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
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.
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
HABITAT AND DISTRIBUTION
In North America, Nerodia clarkii are found from the eastern coast of
Florida to Texas.
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.
LIFE HISTORY AND POPULATION BIOLOGY
Adult Size: 15-30 inches
Crawls; can also swim short distances in calm waters
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.
Egg form in Nerodia clarkii is ovoviviparous.
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).
Little work has been done on
the ecology of the salt marsh snakes in the Indian River Lagoon system. Studies that have taken place have mostly been surveys for snakes. On the West Coast of
Florida some work has been done on the ecology of N. c. compressicauda (Miller
and Mushinsky 1990, Mushinsky and Miller 1993, Mullin 1994, and Mullin and
Mushinsky 1995, 1997).
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.
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.
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
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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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Miller DE, Mushinsky HR. 1990. Foraging ecology and prey size in the mangrove water snake, Nerodia fasciata compressicauda. Copeia 1990: 1099-1106.
Mullin SJ. 1994. Life history characteristics of Nerodia clarkii compressicauda at Placido Bayou, Florida. J Herpetol 28: 371-374.
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