Species Description: Nerodia clarkii is a collective term assigned to a group that includes three subspecies (Conant and Collins 1998) of salt marsh snakes, 2 of which are found in the Indian River Lagoon system: the Atlantic Salt Marsh Snake, Nerodia clarkii taeniata; and N. clarkii compressicauda, the mangrove salt marsh snake.
The Federally listed Atlantic Salt Marsh Snake, N. c. taeniata can breed with other subspecies of salt marsh snakes and also with a freshwater subspecies, Nerodia fasciata, producing hybrids with various mixtures of physical characteristics. Its original origin is unknown.
The taxonomy of the salt marsh snakes has been, and continues to be somewhat controversial. Some experts have postulated N. c. taeniata is a relict hybrid produced from other snake subspecies during the Pleistocene (1.8 million years ago to 11,000 years ago). Others suggest that it is not truly a unique subspecies, but a population of N. c. compressicauda that has developed different physical characteristics in response to different selective pressures (Kochman 1992).
Nerodia c. compressicauda, the Mangrove Salt Marsh Snake, is the larger of the 2 subspecies and has little to no dorsal striping. It also has a unique red phase that helps it blend in with the prop roots of mangroves.
The threatened Atlantic Salt Marsh Snake, Nerodia c. taeniata, is the smallest of the salt marsh snakes and has a maximum length of 61 cm (2 feet) (Conant and Collins 1998). Its dorsal body coloration is generally rust to brown or olive, with 2 longitudinal stripes along each side of the body. The stripes eventually fragment near the tail and appear as blotches. The ventral surface has 1 row of pale colored spots. There are 21 - 25 scale rows at midbody, and the scales are keeled. The anal plate is divided.
Potentially Misidentified Species: Nerodia fasciata pictiventris
Regional Occurrence: In North America, Nerodia clarkii are found from the eastern coast of Florida to Texas.
IRL Distribution: Nerodia c. taeniata is restricted to the Atlantic coast of central Florida. Historically it occurred in Volusia, Brevard and Indian River counties; but, has recently been found only along a coastal strip in Volusia County (Kochman 1992). Surveys conducted at Kennedy Space Center (Canaveral National Seashore) in 1979 and 1980 found that most of the salt marsh snakes in that area were probably N. c. compressicauda or N. compressicauda/taeniata hybrids.
Locomotion: Crawls; can also swim short distances in calm waters
Reproduction: Duration of the reproductive season for Nerodia clarkii is unknown. In captivity, the number of young per reproductive event ranges from 3 - 9. Nerodia clarkii give birth to live young.
Embryology: Egg form in Nerodia clarkii is ovoviviparous.
Salinity: Some work on the physiology of this group has been completed, but little can be generalized for the entire salt marsh snake group (Kochman 1977). Salt marsh snakes are physiologically well adapted to exploit a saline environment (Lawson, et. al. 1991) despite the fact that they appear to have no salt excreting organs (Kochman 1977).The salinity range of adults and juveniles of this group is considered range from oligosaline to hypersaline. It is one of the few North American reptiles that is successful in estuarine habitats (Kochman 1992).
Habitat: The salt marsh snakes are generally terrestrial in nature, and can be found primarily in the littoral zone in muddy, vegetated areas. N. c. compressicauda, which primarily occupies red mangroves, can occasionally be seen moving through protected, slow moving waters. N. c. taeniata favors glasswort (Salicornia spp.), salt grass (Distichilis spicata), and sometimes, black mangroves (Avicennia germinans) (Lawson et. al. 1991) as habitat. They are primarily nocturnal and may seek shelter during the day in fiddler crab burrows.
Activity Time: Evidence supports salt marsh snakes being primarily nocturnal (Carr and Goin 1942, Wright and Wright, 1957). However, scientists have found these snakes actively feeding and basking during the day.
Special Status: Threatened
Notes on Special Status: As of 15 January 1997, Nerodia clarkii taeniata was federally listed as threatened in Indian River County and Brevard County, FL.
Benefit in the IRL: Aesthetic, scientific
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Conant R, Collins JT. 1998. A field guide to reptiles & amphibians: eastern and central North America (Vol. 12). Houghton Mifflin Harcourt. 640 p.
Kochman HI. 1977. Differentiation and hybridization in the Natrix fasciata complex (Reptilia: Serpentes): A nonmorphological approach. Unpublished Master's Thesis, University of Florida, Gainesville.
Kochman HI, Christman SP. 1992. Atlantic salt marsh snake. Rare and Endangered Biota of Florida 3: 111-116.
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