Most species of water snakes are non-poisonous, such as this banded water snake (pictured right). The poisonous cottonmouth snake is found in the southern part of the United States, up into extreme southern Missouri. It has a broad head that is wider than its neck. The cottonmouth feeds on frogs, salamanders, small turtles, fish, baby alligators, lizards, small mammals and birds. If agitated, it will vibrate its tail and open its mouth to reveal a white lining from which it gets its name.