Diamondback terrapins are aquatic turtles with concentric, diamond-shaped markings and grooves on the scutes (plates) of their carapaces (top shells), which range from medium gray or brown to nearly black. Their skin can be pale gray to black, marked with dark spots, blotches or stripes. No two diamondback terrapins are exactly alike in color and pattern.
Their large webbed feet and muscular legs make terrapins strong swimmers, which helps them survive in environments with daily tidal changes and strong currents. Terrapins, like sea turtles, have glands that help remove excess salt from their bodies by secreting tears with high concentrations of sodium chloride.
Terrapins mate in early spring and nest through mid-summer. Females lay two to three clutches of eggs annually, with clutch sizes ranging from 4 to 23 eggs. Sometimes hatchlings overwinter in the nest and emerge the following spring. During the cold winter months, diamondbacks hibernate, buried in the mud at the bottom of tidal creeks, completely submerged and inactive.
Maryland requires all recreational crab pots to be equipped with turtle excluders to protect terrapins.
Learn more about the diamondback terrapin! Did you know that this species is Maryland's state reptile and the mascot of the University of Maryland?
Diamondbacks live in coastal salt marshes, estuaries and tidal creeks along the U.S. Atlantic and Gulf coasts from Cape Cod, Massachusetts, to Corpus Christi, Texas, including the Florida Keys. Seven subspecies occupy this range. The northern diamondback, which you can see at the National Aquarium, can be found from Cape Cod, Massachusetts, to Cape Hatteras, North Carolina.
Diamondback terrapins are almost strictly carnivorous but sometimes ingest small amounts of plant material. They possess strong jaws and crushing plates in their mouths that enable them to eat hard-shelled prey, including aquatic snails, crabs and small bivalves, such as mussels and clams. They also eat carrion, fish, worms and insects.
Adult male terrapins are significantly smaller than adult females in weight and carapace length. Males reach a maximum shell length of 5.5 inches, while females can grow up to 11 inches. Adult females also have larger heads, wider jaws and shorter tails than males.
Diamondback terrapin populations have declined considerably in many parts of their geographic range and are listed as vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Terrapin populations fell to dangerously low levels in the 20th century after a long period of large-scale harvesting for their meat. Commercial harvest of terrapins ended in Maryland in 2007. Other factors causing declines in terrapin populations include the loss of salt marsh habitat and destruction of nesting beaches due to waterfront development, road mortalities of nesting females, boat strikes, bycatch and continued legal commercial harvesting in one state.
Nesting terrapin females are vulnerable to predation by raccoons. Eggs and hatchlings are preyed upon by a wide variety of animals including crabs, crows, gulls, herons, rats, muskrats, foxes, raccoons, skunks and mink. Survival rates of nests and hatchlings are very low due to predation and flooding.
As the National Aquarium's general curator, Jack Cover ensures that all animals in our care thrive in healthy, beautiful habitats.
The National Aquarium—and the aquatic world—is full of amazing animals like this one.