Northern Diamond-Backed Watersnake (Diamond-Backed Water Snake)
A large, heavy-bodied snake with numerous diamond-shaped markings along the back. Missouri's largest watersnake. The ground color is gray, light brown, or dull yellow. Dark brown blotches along the back usually connect to form a chainlike pattern. The common name comes from the light areas along the back, which may be diamond-shaped. The belly is yellow, bordered with irregular rows of dark brown spots or half-moons. Scales along the back have keels, causing the snake to feel rough. If molested, this snake will flatten its head and neck, bite viciously in defense, and secrete a strong-smelling musk from glands at the base of the tail.
Similar species: This and other watersnakes are often confused with the venomous western cottonmouth and needlessly killed. The true cottonmouth does not have a chainlike dark pattern on its back. It is has a distinct, triangular head, a sensory pit between the nostril and eye on either side of the head; and a light line from each eye to the corner of the mouth.