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Atlantic salt marsh snake
[edit]The Atlantic salt marsh snake (Nerodia clarkii taeniata) is one of three subspecies of the salt marsh snake (N. clarkii) that is found on the Atlantic coast of the Florida peninsula[1]. The Atlantic salt marsh snake has an olive color base, with light and dark brown stripes and dark brown blotches further down the back. The snake’s activity is largely dependent on the tidal cycles as low tide offers them the most opportunity for food. They are ovoviparous, but have low fecundity compared to other salt marsh snakes[2].
This subspecies of salt marsh snake is listed as threatened by the U.S Fish and Wildlife Services and the Florida Fish and Wildlife Conservation Commission[2]. The species that it belongs to, Nerodia clarkii, is listed as a species of least concern on the IUCN Red List[3]. The Atlantic salt marsh snake is protected as a threatened species by the Federal Endangered Species Act of 1973[1]. The Atlantic salt marsh snake is also protected as a federally-designated threatened species by Florida’s Endangered and Threatened Species Rule[4].
| Atlantic salt marsh snake | |
|---|---|
| File:No image available | |
| Scientific classification | |
| Kingdom: | Animalia
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| Phylum: | Chordata
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| Class: | Reptilia
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| Order: | Squamata
|
| Family: | Natricidae
|
| Genus: | Nerodia
|
| Species: | Clarkii
|
| Subspecies: | Taeniata
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| |
| Subspecies range: coast of Volusia County, Florida | |
Description
[edit]Physical Characteristics
[edit]The Atlantic salt marsh snake is a keeled water snake that can reach a length of about 2 feet[4]. The dorsal ground color is pale olive, patterned with a pair of dark brown stripes running down the back. These dark stripes usually become a series of elongated blotches further down the body. The ventral surface is black with a median series of yellowish spots[1].
Behavior
[edit]Diet
[edit]The tidal cycles strongly influence the availability of food as well as the activity of N. c. taeniata. The snake is most active at night, during periods of low tide, and feeds on small fish when they become trapped in shallow water, but will also eat frogs when available[2]. Atlantic salt marsh snakes have also been known to eat shrimp and small crabs[4].
Unlike many other salt water-dwelling snakes, N. c. taeniata do not possess salt glands to excrete excess salt after drinking the water in their environment[5]. N. c. taeniata never drink salt water, even when dehydrated. Instead, this species get water from rain or dew[6].
Life History
[edit]Development
[edit]Little is known about the development of members of this subspecies.
Reproduction
[edit]This species is ovoviviparous. In captivity, individuals have given birth to 3 to 9 young from August to October[6]. Fecundity is relatively low compared to the adjacent freshwater species of snake, Nerodia fasciata, which may give birth to 50 or more young[1].
Distribution
[edit]Historical and present range
[edit]The species that the Atlantic salt mark snake belongs to, Nerodia clarkii, is found along the coast from southern Texas to the east coast of Florida at least as far as the Halifax River, Volusia County, in addition to the North coast of Cuba[1]. The subspecies N. c. taeniata covers a smaller geographic range. When the subspecies was originally listed as threatened under the ESA, the Atlantic salt marsh snake was thought to include salt marsh snakes ranging as far south as Indian River County[7]. Researchers now believe the true range may be much more restricted than previously realized, occurring only in the brackish marshes along the coast of Volusia County, ranging form the Halifax River in the south to the north end of the Indian River Lagoon[1]. This limited distribution makes the subspecies particularly vulnerable to habitat destruction[1].
Habitat
[edit]N. c. taeniata is restricted to the salt marshes of Volusia, Brevard, and Indian River Counties, Florida. The subspecies inhabits brackish coastal marshes that are predominantly vegetated with salt grass (Distichlis spicata) and glasswort (Salicornia spp.). The subspecies has no designated critical habitat[2].
Historical and present population size
[edit]Population size is not well known. Species status was listed as unknown without a comprehensive population survey in the 2008 five year review[8]. There were no population or demographic trends available in the five year review published in 2019[9].
Conservation Status
[edit]History of ESA and U.S. Fish and Wildlife Service listings
[edit]The Atlantic salt marsh snake is protected under the Endangered Species Act of 1973 as a threatened species. The snake was listed as threatened under the U.S. Fish and Wildlife Service on November 29, 1977[1][7]. A recovery plan was proposed through the U.S. Fish and Wildlife Service in 1993 with the goal of delisting the Atlantic salt marsh snake when certain recovery criteria are met. The recovery criteria that the plan states must be met for delisting are as follows:[1]
- There is no evidence of significant genetic introgression from the Florida banded water snake, Nerodia fasciata pictiventris, into adjacent populations of N. c. taeniata
- Adequate habitat protection is maintained with habitat loss maintained at or below current levels for 5 years
- Self-sustaining populations of 100-200 adult snakes at each of 10 discrete sites are established throughout Volusia County[1]
The U.S. Fish and Wildlife Service has conducted a series of five year reviews on the Atlantic salt marsh snake. Two relatively recent five year reviews have been conducted, the first of which was published in 2008. This review revealed that 0-25% of recovery goals laid out in the original recovery plan had been achieved[8]. This review also stated that the Service conducted five year reviews for the Atlantic salt marsh snake in 1987 and 1991, evaluating the status of many species alongside N. c. taeniata. No change in the Atlantic salt marsh snake’s listing were warranted by these reviews[8]. The second of the recent five year reviews was published in 2019. This review also revealed that 0-25% of the species’ recovery goals laid out in the original recovery plan had been achieved[9]. No changes in the listing have been made since 1973, and it is still protected as a threatened species under the ESA and the U.S. Fish and Wildlife Service.
