Atlantic salt marsh snake: Difference between revisions

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[[File:Eastern_Indigo_Snake.jpg|alt=Eastern indigo snake (Drymarchon couperi)|thumb|320px|'''[[Eastern indigo snake]]'''<br/> ''Drymarchon couperi''<br/>Status: [[:Category:Endangered Species|Threatened]]]]
[[File:Atlantic_salt_marsh_snake.jpg|alt=Atlantic salt marsh snake (Nerodia clarkii taeniata)|thumb|240px|'''[[Atlantic salt marsh snake]]'''<br/> ''Nerodia clarkii taeniata''<br/>Status: [[:Category:Endangered Species|Threatened]]]]
<p><i><b>''Nerodia clarkii taeniata''</b></i>, commonly known as the <b>Atlantic salt marsh snake</b>, is found only in the coastal salt marshes of Brevard and Volusia, Florida. The Atlantic salt marsh snake was listed as a [[:Category:Endangered Species|threatened species]] on November 29, 1977 by the U.S. Fish and Wildlife Service.<ref name="USFWSdetermination1977"/></p>
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==Description==
<p>There are three subspecies of salt marsh snakes in Florida, the Gulf salt marsh snake (''Nerodia clarkii clarkii''), mangrove water snake (''N. c. compressicauda''), and Atlantic salt marsh snake (''N. c. taeniata'').<ref name="USFWSrecovery1993"/></p>
[[File:Gulf_salt_marsh_snake.jpg|alt=Gulf salt marsh snake (Nerodia clarkii clarkii)|thumb|240px|'''Gulf salt marsh snake'''<br/> ''Nerodia clarkii clarkii'']]
<p>Salt marsh snakes dorsal pattern's are formed from a basic pattern of four rows of dark blotches running from head to tail (two lateral and two dorsolateral rows) on a lighter background. In the striped forms, the blotches join to form stripes; in the banded forms, the blotches join across the back to form bands. In partially striped individuals, it is usually the anterior portion of the body that is striped, with the pattern posteriorly consisting of bands or rows of unfused blotches.</p>
<p>The Gulf salt marsh snake (''Nerodia clarkii clarkii'') has a dorsal pattern that is completely striped, or nearly so, with dark brown to black stripes on a tan background. It is not unusual for the lateral stripes in this form to break down posteriorly into rows of blotches.</p>
[[File:Mangrove_salt_marsh_snake_Nerodia_clarkii_compressicauda.jpg|alt=Mangrove salt marsh snake (Nerodia clarkii compressicauda)|thumb|240px|'''Mangrove salt marsh snake'''<br/> ''Nerodia clarkii compressicauda'']]
<p>The mangrove water snake (''N. clarkii compressicauda'') may be uniformly orange in color, but it more often has a pattern of dark bands on a lighter background. Individuals from throughout the range of the mangrove water snake may be partially striped; in these specimens the striping is typically limited to the neck region, but occasional specimens may be more extensively striped. Coloration in the mangrove water snake is extremely variable, with the background being gray, straw, or reddish and the bands being black, brown, or red. Populations of mangrove water snakes characteristically include at least some individuals that exhibit reddish or orange pigmentation.</p>
[[File:Atlantic_salt_marsh_snake_02.jpg|alt=Atlantic salt marsh snake (Nerodia clarkii taeniata)|thumb|240px|'''Atlantic salt marsh snake'''<br/> ''Nerodia clarkii taeniata'']]
<p>The Atlantic salt marsh snake (''N. c. taeniata'') is a partially striped salt marsh snake that reaches a maximum length of  82 cm (32 in.), although it is typically less than 65 cm (26 in.) in length. The pattern consists of a gray to pale olive background with black to dark brown stripes anteriorly, the stripes breaking up into rows of spots posteriorly. The extent of the striping is variable, but most individuals from the coastal marshes of Volusia County are striped on at least the anterior 30 percent of the body. The venter is black with a central row of large cream to yellowish spots. As in the case of the dorsal striping, this ventral pattern is best developed anteriorly and tends to break down posteriorly. The red pigmentation characteristic of mangrove water snakes is conspicuously lacking in Atlantic salt marsh snakes from the vicinity of Edgewater, Volusia County, and northward.</p>
<p>Hebrard (1979) reported coloration for 23 specimens from the southern Indian River Lagoon, near the Volusia-Brevard county line. Of these, 7 (30 percent) exhibited orange or reddish pigmentation either dorsally or ventrally. It is unclear at this time (1993) whether the reddish pigmentation reported by Hebrard should be interpreted as indicating intergradation with the mangrove water snake. The series of 25 specimens for which Hebrard provided pattern descriptions had dorsal stripes on 0 to 100 percent of the body; only 8 (32 percent) had dorsal stripes on more than 30 percent of the body, but 3 (12 percent) reportedly had dorsal stripes on 100 percent of the body. (In terms of pattern formation, the vertebral stripe is actually the lighter background color which is visible between the two dark, dorsolateral stripes.)</p>
==Distribution==
[[File:Atlantic_salt_marsh_snake_distribution_map.jpg|alt=Atlantic salt marsh snake (Nerodia clarkii taeniata) map|thumb|320px|'''Atlantic salt marsh snake distribution''']]
The species to which the Atlantic salt marsh snake belongs, N. clarkii, is found in a narrow coastal strip from southern Texas, east along the Gulf coast, around the Florida peninsula, and up the east coast of Florida at least as far as Volusia County's Halifax River.
Both Cope’s (1895) type series and the specimens used by Carr and Goin (1942) to resurrect N. c. taeniata came from the brackish coastal marshes of Volusia County, Florida. There is some uncertainty about the precise locality from which Cope’s specimens came, but Carr and Goin restricted the type locality to the vicinity of National Gardens, which lies near the north end of the Halifax River. Salt marsh snakes have not been documented to the north in southern Flagler County. The Carr and Goin series was collected on the barrier island at New Smyrna Beach. Recent records for populations identifiable as Atlantic salt marsh snakes are available from (1) the barrier island a short distance north of Ponce Inlet, (2) the mainland shoreline east ofthe New Smyrna Beach airport, (3) two localities on the barrier island at New Smyrna Beach (Florida Game and Fresh Water Fish Commission (FGFWFC) records), (4) an island in the Indian River east of Edgewater (G. Goode, East Volusia Co. Mosquito Control, pers. comm.) and (5) a single specimen identified as N. c. taeniata was captured just south of the Flagler County line (G. Goode pers. comm.). It is not known if a viable population exists in this area or to the north in Flagler County but if so, these Atlantic salt marsh snakes are now isolated from populations in the northern Indian River Lagoon by the Ormond Beach-Daytona metropolitan area.
A problem attendant to the listing of any subspecies that is distributionally continuous and intergradient with another subspecies is the difficulty of defining the limit(s) of the listed form’s distribution in the area where it contacts the related, unlisted subspecies. To the south, the Atlantic salt marsh snake intergrades with the mangrove water snake along the central Atlantic coast of Florida. As noted above~ both the description and the resurrection of the subspecies were based on specimens from Volusia County, although Carr and Goin (1942) considered a single specimen from Indian River County also to be N. c. taeniata. They also mentioned a specimen of salt marsh snake from Melbourne, Brevard County, but did not indicate whether they considered that specimen to be N. c. taeniata. Wright and Wright (1957) considered N. c. taeniata to extend only as far south as the lower end of Mosquito Lagoon, in northern Brevard County, and Neill (1958) indicated that N. c. taeniata intergraded with the mangrove water snake on Merritt Island. In the final listing of the Atlantic salt marsh snake (FR 42:60743-60745), the Service indicated that “The Atlantic salt marsh snake is known only from coastal areas of Brevard, Volusia, and Indian River counties.” However, Hebrard and Lee (1981) examined a large series of salt marsh snakes from southern Mosquito Lagoon near the Volusia-Brevard county line and reported that they resembled Nerodia fasciata compressicauda quite closely.” Hebrard and Lee further noted that their specimens differed markedly in coloration and pattern from specimens of N. c. taeniata from further north in Volusia County. It is also worth noting that the snakes examined by Hebrard and Lee were collected in mangroves (species not indicated), whereas only about 10 miles farther north, where populations of typical Atlantic salt marsh snakes are found, the habitat consists primarily of glasswort (Salicornia spp.) flats and salt grass (Distichlis spicata)-bordered tidal creeks with only scattered black mangroves (Avicennnia germinans). The zone of intergradation appears to coincide with the increasing dominance of mangrove swamps, eventually as mangrove swamps become predominant so does N. c. compressicauda. Kochman (1992) concluded that “salt marsh snakes from farther south in Brevard and Indian River counties, although occasionally striped, appear to comprise a zone of intergradation with N. c. compressicauda.”
Until a survey and taxonomic assessment have been conducted, it will not be possible to determine the southern distributional limit of the Atlantic salt marsh snake. Nonetheless, it appears that the subspecies may be restricted to the brackish, coastal marshes of Volusia County, from the Halifax River south to the northern portions of the Indian River Lagoon.
==Habitat==
Atlantic salt marsh snakes are restricted to brackish, tidal marshes. They most often have been found in association with saltwort flats and salt grass-bordered tidal creeks. It is not known if they occur in the adjacent black needlerush (Juncus roemerianus) habitat. Atlantic salt marsh snake use of marsh habitats may be limited by water level; with extreme fluctuations making the marsh too hydric or xeric (G. Goode pers. comm.). When inactive or pursued, they frequently retreat into one of the numerous fiddler crab (Uca pugilator) burrows that riddle the edge of the marsh and the banks of the tidal creeks (Carr and Goin 1942, Kochman 1992, P. Moler pers. obs.).
==Life History/Ecology==
Although the Atlantic salt marsh snake is most easily observed at night, it may be active at any time of day. Its activity is influenced by tidal cycles, which strongly influence the availability of food (Neill 1958). Although Carr and Goin (1942) indicated that all of their specimens were collected “just as the tide was beginning to overflow the flats,” Kochman (1992) indicated that it was observed most often “during low tidal stages, when it apparently feeds on small fishes that become trapped in the shallow water.” It feeds primarily on small fish, but it readily takes frogs when available.
This species is ovoviviparous. Captive individuals have given birth to 3 to 9 young from August to October (Kochman 1992). Fecundity is low relative to the adjacent freshwater species, N. fasciata, which may give birth to 50 or more young.
Most snakes adapted to life in salt water (families Hydrophiidae, Achrocordidae, and Homalopsidae) possess salt glands, through which they excrete excess salts (Dunson 1975). The salt marsh snakes apparently lack salt glands (Schmidt-Nielsen and Fange 1958), but they nonetheless exhibit very low dehydration rates in seawater (Pettus 1963, Dunson 1978, 1980). Salt marsh snakes are apparently able to survive in seawater through their reduced rates of cutaneous water and salt exchange and their refusal to drink seawater even when they become dehydrated. By contrast, when held in seawater, their freshwater congeners quickly become dehydrated, which prompts them to drink. This merely exacerbates their dehydration and leads to death (Pettus 1963). Salt marsh snakes readily drink fresh water when it becomes available from rain or dew (Kochman 1992).
==Threats==
The Atlantic salt marsh snake was listed on the basis of two primary concerns, intensive drainage and development in coastal salt marshes resulting in loss of habitat and the accompanying disruption of reproductive isolating mechanisms, leading to hybridization with the Florida banded water snake and potential swamping ofthe Atlantic salt marsh snake gene pool by the much larger Florida banded water snake gene pool.
At the time of its listing, the Atlantic salt marsh snake was thought to include salt marsh snakes as far south as Indian River County (U.S. Fish Wildlife Service 1977). As suggested above, it may actually be much more restricted, occurring only in the brackish, coastal marshes of Volusia County. If so, then given its highly restricted distribution, the Atlantic salt marsh snake’s vulnerability to habitat destruction and modification is even greater than previously realized.
It is well known that salt marsh snakes occasionally hybridize with the closely related freshwater species, Nerodia fasciata, especially in areas of habitat disturbance (Kochman 1977, Dunson 1979, Lawson et al. 1991). Lawson ~ ~j. (1991) demonstrated that, despite the reproductive compatibility of the two forms, there appears to be little or no genetic introgression between them in areas of undisturbed habitat. The extent of genetic introgression associated with the local breakdown of reproductive isolation between the two species has not yet been examined.
Rising sea levels are not an immediate threat but in the long termmay reduce the amount of habitat available to the Atlantic salt marsh snake. As sea levels rise, salinity in the estuaries will also rise correspondingly and possibly change the vegetation ofthe marsh, eventually flooding the area and making it inhospitable for the snake.
==Conservation Measures==
Conservation measures have consisted of limited survey work, genetic comparison with other salt marsh snakes and southern banded water snakes, use ofthe provisions under Section 7 of the Act, Section 404 of the Clean Water Act (CWA), and the Fish and Wildlife Coordination Act (FWCA), and proposals for creation of habitat to mitigate for areas impacted by permitted dredge-and-fill activities.
Sporadic surveys conducted from 1978 to 1988 by personnel of the FGFWFC and the Service confirmed the continued presence of the Atlantic salt marsh snake at several localities in Volusia County, Florida. Personnel of the East Volusia County Mosquito Control District are currently conducting surveys for Atlantic salt marsh snakes associated with mosquito control impoundments on islands in the northern portions of the Indian River Lagoon (G. Goode pers. comm.). A survey was conducted on Merritt Island National Wildlife Refuge in the late 1970’s, and a large population of salt marsh snakes was identified in the vicinity of the Volusia-Brevard county line, but this population seemed to show signs of intergradation with the mangrove water snake (Hebrard and Lee 1981).
Localities in the vicinity of New Smyrna Beach were sampled by FGFWFC for genetic studies (Lawson et M. 1991). Electrophoretic analyses indicated that the salt marsh snakes are closely related to but specifically distinct from the southern banded water snake (Nerodia fasciata), and that the three subspecies of the salt marsh snake are electrophoretically indistinguishable from each other (Lawson et al. 1991). Tissues were saved for possible comparison of mitochondrial DNA variation in the salt marsh snakes, but that work has not yet been performed.
The Atlantic salt marsh snake is protected as a threatened species under the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 ~4seq.). The Act places an affirmative mandate on Federal agencies to carry out programs for the conservation of federally listed endangered and threatened species. Further, the Act requires all Federal agencies to ensure that their actions are not likely to jeopardize the continued existence of any federally listed endangered or threatened species. Federal agency actions that can directly or indirectly affect endangered or threatened species include any activity that is authorized, funded, or carried out by such agency. Compliance with theses standards is ensured under Section 7 of the Act because agencies must consult with the Service or National Marine Fisheries Service on actions that may affect listed species or critical habitat.


