Black Swamp Snake (Seminatrix pygaea)

Black Racer (Coluber constrictor)

Photos by J.D. Willson unless otherwise noted

Description: Black swamp snakes are fairly small (to 22 in – 55 cm), highly aquatic snakes that are glossy black with bright red bellies. They may be confused with small mud snakes (Farancia abacura), but mud snakes have a black checkerboard pattern on the belly and red coloration that extends up onto the sides. Solid black dorsal coloration and aquatic habits distinguish swamp snakes from terrestrial red-bellied snakes (Storeria occipitomaculata). Female black swamp snakes are much longer and heavier-bodied than males, but males have longer, thicker tails. Young black swamp snakes are only 2 – 3 in long, but resemble miniature adults.

Range and Habitat: Black swamp snakes are found in the Coastal Plain of the southeastern United States from eastern North Carolina to southern Alabama and throughout Florida. They are highly aquatic and inhabit a variety of open aquatic habitats including Carolina bays, roadside ditches, sphagnum bogs, sawgrass prairies, and the margins of heavily-vegetated ponds and lakes. Our research suggests that in South Carolina this species fares best in heavily-vegetated wetlands that dry periodically and lack fish (and hence are home to abundant amphibians).

Habits: Because black swamp snakes are highly aquatic and extremely secretive they are seldom seen, even by experienced herpetologists. Occasionally (particularly in southern Florida), individuals are found crossing roads on rainy nights and they may be collected by setting traps in shallow water amidst vegetation. Individuals can also be found hiding under debris or vegetation at the water’s edge, particularly on sunny spring days. When restrained, swamp snakes seldom bite.

Within the water, black swamp snakes are active both during the day and at night and actively forage amidst submerged vegetation. Although a variety of aquatic prey have been recorded in the diet of swamp snakes, including small fish, tadpoles, and small frogs, in South Carolina this species has been found to prey preferentially on aquatic salamanders, particularly larval and paedomorphic Ambystoma (mole salamanders), and leeches. Some Florida herpetologists have suggested that swamp snakes there also prefer aquatic salamanders (Eurycea quadridigitata and Pseudobranchus striatus). Research at the Savannah River Ecology Lab has shown that swamp snakes are able to survive prolonged (multi-year) droughts by aestivating within dried wetlands and that they fare better than other watersnakes during such events. Moreover, they are able to recover rapidly from droughts by feeding during pregnancy (uncommon in snakes) and investing ingested energy directly into offspring (income breeding). Swamp snake populations seem to do particularly well during post-drought years when amphibian prey is abundant within wetlands. Like other natricine watersnakes, this species gives birth to up to 23 live young in the late summer. Much of what is known about the ecology of black swamp snakes stems from research conducted by SREL herpetologists at Ellenton Bay, a large Carolina bay wetland on the Savannah River Site in South Carolina.

Conservation Status: Black Swamp Snakes are presumably uncommon and patchily distributed. However, because of their secretive, highly-aquatic habits, little is known about their status in most areas. For this reason, and because their reliance on fishless wetlands makes them vulnerable to habitat destruction, this species is of conservation concern throughout its range. Anecdotal evidence suggests that the introduction of exotic fish may have had adverse effects on swamp snake populations in southern Florida. This species is protected throughout the state of Georgia.

Pertinent References:

Winne, C.T. & W.A. Hopkins. 2006. Influence of sex and reproductive condition on terrestrial and aquatic locomotor performance in the semi-aquatic snake Seminatrix pygaea. Functional Ecology 20:1054-1061.

Winne, C.T. , J.D. Willson & J.W. Gibbons. 2006. Income breeding allows an aquatic snake (Seminatrix pygaea) to reproduce normally following prolonged drought-induced aestivation. Journal of Animal Ecology 75: 1352–1360.

Willson, J.D., C.T. Winne , M.E. Dorcas & J.W. Gibbons. 2006. Post-drought responses of semi-aquatic snakes inhabiting an isolated wetland: Insights on different strategies for persisting in a dynamic habitat. Wetlands 26:1071-1078.

Winne, C.T. 2005. Increases in capture rates of an aquatic snake (Seminatrix pygaea) using naturally baited minnow traps: evidence for aquatic funnel trapping as a measure of foraging activity. Herpetological Review 36:411–413.

Willson, J.D., C.T. Winne & L.A. Fedewa. 2005. Unveiling escape and capture rates in aquatic snakes and salamanders (Siren spp. and Amphiuma means) in commercial funnel traps. Journal of Freshwater Ecology 20:397-403.

Winne, C.T. , M.D. Dorcas & S.M. Poppy. 2005. Population structure, body size, and seasonal activity of Black Swamp Snakes (Seminatrix pygaea). Southeastern Naturalist 4:1-14. Cover Photo.

Winne, C.T. , T.J. Ryan, Y. Leiden & M.E. Dorcas. 2001. A comparison of evaporative water loss in two natricine snakes: Nerodia fasciata and Seminatrix pygaea. Journal of Herpetology 35:129-133.

Seigel, R. A., J. W. Gibbons, and T. K. Lynch. 1995. Temporal changes in reptile populations: effects of a severe drought on aquatic snakes. Herpetologica 51:424-434.

Seigel, R. A., R. K. Loraine, and J. W. Gibbons. 1995. Reproductive cycles and temporal variation in fecundity in the black swamp snake, Seminatrix pygaea. American Midland Naturalist 134:371-377.

Hopkins, W.A., C.T. Winne & S.E. DuRant. 2005. Differential swimming performance of two Natricine snakes exposed to a cholinesterase-inhibiting pesticide. Environmental Pollution 133:531-540.

Hopkins, W.A. & C.T. Winne . 2006. Influence of body size on swimming performance of four species of neonatal natricine snakes acutely exposed to a cholinesterase-inhibiting pesticide. Environmental Toxicology and Chemistry 25:1208-1213.

Dodd, C. K., Jr. 1993. Population structure, body mass, activity, and orientation of an aquatic snake (Seminatrix pygaea) during a drought. Canadian Journal of Zoology 71:1281-1288.

Godley, J. S. 1980. Foraging ecology of the striped swamp snake, Regina alleni, in Southern Florida. Ecological Monographs 50:411-436.

Account Author: J.D. Willson