Snakes in Montana: identification guide and best places to start

Yes, snakes live throughout Montana, though they are far more common in the central and eastern prairie than in the cold high mountains. The state has roughly 10 native snake species. Nine are completely harmless to people, and one, the prairie rattlesnake, is venomous.

Snakes are cold-blooded, so they depend on outside warmth to move. In Montana that means they spend the long winter underground in dens called hibernacula, often shared with other snakes, then emerge as the ground warms in spring. You are most likely to see one between late April and early October. Western Montana, with its higher elevation and cooler, wetter climate, holds fewer snakes and almost no rattlesnakes. The dry, open country east of the Rocky Mountain front is where snakes are part of everyday outdoor life.

For a wider picture of what shares this habitat, see the Montana wildlife hub, and use the Montana snake guide to match a sighting to a likely species.

Montana has about 10 snake species. Here is a plain rundown of the ones you are most likely to meet, grouped by how common and how harmless they are.

Non-venomous snakes (the large majority):

Bullsnake (gopher snake): Montana's largest snake, often 4 to 6 feet. Tan or yellow with dark brown blotches. It hisses loudly and can vibrate its tail in dry grass, so it is the snake most often mistaken for a rattlesnake. It has no rattle and no fangs.

Common garter snake and terrestrial garter snake: Slim snakes with three light stripes running down a darker body. Common near water, gardens, and damp ground. Harmless.

Racer (yellow-bellied racer): Fast, slender, plain greenish or brown above with a pale yellow belly. Flees quickly when disturbed.

Gopher snake, hognose snake (the western hognose puts on a dramatic bluffing display, flattening its neck and hissing, but rarely bites), milk snake, smooth green snake, and rubber boa round out the harmless list. The rubber boa is a gentle, slow burrower found in moister western areas.

Venomous snakes:

Prairie rattlesnake: the only venomous snake in the state. See the section below on venomous species and the snake facts page for field marks.

Use the Montana snake guide to narrow down a sighting by region and habitat.

Only one venomous snake lives in Montana: the prairie rattlesnake (Crotalus viridis). There are no copperheads, cottonmouths, or coral snakes in the state, so if a Montana snake is venomous, it is a prairie rattlesnake.

The prairie rattlesnake is a pit viper. Key marks are a broad, triangular head that is clearly wider than the neck, vertical cat-like pupils, and a segmented rattle at the end of the tail. Color is usually greenish-gray, olive, or light brown with a row of dark, oval blotches down the back. Adults commonly run 3 to 4 feet. Newborns are dangerous too and carry venom, but they have only a single small button instead of a full rattle, so do not rely on hearing a rattle to judge a young one.

Rattlesnakes are concentrated in the prairie, badlands, and river breaks of central and eastern Montana, such as the Missouri River breaks and the country around Ekalaka. They are scarce or absent in the cool, high western mountains. A rattlesnake will usually try to avoid you and rattles as a warning to be left alone. Give it room and it will move off. See the snake facts page for a closer identification breakdown.

Start with three things: head shape, pattern, and tail.

Head shape: A rattlesnake has a wide, triangular, arrow-shaped head and a thin neck. Harmless snakes like bullsnakes and garter snakes have narrower heads that blend smoothly into the body. Pupils are hard to check safely and from a distance, so do not get close to look, but a rattlesnake has vertical pupils while non-venomous snakes have round ones.

Pattern and color: The prairie rattlesnake has dark oval blotches on a greenish-gray or tan body. The bullsnake is also blotched and similar in color, which is why people confuse the two, but it is longer and lacks a rattle. Garter snakes show three pale stripes. Racers are mostly one plain color. The smooth green snake is bright green.

Tail: A rattle is the surest sign of a rattlesnake. But remember a young rattlesnake may have only a tiny button, and a bullsnake or racer can buzz its tail tip against dry leaves to fake a rattle sound. So judge the whole animal, head plus pattern plus tail, not a single feature.

When in doubt, treat any snake you cannot confidently identify as if it could be venomous, keep your distance, and check the snake facts page or the Montana snake guide afterward.

Focus on warm, dry, open country with cover and prey. Rocky slopes, prairie dog towns, sagebrush flats, and the brushy edges along rivers and creeks all hold snakes. The Missouri River breaks and the badlands around Ekalaka in the southeast are well known rattlesnake areas. In the western part of the state, south-facing hillsides and open pine forest hold smaller numbers, and rattlesnakes thin out fast as elevation climbs.

Snakes pick spots that solve their daily temperature problem. In spring and fall you find them basking in the open on rock, gravel, south-facing banks, and trail edges during the warm middle of the day. In summer they shift to mornings and evenings and shelter from midday heat under rock ledges, logs, and dense grass. Rock outcrops near a den can concentrate many snakes in early spring.

For planning, use the Montana wildlife hub to pick a region, then the Montana snake guide to match habitat and season. If activity is slow, stay longer at one promising rocky, sunny spot rather than rushing between areas, and reset your timing around weather and light.