News  Tracking terrapins in the Buzzards Bay estuary

This summer, MassWildlife launched an exciting new project in partnership with Zoo New England to study diamond-backed terrapins in the unique ecosystem of Buzzards Bay. Northern diamond-backed terrapins are medium-sized turtles that have a distinctive diamond-shaped pattern on their shell. They are native to southeast Massachusetts and depend on salt marshes for finding food, laying their eggs, and overwintering. They are listed as threatened under the Massachusetts Endangered Species Act and face threats from habitat loss, pollution, and climate change.  

The number of terrapins has been decreasing in recent years, so an important first step in bolstering conservation efforts is to assess the current status of terrapins in the Buzzards Bay estuary. Biologists from MassWildlife and Zoo New England used a variety of techniques to find turtles and estimate their numbers. Researchers conduct visual surveys by paddling kayaks along a pre-mapped route while scanning the water and shoreline for swimming and basking terrapins. When a single terrapin or group is spotted, the biologist navigates to the terrapin’s location, records GPS coordinates, and notes the terrapin’s activity. These visual surveys will help provide a better understanding of terrapin distribution and how that distribution changes over their active season (April–October).  

To estimate population and movement patterns of terrapins, biologists use a method called mark-recapture. Some turtles are captured, marked, and released; later, another group is caught and the marked ones are counted. Terrapins are caught either by hand, dipnet, or trap. For trapping, three different sites within the study area were chosen that had high numbers of terrapins. During a “trap run,” a mix of small and large hoop nets are baited and deployed throughout the marsh. To eliminate the possibility of drowning, traps are secured to the marsh and kept afloat using buoyant polyethylene “pool noodles.” Traps are set for four consecutive nights and checked every 24 hours.

During this project, terrapin movement is also being monitored using acoustic telemetry equipment. Currently, there are 25 acoustic receivers moored underwater in terrapin habitat, and 30 sexually mature females have been tagged with transmitters. When a tagged female swims within range of an acoustic receiver, the receiver detects the pulse emitted by the transmitter on the terrapin. Data from the receivers will provide valuable insight on the movement patterns, behavior, habitat use, and possible nesting areas of female terrapins.

The first season of terrapin tracking was a success! Between April 25 and August 13, the team caught 915 diamond-backed terrapins. Biologists will now start to analyze the wealth of data that was collected this year. The next steps in this project are to establish a framework for long-term terrapin monitoring in Buzzards Bay and to identify and prioritize conservation needs in Massachusetts and regionally.

Northern diamond-backed terrapin fast facts:

Common name: Northern diamond-backed terrapin 
Scientific name: Malaclemys terrapin 
Size: Females: 6–9 inches long. Males 4–6 inches long.  
Range: Along the Atlantic coast from Massachusetts south to Florida, along the Gulf coast from the Carolinas to Texas.  
MA Conservation status: Threatened 
Federal conservation status: Not listed

Fun facts:

• Diamond-backed terrapins are the brackish water turtle species in Massachusetts, but they are still sometimes confused for sea turtles. 
• A single female may lay 1-3 nests per year, with each nest having approximately 12 eggs.
• Temperature determines if hatchlings are male or female. Eggs will develop into males if temperatures are below 82º F and will develop into females if temperatures are above 86 º F. When temperatures range between 82 and 86 º F, there will be a mixture of males and females.
• Terrapins forage in the water and feed on crabs, mollusks, crustaceans, insects, fish, and carrion.
• Diamond-backed terrapins get their name from the diamond patterns on their shells. They pattern and colors are highly variable and no two terrapins look exactly the same.