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In addition to Section 7 consultations, protection and conservation of salt marsh habitat is provided by CWA and FWCA. The Service and U.S. Army Corps of Engineers review proposed dredge-and-fill activities and construction projects in waters of the United States where projects may affect the Atlantic salt marsh snake or its habitat. During a 10-year period (1983-1992) a minimum of 36 various projects were permitted in Volusia County’s salt marsh habitat. These projects included dredge-and-fill, shoreline protection projects, construction of piers and marinas, mosquito ditching, and water control structures. However, only 32 acres of salt marsh were destroyed by these projects, most (29.44 acres, 18 projects) before 1988. Loss of salt marsh habitat appears to have slowed since 1988 (2.56 acres, 18 projects) indicating improved protection. If the Atlantic salt marsh snake is limited to Volusia County, any project destroying salt marsh habitat may be detrimental to the species.
<p class="mw-empty-elt"></p><p><i><b>Agkistrodon piscivorus</b></i> is a species of pit viper in the subfamily Crotalinae of the family Viperidae. It is one of the world's few semiaquatic vipers (along with the Florida cottonmouth), and is native to the southeastern United States. As an adult, it is large and capable of delivering a painful and potentially fatal bite. When threatened, it may respond by coiling its body and displaying its fangs. Individuals may bite when feeling threatened or being handled in any way. It tends to be found in or near water, particularly in slow-moving and shallow lakes, streams, and marshes. It is a capable swimmer and, like several species of snakes, is known to occasionally enter bays and estuaries and swim between barrier islands and the mainland.<sup class="reference nowrap"><span title="Page / location: 211 p.">: 211 p. </span></sup></p><p>The generic name is derived from the Greek words <span title="Ancient Greek (to 1453)-language text"><span lang="grc">ἄγκιστρον</span></span> <i>ankistron</i> "fish-hook, hook" and <span title="Ancient Greek (to 1453)-language text"><span lang="grc">ὀδών</span></span> <i>odon</i>  "tooth", and the specific name comes from the Latin  <i>piscis</i> "fish" and <i>voro</i> "(I) eat greedily, devour"; thus, the scientific name translates to "hook-toothed fish-eater". Common names include variants on <b>cottonmouth</b>, <b>water moccasin</b>, <b>swamp moccasin</b>, <b>black moccasin</b>, and simply <b>viper</b>. Many of the common names refer to the threat display, in which this species will often stand its ground and gape at an intruder, exposing the white lining of its mouth. Many scientists dislike the use of the term water moccasin since it can lead to confusion between the venomous cottonmouth and non-venomous water snakes.</p><h2><span id="Description">Description</span></h2><p><i>Agkistrodon piscivorus</i> is the largest species of the genus <i>Agkistrodon</i>. Adults commonly exceed 80 cm (31 in) in total length (including tail); females are typically smaller than males. Total length, per one study of adults, was 65 to 90 cm (26 to 35 in). Average body mass has been found to be 292.5 to 579.6 g (10.32 to 20.44 oz) in males and 201.1 to 254.1 g (7.09 to 8.96 oz) in females. Occasionally, individuals may exceed 180 cm (71 in) in total length, especially in the eastern part of the range.</p><p>Although larger ones have purportedly been seen in the wild, according to Gloyd and Conant (1990), the largest recorded specimen of <i>A. p. piscivorus</i> was 188 cm (74 in) in total length, based on a specimen caught in the Dismal Swamp region and given to the Philadelphia Zoological Garden. This snake had apparently been injured during capture, died several days later, and was measured when straight and relaxed. Large specimens can be extremely bulky, with the mass of a specimen of about 180 cm (71 in) in total length known to weigh 4.6 kg (10 lb).</p><p>The broad head is distinct from the neck, and the snout is blunt in profile with the rim of the top of the head extending forwards slightly further than the mouth. Substantial cranial plates are present, although the parietal plates are often fragmented, especially towards the rear. A loreal scale is absent. Six to 9 supralabials and eight to 12 infralabials are seen. At midbody, there are 23–27 rows of dorsal scales. All dorsal scale rows have keels, although those on the lowermost scale rows are weak. In males/females, the ventral scales number 130-145/128-144 and the subcaudals 38-54/36-50. Many of the latter may be divided.</p><p>Though the majority of specimens are almost or even totally black, (with the exception of the head and facial markings), the color pattern may consist of a brown, gray, tan, yellowish-olive, or blackish ground color, which is overlaid with a series of 10–17 dark brown to almost black crossbands. These crossbands, which usually have black edges, are sometimes broken along the dorsal midline to form a series of staggered halfbands on either side of the body. These crossbands are visibly lighter in the center, almost matching the ground color, often contain irregular dark markings, and extend well down onto the ventral scales. The dorsal banding pattern fades with age, so older individuals are an almost uniform olive-brown, grayish-brown, or black. The belly is white, yellowish-white, or tan, marked with dark spots, and becomes darker posteriorly. The amount of dark pigment on the belly varies from virtually none to almost completely black. The head is a more or less uniform brown color, especially in <i>A. p. piscivorus</i>. Subadult specimens may exhibit the same kind of dark, parietal spots characteristic of <i>A. contortrix</i>, but sometimes these are still visible in adults. Eastern populations have a broad, dark, postocular stripe, bordered with pale pigment above and below, that is faint or absent in western populations. The underside of the head is generally whitish, cream, or tan.</p><p>Juvenile and subadult specimens generally have a more contrasting color pattern, with dark crossbands on a lighter ground color. The ground color is then tan, brown, or reddish brown. The tip of the tail is usually yellowish, becoming greenish yellow or greenish in subadults, and then black in adults. On some juveniles, the banding pattern can also be seen on the tail.  Young snakes wiggle the tips of their tails to lure prey animals.</p><p>This species is often confused with the copperhead, <i>A. contortrix</i>. This is especially true for juveniles, but differences exist. <i>A. piscivorus</i> has broad, dark stripes on the sides of its head that extend back from the eye, whereas <i>A. contortrix</i> has only a thin, dark line that divides the pale supralabials from the somewhat darker color of the head. The watersnakes of the genus <i>Nerodia</i> are also similar in appearance, being thick-bodied with large heads, but they have round pupils, no loreal pit, a single anal plate, subcaudal scales that are divided throughout, and a distinctive overall color pattern.</p><h2><span id="Common_names">Common names</span></h2><p>This is a list of common names for <i>Agkistrodon piscivorus</i>, some of which also refer to other species:</p><h2><span id="Geographic_range">Geographic range</span></h2><p><i>A. piscivorus</i> is found in the eastern US from the Great Dismal Swamp in southeast Virginia, south through the Florida peninsula and west to Arkansas, eastern and southern Oklahoma, and western and southern Georgia (excluding Lake Lanier and Lake Allatoona). A few records exist of the species being found along the Rio Grande in Texas, but these are thought to represent disjunct populations, now possibly eradicated. The type locality given is "Carolina", although Schmidt (1953) proposed this be restricted to the area around Charleston, South Carolina.</p><p>Campbell and Lamar (2004) mentioned this species as being found in Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Mississippi, Missouri,  North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. Maps provided by Campbell and Lamar (2004) and Wright and Wright (1957) also indicate its presence in Western and Middle Tennessee and extreme southeastern Kansas, and limit it to the western part of Kentucky.</p><p>In Georgia, it is found in the southern half of the state up to a few kilometers north of the Fall Line with few exceptions. Its range also includes the Ohio River Valley as far north as southern Indiana, and it inhabits many barrier islands off the coasts of the states where it is found.</p><h2><span id="Conservation_status">Conservation status</span></h2><p>The species <i>A. piscivorus</i> is classified as least concern on the IUCN Red List (v3.1, 2007). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. When last assessed in 2007, the population trend was stable.