Montana’s prairies, river bottoms, and mountain foothills hold more reptile diversity than most residents expect. Wildlife specialists count 10 snake species native to Montana, and once regional garter snake subspecies are counted separately, herpetologists recognize 13 distinct types of snakes in Montana. Only one of them carries venom.
This guide walks through each species and subspecies confirmed by the Montana Natural Heritage Program, covering size, coloring, and the habitats where hikers, gardeners, and anglers are most likely to run into them. Six of the 13 belong to the garter snake family alone, which explains why so many Montanans mistake a harmless garter for something more dangerous.
Quick Reference: Types of Snakes in Montana at a Glance
Before getting into individual profiles, this table breaks down the basics for quick identification in the field.
| Snake | Venomous | Typical Adult Length | Common Habitat |
|---|---|---|---|
| Prairie Rattlesnake | Yes | 15–60 in | Grasslands, rocky outcrops, prairie dog towns |
| Rubber Boa | No | 14–33 in | Forested slopes, western river valleys |
| Yellow-bellied Racer | No | 20–50 in | Open grassland, sagebrush steppe |
| Western Milksnake | No | 14–36 in | Dry prairie, rocky hillsides |
| Gopher Snake (Bullsnake) | No | 36–96 in | Farmland, prairie, open woodland edges |
| Common Garter Snake | No | 18–54 in | Wetlands, streambanks, gardens |
| Plains Garter Snake | No | 15–43 in | Prairie near ponds and irrigation ditches |
| Terrestrial Garter Snake | No | 18–43 in | Mountain meadows, valley floors |
| Valley Garter Snake | No | 18–42 in | Western valleys, riparian corridors |
| Red-sided Garter Snake | No | 18–42 in | Statewide, wetlands and hibernacula sites |
| Wandering Garter Snake | No | 18–42 in | Higher elevations, rocky streams |
| Plains Hognose Snake | Mildly rear-fanged | 16–25 in | Sandy prairie, loose soil |
| Smooth Green Snake | No | 14–20 in | Moist meadows, tall grass |
1. Prairie Rattlesnake
The prairie rattlesnake (Crotalus viridis) is the state’s only venomous reptile, and it accounts for the caution most Montanans show around any coiled snake. The Montana Natural Heritage Program describes adults as having a triangular head, blunt nose, narrow neck, and stout body; they range in length from 15 to 60 inches. The background color above varies from pale green to brown, with a series of brown or black blotches edged with a dark and then a light line extending the length of the body.
Like every pit viper, this species relies on more than eyesight to hunt. All rattlesnakes have a heat-sensing pit located between the nostril and the eye, and the tail ends in a rattle that warns potential predators of the snake’s presence. No other snake in Montana has rattles, which makes this the easiest species to rule in or out once you hear that buzz.
Most bites occur between April and September, when snakes and people are both most active outdoors. Snakes are generally not active once temperatures dip below 60°F, so they seek shade under rocks, logs, or burrows during the hottest part of the day. Readers wanting a broader look at how this species fits among its relatives can check the breakdown of how many types of rattlesnakes exist across North America.
Pro Tip: Watch where you place your hands and feet around rock piles, woodpiles, and spots where grass meets bare rock — these edge habitats are where most accidental encounters happen.
2. Rubber Boa (Northern Rubber Boa)
The northern rubber boa (Charina bottae) looks and moves like nothing else on this list. Its uniform, tube-like shape and coloration easily distinguish this species from other snakes in Montana, and its blunt tail so closely resembles its head that many people can’t tell which end is which at a glance. It is one of only two boa species found anywhere in the continental United States, and the only one that tolerates Montana’s cool climate.
Range maps for this snake keep shifting. The species was historically documented in 16 western counties, but in 2008 a rubber boa turned up in eastern Big Horn County, a range extension of 185 km (115 miles) from the previous easternmost record near Red Lodge. Conservation-wise, the outlook is reassuring: the northern rubber boa is listed as Least Concern, with a growing population across its range.
This same burrowing, secretive species also shows up among the types of snakes in Utah, where it favors similarly rocky, forested slopes at moderate elevation.
