Neither A Sea Turtle nor a River Cooter: Our Special Coastal Terrapin

Most residents of our area have never encountered this beautiful aquatic reptile the Diamondback Coastal Terrapin. Population numbers are small, and they live in a very narrow band of habitat where our coastal salt marshes and sea grass beds occur. All told, we have 7 sub-species of diamondback terrapins along the Gulf and Atlantic coasts of the U.S. and Florida has 3 that don’t occur outside the state. There are also two on Florida’s Atlantic Coast that range farther north and one sub-species occurs all the way up to Cape Cod. This makes Florida a critical component of this animal’s habitat, comprising about 20% of the entire coastal range of the species. Our local sub-species of terrapin is identified as the “ornate diamondback terrapin” (Malaclemys terrapin macrospilota). It is unique in coloration from the other sub-species with its dark scutes on the back that have yellow or orange centers. The light gray skin of the head, neck and legs is covered with dark dots but there can be much variation in the size and number of dots. Many people think these pale-skinned turtles are albinos when they see them but this is not the case. Our ornate sub-species ranges from Florida Bay in the south of the state up to the western panhandle.

The ornate diamond back terrapin lives in some of our coastal bays and tidal creeks
The ornate diamond back terrapin lives in some of our coastal bays and tidal creeks

Throughout their native range terrapins share their habitat with another species that has been linked to precipitous declines in the reptile’s population. It is not, as you might suspect, due to a predatory or parasitic relationship but it is related to the fact that we love to eat blue crabs. In the process of setting crab traps to catch crabs in terrapin-inhabited waters, diamondback terrapins are inadvertently trapped. Terrapins are carnivorous and will enter crab traps to eat the crab bait. If the trap is submerged for very long the air-breathing reptiles ultimately drown. Terrapin enthusiasts around the country have been working to mitigate this issue by encouraging the use of a simple rectangular plastic frame that excludes most of the turtles from the traps and allows legal blue crabs to enter. It has been proven that the use of this excluder does not reduce crab catch rates either. They call the device a BRD (Bycatch Reduction Device) and the simplicity of using a BRD is simply, well, simple! The payoff is more living adult terrapins to perpetuate this unique species.

BRDs are installed by securing them into the funnel openings of crab traps. Generally, they are secured with plastic zip-ties. A picture of one installed in the funnel of a crab trap may be seen at:

If you live in an area where you have observed terrapins and you are also deploying crab traps, I may be able to get some BRD’s for you to install so email me at Typical habitat for terrapins in our area would include tidal creeks that flow from salt marshes into a bay or lagoon. Even if you don’t see the turtle itself, keep your eyes peeled for signs of tracks going up sandy shores to higher ground. Also, nests are often depredated by racoons and you may see the oblong 1.4-inch white egg shells scattered about. Nesting occurs from May through July so right now is prime time.


Posted: June 25, 2019

Category: Coasts & Marine, Natural Resources
Tags: Aquatic Reptile, Atlantic Coast, Coastal Terrapin, Crab Trap, Diamondback, Florida Panhandle, Gulf Coast, Terrapins

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