Western Massasauga Rattlesnake (Sistrurus tergeminus) - Endangered
Description: 18½ - 30 inches. Western Massasauga Rattlesnakes are gray or grayish-brown with dark bands or blotches down the back. Blotches on the back become bands near the tail, which is tipped by a small rattle. The eyes have vertical, cat-like pupils and the head is shaped like a spade, though it is not as wide as the heads of other rattlesnakes in Iowa.
Similar Species: Eastern Massasauga Rattlesnakes are similar in appearance, but are only found in Eastern Iowa. Timber Rattlesnakes usually have a rusty brown stripe running down the back, and have a black tail. Prairie Rattlesnakes are similar in appearance but are not found within the range of Western Massasauga Rattlesnakes in Iowa. Many non-venomous species of snakes in Iowa will wag their tail against grass and other ground debris to produce a rattle-like sound, but rattlesnakes will hold their tails off the ground while rattling them. All non-venomous snakes in Iowa have round pupils.