Saltmarsh Snake

Nerodia clarkii, commonly known as the salt marsh snake or the saltmarsh watersnake, is a species of semi-aquatic, nonvenomous, colubrid snake found in the southeastern United States. Their range extends along the tidal salt marshes of the Gulf of Mexico and the Atlantic Coast from Texas to Florida, with an additional population in northern Cuba. The three subspecies of this snake are primarily distinguished by color pattern and geographic range.

Salt marsh snakes are the only U.S. snake species indigenous to saltwater habitats, being reported as common on coastal barrier islands without freshwater (Allen 1932).

Etymology

The specific name, clarkii, is in honor of American surveyor and naturalist John Henry Clark (1830–1885).

Description and subspecies

General description

Salt marsh snakes grow to a total length (including tail) of 15–30 inches (38–76 cm). They are also highly variable in both pattern and coloration. Found most commonly in coastal salt marshes, this snake inhabits brackish and saltwater habitats; it is also found hiding in crab burrows. Though salt marsh snakes are common in appropriate habitat, they have a tendency to be wary and secretive, so they are rarely seen. All members of this species reproduce via live birth, and all are semi-aquatic. Furthermore, all forms of this species may be distinguished as having either 21 or 23 rows of scales.

The seawater they inhabit exerts a continual draw on their tissue's electrolyte balance, due to osmosis. Its scaly reptilian skin acts as a barrier against external dehydration, but, if ingested, seawater draws the less-salty fluid from blood and tissues into the stomach. N. clarkii is the only species to establish itself in this saline niche, drinking only rainwater when it is available, and at other times swallowing nothing but prey animals with the same diluted body fluids as their own. All water species of snake (including N. clarkii) are typically considered to be non-venomous, though they do employ a complex series of enzymes in their saliva, resulting in some inflammation and edema to those who have been bitten.

Subspecies

The salt marsh snake has three subspecies, all of which were first discovered and classified in the mid to late 1800s. They are as follows:

Gulf salt marsh snake (N. c. clarkii)

The Gulf salt marsh snake is the nominate race of N. clarkii and has the largest geographic distribution. Populations of the Gulf salt marsh snake range along the northern coast of the Gulf of Mexico from the vicinity of Corpus Christi, Texas eastward to the Gulf Hammock region of Florida. They are characterized by their prominent longitudinal striping; members of this race can be black, brown, gray, or reddish but all exhibit three lighter longitudinal stripes which run from the back of their neck to their tail. The venter is dark with a central light line of cream-colored oval blotches, sometimes flanked by a row of pale spots. The scales are in either 21 or 23 rows (usually 21), and the anal plate is divided. There is little ontogenetic difference between juvenile to fully adult snakes. Individuals subsist on a diet of primarily fish, and especially shallows-living species such as killifish and small mullet, as well as crayfish and shrimp. Members of this race are primarily nocturnal during hot summer nights, but may be found basking and foraging during daylight hours in cool weather. Sexual maturity is reached at three years.

Mangrove salt marsh snake (N. c. compressicauda)