Tally-ho! Researchers are asking the public to help count diamondback terrapins
The diamondback terrapin is a turtle identified by the North Carolina Wildlife Resources Commission as a “species of greatest conservation need,” so researchers are asking the community to help count them. This year marks the 9th annual ‘Terrapin Tally.’
Elizabeth Pinnix, the southern sites manager for the North Carolina Coastal Reserve and National Estuarine Research Reserve, described what a diamondback terrapin looks like swimming in the marsh.
“So they can be all different colors, different patterns. When you see them against the water, and it's this white speckled head popping out of the water,” she said.
Sarah Finn is the coastal wildlife diversity biologist for the Wildlife Resources Commission. She said the terrapins can be found anywhere from Cape Cod, Massachusetts to Corpus Christi, Texas.
“They spend all their time in the salt marshes foraging on the mudflats. They like to eat periwinkle snails, other little crustaceans and gastropods that they find out there. And they also burrow down into the mud as well when it's wintertime. They brumate when it gets cold so they can stay warmer down in the mud,” Finn said, referring to an amphibian version of hibernation.
Finn added that the diamondback terrapins provide balance to estuarine habitat. If nothing is eating the periwinkle snails, then they can “mow down the cordgrass beds,” she said.
Pinnix said that it’s important to understand the terrapins’ relationship with their habitat, because “they're only found where salt and freshwater meet. And if that habitat goes away, they don't really have anywhere else to go.”
Threats to the diamondback terrapins
Before the Great Depression, the terrapins faced one threat in particular that decimated their numbers.
“They were considered a delicacy. And so they used them to make turtle soup, basically, and their population suffered greatly because of that,” Finn said.
Current challenges facing the terrapins include environmental loss from development, and “hardening of shorelines things like that taking away their nesting habitats that impact their populations. And other things like crab pot mortality, they can get stuck in blue crab pots and drown,” Finn said.
She added that there was a documented case where up to 25 terrapins ended up in one pot and all drowned.
Pinnix said because of the crab pot issue, in 2021 the Division of Marine Fisheries enacted the diamondback terrapin management areas for Masonboro and Bald Head Island Reserves.
“What that did meant that all of the commercial crabbing pots within those two management areas had to have an excluder device installed on the crab pot. And what that excluder device does is it allows crabs to still go in the pot, but the terrapins, their shells are kind of raised up so it keeps them from being able to get in the crab pot and then becoming stuck,” Pinnix said.
Pinnix and Finn said this outfitting of the pots is fairly easy to do. The hope is that blue crab fishermen up and down the coast will take the initiative to use excluder devices on their own.
According to researchers, North Carolina is in limbo for statewide requirements for excluder devices on pots, which are mandated elsewhere, like New York and New Jersey.
As for the outcome of these crab pot protections, Hope Sutton, the eastern wildlife diversity supervisor for the Wildlife Resources Commission, said it will take a while to see results.
“So any kind of management actions that you put into place, there would be a lag time before you could really see whether or not there's a difference. And blue crab fishermen aren't required to report if they've caught terrapins, so we don't really have a solid data set on how things were before that particular management action was taken as compared to now,” Sutton said.
Pinnix said that, like Sutton and Finn, she’s not involved in ordering regulatory actions or creating management plans. But, she said, the data collected from the Terrapin Tally will help “policymakers make science-based decisions to protect [these] coastal species.”
A tricky tally
While the seasonal protections from March to October on Masonboro and Bald Head are likely to increase turtle populations, Sutton said it’s still hard to say how many diamondback terrapins there are.
“Part of this approach that we're using with the ‘Terrapin Tally’, it will require many years of repeated surveys in the same areas, before we can really start saying anything about population numbers, and certainly about population trends,” Sutton said.
She added that diamondback terrapins are “slow reproducing species,” and while sea turtles can lay up to 100 eggs at a time, terrapins only lay about six – and not much is known about the hatchling and post-hatchling stage.
According to Finn, “They'll will emerge from their nests, and then they'll scatter and they basically hide until they're big enough.”
Females, which are larger than males, are about 6 to 7 inches in length. They typically reach adult size when they’re about four years old.
While the overall count isn’t known, last year’s Terrapin Tally recorded some of their highest totals on record.
“So at Masonboro, we had 132 terrapins sightings. And then the second most was up in Morehead City. There's a route back there called Calico Creek, there were 39 terrapins reported. And there are routes at Cape Lookout National Seashore and there were 28 there,” Pinnix said.
This year’s Tally
The diamondback terrapin data collection routes take place over 10 coastal sites, relying on two-person teams to do the count.
“So you can either do a tandem kayak or two singles. And so they're paddling these defined routes that we've created around the high tide. [...] One person will be the navigator and one person's the recorder. And you wait to see their little heads pop up out of the marsh and you'll document that,” Pinnix said.
Volunteers will also document how many crab pots they see via a smartphone app.
Sutton said the tally provides a way for the community to conduct real-life science – and maybe even meet the terrapins for the first time.
“So many people don't even realize they exist. So this is just an opportunity for people to really connect with a species that specifically lives right in their hometown,” Sutton said.
If you want to volunteer for this year’s Terrapin Tally, you’ll need to attend one training session in April – and one of the two-hour data collection dates, which are offered in May or June.
You’ll also need to be a proficient swimmer and kayaker to participate in the tally.
Sign up for a Terrapin Tally training session and data collection date
- Choose One Training Date – In-person: April 13 (6-7:30 at UNCW Center for Marine Science) or April 15 (10-11:30 am at Pine Knoll Shores Aquarium); Virtual: April 11 (6-7:30 via Zoom)
- Data Collection Sessions (Conducted in 2-hour blocks): May 4-7; May 18-21; June 1-4
- Routes available - Cape Lookout National Seashore, Rachel Carson Reserve, Calico Creek, Hammocks Beach State Park, Lea Hutaff Island, Masonboro Island Reserve, Fort Fisher State Recreation Area, Zeke’s Island Reserve, Bald Head Island, and Bird Island Reserve
North Carolina Marine Fisheries 2020 Revision to the Blue Crab Fishery Management Plan