Human impact
[edit]Habitat destruction through residential and commercial construction and habitat degradation due to human activities such as ditching and water level manipulation have negatively impacted N. c. taeniata[2]. There is little data on the effects these activities have on this subspecies and their habitat during the period of fast, unregulated development that spanned from the 1940s to the 1960s[2]. However, records show that dredge-and-fill projects from 1983-1992, including pier construction, shoreline projection projects, and mosquito ditching, destroyed only 13.2 ha of salt marsh. Loss of salt marsh habitat has apparently slowed since 1988, indicating that protection under local, State, and Federal conservation policies has increased and have been effective in the area[2][7].
Major threats
[edit]A primary concern that led to the Atlantic salt marsh snake being listed as threatened is the loss of habitat resulting from intensive drainage and development in coastal salt marshes. The narrow habitat flexibility and limited geographical range of the subspecies makes them even more vulnerable to habitat disruption and modification. Development along the Atlantic coast of Florida has led to permanent habitat loss for N. c. taeniata[1][2].
Future habitat destruction is also possible through rising sea levels, which could lead to increased salinity in the estuaries, changing the vegetation of the marsh and flooding the area[1][2].
Another primary concern that accompanies this habitat loss is the disruption of reproductive isolating mechanisms, which can lead to hybridization with the Florida banded water snake. This could swamp the Atlantic salt marsh snake gene pool by the Florida banded water snake's larger gene pool[1][2].
Current conservation efforts
[edit]The species in general, N. clarkii, holds an IUCN status of least concern[3]. The conservation actions needed for N. clarkii include land and water protection, site and area protection, land and water management, site and area management, and habitat & natural process restoration[3]. The subspecies N. c. taeniata is of greater concern and has been labeled threatened by the U.S. Fish and Wildlife Services and the state of Florida[4]. A wide range of conservation efforts that have been recommended, some of which have been or are being implemented.
Habitat maintenance and creation
[edit]Survey work and the creation, restoration, and protection of suitable habitats comprise a large part of the current conservation efforts for N. c. taeniata[7]. The range of N. c. taeniata along the Atlantic coast of Florida includes Tomoka State Park and the northern end of Merritt Island National Wildlife Refuges, but the status and ecological needs of the snakes in these areas is not well known and requires further study[3].
Genetic research
[edit]Other conservation efforts include genetic comparison with other salt marsh snakes and southern banded water snakes[7]. Localities near New Smyrna Beach were sampled by personnel from the GFC for genetic studies[1][2][10]. Analysis indicated that the salt marsh snakes are closely related to but distinct from the southern banded water snakes, and that the three subspecies of salt marsh snakes, or N. clarkii, are indistinguishable from each other[1][2][10]. Tissues saved from snakes can be used for continued genetic comparison[1][2].
References
[edit]- ^ a b c d e f g h i j k l m n o p "U.S. Fish and Wildlife Service, Recovery Plan, 1993" (PDF). December 15, 1993.
{{cite web}}: CS1 maint: url-status (link) - ^ a b c d e f g h i j k l m "U.S. Fish and Wildlife Services, Multi-Species Recovery Plan for South Florida" (PDF).
{{cite web}}: CS1 maint: url-status (link) - ^ a b c d "IUCN Red List of Threatened Species: Nerodia clarkii". IUCN Red List of Threatened Species. 2007-03-01. Retrieved 2020-04-18.
- ^ a b c d "Atlantic salt marsh snake". Florida Fish and Wildlife Conservation Commission. Retrieved 2020-04-17.
{{cite web}}: CS1 maint: url-status (link) - ^ Schmidt-Nielsen, Knut; Fange, Ragnär (1958). "Salt Glands in Marine Reptiles". Nature. 182 (4638): 783–785. doi:10.1038/182783a0. ISSN 1476-4687.
- ^ a b Kochman, H.I. (1992). "Atlantic salt marsh snake". Rare and Endangered Biota of Florida: 111–116.
- ^ a b c d e U.S. Fish and Wildlife Service 1977, listing of the Atlantic salt marsh snakes as a threatened species. Fed.Reg 42:60743-60745
- ^ a b c "Atlantic salt marsh snake 5 year review: summary and evaluation" (PDF). 2008.
{{cite web}}: CS1 maint: url-status (link) - ^ a b "Atlantic salt marsh snake 5 year review: summary and evaluation" (PDF). 2019.
{{cite web}}: CS1 maint: url-status (link) - ^ a b Lawson (1991). "Allozyme variation and systematics of the Nerodia fasciae-Nerodia clarkii complex of water snakes". Copeia: 638–659.
External Links
[edit]https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=7729
https://www.fws.gov/northflorida/Species-Accounts/Atl-Salt-Marsh-Snake-2005.htm
https://www.fnai.org/FieldGuide/pdf/Nerodia_clarkii_taeniata.pdf