Texas Parks & Wildlife Magazine   


March 2010 cover image 12 Great State Park Walks

Jewel of the marsh

The legendary diamondback terrapin’s survival depends on a little help from its friends.

By Artussee D. Morris

Way back in a coastal marsh’s upper reaches lurks a creature that few encounter, and whose mysterious existence is seldom documented. Treasured by epicureans _ nearly to extinction _ the diamondback terrapin (Malaclemys terrapin ssp) is considered to be an indicator of a healthy ecosystem. While these terrapins are creatures of legend, their mere presence often eludes us.

Diamondback terrapins get their name from the concentric, diamond-shaped scutes (plates) on their carapace, ranging in color from light brown to gray or black. Their skin usually is a pale gray, flecked with dark spots, blotches and/or stripes. Each color pattern is unique and can be used to identify each individual terrapin.

Photo by Earl Nottingham

There are seven subspecies of diamondback terrapin, found from Cape Cod to South Texas. The Texas subspecies (M. t. littoralis) inhabits the back marshes from western Louisiana to Nueces Bay near Corpus Christi. The diamondback terrapin is the only “sea turtle” that spends its life in brackish coastal marshes, tidal flats, lagoons and creeks.

Myths about the diamondback terrapin predate Columbus in the Americas. Native Americans regarded them either as sacred animals or often as “tricksters.” In a series of late 1800s African American Uncle Remus folk tales, Br’er Fox tricks longtime nemesis Br’er Tarrypin (Brother Terrapin) into letting him see his tail, only to grab it and shake Br’er Tarrypin back and forth. To break free, Br’er Tarrypin tricks Br’er Fox into throwing him into a pond by telling him he’ll drown. Another tale has Br’er Tarrypin beating Br’er Bear in a game of tug-of-war by slipping into the water and tying his end of the rope to a sunken branch. However, not everyone thought of terrapins lightheartedly. Early New England fishermen considered them to be bad luck, calling them “wind turtles” bringing ill fortune.

Photo by Earl Nottingham

Diamondback terrapins played an important role in the culinary history of early America. In the 1700s, diamondback terrapins were an important food source for the Continental Army and later became a major food source for slaves on coastal plantations. Stories from the Chesapeake Bay region in the 1800s refer to indentured servants complaining about the frequency of terrapins in their diets, leading to a Maryland law stating that slaves should not be fed terrapin more than three times a week. Somewhere along the line, terrapins went from slave food to one of the most celebrated dishes of the time.

Around the turn of the 20th century, in the mid-Atlantic and New England states, diamondback terrapins were the main ingredient in a gourmet turtle soup craze. Only the affluent could afford the sherry-laden dish. At the time, diamondback terrapins were so plentiful that fishermen considered them a nuisance because they sometimes were unable to haul in their fishing nets due to the weight of the creatures. The terrapins were sold live for $90 a dozen or $1 per inch of plastron length _ big bucks back then _ and fishermen landed as much as 400,000 pounds of them annually from the East Coast.

Unfortunately, larger females were targeted, and it was not long before populations began to crash. Because of the high demand, populations were locally extirpated near large cities. An attempt was made to create culture farms with some success, but by the end of World War I, markets declined because of lack of product. Finally, during Prohibition (when sherry was not available), the fad fell off, and the Great Depression made the dish too expensive for many people to purchase. This offered the diamondback terrapin a reprieve of sorts, and Atlantic populations gradually began to recover. It is thought that the food craze never got started in the Gulf of Mexico region because the southern populations were said to be not as flavorful as the northern variety, with the Delaware Bay variety being the best of all.

Photo by Earl Nottingham

Today, wild-caught diamondback terrapins are harvested in some states for the same dietary purpose, the pet trade and other uses. In East Asia, turtle, tortoise and terrapin parts are thought to contain medicinal properties and increase longevity. Turtles there are consumed in large quantities, leading to dramatic decreases in turtle populations. Experts suggest that 75 percent of Asia’s roughly 90 species of tortoises and freshwater turtles are threatened. Now, imports are filling the void. Again the fate of the diamondback terrapin is threatened, with offers to buy them “live by the ton” uncovered on the Internet.

Photo by Art Wolfe

Diamondback terrapins exhibit a unique life history. They are the only turtle species whose habitat is limited to brackish/saltwater estuaries. It is thought that while they live in salty waters, they drink fresh water. Often after rains, they will rise to the surface to drink fresh water riding on the surface of the salty water. Females can store sperm up to four years and lay four to 18 eggs in the spring. They can have up to three clutches per year, and they have high nest-site fidelity, going back to the same nesting area for each event.

