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Northern Diamond-backed Terrapin

Fact File

Scientific Name: Malaclemys terrapin terrapin

Classification: Reptilia, Order Testudines, Family Emydidae

Relatives: Diamond-backed-terrapins are the only species in the genus Malaclemys.

Conservation Status:

Size: Female terrapins are larger than males and average around 6-9 inches long while males average between 4.5-5 inches in length.

Life Span: averages between 25-40 years in the wild, and possibly longer in captivity.

Identifying Characteristics

This is a moderate-sized estuarine turtle which is incredibly variable in coloration and pattern. Terrapins display female-biased sexual size dimorphism, meaning adult females are larger that adult males. The carapace is smooth, with the rear half of the shell the widest part. The carapace (upper shell) can be gray, brown, yellowish green, or nearly black, and has brown concentric circles alternating with gray, black, or yellow. The plastron (lower shell) is yellowish to greenish, and often has an irregular pattern of black flecks; it may have a dark brown blotch in each scute and the margins of the scutes may be outlined with thin black lines. The skin varies in shade from white to black, but is usually gray with an irregular pattern of small to large darker colored flecks. The eyes are black and the “lips” are yellow, occasionally presenting with a dark “moustache” above the mouth.


The diamond-backed terrapin is the only exclusively estuarine turtle species in North America. It inhabits brackish water, saltwater estuaries and tidal marshes and can sometimes be seen in the Atlantic Ocean.


This is a carnivorous species which feeds on a variety of snails, bivalves, and crabs with salt marsh periwinkles (Littoraria irrorata) comprising the majority of their diet.


The diamond-backed terrapin is found in estuarine habitats along the U.S. Atlantic and Gulf coasts from Cape Cod, Massachusetts, to Corpus Christi, Texas, including the Florida Keys. In Virginia, this species is found in the Chesapeake Bay and its tidal tributaries as well as on the ocean side of the Eastern shore and southeast Virginia.

Role in the Web of Life

The diamond-backed terrapin is considered a keystone species due to its role as a predator of herbivorous invertebrates such as crabs and snails in salt marsh ecosystems across the east coast of the United States. It’s regulation of these organisms is critical to the maintenance of salt marsh plants and overall estuarine health in its native environment.  Terrapins also ingest viable eelgrass seeds incidental to the  consumption of prey items.  These seeds are ultimately redistributed throughout the estuarine environment, playing an important ecological role of seed dispersal.

This species breeds and lays eggs in the spring and summer and mating always occurs in the water. Nests are usually constructed in sand, but may also be in fill dirt. These turtles typically overwinter in the mud within channels and tidal flats.

Last updated: January 19, 2024

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