The Mississippi green watersnake is a medium-sized, dark-colored, heavy-bodied, semiaquatic snake. It was once somewhat common in southeastern Missouri but is now endangered and possibly extirpated from our state.
This nonvenomous snake will bite viciously and smear a foul-smelling musk if captured.
The back is greenish brown with numerous small, obscure olive-brown or dark brown markings. The belly is dark gray or brown with numerous yellow markings, most of them shaped like half-moons. A sure way of distinguishing between the Mississippi green watersnake and all of Missouri's other watersnakes is that it has subocular scales: a short row of small scales between the eye and the row of large labial (upper lip) scales.
Similar species:
- Other watersnakes (Nerodia spp.) also live in Missouri's Bootheel: the plain-bellied, broad-banded, and northern diamond-backed watersnakes, and the midland watersnake subspecies of the common watersnake. They differ from the Mississippi green watersnake by having some combination of prominent bands on the back, or a plain yellow belly, or a yellow belly strongly marked with black patches.
- Watersnakes are often confused with the venomous northern cottonmouth (Agkistrodon piscivorus) and killed because of unwarranted fear. The cottonmouth is more heavy-bodied, with a larger, chunky head; has a facial pit between the nostril and eye on either side of the head; is darker; and has a light line from each eye to the corner of the mouth.
Adult length: 30 to 45 inches; occasionally to 51 inches.
Presumed to occur in the natural cypress swamps of extreme southeastern Missouri. The larger range extends southward along the Mississippi River, into most of Louisiana, and along the Gulf Coast from Texas to Florida.
Habitat and Conservation
This is primarily a swamp-dwelling snake. In Missouri, it prefers the cypress swamps, oxbows, river sloughs, and lakes of the Mississippi Alluvial Basin. In our state, it is restricted to the Bootheel lowlands.
It is active between late March and October, usually on warm days, often basking on branches overhanging water. Foraging occurs in early evening or at night.
This species overwinters in burrows in earthen banks, in rock crevices, and in levees with riprap rock.
Food
This watersnake feeds mainly on fish, but it also eats salamanders, frogs, and crayfish. Foraging occurs during early evening or, when the weather is hot, at night.
Status
Endangered and possibly extirpated in Missouri due to few confirmed reports of this species and the drastic reduction of native cypress swamps in southeastern Missouri.
Missouri and southern Illinois represent the northern extent of this species range, which extends along the Gulf Coast and northward along the Mississippi River.
Some individuals were spotted in southern Dunklin County in 1994, and several dead specimens have been collected from roads just across the border in Mississippi County, Arkansas. There is reason to hope that some Mississippi green watersnakes may still be found on the Missouri side of the border, enriching our state with their presence.
Life Cycle
Courtship and mating apparently occur in April or May. Females give birth to live young during August and early September, with the litter containing some 7–35 young, with an average of about 18 or 19. Larger females generally produce more young per litter. Mississippi green watersnakes become sexually mature at three or four years of life.
Human Connections
Intensive surveys throughout the rivers and wetlands of southeastern Missouri are needed to better understand the status of this animal in our state. Efforts to restore and preserve native cypress swamps in southeastern Missouri can help not only this species but also many other animals and plants special to Missouri's Bootheel lowlands.
Often when we think of our interactions with animals, we focus on what they mean to us: Can we eat them, do they harm us, and so on. But with most declining species, the situation is reversed: What can we do to help them? Our human activities, such as draining swamps, have eliminated most of their ancestral habitat in Missouri.
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.
Missouri's populations of Mississippi green watersnakes are on the northern edge of their species' broader range. Biologists point out the importance of such marginal populations. Whether you're talking about watersnakes or wildflowers, marginal populations often have slightly different genetic makeups that make them important for the species as a whole: perhaps they are better suited to certain habitats or climate patterns, or resistant to certain diseases. Sometimes, after they have been thoroughly studied, they even turn out to be different subspecies or species.