</p><p>Constant persecution of the species and drainage of wetland habitat prior to development has taken a heavy toll on local populations. Despite this, it remains a common species in many areas.</p><p>In Indiana, the cottonmouth is listed as an endangered species.</p><h2><span id="Habitat">Habitat</span></h2> <p><i>Agkistrodon piscivorus</i> is the most aquatic species of the genus <i>Agkistrodon</i>, and is usually associated with bodies of water, such as creeks, streams, marshes, swamps, and the shores of ponds and lakes. The U.S. Navy (1991) describes it as inhabiting swamps, shallow lakes, and sluggish streams, but it is usually not found in swift, deep, cool water. Behler and King (1979) list its habitats as including lowland swamps, lakes, rivers, bayheads, sloughs, irrigation ditches, canals, rice fields, and small, clear, rocky, mountain streams.</p><p>It is also found in brackish-water habitats and is sometimes seen swimming in salt water. It has been much more successful at colonizing Atlantic and Gulf coast barrier islands than the copperhead. However, even on these islands, it tends to favor freshwater marshes. A study by Dunson and Freda (1985) describes it as not being particularly salt-tolerant.</p><p>The snake is not limited to aquatic habitats, however, as Gloyd and Conant (1990) mentioned large specimens have been found more than a mile (1.6 km) from water. In various locations, the species is well-adapted to less moist environments, such as palmetto thickets, pine-palmetto forest, pine woods in East Texas, pine flatwoods in Florida, eastern deciduous dune forest, dune and beach areas, riparian forest, and prairies.</p><h2><span id="Behavior">Behavior</span></h2><p>In tests designed to measure the various behavioral responses by wild specimens to encounters with people, 23 of 45 (51%) tried to escape, while 28 of 36 (78%) resorted to threat displays and other defensive tactics. Only when they were picked up with a mechanical hand were they likely to bite.</p><p>When sufficiently stressed or threatened, this species engages in a characteristic threat display that includes vibrating its tail and throwing its head back with its mouth open to display the startlingly white interior, often making a loud hiss while the neck and front part of the body are pulled into an S-shaped position. Many of its common names, including "cottonmouth" and "gaper", refer to this behavior, while its habit of snapping its jaws shut when anything touches its mouth has earned it the name "trap jaw" in some areas. Other defensive responses can include flattening the body and emitting a strong, pungent secretion from the anal glands located at the base of the tail. This musk may be ejected in thin jets if the snake is sufficiently agitated or restrained. The smell has been likened to that of a billy goat, as well as to a genus of common flood-plain weeds, <i>Pluchea</i>, that also have a penetrating odor.</p><p>Harmless watersnakes of the genus <i>Nerodia</i> are often mistaken for it. These are also semiaquatic, thick-bodied snakes with large heads that can be aggressive when provoked, but they behave differently. For example, watersnakes usually flee quickly into the water, while <i>A. piscivorus</i> often stands its ground with its threat display. In addition, watersnakes do not vibrate their tails when excited. <i>A. piscivorus</i> usually holds its head at an angle around 45° when swimming or crawling.</p><p>Brown (1973) considered their heavy muscular bodies to be a striking characteristic, stating this made it difficult to hold them for venom extraction owing to their strength.</p><p>This species may be active during the day and at night. However, on bright, sunny days, they are usually found coiled or stretched out somewhere in the shade. In the morning and on cool days, they can often be seen basking in the sunlight. They often emerge at sunset to warm themselves on warm ground (i.e., sidewalks, roads) and then become very active throughout the night, when they are usually found swimming or crawling. Contrary to popular belief, they are capable of biting while under water.</p><p>In the north, they hibernate during the winter. Niell (1947, 1948) made observations in Georgia, and noted they were one of the last species to seek shelter, often being found active until the first heavy frosts. At this point, they moved to higher ground and could be found in rotting pine stumps by tearing away the bark. These snakes could be quite active upon discovery and would then attempt to burrow more deeply into the soft wood or escape to the nearest water. In southeastern Virginia, Wood (1954) reported seeing migratory behavior in late October and early November. During a period of three or four days, as many as 50 individuals could be seen swimming across Back Bay from the bayside swamps of the barrier islands to the mainland. He suggested this might have something to do with hibernating habits. In the southern parts of its range, hibernation may be short or omitted altogether.</p><h2><span id="Feeding">Feeding</span></h2><p>Raymond Ditmars (1912) described <i>A. piscivorus</i> as carnivorous. Its diet includes mammals, birds, amphibians, fish, snakes, small turtles, and small alligators. Cannibalism has also been reported. Normally, though, the bulk of its diet consists of fish and frogs. On occasion, juvenile specimens feed on invertebrates. Catfish are often eaten, although the sharp spines sometimes cause injuries. Toads of the genus <i>Bufo</i> are apparently avoided.</p><p>Many authors have described the prey items taken under natural circumstances. Although fish and frogs are their most common prey, they eat almost any small vertebrate. Fish are captured by cornering them in shallow water, usually against the bank or under logs. They take advantage when bodies of water begin to dry up in the summer or early fall and gorge themselves on the resulting high concentrations of fish and tadpoles. They are surprisingly unsuccessful at seizing either live or dead fish under water.</p><p>They are opportunistic feeders and sometimes eat carrion, making them one of the few snakes to do so. Campbell and Lamar (2004) described having seen them feeding on fish heads and viscera that had been thrown into the water from a dock. Heinrich and Studenroth (1996) reported an occasion in which an individual was seen feeding on the butchered remains of a feral hog (<i>Sus scrofa</i>) that had been thrown into Cypress Creek. Northern Cottonmouths have an unusual feeding adaptation that allows them to adhere to prey through rotation of their head during swallowing because it aids the jaws in clearing the prey and contributes to the advance of the jaws along the prey. </p><p>Conant (1929) gave a detailed account of the feeding behavior of a captive specimen from South Carolina. When prey was introduced, the snake quickly became attentive and made an attack. Frogs and small birds were seized and held until movement stopped. Larger prey was approached in a more cautious manner; a rapid strike was executed after which the snake would withdraw. In 2.5 years, the snake had accepted three species of frogs, including a large bullfrog, a spotted salamander, water snakes, garter snakes, sparrows, young rats, and three species of mice. Brimley (1944) described a captive specimen that ate copperheads (<i>A. contortrix</i>), as well as members of its own species, keeping its fangs embedded in its victims until they had been immobilized. Another study done in 2018 found that northern cottonmouths on a diet of only fish when compared to a diet of mice had to eat 20% more to achieve the same growth.</p><p>Young individuals have yellowish or greenish tail tips and engage in caudal luring. The tail tip is wriggled to lure prey, such as frogs and lizards, within striking distance. Wharton (1960) observed captive specimens exhibiting this behavior between 07:20 and 19:40 hours, which suggests it is a daytime activity.</p><h2><span id="Predators">Predators</span></h2><p><i>Agkistrodon piscivorus</i> is preyed upon by snapping turtles (<i>Chelydra serpentina</i>), falcons, American alligators (<i>Alligator mississippiensis</i>), horned owls (<i>Bubo virginianus</i>), eagles, red-shouldered hawks (<i>Buteo lineatus</i>), loggerhead shrikes (<i>Lanius ludovicianus</i>), and large wading birds, such as herons, cranes, and egrets.</p><p>It is also preyed upon by ophiophagous snakes, including their own species. Humphreys (1881) described how a 34-inch (86 cm) specimen was killed and eaten by a 42-inch (1.1 m) captive kingsnake. On the other hand, Neill (1947) reported captive kingsnakes (<i>Lampropeltis getula</i>) were loath to attack them, being successfully repelled with "body blows". Also called body-bridging, this is a specific defensive behavior against ophiophagous snakes, first observed in certain rattlesnake (<i>Crotalus</i>) species by Klauber (1927), that involves raising a section of the middle of the body above the ground to varying heights. This raised loop may then be held in this position for varying amounts of time, shifted in position, or moved towards the attacker. In the latter case, it is often flipped or thrown vigorously in the direction of the assailant. In <i>A. piscivorus</i>, the loop is raised laterally, with the belly facing towards the attacker.