The clutch incubates from 60 to 100 days, and nest temperatures determine the sex of the clutch. Warmer temperatures will produce an all-female clutch. The sexes mature at different rates, with males reaching sexual maturity at 3.5 inches and 3 years of age, while females mature at 4 inches and 6 years of age. Living up to 50 years, they feed along the marsh edge on crabs, shrimp, bivalves and fish. Marsh periwinkles are a favorite prey item.

Although not so much of a problem here in Texas, roadway mortality is a significant threat to females in search of nesting areas on the Atlantic coast. Additionally, raccoons have been introduced to nesting islands, where they prey on the incubating nests. Boat propellers and loss of habitat from coastal development have been listed as threats. Arguably, the key threat to Atlantic coast and Gulf of Mexico populations is the wire crab trap.

Each February since 2002, the Texas Parks and Wildlife Department has hosted the annual Abandoned Crab Trap Removal Program. Concerned with the ghost fishing effects of these derelict traps, coastal biologists examine each trap brought in for any evidence of diamondback terrapin mortality. Unfortunately, they find it.

All told, since the trap removal program began, 31 terrapins have been found in derelict traps from Sabine Lake to San Antonio Bay. In 2005, 22 diamondback terrapins were found in four traps (20 in two traps) in Galveston Bay. All had drowned. Four more were found in one trap the following year. All were alive and released unharmed. This may not sound like a lot when you consider the nearly 26,000 traps removed coastwide since the program began, but it does illustrate the trouble crab traps may cause for diamondback terrapins in Texas. Other states share similar concerns.

Environmental Institute of Houston (EIH) Executive Director George Guillen works with his students to conduct mark-recapture population estimates and radio and acoustic telemetry research on diamondback terrapins in Galveston Bay. “Terrapins are considered the only truly estuarine species of turtle,” he notes, “and their health is directly indicative of the overall health of the estuary.” Unfortunately, very little is known about diamondback terrapins in Texas.

Historical records of diamondback terrapins reviewed by the staff of the EIH date back to the 1880s. These records show that terrapins were common in Galveston Bay and nested on shell islands now under water. The Texas Memorial Museum in Austin houses specimens dating back to the late 1940s. Wildlife biologists with TPWD surveyed crab trap fishermen, other coastal fishermen and game wardens in the early 1980s to determine sightings of terrapins in Texas. About 40 percent of the respondents said that terrapin populations appeared to have decreased over the previous 10 years.

The most extensive study on diamondback terrapins in Texas was conducted from 2001 to 2002 by U.S. Geological Survey researcher Jennifer Hogan. Through monthly surveys, she documented a subpopulation of diamondback terrapins in Galveston Bay using modified crab traps, lagoon surveys and nesting and basking surveys. She captured 135 terrapins and scientifically described for the first time a diamondback terrapin nest in Texas.

Throughout the diamondback terrapin’s range, they are protected to varying degrees — with measures such as closed seasons for harvest, size and bag limits and full protected status with no collection of wild specimens. However, before 2007, there were few protective measures in place in Texas. In light of a possible export trade opening up, and considering that available information indicates that the species could not withstand an increase in harvesting, the TPWD Coastal Fisheries Division proposed a regulation that prohibited the possession of wild-caught diamondback terrapins.

While it might seem odd that the Coastal Fisheries Division would be involved with diamondback terrapins, where they are found (coastal marshes) and the gear by which they would likely be taken (crab traps) do fall under the division’s supervision. The regulation went into effect Sept. 1, 2007.

Other folks are getting into protecting Texas terrapins as well. In October 2008, noted naturalist Tony Amos with the Animal Rehabilitation Keep at the University of Texas Marine Science Institute in Port Aransas discovered 14 hatchlings roughly the size of quarters washed up on the Mustang Island beach a few weeks after Hurricane Ike ravaged the upper coast.

Thinking of them as refugees, Amos and staff took care of them over the winter with intentions of releasing them back to the wild the following spring. Twelve survived the winter holiday and were released in the spring. Speculating that they were originally washed out from the Galveston Bay area by the big storm, George Guillen of EIH took eight of the now coffee-cup-sized terrapins and gave them a resurrection of sorts back in the Galveston Bay marsh. The others were released near Matagorda Island and Port Aransas.

When asked why efforts should be made to rehabilitate diamondback terrapins, Amos responds: “For terrapin society, it’s a matter of survival. We benefit from this being just one of the whole variety of interesting animals that make this planet a desirable place for us to inhabit.”

Currently, diamondback terrapins are a species of special concern to Texans. While we may not know much about this shy and elusive creature, research currently being conducted by Guillen and his graduate students may shed some light into the terrapin world. As public sentiment grows to assist the terrapins — like the Blackhawk helicopter pilot who asked permission to exit the craft to remove a hatchling terrapin from the tarmac in Corpus Christi last spring — there is optimism. Threats still exist, but with a little bit of help from its friends, the diamondback terrapin has a radiant future as the jewel of the marsh.

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