Bald Head Island Conservancy

Get to Know Diamondback Terrapins

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By Heather Bariso, Coastal Educator

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The Diamondback Terrapin (Malaclemys terrapin) is a species of Special Concern in North Carolina. They get their name from the diamond shaped swirls on their shells. Each scute, or shell scale, has a unique pattern of whorls that makes each turtle different. Skin color and pattern varies between turtles as well! Some can have white skin with black lines, gray skin with black dots, or a mix of the two. I call these amazing little turtles the “fingerprints” or “snowflakes” of the turtle world, since no two look exactly alike! 

These turtles are sexually dimorphic, meaning the males are much smaller than the females. Females need to be much bigger since they have the challenging job of carrying the eggs and finding a suitable nesting habitat. Female terrapins will climb up the bank of a salt marsh into more sandy vegetated areas and use their powerful back legs to dig a hole. There she deposits 7–15 eggs, which will incubate for 60–100 days. The babies know just what to do after they chew through their eggs and return to the salt marsh, where the cycle begins again. 

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Since there is such variability between their looks, you might be wondering, “how do I identify a terrapin?” One way to determine if it’s a terrapin is to assess your location. Terrapins are one of the only turtles (aside from sea turtles) who are able to live in the salt marsh. They have adapted both behaviorally and physically to spend their entire lives in the salt marsh. Special glands near their eye allows them to “cry” out excess salt to maintain a healthy salt balance. They are able to tolerate a wide range of salinities this way, so their range extends around the Atlantic and Gulf coasts from Cape Cod, Massachusetts, to Corpus Christi, Texas.

One of the easiest ways to identify a terrapin is to take a look at its face. If you see big, tan“lips,” you’re looking at a terrapin! While all turtles have beaks to help them grasp and chew their food, terrapins have some of the most pronounced beaks of turtle species.

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Terrapins, like many of their freshwater cousins, forage for food on the bottom of the marsh. Their diet consists of snails, crabs, clams, mussels, worms, and small fish. Their foraging strategy makes them especially vulnerable to drowning in crab traps. The Atlantic Blue Crab (Callinectes sapidus) is one of the most commercially sought after species in large scale and local crabbing operations. Blue crabs are attracted to the stinky and pungent smell of decaying bait within the crab trap, enter the narrow funnel, and then are unable to crawl back out the way they entered, effectively trapping them. Terrapins follow the same scent and once they enter, they are unable to escape and get a much needed breath of air, effectively drowning and killing them.  

Screen Shot 2024 03 13 at 12.58.24 PMThis species of terrapin was almost brought to extinction due to overharvesting for terrapin soup, as well as unsustainable fishing practices. Now, crab trap mortality threatens to drop their population numbers once again. Due to this threat, the North Carolina Division of Marine Fisheries (NCDMF) created Diamondback Terrapin Management Areas (DTMA) where terrapin excluder devices (TEDs) are required. A TED is an insert that goes into the funnel of your crab trap and allows the entry of blue crabs, but restricts terrapins. If a terrapin does manage to get into the crab trap, the TED allows an opening for it to exit as well, benefiting both crabbers and turtles. Bald Head is one of the DTMA zones, so the island requires that TEDs be used on all crab traps within our creeks.

Although these turtles have proven to be resilient, they still need our help in ensuring their future survival. Luckily, there are steps we can take to help! One of those is to use regulation size TEDs on your crab traps. If you don’t participate in crabbing, you can encourage friends and family to employ TEDs on their traps as well. Additionally, you can take part in population studies on terrapins via the Terrapin Tally! For this survey, kayakers paddle specified routes while searching for diamondback terrapins. Each terrapin spotted is recorded, along with any “ghost” or abandoned crab traps. This data is then compiled to show terrapin population trends over the years and allows marine patrol to assist in crab trap removal!


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