|Scientific Name:||Nerodia clarkii|
|Species Authority:||(Baird & Girard, 1853)|
Nerodia fasciata subspecies taeniata (Cope, 1895)
Nerodia clarkii formerly was included in N. fasciata. Allozyme data support separation of clarkii and fasciata as distinct species (Lawson et al. 1991). Nerodia clarkii may interbreed with N. fasciata in areas of distributional overlap; this may be related to habitat disturbance caused by humans or hurricanes (Lawson et al. 1991).
Three subspecies have been recognized (clarkii, compressicauda, and taeniata). Dunson (1979) lumped taeniata with compressicauda. Based on allozyme data, Lawson et al. (1991) resurrected taeniata as a valid subspecies, but the genetic distances used to support this action were quite small.
This species formerly was included in the genus Natrix.
|Red List Category & Criteria:||Least Concern ver 3.1|
|Reviewer/s:||Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)|
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
|Range Description:||This species occurs in coastal areas on the southern United States and on the northern coast of Cuba. Its range includes brackish coastal habitats of the northern Gulf of Mexico, from the vicinity of Corpus Christi, Texas, eastward to Florida and including most of that state's coastline, including the Keys, then northward on the Atlantic coast to Volusia County; also the northern coast of Cuba (Lawson et al. 1991, Schwartz and Henderson 1991). The subspecies Nerodia clarkii clarkii occurs from the vicinity of Corpus Cristi in southern Texas east along the Gulf Coast to south of Cedar Key, Levy County, Florida. The subspecies N. c. compressicauda ranges from northern Pinellas County, Florida, around the southern tip of Florida and north to at least Merritt Island, including the Florida Keys and northern Cuba. The subspecies clarkii and compressicauda intergrade in a zone that may extend from Cedar Key to northern Pinellas County. The subspecies N. c. taeniata occurs on the Atlantic coast of Florida north of the range of compressicauda, in Volusia County, and apparently intergrading with compressicauda in Brevard and Indian River counties (Kochman and Christman 1992).|
Native:Cuba; United States
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is represented by a large number of occurrences (subpopulations). Many subpopulations are discontinuous and isolated by lack of habitat. The adult population size is unknown but presumably exceeds 10,000. Large numbers still exist in some parts of the range (Ernst and Ernsat 2003). In Florida, this snake is common on the Gulf Coast but rare on the Atlantic coast at the northern extent of the range (subspecies taeniata) (Tennant 1997). Abundance has declined throughout much of the range, particularly where coastal marshes have been degraded (Werler and Dixon 2000). Large numbers are still present in some areas, but elsewhere they have become scarce (Ernst and Ernst 2003). Current trend is unknown; extent of occurrence, area of occupancy, and number of subpopulations are probably relatively stable or declining at a rate of less than 10% over 10 years or three generations, whereas population size may be declining at an unknown rate.|
|Habitat and Ecology:||This snake is most common in estuarine situations, such as coastal brackish and salt marshes containing Spartina, Juncus, Salicornia; it occurs in lesser abundance farther inland in freshwater marshes with arrowheads, sedges, and naiads (Dundee and Rossman 1989, Werler and Dixon 2000, Ernst and Ernst 2003). Toward the southern end of the range in Florida, it also inhabits buttonwood and red mangrove swamps and saline offshore islands (Tennant 1997). Microhabitats include the burrows of crayfish, fiddler crabs, or muskrats (Dundee and Rossman 1989, Tennant 1997). Sometimes it can be found on shore under rocks, logs, and other cover (Schwartz and Henderson 1991).|
|Major Threat(s):||A major threat along the Gulf Coast is degradation of habitat by dredging, diking, development, and chemical pollution (Werler and Dixon 2000). Loss of salt marsh habitat appears to have slowed since 1988 (USFWS 1998). Insecticides may be lethal to the snake. Oil spills pose a potential threat. Along the Atlantic coast of Florida much habitat has been lost to commercial development (Tennant 1997). As habitat shrinks, the probability of interbreeding with Nerodia fasciata may increase, particularly along the Atlantic coast (Kochman and Christman 1992, Ernst and Ernst 2003).|
|Conservation Actions:||Several occurrences on the Gulf Coast are in protected areas, including Gulf Islands National Seashore (Mississippi) and possibly St. Marks and Chassahowitzka National Wildlife Refuges (NWRs) (Florida). The range of subspecies taeniata on the Atlantic coast of Florida includes Tomoka State Park and perhaps northern end of Merritt Island NWR, but the status of snakes there requires study, as do their ecological needs.|
Bartlett, R D. and Bartlett, P.P. 1999. A Field Guide to Texas Reptiles and Amphibians. Gulf Publishing Company, Houston, Texas. xviii + 331 pp.
Conant, R. and Collins, J.T. 1991. A Field Guide to Reptiles and Amphibians: Eastern and Central North America. Third Edition. Houghton Mifflin Company, Boston, Massachusetts.
Dixon, J.R. 2000. Amphibians and Reptiles of Texas. With Keys, Taxonomic Synopses, Bibliography, and Distribution Maps. Second edition. Texas A & M University Press, College Station, College Station, Texas.
Dundee, H.A. and Rossman, D.A. 1989. The Amphibians and Reptiles of Louisiana. Louisiana State University Press, Baton Rouge, Louisiana.
Ernst, C.H. and Ernst, E.M. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
Gibbons, J.W. and Dorcas, M.E. 2004. North American Watersnakes: A Natural History. University of Oklahoma Press, Norman, Oklahoma. xxvi + 439 pp.
IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed: 12th September 2007).
Mount, R.H. 1975. The Reptiles and Amphibians of Alabama. Auburn University Agricultural Experiment Station, Auburn, Alabama. vii + 347 pp.
Schwartz, A. and Henderson, R.W. 1991. Amphibians and Reptiles of the West Indies: Descriptions, Distributions and Natural History. University of Florida Press, Gainesville, Florida. xvi + 720 pp.
Tennant, A. 1997. A Field Guide to Snakes of Florida. Gulf Publishing Company, Houston, Texas. xiii + 257 pp.
Tennant, A. 1998. A Field Guide to Texas Snakes. Second edition. Gulf Publishing Company, Houston, Texas.
Werler, J.E. and Dixon, J.R. 2000. Texas Snakes: Identification, Distribution, and Natural History. University of Texas Press, Austin, Texas.
|Citation:||Hammerson, G.A. 2007. Nerodia clarkii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 December 2013.|
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