</p><h2><span id="Reproduction">Reproduction</span></h2><p><i>Agkistrodon piscivorus</i> is ovoviviparous, with females usually giving birth to one to 16 live young and possibly as many as 20. Litters of six to eight are the most common. Neonates are 22–35 cm in length (excluding runts), with the largest belonging to <i>A. p. conanti</i> and <i>A. p. leucostoma</i> the smallest. If weather conditions are favorable and food is readily available, growth is rapid and females may reproduce at less than three years of age and a total length of as little as 60 cm. The young are born in August or September, while mating may occur during any of the warmer months of the year, at least in certain parts of its range.</p><p>Regarding <i>A. p. piscivorus</i>, an early account by Stejneger (1895) described a pair in the Berlin Zoological Garden that mated on January 21, 1873, after which eight neonates were discovered in the cage on July 16 of that year. The young were each 26 cm in length and 1.5 cm thick. They shed for the first time within two weeks, after which they accepted small frogs, but not fish.</p><p>Combat behavior between males has been reported on a number of occasions, and is very similar in form to that seen in many other viperid species. An important factor in sexual selection, it allows for the establishment and recognition of dominance as males compete for access to sexually active females.</p><p>A few accounts exist that describe females defending their newborn litters. Wharten (1960, 1966) reported several cases where females found near their young stood their ground and considered these to be examples of guarding behavior. Another case was described by Walters and Card (1996) in which a female was found at the entrance of a chamber with seven neonates crawling on or around her. When one of the young was moved a short distance from the chamber, she seemed to be agitated and faced the intruder. Eventually, all of her offspring retreated into the chamber, but the female remained at the entrance, ready to strike.</p><h3><span id="Facultative_parthenogenesis">Facultative parthenogenesis</span></h3><p>Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilization. <i>A. piscivorus</i> can reproduce by facultative parthenogenesis, that is, they are capable of switching from a sexual mode of reproduction to an asexual mode.  This likely involves recombination at the tips of the chromosomes, which leads to genome wide homozygosity. The result is the expression of deleterious recessive alleles and often to developmental failure (inbreeding depression).  Both captive-born and wild-born <i>A. piscivorus</i> specimens appear to be capable of this form of parthenogenesis.</p><h2><span id="Venom">Venom</span></h2><p><i>Agkistrodon piscivorus</i> venom is more toxic than that of <i>A. contortrix</i>, and is rich with powerful cytotoxic venom that destroys tissue. Although deaths are rare, the bite can leave scars, and on occasion, require amputation. Absent an anaphylactic reaction in a bitten individual, however, the venom does not cause systemic reactions in victims and does not contain neurotoxic components present in numerous rattlesnake species. Bites can be effectively treated with CroFab antivenom; this serum is derived using venom components from four species of American pit vipers (the eastern and western diamondback rattlesnakes, the Mojave rattlesnake, and the cottonmouth).</p><p>Bites from the cottonmouth are relatively frequent in the lower Mississippi River Valley and along the coast of the Gulf of Mexico, although fatalities are rare. Allen and Swindell (1948) compiled a record of <i>A. piscivorus</i> bites in Florida from newspaper accounts and data from the Bureau of Vital Statistics: 1934, eight bites and three fatalities (no further fatalities were recorded after this year); 1935, 10; 1936, 16; 1937, 7; 1938, 6; 1939, 5; 1940, 3; 1941, 6; 1942, 3; 1943, 1; 1944, 3; 1998, 1. Wright and Wright (1957) report having encountered these snakes on countless occasions, often almost stepping on them, but never being bitten. In addition, they heard of no reports of any bites among 400 cypress cutters in the Okefenokee Swamp during the entire summer of 1921. These accounts suggest that the species is not particularly aggressive.</p><p>Brown (1973) gave an average venom yield (dried) of 125 mg, with a range of 80–237 mg, along with LD<sub style="font-size:-1">50</sub> values of 4.0, 2.2, 2.7, 3.5, 2.0 mg/kg IV, 4.8, 5.1, 4.0, 5.5, 3.8, 6.8 mg/kg IP and 25.8 mg/kg SC for toxicity. Wolff and Githens (1939) described a 152 cm (60 in) specimen that yielded 3.5 ml of venom during the first extraction and 4.0 ml five weeks later (1.094 grams of dried venom). The human lethal dose is unknown, but has been estimated at 100–150 mg.</p><p>Symptoms commonly include ecchymosis and swelling. The pain is generally more severe than bites from the copperhead, but less so than those from rattlesnakes (<i>Crotalus</i> spp.). The formation of vesicles and bullae is less common than with rattlesnake bites, although necrosis can occur. Myokymia is sometimes reported. However, the venom has strong proteolytic activity that can lead to severe tissue destruction.</p><h2><span id="Subspecies_and_taxonomic_changes">Subspecies and taxonomic changes</span></h2><p>For many decades, one species with three subspecies were formally recognized: eastern cottonmouth, <i>A. p. piscivorus</i> (Lacépède, 1789); western cottonmouth, <i>A. p. leucostoma</i> (Troost, 1836); and Florida cottonmouth, <i>A. p. conanti</i> Gloyd, 1969. However, a molecular (DNA) based study was published in 2014, applying phylogenetic theories (one implication being no subspecies are recognized), changing the long-standing taxonomy. The resulting and current taxonomic arrangement recognizes two species and no subspecies. The western cottonmouth (<i>A. p. leucostoma</i>) was synonymized with the eastern cottonmouth (<i>A. p. piscivorus</i>) into one species (with the oldest published name, <i>A. p. piscivorus</i>, having priority). The Florida cottonmouth (<i>A. p. conanti</i>) is now recognized as a separate species.</p><ul><li><i><b>Agkistrodon piscivorus</b></i> (Lacépéde, 1789), northern cottonmouth</li><li><i><b>Agkistrodon conanti</b></i> Gloyd, 1969, Florida cottonmouth (south Georgia and Florida peninsular)</li></ul><h2><span id="References">References</span></h2><h2><span id="Further_reading">Further reading</span></h2><h2><span id="External_links">External links</span></h2><ul><li><i>Agkistrodon piscivorus</i> at the Reptarium.cz Reptile Database. Accessed 7 December 2007.</li><li><i>Agkistrodon piscivorus</i> in the CalPhotos photo database, University of California, Berkeley</li><li>Cottonmouth Fact Sheet Archived 2005-10-26 at the Wayback Machine at Smithsonian National Zoological Park. Accessed 7 December 2007.</li><li>Cottonmouth snake – bites, identification, diet and habitat. Archived 2011-12-28 at the Wayback Machine</li><li>Water Moccasin Snake * information on identification, range and natural history. Archived 2012-03-05 at the Wayback Machine</li><li><span>Video of <i>Agkistrodon piscivorus</i></span> on YouTube. Accessed 3 July 2008.</li></ul>
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==Video==
<p>University of Central Florida - So where are all the Atlantic salt marsh snakes? We know that changes in our environment affect our ecosystem, and now biologists are wondering if manmade changes to the snake habitat in Volusia County are making them all but disappear in this segment of WUCF TV's "ONE."
<youtube>https://youtube.com/watch?v=NbDd9dJm0Yg</youtube>
==Documents==
==Documents==
* [https://www.fws.gov/verobeach/msrppdfs/easternindigosnake.pdf FWS - Eastern Indigo Snake ''Drymarchon corais couperi'' (PDF 16pp)]
* [https://www.govinfo.gov/content/pkg/FR-1977-11-29/pdf/FR-1977-11-29.pdf#page=35 Federal Register - USFWS Determination for Atlantic Salt Marsh Snakes 1977 (PDF 168pp 43MB)]. Retrieved May 23, 2022.
* [https://ecos.fws.gov/docs/recovery_plan/931215.pdf USFWS Atlantic Salt Marsh Snake Recovery Plan 1993 (PDF 24pp 1.6MB)]. Retrieved May 23, 2022
* [https://www.fnai.org/PDFs/FieldGuides/Nerodia_clarkii_taeniata.pdf FNAI - Atlantic salt marsh snake (''Nerodia clarkii taeniata'') (PDF 2pp)]
* [https://ecos.fws.gov/docs/tess/species_nonpublish/2908.pdf ECOS - Atlantic salt marsh snake - Nerodia clarkii taeniata - 2019 Review  (PDF 19pp)]. Retrieved May 23, 2022.


