Diamondback terrapin
The diamondback terrapin or simply terrapin is a species of terrapin native to the brackish coastal tidal marshes of the East Coast of the United States and the Gulf of Mexico coast, as well as in Bermuda. It belongs to the monotypic genus Malaclemys. It has one of the largest ranges of all turtles in North America, stretching as far south as the Florida Keys and as far north as Cape Cod.
The name "terrapin" is derived from the Algonquian word. It applies to Malaclemys terrapin in both British English and American English. The name originally was used by early European settlers in North America to describe these brackish-water turtles that inhabited neither freshwater habitats nor the sea. It retains this primary meaning in American English. In British English, however, other semi-aquatic turtle species, such as the red-eared slider, might also be called terrapins.
Description
The common name refers to the diamond pattern on top of its shell, but the overall pattern and coloration vary greatly. No two diamondback terrapins look alike. The shell is usually wider at the back than in the front, and from above it appears wedge-shaped. The shell coloring can vary from brown to grey, and its body color can be grey, brown, yellow, or white. All have a unique pattern of wiggly, black markings or spots on their body and head. The diamondback terrapin has large webbed feet. The species is sexually dimorphic in that the males grow to a carapace length of approximately, while the females grow to an average carapace length of around, though they are capable of growing larger. The largest female on record was just over in carapace length. Specimens from regions that are consistently warmer in temperature tend to be larger than those from cooler, more northern areas. Male diamondback terrapins weigh on average, while females weigh around. The largest females can weigh up to.Diamondback terrapins can live up to 40 years in captivity, but scientists estimate they typically live for about 25 years in the wild.
Adaptations to their environment
Terrapins look much like their freshwater relatives, but are well adapted to the near shore marine environment. They have several adaptations that allow them to survive in varying salinities. They can live in full strength salt water for extended periods, and their skin is largely impermeable to salt. Terrapins have lachrymal salt glands, not present in their relatives, which are used primarily when the turtle is dehydrated. They can distinguish between drinking water of different salinities. Terrapins also exhibit unusual and sophisticated behavior to obtain fresh water, including drinking the freshwater surface layer that can accumulate on top of salt water during rainfall and raising their heads into the air with mouths open to catch falling rain drops.Terrapins are strong swimmers. They have strongly webbed hind feet, but not flippers like sea turtles do. Like their relatives, they have strong jaws for crushing shells of prey, such as clams and snails. This is especially true of females, who have larger and more muscular jaws than males.
Subspecies
Seven subspecies are recognized, including the nominate race.- M. t. centrata – Carolina diamondback terrapin
- M. t. littoralis – Texas diamondback terrapin
- M. t. macrospilota – ornate diamondback terrapin
- M. t. pileata – Mississippi diamondback terrapin
- M. t. rhizophorarum Fowler, 1906 – mangrove diamondback terrapin
- M. t. tequesta Schwartz, 1955 – East Florida diamondback terrapin
- M. t. terrapin – northern diamondback terrapin
Distribution and habitat
Diamondback terrapins live in the very narrow strip of coastal habitats on the Atlantic and Gulf Coasts of the United States, from as far north as Cape Cod, Massachusetts, to the southern tip of Florida and around the Gulf Coast to Texas. In most of their range, terrapins live in Spartina marshes that are flooded at high tide, but in Florida they also live in mangrove swamps. This turtle can survive in freshwater as well as full-strength ocean water, but adults prefer intermediate salinities. Despite its preference for salt water, it is not a true sea turtle and is not fully marine. They have no competition from other turtles, although common snapping turtles do occasionally make use of salty marshes. It is unclear why terrapins do not inhabit the upper reaches of rivers within their range, as in captivity they tolerate fresh water. It is possible they are limited by the distribution of their prey. Terrapins live quite close to shore, unlike sea turtles, which wander far out to sea; however, a population of terrapins on Bermuda has been determined to be self-established rather than introduced by humans. Terrapins tend to live in the same areas for most or all of their lives, and do not make long-distance migrations.Life cycle
Adult diamondback terrapins mate in the early spring, and clutches of 4–22 eggs are laid in sand dunes in the early summer. They hatch in late summer or early fall. Maturity in males is reached in 2–3 years at around in length; it takes longer for females: 6–7 years at a length of around.Reproduction
Like all reptiles, terrapin fertilization occurs internally. Courtship has been seen in May and June, and is similar to that of the closely related red-eared slider. Female terrapins can mate with multiple males and store sperm for years, resulting in some clutches of eggs with more than one father.Like many turtles, terrapins have temperature dependent sex determination, meaning that the sex of hatchlings is the result of incubation temperature. Females can lay up to three clutches of eggs/year in the wild, and up to five clutches/year in captivity. It is not known how often they may skip reproduction, so true clutch frequency is unknown.
