Montana is a northern state known for its vast, rugged landscapes and cold climate, which results in a relatively low diversity of reptile species. The state is home to a small number of native snake species, typically totaling around ten, which have adapted to survive the long, harsh winters. Understanding the types of snakes present is valuable for anyone exploring Montana’s diverse habitats.
Categorizing Montana’s Snake Population
The native snakes in Montana fall into two distinct categories: a single species that possesses venom and a majority of species that are entirely non-venomous. This simple classification is a useful starting point for identification in the field. The single venomous species is a member of the pit viper family, while all other resident snakes belong to the Colubrid family, which is the largest and most diverse group of snakes globally.
Identifying Montana’s Sole Venomous Species
The Prairie Rattlesnake, Crotalus viridis, is the only naturally occurring snake in the state capable of delivering a medically significant venomous bite. As a pit viper, it possesses a broad, triangular head that is wider than its neck, along with heat-sensing pits located between the eyes and nostrils. Its body is typically greenish-gray, olive green, or light brown, marked with a series of dark brown, oval-shaped blotches along the back. The most definitive feature is the segmented rattle at the tail’s end, which the snake uses to issue a loud warning when disturbed.
Prairie Rattlesnakes are primarily found in the eastern and central plains of Montana, preferring arid grasslands, sagebrush habitats, and rocky outcrops at elevations generally below 6,500 feet. They are not inherently aggressive and will almost always use their rattle as a warning before resorting to a strike. To minimize the risk of an encounter, hikers should stay on marked trails and avoid placing hands or feet into rocky crevices or dense brush without a visual check. If a rattlesnake is encountered, slowly backing away to create distance is the safest and most recommended course of action.
Common Non-Venomous Residents
The majority of snakes encountered in Montana are harmless constrictors or passive hunters that play a beneficial role in controlling rodent and insect populations. Among the most widespread non-venomous residents are the three species of Garter Snakes (Thamnophis species), easily identified by their characteristic longitudinal stripes. These slender snakes typically have three light-colored stripes—often yellow, orange, or white—running the length of a dark body. Garter Snakes are frequently found near water sources like streams and ponds and range in size from 16 to 43 inches.
The Bullsnake (Pituophis catenifer), also known as the Gopher Snake, is a large and frequently observed species that can grow up to six feet. These snakes have a cream or yellowish background covered in large, dark brown or black blotches, which can lead to them being mistakenly identified as rattlesnakes. When threatened, the Bullsnake flattens its head into a triangular shape, hissing loudly, and rapidly vibrates its tail against dry vegetation to mimic a rattle. Bullsnakes are non-venomous constrictors that primarily prey on small mammals.
The North American Racer (Coluber constrictor) is known for its speed and slender, whip-like body. Adult Racers are distinct because they typically lack a pattern, displaying a uniform coloration that can be gray, olive-green, or bluish on the back, with a pale or yellow underside. Juvenile Racers have a blotched pattern that they gradually lose as they mature into their solid adult color. These diurnal hunters are often found in open habitats like grasslands and prairies.
Habitat and Seasonal Activity
The long, cold Montana winter necessitates a period of dormancy, known as brumation, for all snake species. Snakes seek out winter dens, called hibernacula, as temperatures drop, typically moving underground into rock crevices or abandoned mammal burrows by late September or October. This communal overwintering allows them to retreat below the frost line where temperatures remain stable and above freezing.
Activity resumes in the spring, generally from late March or early April, once ambient temperatures consistently begin to rise. Their activity levels are dependent on environmental temperature, making them most visible during the warmer months, extending through early fall. They are often seen basking on sun-exposed rocks, trails, or roadsides in the morning to raise their body temperature. During the peak heat of summer, snakes may become more active during the cooler hours of the early morning and late evening to avoid overheating.