==Web Links==
==Web Links==
* [https://myfwc.com/wildlifehabitats/profiles/reptiles/snakes/eastern-indigo-snake/ FWC Species Profile - Eastern indigo snake]  
* [https://www.fws.gov/species/atlantic-salt-marsh-snake-nerodia-clarkii-taeniata USFWS Atlantic salt marsh snake (''Nerodia clarkii taeniata'')]
* [https://ecos.fws.gov/ecp/species/7729 ECOS Atlantic salt marsh snake]
* [https://myfwc.com/wildlifehabitats/profiles/reptiles/snakes/atlantic-salt-marsh-snake/ FWC Atlantic salt marsh snake Nerodia clarkii taeniata profile]
* [https://eol.org/pages/1243758 EOL Atlantic salt marsh snake (''Nerodia clarkii clarkii'')]
* [https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=209380#null ITIS Nerodia clarkii taeniata]


==References==
==References==
<references/>
<references>
<ref name="USFWSdetermination1977">[https://www.govinfo.gov/content/pkg/FR-1977-11-29/pdf/FR-1977-11-29.pdf#page=35 Federal Register - USFWS - Determination for Atlantic Salt Marsh Snakes 1977 (PDF 168pp 43MB)]. Article source. Published 1977-11-29. Retrieved 2022-05-23.</ref>
<ref name="USFWSrecovery1993">[https://ecos.fws.gov/docs/recovery_plan/931215.pdf USFWS Atlantic Salt Marsh Snake Recovery Plan 1993 (PDF 24pp 1.6MB)]. Published 1993-12-15. Retrieved 2022-05-23.</ref>
</references>
 
