Malaclemys terrapin occurs along parts of the eastern coast of the United States from as far north as Cape Cod, Massachusetts, to the southernmost Florida Keys. The turtles are also abundant in the Gulf Coast, from Florida to Texas. (Loutrell and Cornett 1993).

Biogeographic Regions: nearctic (Native ); atlantic ocean (Native )

Gulf of Mexico

endemic to a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Atlantic and Gulf coasts from Cape Cod to Texas. Subspecies CENTRATA: Restricted to brackish coastal waters (Morreale 1992) along the Atlantic Coast from Cape Hatteras, North Carolina, south to northern Florida (Ernst et al. 1994); occurs in Florida from the southern edge of Flagler County north to the state line (Ashton and Ashton 1988). Subspecies LITTORALIS: brackish coastal waters (Morreale 1992) along the Gulf Coast from western Louisiana to western Texas (Ernst et al. 1994); localized populations are patchily distributed along the Texas coast (A. Price, pers. comm., 1997).

Continent: North-America
Distribution: USA (along the Atlantic amd Gulf coasts in Massachusetts, Connecticut, New Jersey, Delaware, Virginia, North Carolina, South Carolina, Georgia, Florida including the Keys, Alabama, Mississippi, Louisiana, Texas), Bermuda Island  centrata: USA (Georgia, Florida, North Carolina, South Carolina)  littoralis: Texas.
Type locality: “Rockport, Texas” [Aransas County, Texas].  macrospilota: Florida;
Type locality: “Charlotte Harbor, Florida” [Charlotte County, Florida].  pileata: USA (Alabama, Florida, Louisiana, Mississippi, Texas)  rhizophorarum: Florida keys  tequesta: Florida;
Type locality: “Miami Beach, Dade County, Florida”

A grayish to nearly black carapace usually has spots or streaks of black on gray skin, making Malaclemys terrapin one of the darkest turtle species. The species is also distinguished from the other species by a tuberculate, or a knobbed keel; a higher shell with deeper bridge; a deeper gular notch; a consistently white upper lip; and a uniformly colored carapace and plastron (Alderton 1988). The skull has a long, bony temporal arch. The hind legs are relatively large and the toes are webbed beyond the bases of the nails. This species is known to have the greatest sexually dimorphic size disparity found in any North American turtle. Males are usually smaller in both body and head size, while the females are large. Females often attain carapace length of 9 inches, while males usually reach a maximum of 5.5 inches. Malaclemys terrapin is the only diamondback terrapin to occur in Texas (Carr 1952).

Average mass: 720 g.

Average basal metabolic rate: 0.140702 W.

Length: 24 cm

Differs from the snapping turtle in having conspicuous black spots on the head and neck and in lacking a long tail with a saw-toothed middorsal margin. Differs from mud turtles in lacking a hinged plastron. Differs from the wood turtle in habitat and in lacking orange on the neck and limbs.

Paratype for Malaclemys terrapin littoralis
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1904
Locality: Rockport, Aransas, Texas, United States, North America

Paratype for Malaclemys terrapin littoralis
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1904
Locality: Rockport, Aransas, Texas, United States, North America

Holotype for Malaclemys terrapin littoralis
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Female;
Preparation: Ethanol
Year Collected: 1904
Locality: Rockport, Aransas, Texas, United States, North America

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Diamondback terrapins inhabit saltwater habitats, including brackish channels, lagoons, tidal flats, marshes, estuarine areas, and coastlines. They particularly favor reedy marshes, and while they live near saltwater, they require fresh water for drinking purposes (Garrett and Baike 1987).

Aquatic Biomes: coastal

Depth range based on 7 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 1.7 - 2.5

Graphical representation

Depth range (m): 1.7 - 2.5
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Coastal marshes, tidal flats, coves, estuaries, and lagoons behind barrier beaches; brackish and salt water (but basically retricted to estuarine situations; intolerant of long-term exposure to freshwater or 100% salt water). Burrows into mud when inactive (Ernst and Barbour 1972); in Virginia, has been observed hibernating in moist sand 8 m from the high tide mark. May venture into grassy lowlands at high tide (Ashton and Ashton 1985). Hatchlings move to the closest terrestrial vegetation after emergence from nest. Small individuals may use cover of tidal wrack and dense mats of vegetation (Lovich et al. 1991). In Maryland, adult females moved farther from shore and spent more time in deeper water than did males, and juveniles remained near shore in shallow water (Roosenburg et al. 1999).