Females may wander considerable distances on land before nesting. Nests are usually laid in sand dunes or scrub vegetation near the ocean in June and July, but nesting may start as early as late April in Florida. Females will quickly abandon a nest attempt if they are disturbed while nesting. Clutch sizes vary latitudinally, with average clutch sizes as low as 5.8/eggs/clutch in southern Florida to 10.9 in New York. After covering the nest, terrapins quickly return to the ocean and do not return except to nest again.
The eggs usually hatch in 60–85 days, depending on the temperature and the depth of the nest. Hatchlings usually emerge from the nest in August and September, but may overwinter in the nest after hatching. Nest predation is a large threat to Diamondback Terrapins. A study was done on 3159 nests finding that the greatest predator was racoons and predated nests were completely emptied of egg. Hatchlings sometimes stay on land in the nesting areas in both fall and spring and they may remain terrestrial for much or all of the winter in some places. Hatchling terrapins are freeze tolerant, which may facilitate overwintering on land. Hatchlings have lower salt tolerance than adults and Gibbons et al. provided strong evidence that one- and two-year-old terrapins use different habitats than do old individuals.
Growth rates, age of maturity, and maximum age are not well known for terrapins in the wild, but males reach sexual maturity before females because of their smaller adult size. In females at least, sexual maturity is dependent on size rather than age. Estimations of age based on counts of growth rings on the shell are as yet untested, so it is not clear how to determine the ages of wild terrapins.
Seasonal activities
Because nesting is the only terrapin activity that occurs on land, most other aspects of terrapin behavior are poorly known. Limited data suggest that terrapins hibernate in the colder months in most of their range, in the mud of creeks and marshes.Diet
The diamondback terrapin typically feeds on fish, crustaceans marine worms, marine snails, clams, barnacles, mussels, other mollusks, insects, carrion, and sometimes ingest small amounts of plant material, such as algae. At high densities the terrapin may eat enough invertebrates to have ecosystem-level effects, partially because periwinkles themselves can overgraze important marsh plants, such as cordgrass. Gender and age can greatly affect the diet of the diamondback terrapin, males and juvenile females tend to have less diversity in their diet. Adult females, due to their powerful, defined jaw, will occasionally feed on crustaceans such as crabs and are more likely to consume hard-shelled mollusks.Conservation
Status
In the early 1900s, the species was considered a delicacy and was hunted almost to extinction. The population also decreased due to the development of coastal areas, terrapins being susceptible to wounds from the propellers on motorboats.Another common cause of death is the trapping of the turtles in recreational crab traps, as the turtles are attracted to the same bait as the crabs. The Wetlands Institute estimates that a minimum of 14,000 to 15,000 terrapins drown in crab traps annually set along the New Jersey coast alone. Countless more drown or starve to death in ghost traps, abandoned or lost crab traps along with discarded nets, throughout their habitat. Among two such abandoned crab pots in a tidal marsh in Georgia, a study found 133 dead terrapins, according to the Center for Biological Diversity.
Further, an increase in seawalls and bulkheads being built for storm and erosion control, exacerbated by climate change and sea level rise, inadvertently eliminate terrapin's nesting habitat on beaches and upland areas with soft shorelines.
Due to these factors, the diamondback terrapin is listed as an endangered species in Rhode Island, a threatened species in Massachusetts and is considered a "species of concern" in Georgia, Delaware, Alabama, Louisiana, North Carolina, and Virginia. The diamondback terrapin is listed as a "high priority species" under the South Carolina Wildlife Action Plan. In New Jersey, it was recommended to be listed as a Species of Special Concern in 2001. In July 2016, the species was removed from the New Jersey game list and is now listed as non-game with no hunting season. In Connecticut, there is no open hunting season for this animal. However, it holds no federal conservation status. In 2021, a terrapin was hatched in Massachusetts with two heads, two gastrointestinal systems, and two spines that are fused together.