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Latest revision as of 09:03, May 30, 2022

Indian River Lagoon Encyclopedia
Indian River Lagoon Encyclopedia - Land Animals
Land Animals
Atlantic salt marsh snake (Nerodia clarkii taeniata)
Atlantic salt marsh snake
Nerodia clarkii taeniata
Status: Threatened

Nerodia clarkii taeniata, commonly known as the Atlantic salt marsh snake, is found only in the coastal salt marshes of Brevard and Volusia, Florida. The Atlantic salt marsh snake was listed as a threatened species on November 29, 1977 by the U.S. Fish and Wildlife Service.[1]

Description

There are three subspecies of salt marsh snakes in Florida, the Gulf salt marsh snake (Nerodia clarkii clarkii), mangrove water snake (N. c. compressicauda), and Atlantic salt marsh snake (N. c. taeniata).[2]

Gulf salt marsh snake (Nerodia clarkii clarkii)
Gulf salt marsh snake
Nerodia clarkii clarkii

Salt marsh snakes dorsal pattern's are formed from a basic pattern of four rows of dark blotches running from head to tail (two lateral and two dorsolateral rows) on a lighter background. In the striped forms, the blotches join to form stripes; in the banded forms, the blotches join across the back to form bands. In partially striped individuals, it is usually the anterior portion of the body that is striped, with the pattern posteriorly consisting of bands or rows of unfused blotches.

