Water moccasins, also known as cottonmouths (Agkistrodon piscivorus), are not found in Colorado. This venomous snake species inhabits a distinct geographic range far from the state’s borders. Knowing which snakes do reside in Colorado, both non-venomous and venomous, helps residents and visitors safely navigate outdoor environments.
Geographic Range of Water Moccasins
Water moccasins are semiaquatic pit vipers native exclusively to the southeastern United States. Their natural habitat spans from southeastern Virginia, west to central Texas, and north to southern Illinois and Indiana. These snakes thrive in warm, humid climates and are closely associated with bodies of water such as swamps, marshes, sluggish streams, and the shores of ponds and lakes. Colorado’s arid and mountainous ecosystems, characterized by cooler temperatures and different aquatic environments, do not provide the specific conditions necessary for water moccasins to survive and establish populations.
Snakes Found in Colorado
While water moccasins are absent, Colorado is home to approximately 30 species of snakes, most of which are non-venomous. Common harmless snakes encountered in the state include garter snakes, bullsnakes, and gopher snakes. Garter snakes are often found near water sources, while bullsnakes and gopher snakes are widespread in grasslands and open woodlands. Colorado’s only native venomous snakes belong to the rattlesnake family.
Identifying Colorado’s Venomous Snakes
Colorado hosts three species of rattlesnakes: the prairie rattlesnake, the midget faded rattlesnake, and the western massasauga. Prairie rattlesnakes are the most common and widespread, found in various habitats below 9,000 feet. Key identification features for rattlesnakes include:
A broad, triangular head wider than their neck.
Elliptical (cat-like) pupils.
Heat-sensing pits located between their eyes and nostrils.
A rattle on the end of their tail; young rattlesnakes may only have a small button or no developed rattle.
Distinguishing Harmless Snakes from Venomous Ones
Many non-venomous snakes in Colorado are often mistaken for rattlesnakes due to similar markings or defensive behaviors. Bullsnakes and gopher snakes, for instance, can hiss loudly, flatten their heads to appear more triangular, and vibrate their tails, especially in dry leaves, mimicking a rattlesnake’s sound. Non-venomous snakes typically have round pupils, more slender heads not distinctly wider than their bodies, and tails that taper to a point, lacking a rattle. Observing these physical differences from a safe distance aids accurate identification. Always give snakes space to avoid provoking a defensive reaction.