Eggs are laid in a nest dug in sandy marsh edge, offshore island, or dune (vegetated or unvegetated), above high tide mark (e.g., see Feinberg and Burke 2003). Nests of different females may be dispersed or aggregated.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Malaclemys terrapin eat snails, other mollusks, crustaceans, fish, insects, and carrion (Bartlett and Bartlett 1999). They use the ridges in their jaw to crush their prey. Therefore, M. terrapin will only eat the soft-shelled mollusks and crustaceans (Tucker, et al 1997).

Comments: Eats mainly marine clams, snails, worms, crabs; scavenges and takes live food (Ernst and Barbour 1972). High tides permit aquatic foraging in upper salt marsh (Tucker et al. 1995).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Occurrences have not been defined using consistent criteria, so the number of occurrences is uncertain. However, there are many.

100,000 - 1,000,000 individuals

Comments: Total population size is unknown but surely exceeds 100,000. In New York, one island had 2,053 nests in one year (suggesting that about 1,000 females nested there, based on two clutches per female); this is one of the largest nesting populations observed anywhere in the range (Feinberg and Burke 2003).

Densities of 53/ha and 73/ha were recorded in two areas on the Atlantic coast of Florida; these estimates were judged to be possibly somewhat inflated (Seigel 1984). In New York, Morreale (1992) recorded conservative estimates of 344 terrapins in approximately 200 ha and 341 in 12 ha. Juveniles generally are very infrequently recorded in population surveys.

Barnacle infestations on shell may interfere with nesting or cause fatal injuries (Seigel 1983).

In South Carolina, annual survival rates of adult females in different creeks ranged from 0.748 to 0.971 (Tucker et al. 2001). In New Jersey, egg survivorship to hatching was 0.23 (Burger 1977). In Rhode Island, mammalian predators destroyed most monitored nests (Goodwin 1994).

In South Carolina, most individuals showed high site fidelity and remained in the same creek from year to year, although similar creeks were nearby (Gibbons et al. 2001).

Observations: One animal lived 14.1 years in captivity (http://www.pondturtle.com/). Lifespan is probably underestimated, though, with anecdotal reports of one animal living over 40 years in captivity (http://www.pwrc.usgs.gov/neparc/).

While all turtles reproduce by eggs, the genus Malaclemys usually does not produce more than 4-8 eggs in a clutch. Females typically nest several times annually. The duration of incubation varies between 60 and 85 days, depending on soil temperature and nest depth. During April and May, the female digs a nest cavity 4-8 inches deep in sand. The oval eggs are 1 * inches long, pinkish-white, and covered with leathery shells.

Wild hatchlings may spend their first years upstream in creeks. These creeks may either be brackish or relatively fresh water. As the hatchlings age, they move down to the salty marshes where nutrients and good nesting sites are plentiful. Hatchlings are 1 to 1.5 inches long and are known to be able to produce eggs for several years after a single mating. Females reach sexual maturity in approximately 7 years and males a little earlier. Interestingly, the sex ratio appears to favor females. In a sample of 1,433 individuals, females outnumbered males nearly six to one (Alderton 1988).

Average gestation period: 84 days.

Average number of offspring: 9.

Average age at sexual or reproductive maturity (male)

Sex: male: 910 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 2190 days.

Lays one or more clutches of 4-22 eggs (Copeia 1997:290-297), April-May in south, June-July in north; early June through early August, with at least two clutches per year, in New York (Feinberg and Burke 2003). Eggs hatch in 9-15 weeks depending on temperature. Hatchlings may emerge from nest in late summer or fall or overwinter in nest. In New Jersey, most hatchlings emerge from the nest in the daytime, 1-9 days after hatching. Sexually mature in about 3-6 years in South Carolina (Lovich and Gibbons 1990); males in 2-3 years, females in 4-5 years on the Atlantic coast of Florida (Seigel 1984).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 1
Species With Barcodes: 1

In the past, Malaclemys sp. were often considered a delicacy because of the sweet meat. These turtles were almost brought to extinction in the early years of the present century. They were either relentlessly hunted for their flesh or died of drowning in underwater crab traps. The group suffered worse than the snapping turtles of family Chelydridae, but has since recovered in numbers (Dixon 1987).

