These turtles occur from Cape Cod, Massachusetts down the entire eastern seaboard, around the Florida peninsula, and across the Gulf Coast to Texas. As full-time inhabitants of the salt marsh ecosystem, terrapins are the only turtle species in the U.S. that lives in the brackish water zone between fresh water habitats and the ocean. Diamondback terrapins feed on a variety of crustaceans, fish, insects, and mollusks. Mature female diamondbacks are almost twice the size of mature males, with females having disproportionately larger heads. These turtles spend most of their time in the water and only come onto land to bask or lay eggs.
Diamondback terrapins breed, in the water, in the early spring.
In the late spring and summer, females will lay 4-18 eggs in the sand above the high tide line. The inch-long babies hatch about three months later. In the late 1800 s and early 1900 s, diamondback terrapins were considered a delicacy. Terrapin soup was served in many of the finer restaurants on the east coast. The over-harvesting of these turtles for such haute cuisine led to a major decline in terrapin numbers.