Diamondback terrapin

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Seven subspecies of diamondback terrapin have been described. The carapace (upper shell) and skin can vary widely in color. The carapace may be light gray, brown, or black. Skin color ranges from light green to very dark gray, with black markings.
Older individuals tend to have much darker shells than younger animals.
The name “diamondback terrapin” derives from the shape of their scutes (bony plates on the shell). Although not specifically diamond-shaped, the scutes do have diamond-like points. Each scute contains a clear pattern of concentric circles which have been described as growth rings.
Diamondback terrapins have webbed feet, large heads, and strong beaks, which help them crush hard-bodied prey, like clams or shrimp.
They are sexually dimorphic. Maximum carapace length for females is about 9 inches, but only 5.5 inches for males. Females have wider heads, but shorter tails.

Range – Atlantic and Gulf Coasts of the United States, from Massachusetts to Texas
Habitat – Only turtle known to live in brackish water, including bays, rivers, sounds, creeks, and coastal marine areas; they require access to fresh water for drinking and often bask in the sun on mud flats.

Wild – Snails, soft-shelled mollusks (bivalves) and crustaceans, fish, insects, plants, algae, carrion
Zoo – Turtle pellets, fish, shrimp, worms, insects

Females reach sexual maturity at 5 to 7 years of age, while males do so earlier, at around 2 to 3 years.
Courtship and mating occur from late March through May. A Florida study found that mating begins with the turtles forming groups of six to 75 individuals.
During mating, females float on the water’s surface, while males approach from behind. If the female remains still, copulation occurs. If the female swims away, the male may pursue her for a long distance.
In June or July, females seek out a dry spot on land and dig a nest hole four to eight inches deep. The clutch typically includes four to 18 eggs which are about one-and-a-half inches long and covered with a leathery shell. Females may lay several clutches each year.
The eggs incubate for around 60-85 days. Sex of the hatchings is determined by the prevailing temperature during this period. Warmer temperatures produce females, while cooler temperatures produce males.
Hatchlings emerge in summer or early fall and are only about one inch in length. Both eggs and hatchlings are vulnerable to a variety of predators.
Hatchlings may spend their first years upstream in creeks which are either brackish or contain relatively fresh water. As they age, they move down to the salty marshes where nutrients and nesting sites are plentiful.

Coastal development creates loss of habitat and nesting sites. Chemicals, heavy metals, and microplastics pollute their waters. Vehicular accidents kill nesting females crossing the road.
Many diamondback terrapins drown in crab traps after they are initially attracted by the bait, then are unable to escape. More than 90 dead terrapins were found in a single crab trap in Georgia. This can be prevented through the use of bycatch reduction devices.
Recreational crab traps that are left in the marsh and forgotten about, known as "ghost traps," are another threat to terrapins.

Diamondback terrapins contribute to the health of the coastal marine ecosystem in which they live. As omnivores, they help to control the growth of both flora and fauna by eating plants, algae, and smaller animals.

Zoo Atlanta supports the Georgia Sea Turtle Center’s Jekyll Island Causeway Conservation Program, which seeks to raise awareness of and mitigate the threats to wild diamondback terrapins. Zoo Atlanta supports the project by rearing young diamondback terrapins hatched from eggs from females killed or injured by automobiles. To increase their odds of survival, the young terrapins are raised at the Zoo for around one year before they are returned to the Georgia Sea Turtle Center, which prepares them for release into the wild in Jekyll’s coastal marshes.

Support organizations working to protect wetlands, especially in coastal areas, and organizations which help to protect turtles by maintaining or restoring habitat, protecting nesting sites, or installing barrier fencing on roadways.
Support sustainable seafood initiatives, such as regulations requiring crab traps to have bycatch reduction devices.
Crab responsibly! If you put out a trap, retrieve it and don't leave it in the water after you are done crabbing.
When driving in coastal areas, be alert for terrapin road crossings, especially during spring nesting season.
Help keep terrapin habitats clean by properly disposing of waste and recycling as much as possible.

In the early 1900s, diamondback terrapins were considered a gourmet treat and were used in preparing soups and stews. Commercial harvesting significantly reduced their numbers, but regulation in the 1930s helped to restore the population. They are now protected in several states.
Diamondback terrapins are typically inactive from November to early spring. During winter, they may hibernate by burying themselves in the mud. They often spend their entire adult life in the same habitat area.
Diamondback terrapins have special glands near their eyes which excrete excess salt from their bloodstream. This adaptation helps them survive in their brackish habitat.
Eggs and hatchlings have many predators, including raccoons, skunks, foxes, gulls, crows, and herons. Hatchlings are also vulnerable to predatory fish. Adults have few predators due to their size and hard shells.
To reduce road deaths, a “turtle patrol” from the Georgia Sea Turtle Center helps nesting females cross roadways. On one coastal road, 150 terrapins were killed during a single nesting season.
Diamondback terrapins, along with most other native species, may not be kept as pets under Georgia law.

Diamondback terrapin. (2020). Animals. Retrieved May 9, 2020 from https://www.nationalgeographic.com/animals/reptiles/d/diamondback-terrapins/
Diamondback terrapin. (2020). Georgia Wildlife. Retrieved May 9, 2020 from https://georgiawildlife.com/diamondback-terrapin
Diamondback terrapin. (2020). Animal. Retrieved May 9, 2020 from https://zooatlanta.org/animal/diamondback-terrapin/
Dodd, M. (2009). Malaclemys terrapin. Retrieved May 8, 2020 from Georgia DNR Biodiversity Portal: https://georgiabiodiversity.a2hosted.com/natels/profile?es_id=18644
Park, I. (2000). Malaclemys terrapin. Retrieved May 08, 2020, from Animal Diversity Web: https://animaldiversity.org/accounts/Malaclemys_terrapin/
Roosenburg, W.M., Baker, P.J., Burke, R., Dorcas, M.E. & Wood, R.C. (2019). Malaclemys terrapin. Retrieved May 10, 2020, from The IUCN Red List of Threatened Species 2019: e.T12695A507698. https://dx.doi.org/10.2305/IUCN.UK.2019-1.RLTS.T12695A507698.en.
Zoo Atlanta Animal Care Team.

Updated September 2024

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