Currently, seaside development has led to the loss of nesting beaches. Tire tracks from vehicles used on the sand pose a hazard to hatchlings. The tiny turtles get trapped in the tire tracks and die of dehydration before reaching water.

To prevent extinction, however, diamondbacks are protected in several states. Interestingly, in some places the native beachgrass is now also protected and removal is against the law. Researchers have found that the presence of the beachgrass lowers the temperature of the nesting areas and can affect the sex of the hatchlings. The terrapin populations were also revived by activists who consider the gentle creature a good pet (Loutrel and Cornett 1993).

US Federal List: no special status

IUCN Red List of Threatened Species: lower risk - near threatened

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Range is fairly extensive along the Atlantic and Gulf coasts from Cape Cod to Texas, but some populations evidently are declining and population trend is unknown in many areas; incidental mortality in crab traps appears to be a major problem, as is habitat loss and degradation; better information is needed on population trend and sources of mortality in most of the range; nominal subspecies probably have little biological significance.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Global Short Term Trend: Relatively stable to decline of 30%

Comments: Adequate data on population trends are not available for most of the range; in general, there may be an overall decline (Seigel and Gibbons 1995). Apparently stable or increasing in Massachusetts and New York, apparently declining in Connecticut, New Jersey, and Mississippi, trend uncertain or varies among different localities in other states (Seigel and Gibbons 1995). An apparent long-tern decline has occurred in east-central Florida (Seigel 1993), but populations in the Keys are thought to be stable (Seigel and Gibbons 1995). Subspecies CENTRATA: Marked decline in abundance in local South Carolina populations along a creek and at Kiawah Island (J. Butler, pers. comm., 1997). Trend is unknown in Georgia (Siegel and Gibbons 1995). In North Carolina, populations in many areas continue to decline (Palmer and Braswell 1995). Subspecies LITTORALIS: Declining in Louisiana (Siegel and Gibbons 1995). Probably declining in Texas, but adequate population information is not available (A. Price, pers. comm., 1997). Majority of range occurs along the Texas coast.

Global Long Term Trend: Increase of 10-25% to decline of 50%

Comments: Declined in the late 1800s and early 1900s as a result of heavy commercial harvest; subsequent scarcity led to a decline in use and popularity; then populations increased in many areas. The decline has been primarily in abundance and less so in occupied habitat.

Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable

Comments: One of the major threats appears to be incidental drowning in crab traps (Seigel and Gibbons 1995, Hoyle and Gibbons 2000). The combination of high site fidelity, limited dispersal, and recreational crab trapping and other human activities likely resulted in the extirpation of a population in South Carolina (Gibbons et al. 2001). In South Carolina, the average female did not survive to its estimated age at maturity, likely because of excessive mortality in crab pots (Tucker et al. 2001). Estimates of the effects of crab trapping on a Chesapeake Bay population suggest that 15-78% of a local population dies annually in shallow-water crab-trapping localities and that a population can be extirpated in 3-4 years (Roosenburg et al. 1997). Due to size differences, males are more often caught in crab traps disrupting local sex ratios (Roosenburg et al. 1997). Crab trapping is negatively affecting populations on Little Talbot Island State Park in Florida (J. Butler, pers. comm., 1997). Drowning in crab traps has been observed in North Carolina and South Carolina, and populations have declined in areas of expanding crab fisheries in Florida and South Carolina (see Roosenburg et al. in press). Drowning has also been observed in fishing nets and trawls in the Pamlico Sound area, North Carolina (Palmer and Braswell 1995).

