Colorado's Reptiles & Amphibians

Western Rattlesnake
(Crotalus viridis)

The Western or Prairie Rattlesnake (Crotalus viridis ) has one of the largest home ranges of rattlesnakes in North America. This rattlesnake or its subspecies can be found in the Canadian provinces and southward across the central United States to Mexico. In Colorado, the subspecies is called the Prairie Rattlesnake (C. v. viridis ) and found in the deserts, open prairies, haylands, and croplands -- any area with an abundance of food.

The rattles and their distinctive rattling sound are the most recognizable feature of this snake . The Prairie Rattlesnake is one of only two venomous snakes native to Colorado. Young rattlesnakes are born with a prebutton, a rattle segment at the tip of their tail. All other Colorado snakes are born with a pointed tail. Rattlesnakes (along with copperheads and cottonmouths) are members of the Pit Viper family. The "pit vipers" have a triangular shaped head with a small cavity or pit on each side, between the eye and the nostril. They can sense warm-blooded prey in complete darkness up to 2 feet away. These thermoreceptor organs contain nerves that are sensitive to heat or warmth and can detect temperature differences within several thousandths of a degree.

The color of the Prairie Rattlesnake varies from light brown to green, with a yellowish belly. Dark oval blotches with light colored borders run along the center of its back. The blotches become crossbands on the back part of the body and rings around the tail. Adults will range in length from 30-40 inches, with a record of 57 inches. 3 foot rattlesnakes normally weigh 1 pound (a 54 incher weighed 4 1/2 pounds).