brackish marine estuary carapace mollusk
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Background

Malaclemys terrapin, or the diamondback terrapin, is the only North American turtle that lives exclusively in brackish water, inhabiting estuarine embayments and marshes from southern New England to the Gulf of Mexico. The word "terrapin" is an Algonquin word for edible turtles that live in brackish water. Indeed, terrapin soup laced with sherry was so appealing to gourmands during the late 19th century that the animals were hunted vigorously. More than 89,000 pounds were caught in the Bay in 1891–and they also commanded the highest price: between $30 and $120 per dozen. Their abundance wasn't always so appealing–according to one account, slaves on the Bay's Eastern Shore were fed so much terrapin during the 18th century that they protested. Nonetheless, the continued harvest pressure on terrapins combined with their low reproductive rates and longevity resulted in decimating terrapin populations throughout the Bay by the early 1900's.

Like other turtles, diamondbacks lay eggs, and their scaly appendages or skins resemble the rough skin of a bird's leg. The diamondback is a medium-sized turtle in which the female grows larger than the male, usually to an adult length of nine inches. The carapace or upper shell is covered with scutes made of keratin (the same protein found in hair and nails), and often is patterned in black and grey, markings that are as particular to each member of the species as a zebra's stripes or a human fingerprint. The scutes on the carapace appear to form diamond-shaped concentric rings. The diamond shaped patter is a function of the coloring - aging can be done by counting annual growth rings that appear on the scutes of both the plastron and the carapace - these can contribute to the rough nature of the shells of younger individuals, but adults have a smooth shell.

The diamondback's plastron, or underside shell, is usually a yellowish or greenish gray color. Like other turtles they have horny beaks rather than teeth, but unlike some species, they have webbed feet for swimming, and strong claws for climbing up riverbanks.

Life Cycle

• Diamondbacks feed mostly on mollusks: snails, clams and mussels.
• Females begin to reproduce usually between ages 8 and 13, while males start between 4 and 7 years.
• Mating always occurs in water, usually at night, usually in May in the mid-Atlantic region.
• A female may lay fertilized eggs for four years before she mates again, and makes her nests in sandy rims above the high tide mark.
• The female digs an oval six-inch-deep hole in the sand and lays between 5 and 22 pink-white eggs, which take about 60 to 100 days to hatch.
• As in the case of most turtle species, the temperature of the diamondback's nest determines the gender of the hatchlings. The warmer the nest, the more females develop; the lower the temperature, the more males.
• If hatchlings haven't emerged by the onset of cold weather, they often winter over in the sand and hatch the following spring. Adult diamondbacks hibernate in layers of mud along embankments and at the bottom of creeks and rivers.
• Although many diamondback terrapins can live to be 40 or more years old, most never make it past the hatchling stage. Predators include small mammals that frequent wetland areas, such as foxes, otters, raccoons, and skunks, which eat either eggs or juveniles; and birds, which attack the hatchlings as they emerge. Adult diamondbacks also are killed by cars while trying to cross roads to lay their eggs near the water, many are injured or killed by boat propeller blades, and still more drown in crab pots.
• Despite legislation passed in 1878 in Maryland which curtailed the taking of terrapin to late autumn, winter and early spring months, by 1920 the catch had fallen to less than 900 pounds. In 1929 new laws were enacted, some of which are still in effect: it is still against the law to catch terrapins between May 1 and July 31. Terrapins with plastrons less than six inches long are not to be collected, and it is illegal to "take, destroy or tamper with" terrapin eggs. Terrapin hunting requires a license, but there is no limit to the numbers that may be taken each time.

Photo courtesy: Willem M. Roosenburg (http://www.biosci.ohiou.edu/faculty/roosenburg/)

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Last modified: 3/1/06