From The Blog
Conserving Diamondback Terrapins on Kiawah Island
Diamondback Terrapin is the only turtle that lives in brackish water. Although their coloring varies, all Diamondback Terrapins have a unique pattern of wiggly, black markings or spots on their body and head. Their feet are strongly webbed with especially large, flat hind feet. They are sexually dimorphic, with the males being significantly smaller than the females in weight and carapace length, though the males tend to be larger in warmer regions. Renowned naturalist Whit Gibbons presided over a lively presentation and answered numerous questions from the audience.
Whit has been studying Kiawah’s abundant natural wonders since the 1970s. In 1983, his son caught his first Diamondback Terrapin here on Kiawah. Whit noted that his naturalist group captured this same terrapin, identified by a mark made on its shell when it was first captured, in 2005 and then again in 2007. Whit emphasized that Diamondback Terrapins have wonderful longevity when allowed by the environment to survive.
Utilizing a series of slides, Whit discussed the dramatic decrease in Diamondback Terrapin population on and around Kiawah. For example, he said that a local creek (referred to as “Terrapin Creek” by Whit) has always been highly populated area for the diamondbacks. When Whit did the first seining of this creek, 27 terrapins were found. Even after Hurricane Hugo hit in 1989 they were still abundant, but they have since disappeared from this creek. He also noted Fiddler Creek (known locally as Cinder Creek) as another dramatic example. There used to be approximately 400 Diamondback Terrapins in Cinder Creek, but recent studies have found less than 100.
Whit believes that there are three major reasons for this decline in population:
• Habitat loss and/or degradation, principally over-development and run off from development,
• Road mortality, and
• Crab traps.
Of these, Whit believes that the crab traps have killed the most Diamondback Terrapins on Kiawah. They get caught in the crab traps, can’t swim back out and ultimately die.Whit also showed us data that demonstrated that the average size of Diamondback Terrapins in our area is getting larger due to the smaller (male) Diamondback Terrapins getting killed more often than the females.
In his early studies, 20-30% of the Diamondback Terrapin population was female, while 50% are females today. Since females are larger, they are not caught as often in the crab traps, though Whit believes the entire Diamondback Terrapin population on Kiawah is at risk.
Since Diamondback Terrapins are solid indicators of the health of Kiawah’s waters, their recent decline in population is an urgent problem. Whit cited the following actions as necessary to improve their survival:
• Remove “ghost crab traps.” These are crab taps that are no longer being used, but that are still in the water, capturing and
killing Diamondback Terrapins.
• Install By-catch Reduction Devices, known as BRDs, which create smaller openings in the crab traps, keeping most Diamondback Terrapins from entering. Also, don’t leave a crab trap in the water if you no longer intend to use it. (Note that crab traps are prohibited in Kiawah’s lakes, lagoons and ponds due to the depletion of the crab population.)
• Advocate for Kiawah’s natural habitat and the Diamondback Terrapins. Make sure that areas like Terrapin Creek and Cinder Creek, which are home to Diamondback Terrapins, fully support these beautiful turtles. Degradation of these areas not only impacts the Diamondback Terrapin, but also glass lizards and coach whip snakes which require a healthy environment to reproduce and thrive.
The next Conservation Matters presentation, to be held on March 4 at 1 p.m. at the Sandcastle, will feature a presentation by Karl Ohlandt on Sweetgrass.. For more information on the series, or on the conservancy, please visit www.kiawahconservancy.org