The Gulf salt marsh snake (Nerodia clarkii clarkii) has a dorsal pattern that is completely striped, or nearly so, with dark brown to black stripes on a tan background. It is not unusual for the lateral stripes in this form to break down posteriorly into rows of blotches.

Mangrove salt marsh snake (Nerodia clarkii compressicauda)
Mangrove salt marsh snake
Nerodia clarkii compressicauda

The mangrove water snake (N. clarkii compressicauda) may be uniformly orange in color, but it more often has a pattern of dark bands on a lighter background. Individuals from throughout the range of the mangrove water snake may be partially striped; in these specimens the striping is typically limited to the neck region, but occasional specimens may be more extensively striped. Coloration in the mangrove water snake is extremely variable, with the background being gray, straw, or reddish and the bands being black, brown, or red. Populations of mangrove water snakes characteristically include at least some individuals that exhibit reddish or orange pigmentation.

Atlantic salt marsh snake (Nerodia clarkii taeniata)
Atlantic salt marsh snake
Nerodia clarkii taeniata

The Atlantic salt marsh snake (N. c. taeniata) is a partially striped salt marsh snake that reaches a maximum length of 82 cm (32 in.), although it is typically less than 65 cm (26 in.) in length. The pattern consists of a gray to pale olive background with black to dark brown stripes anteriorly, the stripes breaking up into rows of spots posteriorly. The extent of the striping is variable, but most individuals from the coastal marshes of Volusia County are striped on at least the anterior 30 percent of the body. The venter is black with a central row of large cream to yellowish spots. As in the case of the dorsal striping, this ventral pattern is best developed anteriorly and tends to break down posteriorly. The red pigmentation characteristic of mangrove water snakes is conspicuously lacking in Atlantic salt marsh snakes from the vicinity of Edgewater, Volusia County, and northward.

Hebrard (1979) reported coloration for 23 specimens from the southern Indian River Lagoon, near the Volusia-Brevard county line. Of these, 7 (30 percent) exhibited orange or reddish pigmentation either dorsally or ventrally. It is unclear at this time (1993) whether the reddish pigmentation reported by Hebrard should be interpreted as indicating intergradation with the mangrove water snake. The series of 25 specimens for which Hebrard provided pattern descriptions had dorsal stripes on 0 to 100 percent of the body; only 8 (32 percent) had dorsal stripes on more than 30 percent of the body, but 3 (12 percent) reportedly had dorsal stripes on 100 percent of the body. (In terms of pattern formation, the vertebral stripe is actually the lighter background color which is visible between the two dark, dorsolateral stripes.)

Distribution

Atlantic salt marsh snake (Nerodia clarkii taeniata) map
Atlantic salt marsh snake distribution

The species to which the Atlantic salt marsh snake belongs, N. clarkii, is found in a narrow coastal strip from southern Texas, east along the Gulf coast, around the Florida peninsula, and up the east coast of Florida at least as far as Volusia County's Halifax River.

Both Cope’s (1895) type series and the specimens used by Carr and Goin (1942) to resurrect N. c. taeniata came from the brackish coastal marshes of Volusia County, Florida. There is some uncertainty about the precise locality from which Cope’s specimens came, but Carr and Goin restricted the type locality to the vicinity of National Gardens, which lies near the north end of the Halifax River. Salt marsh snakes have not been documented to the north in southern Flagler County. The Carr and Goin series was collected on the barrier island at New Smyrna Beach. Recent records for populations identifiable as Atlantic salt marsh snakes are available from (1) the barrier island a short distance north of Ponce Inlet, (2) the mainland shoreline east ofthe New Smyrna Beach airport, (3) two localities on the barrier island at New Smyrna Beach (Florida Game and Fresh Water Fish Commission (FGFWFC) records), (4) an island in the Indian River east of Edgewater (G. Goode, East Volusia Co. Mosquito Control, pers. comm.) and (5) a single specimen identified as N. c. taeniata was captured just south of the Flagler County line (G. Goode pers. comm.). It is not known if a viable population exists in this area or to the north in Flagler County but if so, these Atlantic salt marsh snakes are now isolated from populations in the northern Indian River Lagoon by the Ormond Beach-Daytona metropolitan area.

A problem attendant to the listing of any subspecies that is distributionally continuous and intergradient with another subspecies is the difficulty of defining the limit(s) of the listed form’s distribution in the area where it contacts the related, unlisted subspecies. To the south, the Atlantic salt marsh snake intergrades with the mangrove water snake along the central Atlantic coast of Florida. As noted above~ both the description and the resurrection of the subspecies were based on specimens from Volusia County, although Carr and Goin (1942) considered a single specimen from Indian River County also to be N. c. taeniata. They also mentioned a specimen of salt marsh snake from Melbourne, Brevard County, but did not indicate whether they considered that specimen to be N. c. taeniata. Wright and Wright (1957) considered N. c. taeniata to extend only as far south as the lower end of Mosquito Lagoon, in northern Brevard County, and Neill (1958) indicated that N. c. taeniata intergraded with the mangrove water snake on Merritt Island. In the final listing of the Atlantic salt marsh snake (FR 42:60743-60745), the Service indicated that “The Atlantic salt marsh snake is known only from coastal areas of Brevard, Volusia, and Indian River counties.” However, Hebrard and Lee (1981) examined a large series of salt marsh snakes from southern Mosquito Lagoon near the Volusia-Brevard county line and reported that they resembled Nerodia fasciata compressicauda quite closely.” Hebrard and Lee further noted that their specimens differed markedly in coloration and pattern from specimens of N. c. taeniata from further north in Volusia County. It is also worth noting that the snakes examined by Hebrard and Lee were collected in mangroves (species not indicated), whereas only about 10 miles farther north, where populations of typical Atlantic salt marsh snakes are found, the habitat consists primarily of glasswort (Salicornia spp.) flats and salt grass (Distichlis spicata)-bordered tidal creeks with only scattered black mangroves (Avicennnia germinans). The zone of intergradation appears to coincide with the increasing dominance of mangrove swamps, eventually as mangrove swamps become predominant so does N. c. compressicauda. Kochman (1992) concluded that “salt marsh snakes from farther south in Brevard and Indian River counties, although occasionally striped, appear to comprise a zone of intergradation with N. c. compressicauda.”

Until a survey and taxonomic assessment have been conducted, it will not be possible to determine the southern distributional limit of the Atlantic salt marsh snake. Nonetheless, it appears that the subspecies may be restricted to the brackish, coastal marshes of Volusia County, from the Halifax River south to the northern portions of the Indian River Lagoon.

