By Aaron Tucker Litwiler The Atlantic coast salt marshes of the United States are incredibly biodiverse and are home to many unique species of flora and fauna. One such species that calls this ecosystem home is the diamondback terrapin, Malaclemys terrapin. This turtle belongs to the family Emydidae which includes many common North American turtles such as box turtles, spotted turtles, and sliders (Seidel and Ernst). However, unlike the rest of the American turtles in this family, diamondback terrapins reside in the brackish waters of North America’s eastern coastline. The diamondback terrapin can be found in salt marsh, tidal flats, and estuaries from Cape Cod, Massachusetts down to Corpus Christi, Texas (Roosenburg, Willem). These turtles are known to prefer areas of low marsh that are frequently flooded, however they can be found in deeper grass beds, bays, and other deeper bodies of water. The salt marsh habitat is characterized by saltmeadow cordgrass (Spartina alterniflora), black needle rush (Juncus romerianus), and sea oxeye (Borrichea frutescens) (ATHENS, GEORGIA). The diamondback terrapin shares this habitat with countless species of fauna including Atlantic blue crabs (Callinectes sapidus) and common marsh snail (Melampus bidentatus), both of which fall prey to the terrapin (ATHENS, GEORGIA). The diet of diamondback terrapin mostly consists of snails, crabs, and mussels; however, they have been known to feed on aquatic worms, fish, insects, and even decomposing flesh. Large, more matured terrapins typically consume larger prey such as fiddler crabs, Uca pugilator, and the aforementioned Atlantic blue crab. Young terrapins and smaller males prey on snails such as marsh periwinkles, Littoraria irrorate, and the common marsh snail (ATHENS, GEORGIA). The difference in prey size amongst mature turtles is due to sexual dimorphism. Female diamondback terrapins are considerably larger than males of the species and have broader heads and larger grinding surfaces to accommodate larger prey selection. Male terrapins reach a maximum carapace length of 5.5 inches while females can grow twice that size maxing out at 11 inches of carapace length. Female terrapins also have broader heads, shorter tails, and taller shells. The latter two characteristics are due to the reproductive requirements of female turtles (Seidel and Ernst). Despite their sexual dimorphism, all diamondback terrapins share traits that are characteristic of the species. Several variations can occur amongst the seven subspecies terrapins such as carapace shape, shape of keel knobs, head and neck markings, and shell pigmentation, however they all share the same general appearance that sets diamondback terrapins apart from other species (Seidel and Ernst). They are excellent swimmers with large, stocky hind legs and smaller forelegs. Though terrapins inhabit saline environments they do not possess flippers like their sea turtle cousins; they have webbed feet instead. These turtles are flat-bodied with a grey, keeled carapace that has light and concentric markings. The plastron of this species lacks a hinge, is yellow in color, and is connected to the carapace by a flat bridge (Seidel and Ernst). Terrapins have grey or black skin that can be accompanied by dark speckling or mottling. Terrapins have adapted to the saline environment due to their development of lachrymal salt glands that help the turtles to expel salt (Gosse). Male terrapins have longer tails in order to grasp the female during mating as well as to accommodate presence of larger reproductive organs within their cloaca. Diamondback terrapins are oviparous, meaning the females must carry and lay their eggs before hatching. Consequently, females are larger in both carapace length and depth in order to accommodate a full clutch of eggs. Females lay their eggs in open, dry, sandy soil where they deposit anywhere between four to twenty-three eggs. Females can produce up to three clutches of eggs between early spring and late summer, however, they return to the same beach every year to lay (National Aquarium). The sex of the clutch is determined by the temperature at which they are incubated, much like sea turtles. The survivorship of the hatchling turtles is affected by factors such as the microclimate of the nesting area as well as the turtles’ energy store and nest predation (Seidel and Ernst). As a consequence of these, nest survivorship is typically between one and three percent. Raccoons are the primary consumer of turtle eggs, and are a large threat to their population. Raccoons are very tolerant of human development, and even flourish in developed habitat. These human developments are a threat to all brackish and saltwater turtles. The development of shorelines decreases breeding grounds for turtles along with the erosion control that is put to use. Bulkheads block turtles from accessing the dry sand, and the grasses that are planted tangle hatchling turtles and penetrate eggs. Crab pots have also been known to kill turtles by attracting curious turtles and trapping them underwater until they drown (Roosenburg, Willem) . Considering these threats to the diamondback terrapin, it is not hard to understand why they are threatened throughout much of their range. However, there is much that can be done to prevent the extinction of these turtles. Conservation efforts such as nest site protection, education of coastal communities, habitat protection, and crab pot restriction can increase the odds of survival of this incredible species (Roosenburg, Willem). Citations
Gosse, Andrew M. “Diamondback Terrapin (Malaclemys terrapin).” Savannah River Ecology Laboratory, University of Georgia, srelherp.uga.edu/turtles/malter.htm. Seidel, Michael E., and Carl H. Ernst. "A systematic review of the turtle family Emydidae." Vertebrate Zoology 67.1 (2017): 1-122. ATHENS, GEORGIA. Home range, habitat selection, and diet of the diamondback terrapin (Malaclemys terrapin) in a North Carolina estuary. Diss. The University of Georgia, 1998. Roosenburg, Willem M. "The diamondback terrapin: population dynamics, habitat requirements, and opportunities for conservation." New Perspectives in the Chesapeake System: A Research and Management Partnership. Proceedings of a Conference. CRC Publ. No. 137. 1991. “Diamondback Terrapin ( Malaclemys Terrapin).” National Aquarium, National Aquarium, aqua.org/explore/animals/diamondback-terrapin
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