DIAMONDBACK TERRAPINS JOIN THE LIST OF TURTLES NEEDING PROTECTION

by Whit Gibbons

June 23, 2003

I once said diamondback terrapins were my favorite turtle. Imagine a reptile with the dreamy eyes of a golden retriever and the unassuming face of a manatee. Add the docile temperament of a lamb and the beauty of the prettiest seashell. For extra credit include perseverance against natural hazards of coastal weather, a sea full of predators, and a century of human-caused adversity. This tough, attractive little turtle has a record for getting through rough times with no complaints.

Restricted to the narrow brackish region between saltwater and fresh, terrapins are the only U.S. turtle to live exclusively in coastal salt marshes, from Cape Cod to coastal Texas. Sea turtles live in the ocean; freshwater turtles live inland.

Among the prettiest turtles in the world, terrapins are highly variable in color. Some are almost black, others milky gray, and some have splashes of yellow or green. Their faces and shells look like hand-painted sculptures. Their name comes from brightly colored, diamond-shaped concentric markings visible on the upper shell of many. Females reach up to nine inches in shell length and appear to be three times as large as the smaller males, which are little larger than a person's hand.

Terrapins were seriously overexploited as a luxury food item in the early part of the last century when terrapin stew was a delicacy in many restaurants, and millions, especially the large females, were removed from marshes and estuaries. But even today, things are not looking up for my favorite turtle, as with many of the world's turtles. We know that diamondback terrapins are in trouble in one location because we have been studying them for more than twenty years and have clear records of their declining numbers. A serious collapse has been observed in the numbers of terrapins that inhabit the coastal waters around Kiawah Island, South Carolina.

I just returned from two weeks of sampling terrapins in the coastal salt marshes, a habitat most beachgoers only see from a car but one that is home to these magnificent turtles. And they are clearly disappearing. We were able to capture fewer than fifty turtles with an effort that fifteen years ago would have yielded as many as two hundred. And virtually all we caught were old, most being ones we had previously caught more than a decade ago. Young turtles are not replacing those that die, which could lead to local extinction.

The terrapin decline may have several causes, and no single culprit has been identified. Crab trapping unquestionably kills terrapins each year, especially small ones, when they enter and drown in crab pots left underwater too long. Dead terrapins have been found in both commercial and recreational crab traps in our study along the Kiawah River. Commercial crab trappers are responsible for some terrapin deaths, but a more serious cause may be from visiting tourists who abandon thousands of recreational crab traps each year in all coastal states. These "ghost traps" can do endless damage to terrapins and other marsh wildlife by continuing to kill animals that enter them. People who leave untended traps mean no harm, as they are unaware of the trouble they can cause. Thus a strong educational program to inform visitors of the environmental hazards of deserted traps might solve much of that problem.

The absence of juvenile terrapins may also be exacerbated by the loss of nesting habitat and siltation due to development, and the presence of pesticides from agricultural runoff. Another suggested cause is an increase in the mink population, an effective turtle predator, as the result of a reintroduction program. Or perhaps a critical food source of young turtles is no longer abundant.

And the decline in terrapins may mean more than merely the loss of a spectacular turtle. Terrapins may be harbingers of a deeper lying problem: that the coastal marshes themselves are being environmentally stressed beyond a sustainable limit, an issue that bears scrutiny. Whatever the cause, terrapins are in far fewer numbers in the creeks we have studied, and presumably the same holds for unstudied areas along much of the coast. People who come to know terrapins may well decide these lovely animals are among their own favorites, which should be justification enough to be concerned about their welfare.



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