Prairie rattlesnakes are large members of the pit viper family. Pit vipers have heat-sensing organs between their nostrils and eyes that are used to locate prey. Prairie rattlesnakes can grow to almost 1.6m in length, though they are more commonly about 1m long. They are lightly coloured in hues of brown, beige and green, and often have patches of darker coloured blotches or saddles along their back.