Illinois is home to 40 species of snakes that inhabit a variety of habitats. The two most common species we encounter on the river near Havana, Illinois are the common watersnake (Nerodia sipedon) and the diamond-backed watersnake (Nerodia rhombifer).
The common watersnake is light brown or gray with around 30 reddish or dark brown crossbands and blotches along its back and sides. It averages around 2–3.5 feet in length. Found throughout Illinois, the common watersnake often basks on logs and rocks. It also basks or hides in reservoirs and in the limestone rip-rap that lines the river’s shoreline.
The diamond-backed watersnake can grow up to 4 feet long and is characterized by a chain-like pattern on a lighter brown or yellow background. The species is common in southwest Illinois and along major rivers, where it can often be found basking in tree limbs hanging over water.
Like most watersnakes, the common watersnake and diamond-backed watersnake are live-bearers. Instead of laying eggs, females give birth to 10–60 live young in late summer to fall.
Both of these species feed primarily on fish and amphibians.
Though non-venomous, these species, and watersnakes in general, are known for their readiness to bite, so care should be taken when interacting with them. When threatened, they will often flatten their bodies and/or release musk (similar to skunks!) from glands located at the base of their tail.
These non-venomous snakes (and others) are often mistaken for the venomous cottonmouth (also called the water moccasin, Agkistrodon piscivorus), or copperhead (Agkistrodon contortris). However, current records for the cottonmouth only occur in the southernmost counties of Illinois. The copperhead is more common than the cottonmouth, but is generally restricted to the southern part of the state and bluffs along the Mississippi River.
As always, if you are unsure of what snake species you encounter, it is best to admire from a distance and allow it to go on its way!