Habitat

Atlantic salt marsh snakes are restricted to brackish, tidal marshes. They most often have been found in association with saltwort flats and salt grass-bordered tidal creeks. It is not known if they occur in the adjacent black needlerush (Juncus roemerianus) habitat. Atlantic salt marsh snake use of marsh habitats may be limited by water level; with extreme fluctuations making the marsh too hydric or xeric (G. Goode pers. comm.). When inactive or pursued, they frequently retreat into one of the numerous fiddler crab (Uca pugilator) burrows that riddle the edge of the marsh and the banks of the tidal creeks (Carr and Goin 1942, Kochman 1992, P. Moler pers. obs.).

Life History/Ecology

Although the Atlantic salt marsh snake is most easily observed at night, it may be active at any time of day. Its activity is influenced by tidal cycles, which strongly influence the availability of food (Neill 1958). Although Carr and Goin (1942) indicated that all of their specimens were collected “just as the tide was beginning to overflow the flats,” Kochman (1992) indicated that it was observed most often “during low tidal stages, when it apparently feeds on small fishes that become trapped in the shallow water.” It feeds primarily on small fish, but it readily takes frogs when available.

This species is ovoviviparous. Captive individuals have given birth to 3 to 9 young from August to October (Kochman 1992). Fecundity is low relative to the adjacent freshwater species, N. fasciata, which may give birth to 50 or more young.

Most snakes adapted to life in salt water (families Hydrophiidae, Achrocordidae, and Homalopsidae) possess salt glands, through which they excrete excess salts (Dunson 1975). The salt marsh snakes apparently lack salt glands (Schmidt-Nielsen and Fange 1958), but they nonetheless exhibit very low dehydration rates in seawater (Pettus 1963, Dunson 1978, 1980). Salt marsh snakes are apparently able to survive in seawater through their reduced rates of cutaneous water and salt exchange and their refusal to drink seawater even when they become dehydrated. By contrast, when held in seawater, their freshwater congeners quickly become dehydrated, which prompts them to drink. This merely exacerbates their dehydration and leads to death (Pettus 1963). Salt marsh snakes readily drink fresh water when it becomes available from rain or dew (Kochman 1992).

Threats

The Atlantic salt marsh snake was listed on the basis of two primary concerns, intensive drainage and development in coastal salt marshes resulting in loss of habitat and the accompanying disruption of reproductive isolating mechanisms, leading to hybridization with the Florida banded water snake and potential swamping ofthe Atlantic salt marsh snake gene pool by the much larger Florida banded water snake gene pool.

At the time of its listing, the Atlantic salt marsh snake was thought to include salt marsh snakes as far south as Indian River County (U.S. Fish Wildlife Service 1977). As suggested above, it may actually be much more restricted, occurring only in the brackish, coastal marshes of Volusia County. If so, then given its highly restricted distribution, the Atlantic salt marsh snake’s vulnerability to habitat destruction and modification is even greater than previously realized.

It is well known that salt marsh snakes occasionally hybridize with the closely related freshwater species, Nerodia fasciata, especially in areas of habitat disturbance (Kochman 1977, Dunson 1979, Lawson et al. 1991). Lawson ~ ~j. (1991) demonstrated that, despite the reproductive compatibility of the two forms, there appears to be little or no genetic introgression between them in areas of undisturbed habitat. The extent of genetic introgression associated with the local breakdown of reproductive isolation between the two species has not yet been examined.

Rising sea levels are not an immediate threat but in the long termmay reduce the amount of habitat available to the Atlantic salt marsh snake. As sea levels rise, salinity in the estuaries will also rise correspondingly and possibly change the vegetation ofthe marsh, eventually flooding the area and making it inhospitable for the snake.

Conservation Measures

Conservation measures have consisted of limited survey work, genetic comparison with other salt marsh snakes and southern banded water snakes, use ofthe provisions under Section 7 of the Act, Section 404 of the Clean Water Act (CWA), and the Fish and Wildlife Coordination Act (FWCA), and proposals for creation of habitat to mitigate for areas impacted by permitted dredge-and-fill activities.

Sporadic surveys conducted from 1978 to 1988 by personnel of the FGFWFC and the Service confirmed the continued presence of the Atlantic salt marsh snake at several localities in Volusia County, Florida. Personnel of the East Volusia County Mosquito Control District are currently conducting surveys for Atlantic salt marsh snakes associated with mosquito control impoundments on islands in the northern portions of the Indian River Lagoon (G. Goode pers. comm.). A survey was conducted on Merritt Island National Wildlife Refuge in the late 1970’s, and a large population of salt marsh snakes was identified in the vicinity of the Volusia-Brevard county line, but this population seemed to show signs of intergradation with the mangrove water snake (Hebrard and Lee 1981).

Localities in the vicinity of New Smyrna Beach were sampled by FGFWFC for genetic studies (Lawson et M. 1991). Electrophoretic analyses indicated that the salt marsh snakes are closely related to but specifically distinct from the southern banded water snake (Nerodia fasciata), and that the three subspecies of the salt marsh snake are electrophoretically indistinguishable from each other (Lawson et al. 1991). Tissues were saved for possible comparison of mitochondrial DNA variation in the salt marsh snakes, but that work has not yet been performed.

The Atlantic salt marsh snake is protected as a threatened species under the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 ~4seq.). The Act places an affirmative mandate on Federal agencies to carry out programs for the conservation of federally listed endangered and threatened species. Further, the Act requires all Federal agencies to ensure that their actions are not likely to jeopardize the continued existence of any federally listed endangered or threatened species. Federal agency actions that can directly or indirectly affect endangered or threatened species include any activity that is authorized, funded, or carried out by such agency. Compliance with theses standards is ensured under Section 7 of the Act because agencies must consult with the Service or National Marine Fisheries Service on actions that may affect listed species or critical habitat.

In addition to Section 7 consultations, protection and conservation of salt marsh habitat is provided by CWA and FWCA. The Service and U.S. Army Corps of Engineers review proposed dredge-and-fill activities and construction projects in waters of the United States where projects may affect the Atlantic salt marsh snake or its habitat. During a 10-year period (1983-1992) a minimum of 36 various projects were permitted in Volusia County’s salt marsh habitat. These projects included dredge-and-fill, shoreline protection projects, construction of piers and marinas, mosquito ditching, and water control structures. However, only 32 acres of salt marsh were destroyed by these projects, most (29.44 acres, 18 projects) before 1988. Loss of salt marsh habitat appears to have slowed since 1988 (2.56 acres, 18 projects) indicating improved protection. If the Atlantic salt marsh snake is limited to Volusia County, any project destroying salt marsh habitat may be detrimental to the species.

Video

University of Central Florida - So where are all the Atlantic salt marsh snakes? We know that changes in our environment affect our ecosystem, and now biologists are wondering if manmade changes to the snake habitat in Volusia County are making them all but disappear in this segment of WUCF TV's "ONE."

Documents

Web Links

References

  1. ↑ Federal Register - USFWS - Determination for Atlantic Salt Marsh Snakes 1977 (PDF 168pp 43MB). Article source. Published 1977-11-29. Retrieved 2022-05-23.
  2. ↑ USFWS Atlantic Salt Marsh Snake Recovery Plan 1993 (PDF 24pp 1.6MB). Published 1993-12-15. Retrieved 2022-05-23.
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