Diamondback terrapins are turtles that live in marshes and tidal waters along the Atlantic and Gulf coasts. The northern diamondback terrapin (Malaclemys terrapin terrapin) is the species that graces the Chesapeake Bay.
Because of its elusive behavior, many people never see this turtle. The diamondback terrapin, however, ranks with the blue crab, oyster, great blue heron or osprey as a symbol Chesapeake Bay ecology and history. It’s also the state reptile of Maryland and mascot for the University of Maryland.
The northern diamondback terrapin is one of the Chesapeake’s most beautiful animals. The top of its shell is covered with thin, shiny scales called scutes. Concentric diamond-shaped rings on these scutes give the terrapin its name.
Diamondbacks are also very colorful. The upper shell, known as the carapace, can be gray, black or brown and the bottom shell, the plastron, is yellow or olive and often mottled with dark blotches. The skin is pale or white with striking black flecks and lines that create a design unique to each individual terrapin, just like a person’s fingerprint.
Males are mature at about age 7, weigh about a pound and are about 4 inches along the plastron. Females mature at about 12 years, and can weigh up to 7 pounds and and reach a length of 9 inches.
Diamondbacks live in brackish and coastal waters and marshes. Their webbed feet make them agile swimmers and sharp claws help them move about the marshes. They eat clams, snails, worms, crabs, insects and fishes.
Diamondbacks usually mate in May, and always mate in the water, usually at night. Females can store sperm and produce fertilized eggs up to four years after mating.
They lay their pinkish, leathery eggs in June and July in nests dug out of sandy beaches or marsh edges above the high tide line. An average nest will contain about 13 eggs. Eggs hatch between August and October. A very late hatch, though, may cause hatchlings to overwinter and hibernate in the nest and emerge the next year.
As with most turtles, temperature is believed to influence the sex of the hatchlings. Higher temperatures produce more females while lower temperatures produce more males. When hatched, the terrapins are about an inch long.
But only a small percentage (1–3 percent) of the eggs will hatch, owing to nest disturbance and predators such as foxes, crows and raccoons, who dig up the nests and eat the eggs and baby terrapins. Hatchlings are also a favorite food of herons.
Survivors hibernate in the winter. The first cold temperatures signal terrapins to bury themselves in mud banks. Body functions slow down to the point where terrapins do not need to come up to breathe.
Hibernation ends in the spring and mating takes place soon after. Terrapins can live to be as old as 50.
During colonial times, these turtles were a plentiful source of food, and terrapin soup soon went from a dish for slaves and servants to a favorite among all colonists.
Demand for terrapins continued into the late 1800s as supplies continued to decrease. Today, terrapin season is closed from May 31 through July 31 to allow for mating and nesting. All harvested terrapins must be at least 6 inches long on the plastron.
Predators are not the only threat to terrapins. Habitat loss is a big factor. Terrapins appear to stay close to the beaches and waterways where they are hatched. If traditional nesting areas are altered by waterfront development, it is not likely that the terrapins will nest elsewhere. Bulkheads, stone revetments and even shoreline grass plantings can ruin nesting habitat.
Increased motor boat traffic increases the likelihood that terrapins will be hit by propellers.
Crab pots in shallow water areas, such as private docks, also pose a problem. Terrapins go after the crab bait, get stuck in the pots and drown. Today, bycatch reduction devices are required in all non-commercial crab pots. The wire device let crabs in but keeps terrapins out.
To protect and conserve this wonderful creature, we must continue to learn more about its habits and habitat.
The Terrapin Research Consortium is a research advisory group independent of political, academic and government organizations. Its goal is to develop sound research and management for diamondback terrapins throughout their range. For information, visit the group’s web site at:
For information about diamondbacks or to get involved in terrapin conservation, visit the Maryland Department of Natural Resources “Terrapin Station” at www.dnr.state.md.us/fisheries/recreational/terpstation.htm
Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis.