The northern diamond-backed watersnake is a large, heavy-bodied snake with numerous diamond-shaped light markings along the back. It is Missouri's largest watersnake. The ground color is gray, light brown, or dull yellow. The 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 with several irregular rows of dark brown spots or half-moon-shaped marks. As with other watersnake species, the scales along the back have keels, causing the snake to feel rough.
This nonvenomous snake will bite viciously and smear a foul-smelling musk if captured.
Similar species:
- Missouri has four other species of watersnakes (Nerodia spp.). The range and coloration, particularly the dark chainlike pattern with light-colored diamond shapes on the back, and the yellow belly with irregular rows of dark brown spots or half-moons, help distinguish the northern diamond-backed watersnake from the others.
- This and other watersnakes are often confused with the venomous northern cottonmouth (Agkistrodon piscivorus) and killed because of unwarranted fear. 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.
Adult length: 30 to 48 inches; occasionally to 69 inches.
Occurs in the southeastern corner of the state (Bootheel) and north along the Mississippi River floodplain. Also occurs in the northwestern quarter of Missouri and southward through the plains in the western edge of the state. Absent from the Ozarks.
Habitat and Conservation
In Missouri, the northern diamond-backed watersnake is active from late March through October. Except for the hottest time of year, they often bask on branches, logs, tree roots, or along the banks of streams. In July, August, and September, they become nocturnal.
They quickly enter the water to escape predators or to capture prey and can remain underwater for more than an hour.
This species lives in a variety of aquatic habitats but is most common in swamps, sloughs, oxbow lakes, marshes, and drainage ditches. They are very common in the northern and western sections of Missouri, especially in bottomland prairies associated with nearby wetland pools, drainage ditches, and rivers.
These snakes overwinter underground below the frost line in animal burrows and in the holes that remain after a dead tree's root systems have rotted away. This is one of the snake species that overwinter in crayfish burrows.
Food
Northern diamond-backed watersnakes mostly eat fish and amphibians. Most of the fish they eat are small, slow moving, or dead. The amphibians they consume include adult and larval frogs, toads, and salamanders. They may also eat small snakes and turtles, earthworms, leeches, crayfish, and insects.
Status
Very common in northwestern and western Missouri, where the habitat is optimal: bottomland prairie with nearby wetlands, pools, ditches, or rivers.
Taxonomy: populations of this snake east of the Mississippi River might be separate species or even different species than the populations in Missouri. Future research into the genetics of these snakes will eventually sort out their true relationships.
Life Cycle
Courtship and mating take place in April and early May, and females give birth to live young during late August through early October. A litter can comprise some 8–62 young. Individuals become sexually mature between two and a half to three years of age.
Human Connections
When threatened and not allowed to escape, this species will flatten its head and neck and try vigorously to defend itself. As with most of our watersnakes, although it is nonvenomous, it is pugnacious. When cornered, an individual will strike or bite viciously. When captured, watersnakes also excrete a foul-smelling musk from glands in the base of the tail that it is often mixed with feces and smeared on the captor.
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 fear of them. Curiosity and knowledge helps us overcome our prejudices.
Ecosystem Connections
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. Their defensive behaviors are a reminder that they frequently become prey themselves.
