Categorize the snake as venomous or non-venomous. Both of Wisconsin's venomous snakes are pit vipers and have several distinctive features. They have pit organs---that appear as indentations---between the eyes and nose, and their eyes have slit-like pupils instead of rounded ones. Both of the state's pit vipers are rattlesnake
species, with rattles at the end of the tail. If these characteristics are not present, the snake is either non-venomous or not native to the state. Massasauga Rattlesnake (pictured below).