2)
“Use a flashlight at night. Rattlesnakes are often active at night in the summer.”
“Rattlesnakes are often active at night in the summer.”
Mountain Lions in Wyoming. Wyoming Game and Fish Department. no page date shown; checked November 3, 2026.
Quoted passages (1)
“Please report sightings to Game and Fish at 1-877-WGFD-TIP or the non-emergency Police Department phone.”
Amphibians and Reptiles. Wyoming Game and Fish Department. no page date shown; checked November 3, 2026.
Quoted passages (1)
“Rattlesnakes occur in many parts of Wyoming.”
GBIF.org occurrence records, human observations licensed CC0 1.0 or CC BY 4.0 only, accessed November 3, 2026. The datasets behind these counts are listed on our Sources page.