Malaclemys terrapin

The diamondback terrapin (Malaclemys terrapin) or simply terrapin, is a species of turtle native to the brackish coastal tidal marshes of the eastern and southern United States, and 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 torope. 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 be called a terrapin. The common name refers to the diamond pattern on top of its shell (carapace), but the overall pattern and coloration vary greatly. 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 13 cm (5.1 in), while the females grow to an average carapace length of around 19 cm (7.5 in), though they are capable of growing larger. The largest female on record was just over 23 cm (9.1 in) 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 300 g (11 oz) on average, while females weigh around 500 g (18 oz). The largest females can weigh up to 1,000 g (35 oz). 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 of time 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 as do sea turtles. Like their relatives (Graptemys), 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. Seven subspecies are recognized including the nominate race. The isolated Bermudan population, which arrived on its own (and was not introduced by humans), has not been officially assigned to a subspecies, but based on mtDNA it is closely related to the population from the Carolinas. 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. They have no competition from other turtles, although 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 (not 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.