Harvesting by indigenous people and the Asian population for meat is a major threat in Texas; under current Texas regulations unlimited take is allowed with a current Texas hunting or fishing license (A. Price, pers. comm., 1997). Substantial unregulated harvest exists in Chesapeake Bay; undetermined numbers of terrapins are transported across state lines for resale in the urban Asian seafood markets in the northeastern United States, chiefly New York City. Growth of U.S. urban Asian market consumption of turtles is on the rise and expected to accelerate in the near future.

Other threats include drainage and impoundment of salt marshes, human disturbance of nesting sites (heavy human use of nesting areas could interfere with successful nesting), and changes in the flow of fresh water into estuarine systems (Seigel and Gibbons 1995).

Potential threats in need of further study include commercial harvesting for meat and pet trade, incidental kills by motor boats, road mortality (especially of nesting females), and predation on adults and eggs by raccoons and other predators (Seigel and Gibbons 1995). In New York, Feinberg and Burke (2003) documented a high level of predation on terrapin nests by introduced raccoons, plus evidence of raccoon predation on adult females as well. Also in New York, Draud et al. (2004) documented a high rate of predation on hatchlings and juveniles by Norway rats.

Restoration Potential: Many populations eventually rebounded when excessive harvest of adults for human food ceased.

Preserve Selection and Design Considerations: Preserves should encompass, in close proximity, adequate habitat for both nesting and feeding.

Management Requirements: Immediate efforts should be made to reduce incidental killing in crab traps; excluder devices have been developed by Roger C. Wood (Stockton State College, Pomona, NJ 08240) (Seigel and Gibbons 1995). See Roosenburg et al. (1997) and Hoyle and Gibbons (2000) for information on trap modifications that might reduce mortality. See also Cole and Helser (2001) for information on bycatch reduction devices.

See Lovich et al. (1991) for information on the behavior of artificially incubated hatchlings released in a South Carolina salt marsh.

Management Research Needs: The following topics are in need of further study: demography, genetics, habitat use, movement patterns, home range, ecology of juveniles, life history (based on long-term studies), subspecific taxonomy, and behavioral ecology (Seigel and Gibbons 1995). Also, better information is needed on the extent of mortality in crab traps and on natural mortality rates, and the present extent of habitat suitable for nesting and feeding needs to be determined (Seigel and Gibbons 1995).

Biological Research Needs: Determine extent of mortality in crab traps and natural mortality rates. Estimate loss of nesting areas and feeding habitat.

Global Protection: Several to many (4-40) occurrences appropriately protected and managed

Comments: Subspecies CENTRATA: Probably at least a dozen or so occurrences are protected in North Carolina. In Florida occurs on Little Talbot State Park, where crab trapping is a problem; a seasonal trapping restriction may be necessary for protection (J. Butler, pers. comm., 1997).

Needs: Many populations may merit protected status (or at least regulated game status) in states where such protection is not already provided (Seigel and Gibbons 1995).

Stewardship Overview: Management should focus on protecting adults and older juveniles from excessive mortality, especially incidental deaths in crab traps. In addition, adequate nesting and feeding habitat needs to be maintained and protected from excessive disturbance.

Comments: There is a high level of individual variation in this species, and some individuals of a particular subspecies may resemble those of other subspecies. The validity of at least some subspecies is questionable (see Mount 1975, Ernst and Bury 1982, Palmer and Braswell 1995). "In general, geographic variation is poorly defined and may be clinal" (Ernst et al. 1994). Mitochondrial DNA genotypic diversity and divergence levels are exceptionally low among putative subspecies (Lamb and Avise 1992). Further study of geographic variation in these turtles is needed.

Ernst and Hartsell (2000) showed that Malaclemys tuberculifera Gray 1844 predates the currently used name for the mangrove diamondback terrapin, Malaclemys terrapin rhizophorarum Fowler 1906. They stated that the ICZN has been petitioned to conserve the name rhizophorarum.

McDowell (1964) concluded that the genus Graptemys should be included in the genus Malaclemys , but this arrangement has been rejected (e.g., see Dobie [1981] for information on osteological differences between the two genera). Lamb and Osentoski (1997) conducted a molecular genetic assessment and concluded that Malaclemys and Graptemys are distinct, monophyletic clades.