3. North American/Yellow-bellied Racer
The yellow-bellied racer (Coluber constrictor) earns its name from the smooth yellow scales on its belly, paired with an olive or brown back and large, alert eyes. Unlike the rubber boa’s slow crawl, this species is much more active, has larger eyes, and has a thin, tapered tail — field marks that biologists use specifically to separate the two when they’re found in the same brushy habitat.
Racers hunt by sight during the warmest hours of the day, chasing down grasshoppers, small rodents, and other snakes rather than ambushing prey. They don’t constrict their meals despite the genus name; instead, they pin prey with their body weight and swallow it whole. Racers in the eastern United States, including the black racer found among the types of snakes in South Carolina, share this same slender build and quick temperament, though they wear much darker, almost jet-black scales.
4. Western Milksnake
The western milksnake (Lampropeltis gentilis) is one of the more strikingly patterned types of snakes in Montana, banded in red, black, and cream or yellow in a sequence that mimics the far more dangerous coral snakes found much farther south. In Montana, where no coral snakes exist, the pattern still works as a bluff against predators that have learned to avoid brightly banded snakes on instinct.
This species stays hidden under rocks, logs, and loose soil through most of the day, becoming active at dusk to hunt lizards, small rodents, and other snakes, including young rattlesnakes. Because it favors dry prairie and rocky hillsides at the edge of its range, sightings in Montana are less frequent than in states farther south and east. Its relative found among the types of snakes in Maryland wears a similar banded pattern but tends toward brighter, more saturated reds.
5. Gopher Snake (Bullsnake)
The bullsnake (Pituophis catenifer) is Montana’s largest native snake, with some adults stretching past six feet. When threatened, it flattens its head, hisses loudly, and vibrates its tail against dry vegetation, a performance convincing enough that many people mistake it for a rattlesnake on sight. The giveaway is simple: the bullsnake has no rattle, and it also lacks the rattlesnake’s heat-sensing facial pits and triangular head shape.
Common Mistake: Killing a hissing, tail-shaking snake out of fear it’s a rattlesnake is one of the most frequent wildlife mistakes in rural Montana. Bullsnakes are harmless constrictors that eat enormous numbers of ground squirrels and pocket gophers.
Farmers and gardeners often leave bullsnakes alone specifically for that pest control benefit. For a broader look at what preys on snakes themselves, see the roundup of animals that eat snakes. The same species fills an identical ecological role farther east among the types of snakes in Iowa, where local bullsnakes patrol cropland edges the same way.
6. Common Garter Snake
The common garter snake (Thamnophis sirtalis) is the most widespread garter snake species in North America, and Montana hosts three of its recognized subspecies. All share the same basic pattern: a dark body broken by three light stripes running the length of the back and sides, though exact shade and stripe width vary by population.
Garter snakes stay close to water, hunting frogs, small fish, earthworms, and slugs in wet meadows, streambanks, and even suburban gardens. They’re active during the day and tolerate cooler temperatures better than most Montana snakes, which is why they’re often the first species spotted after winter dens open in spring. Readers who want to compare every regional variety side by side can browse the full rundown of types of garter snakes found across North America.
Key Insight: Valley, red-sided, and wandering garter snakes described below are not separate species — they’re regional subspecies of the common garter snake and the western terrestrial garter snake, distinguished mainly by stripe color and geographic range within Montana.
7. Plains Garter Snake
The plains garter snake (Thamnophis radix) stands out from its common garter relative through a bright orange or yellow-orange stripe running down the center of its back, bordered by two rows of dark, checkered blotches. It favors open prairie and grassland near permanent water sources, including irrigation ditches and stock ponds that dot Montana’s eastern plains.
Like other garter snakes, this species gives live birth rather than laying eggs, typically producing a dozen or more young in late summer. It adapts well to human-modified landscapes, often turning up in vacant lots, roadside ditches, and farm outbuildings near the eastern half of the state. Populations here connect to a much wider range that stretches east into states like Maine, where garter snakes are similarly common in disturbed, semi-open habitat.
8. Terrestrial Garter Snake (Western Terrestrial Garter Snake)
The western terrestrial garter snake (Thamnophis elegans) shows more color variation than any other garter species in the state, ranging from olive and gray to nearly black, with stripe color shifting from yellow to orange depending on the population. True to its name, it spends more time away from water than other garter species, foraging through meadows, rocky slopes, and forest edges from valley floors up into mountain elevations.
