Nerodia erythrogaster

The plain-bellied water snake is a large, thick-bodied, solid-colored snake. Subspecies can be brown, gray, olive green, greenish-gray, and black in color. Some lighter colored snakes dispaly dark dorsal blotches.[2] This snake can be distinguished from other water snakes by its plain, unmarked underside varying in color from red to yellow. It gets its common name because it has no marking on its underside. Adults vary in size from 24–40 inches (76–122 cm) in total length.[3] Juvenile snakes have banding patterns similar to banded water snakes, but can be identified by their unmarked bellies.[4]

Plain-bellied water snakes are found in every southeastern state of the U.S., from Florida to southeastern Virginia on the east coast, and to the borders of eastern North Carolina and western Tennessee. The snakes are almost always found near a permanent water source. They are usually seen near rivers and floodplains, lakes and ponds and any natural wetlands in their geographic range.[4]

Plain-bellied water snakes are active in the warmest months of the year. During the hottest months of summer, they will be active both during the day and at night. In warmer months, they are typically found basking on logs or near bodies of water, swimming in water or traveling over land. During hot, humid weather, they will travel long distances away from water.[3] They are unusual for a water snake in the amount of time that they are found on land. They hibernate during the coldest months of the winter.[4]

The species gets most of its food from the water. They feed primarily on fish, crayfish, salamanders, and frogs. Because of the amount of time they spend on land, the snake's includes a large quantity of amphibians. Like most other snakes, it will hunt for prey, but the snake has been observed, sitting in aquatic areas, waiting for prey to approach them. They apprehend and swallow prey alive without using constriction.[4][3]

This species bears live young (ovoviviparous) like other North American water snakes and garter snakes. The snake breeds from April until mid-June in the southeast U.S. The female gives birth during the months from August to September. Large broods have been observed, but a typical litter size is around eighteen. One female was observed with a litter of fifty five baby snakes in North Carolina,[4] In 2014 a captive female produced two healthy offspring via parthenogenesis.[5]

The plain-bellied water snake is prey to both terrestrial and aquatic predators. Reported predators include largemouth bass, kingsnakes, cotton mouths, and several species of egrets, and hawks. Their usual reaction to threats of being captured are: attempts to escape, biting and releasing a foul odor. Unlike the common water snake, the plain-bellied water snake will leave water and try to escape over land if threatened.[4]

These six subspecies of N. erythrogaster have been historically recognized, including the nominotypical subspecies. However, in 2010, Makowsky, et. al. determined that there was "little support for the recognized subspecies as either independent evolutionary lineages or geographically circumscribed units and conclude that although some genetic and niche differentiation has occurred, most populations assigned to N. erythrogaster appear to represent a single, widespread species."[6][7]

• Nerodia erythrogaster alta (Conant, 1963) - plainbelly water snake
• Nerodia erythrogaster bogerti (Conant, 1953) - Bogert's water snake
• Nerodia erythrogaster erythrogaster (Forster, 1771) - redbelly water snake
• Nerodia erythrogaster flavigaster (Conant, 1949) - yellowbelly water snake
• Nerodia erythrogaster neglecta (Conant, 1949) - copperbelly water snake
• Nerodia erythrogaster transversa (Hallowell, 1852) - blotched water snake

The plain-bellied water snake is considered a conservation risk because of its tendency to travel over land on roads and highways. Destruction or damage to wetlands is also a threat to the species's habitat. It is not a protected species in the southeastern states. In 1997, the subspecies, copper-bellied water snake was designated a threatened species in Ohio, Michigan and northern Indiana under the Federal Endangered Species Act.[4]

• Conant, R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Houghton Mifflin. Boston. xviii + 429 pp. ISBN 0-395-19977-8 (paperback). (Natrix erythrogaster, pp. 142–144 + Plate 20 + Map 103.)
• Schmidt, K.P., and D.D. Davis. 1941. Field Book of Snakes of the United States and Canada. G.P. Putnam's Sons. New York. 365 pp. (Natrix erythrogaster, pp. 224–225.)
• Smith, H.M., and E.D. Brodie Jr. 1982. Reptiles of North America: A Guide to Field Identification. Golden Press. New York. 240 pp. ISBN 0-307-13666-3 (paperback). (Nerodia erythrogaster, pp. 154–155.)
• Wright, A.H., and A.A. Wright. 1957. Handbook of Snakes of the United States and Canada. Comstock. Ithaca and London. 1,050 pp. (in 2 volumes) (Natrix erythrogaster, pp. 477–490, Figures 141.-143., Map 39.)