Yellowstone National Park is home to a variety of wildlife, and snakes do live within its boundaries. The park’s high elevation and often cold climate severely limit the number of species and their overall population density compared to warmer regions. This environment results in an extremely low diversity of snake life. Visitors are far more likely to encounter the park’s famous large mammals than any of its secretive, cold-blooded residents. The scarcity of snakes means that encounters are rare, but awareness of the species present is still beneficial for anyone exploring the park.
Identification of Species
Yellowstone is home to a small number of snake species, including two types of garter snakes and one venomous snake. The most common is the Wandering Garter Snake, a subspecies of the Terrestrial Garter Snake, often found near water sources. This non-venomous snake typically has a dark background color with three lighter stripes running down its body and is frequently seen basking. The Valley Garter Snake, a subspecies of the Common Garter Snake, is also present.
The Valley Garter Snake can be identified by its pale yellow or bluish-gray belly and three bright longitudinal stripes, sometimes featuring irregular red spots on its sides. Both garter snake species are harmless to humans, feeding primarily on small prey like fish, amphibians, and rodents.
The Prairie Rattlesnake is the only venomous snake found in the park. This pit viper can grow to over 48 inches and ranges from greenish-gray to light brown with dark, white-bordered blotches down its back. Its presence is restricted to the lower elevations and drier, warmer areas, particularly along the lower Yellowstone River near Reese Creek and Rattlesnake Butte. Rattlesnake bites are extremely uncommon, with only two reported in the history of the park. Other non-venomous species include the Bullsnake and the Rubber Boa.
Habitat and Rarity
The rarity of snake sightings in Yellowstone is directly linked to its high elevation and short summers. As cold-blooded reptiles, snakes require external heat to regulate their body temperature and maintain activity. Much of the park’s terrain remains too cold to support widespread snake populations.
Sightings are predominantly concentrated in the northern range, which features the lowest elevations and a warmer, drier climate, making it the most suitable habitat. Areas around Gardiner and the Mammoth Hot Springs region offer the necessary warmth and open terrain. Additionally, some snakes utilize warm microclimates near thermal features like hot springs and geysers to extend their active season.
To survive the long, harsh winters, Yellowstone’s snakes rely on communal underground dens known as hibernacula. These dens are often located in rocky crevices or mammal burrows that extend below the frost line, allowing the snakes to enter a state of brumation. The need for these specific, well-insulated overwintering sites further restricts their distribution within the park.
Safety and Encounters
Encountering a snake in Yellowstone is uncommon, but visitors should always maintain a respectful distance from all wildlife. If you spot a snake, never attempt to touch, handle, or harass it, as defensive strikes are most likely to occur. Federal regulations prohibit disturbing any park wildlife, including snakes.
When hiking, especially in the lower elevation northern parts of the park, remain on established trails and watch where you place your hands and feet. This awareness is important near rocky outcrops, which are favored basking and denning sites. If you hear the distinctive warning rattle of a Prairie Rattlesnake, stop immediately and slowly move away from the sound. Notify a park ranger if a rattlesnake encounter requires intervention.