These are photos of a western cottonmouth (Agkistrodon piscivorus), AKA the water moccasin, from southern Illinois. I actually took these photos at a place locally called “Snake Road” because during the spring and fall you can find many species of snakes migrating across it but more on that in a later post. The western cottonmouth is a venomous pit viper with a stout body reaching approximately 76-107 centimeters in length. these snakes can be quite variable in appearance but most adults are a uniform dark color sometimes with faint traces of bands along their back. These snakes are highly aquatic with a diet consisting mainly of fish however they will also eat other snakes, amphibians, and even small mammals.
The second picture shows a cottonmouth performing its defense mechanism. When these snakes feel threatened they will raise their heads and open their mouths exposing the white flesh within for which this species is named. I assure you this snake is not striking at me. He feels very scared with me so close so he is trying to look very fearsome so that I will leave him alone and while this pose may seem aggressive when I moved away he closed his mouth and continued on his way.
Cottonmouths are often confused with nonvenomous species of water snakes such as the yellow-beillied watersnake (Nerodia erythrogaster flavigaster) above leading to the killing of many completely harmless snakes. An easy way to tell the difference between these snakes when they are in the water is that watersnakes will swim with most of their body under the water with just their head and neck sticking out while a cottonmouth willswim with all or most of its body on top of the water. However, if you see any snake in the water it is best to just let them be and go on your way. They will do the same.
The Bearded Biologist 