The northern diamond-backed watersnake is a large, heavy-bodied snake with numerous diamond-shaped markings along the back. It is 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. As with other watersnake species, the 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 northern cottonmouth (Agkistrodon piscivorus) and needlessly killed. The cottonmouth does not have a chainlike dark pattern on its back. Also, the cottonmouth has a distinctly 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.
Length: 30 to 48 inches.
Absent from the Ozarks; common in the southeastern corner, north along the Mississippi River floodplain, and in northern and western Missouri. Except along the Mississippi and Missouri floodplains, it generally does not occur in our extreme northern counties.
Habitat and Conservation
This species may live along slow-moving rivers but is more commonly are seen along river sloughs, swamps, oxbow lakes, and marshes. This watersnake often basks on branches or logs during spring, early summer, and autumn. In the hottest months, it is distinctly nocturnal.
Northern diamond-backed watersnakes eat fish, especially slow-moving or dead fish, frogs, toads, and salamanders.
Active from late March through October. Courtship and mating take place in April and early May, and females give birth to live young (they do not lay eggs) during late August through early October. A litter can comprise some 13-62 young. These are about 8-13 inches long at birth, and they often have some orange coloration on their bellies.
Many snake species are burdened with unfair, undying myths that paint them to be much more dangerous and harmful than they are. This species, though it fights fiercely to defend itself, is harmless. Our many myths about snakes reflect our innate fear of them. Education corrects our prejudice.
As predators, watersnakes control populations of the animals they consume. But snakes are preyed upon themselves. Their defenseless newborns are gobbled by animals ranging from large frogs and fish to other snakes and birds and mammals. Adults are eaten by predatory mammals and birds.