This species eats a wider diet than most garters, including slugs, worms, small fish, and occasionally small mammals, which helps explain why it thrives across such a broad elevation range. Its distribution extends west into the types of snakes in Oregon, where similar populations occupy comparable mixed forest and grassland terrain.
9. Valley Garter Snake
The valley garter snake (Thamnophis sirtalis fitchi) is a subspecies of the common garter snake found mainly in Montana’s western valleys, where it’s identified by bold reddish or orange bars filling the dark spaces between its three light body stripes. That extra color makes it one of the more visually striking garter snakes in the state, especially compared to the plainer coloring typical farther east.
It shares the same semi-aquatic habits as other common garter subspecies, staying near streams, wetlands, and riparian corridors where amphibian prey is abundant. Because its range is largely confined to valley bottoms west of the Continental Divide, hikers in the Bitterroot or Flathead valleys are more likely to encounter this variety than travelers on the state’s eastern plains.
10. Red-sided Garter Snake
The red-sided garter snake (Thamnophis sirtalis parietalis) is probably the subspecies most people picture when they hear “garter snake,” combining black body color with vivid red or orange bars and bright yellow stripes. It has the widest distribution of Montana’s garter snake subspecies, turning up in wetlands, roadside ditches, and yards across nearly the entire state.
This subspecies is known for forming large communal groups at shared overwintering dens, sometimes gathering by the dozens in a single rocky crevice or burrow system before temperatures drop. Come spring, those same dens empty out almost overnight as snakes disperse to feeding grounds, which is why sudden garter snake sightings after a warm early-spring day are common near known den sites.
11. Wandering Garter Snake
The wandering garter snake (Thamnophis elegans vagrans) is a subspecies of the western terrestrial garter snake and the most widely distributed garter snake variety in Montana, tolerating higher elevations and rockier terrain than almost any other snake in the state. Its coloring runs from brown to olive-gray, usually with a faint yellow or tan stripe down the back that’s less vivid than the markings on lowland garter snakes.
Because it adapts to mountain streams, talus slopes, and even alpine meadows, this subspecies covers ground that few other Montana reptiles reach. It shares that high-elevation toughness with populations found among the types of snakes in Utah, where the same subspecies climbs into similarly rugged mountain habitat.
12. Plains Hognose Snake
The plains hognose snake (Heterodon nasicus) is built for digging, with an upturned, shovel-like snout it uses to burrow through loose, sandy soil in search of its favorite prey: toads. When threatened, it puts on one of the more theatrical defense displays of any Montana snake, flattening its neck into a hood, hissing, and striking with a closed mouth in an act often mistaken for cobra behavior.
If bluffing doesn’t work, the hognose has a second act: it rolls onto its back, opens its mouth, lets its tongue loll out, and plays dead until the threat passes. It does have mildly enlarged rear teeth used to puncture inflated toads, but it poses no real danger to people or pets. Ground-nesting hawks and other predators still take a toll on this species, a dynamic covered in more depth in the guide to animals that eat snakes statewide.
13. Smooth Green Snake
The smooth green snake (Opheodrys vernalis) is one of the easiest types of snakes in Montana to overlook, thanks to bright grass-green scales that blend perfectly into tall meadow vegetation. It’s slender, small, and entirely harmless, spending its days hunting soft-bodied insects and spiders rather than the rodents and amphibians that larger Montana snakes target.
That insect-heavy diet makes this species a natural predator of many creatures covered in the guide to types of spiders in Montana, since spiders make up a meaningful share of its meals alongside crickets and caterpillars. One quirk worth knowing: green pigment in this snake’s skin breaks down quickly after death, so preserved specimens and roadkill often appear blue rather than green, which can confuse first-time identifiers.
Montana’s snake diversity extends well beyond these 13 species and subspecies once related wildlife groups are factored in. Readers curious about the rest of the state’s reptile and invertebrate neighbors can browse the guides to types of bats in Montana and endangered animals in Montana for a fuller picture of what shares this landscape.
Identifying a snake correctly starts with a few consistent field marks: head shape, eye pupil shape, presence or absence of a rattle, and belly pattern tend to matter more than body color alone, since coloring varies so widely even within a single species. With only one venomous species among the entire group, most encounters with Montana snakes end the same way they should — with the snake moving off into the grass and the person walking away with a good story.