Diamondback Terrapins: A Chesapeake Treasure

By Kathy Reshetiloff

Diamondback terrapins are turtles that live in marshes and tidal waters along the Atlantic and Gulf coasts. But it is the northern diamondback terrapin (Malaclemys terrapin terrapin) that graces the Chesapeake Bay.

The northern diamondback terrapin is one of the Chesapeake's most beautiful animals. Because of its elusive behavior, many people never see this turtle. The diamondback terrapin, however, ranks right up with the blue crab, oyster, great blue heron or osprey as a symbol of Chesapeake Bay ecology and history. It's also the state reptile of Maryland and mascot for the University of Maryland.

The top of the turtle is covered with thin, shiny scales called scutes. This terrapin gets its common name from the concentric diamond-shaped rings on the scutes of its upper shell. In addition to this unique pattern, 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 black flecks and lines that create a design unique to each individual terrapin, just like a person's fingerprint.

Males are mature at about 7 years old, weigh about a pound and are about four inches along the plastron. Mature females are about 12 years old, can weigh up to seven pounds and can reach a length of nine 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. Females can store sperm and produce fertilized eggs up to four years after mating. Diamondbacks always mate in the water, usually at night. 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. On average, a nest will contain about 13 eggs.

Eggs hatch between August and October. With most turtles, temperatures influence the sex of the hatchlings. Higher temperatures produce more females while lower temperatures produce more males. It is believed the same applies to diamondback terrapins. A very late hatch may cause hatchlings to actually overwinter and hibernate in the nest and emerge the next year. When they hatch, the turtles are only about an inch long. Only a small percentage (1-3 percent) of eggs hatch due to disturbance of the nest or predators. Foxes, crows and raccoons dig up the nests and eat the eggs and baby terrapins. Hatchlings are favorite food for herons.

If the hatchlings survive, they will hibernate through the winter. The first cold temperatures signal terrapins to bury themselves in mud banks. Body functions slow down so much that the terrapins do not need to come up to breathe. Hibernation ends in the spring and mating takes place soon afterwards. Terrapins can live to be as much as 50 years old.

During colonial times, terrapins 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 but 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 six inches long on the plastron.

Besides natural predators, terrapins face other threats. Habitat loss is a big factor. Terrapins appear to stay close to beaches and waterways where they 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, like off of docks, also pose a problem. Terrapins go after the crab bait, get stuck in the pots and drown. Today, catch reduction devices are required in all non-commercial crab pots. The wire device lets crabs in but keeps terrapins out.

In order 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 of diamondback terrapins throughout their range. For more information about this group, visit their website at www.terrapininstitute.org/consortium.htm.

For more information about diamondbacks or to get involved in terrapin conservation, visit the Maryland Department of Natural Resources "Terrapin Station" www.dnr.state.md.us/fisheries/recreational/terpstation.htm.