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CITIZEN SCIENTISTS: Spotting diamondback terrapins for data-collecting comes with its own setbacks

At the edge of a saltwater creek behind Masonboro Island, where the rippled water stills to meet green groves of Spartina, Elizabeth Colhoun, education and stewardship specialist for the NC Coastal Reserve, spots something in the water. Just for an instant it was visible, but by the time I put down my paddle and look toward where she was pointing, it had vanished. Still, she saw it and it counted.

?: John Wolfe paddles out with Elizabeth Colhoun and Rachel Shoemaker to spot terrapins for data-collecting. Photo by Elizabeth Colhoun.

DATA COLLECTING: John Wolfe paddles out with Elizabeth Colhoun and Rachel Shoemaker to spot terrapins for data-collecting. Photo by Elizabeth Colhoun.

“Sometimes you’ll see something small and dark bobbing in the water, and if you’re not sure what it is, you keep looking,” she tells, “and if it keeps floating or bobbing, it’s probably just a stick or the edge of an oyster reef. But if it disappears, it’s a terrapin.”

Colhoun takes note of it on her cellphone, picks up her paddle, and keeps scanning the marsh. “They’re not easy to spot,” she assures. She’s right; despite my best squinted attempts, and the visual endeavors of Rachel Shoemaker, the work-study assistant out here with us on a bright April morning, our brief encounter will be the only glimpse of a diamondback terrapin for the day. Perhaps other teams of volunteers will have more luck.

We are participating in the fourth annual Terrapin Tally, a data-gathering and community outreach event organized by the NC Coastal Reserve, in conjunction with the NC Wildlife Resources Commission. There are 11 other groups paddling routes which span the entire 8 1/2-mile length of the island; today is one of six data collection sessions spanning three weekends, something Hope Sutton, stewardship coordinator for the NCCR and site manager of Masonboro Island, calls a snapshot or blitz approach.

“The idea is to get some kind of repeatable process so we can build a data set over time,” Sutton tells. “That helps us make some projections about relative abundance and density, and even potentially population trends.”

Volunteers—of whom Sutton calls “citizen scientists”—are used because spotting terrapins is a relatively simple thing to do, scientifically speaking. But gathering the data requires more time and people than the NCCR has in the necessary quantities. Plus, it’s a fun way for the non-professional scientific public to engage with and learn about the natural resource. Sutton says some people are better at spotting terrapins than others, something she half-jokingly calls “turtle mojo.”

Maybe my own mojo is off this morning, but other factors are at play. If the wind is over 11 mph, the ripples in the water make it even more difficult to spot a tiny turtle head poking above the surface. “We have seen fewer terrapins,” Sutton says, referring to the data-collecting they’ve endured in prior years. “But because of all the different variables, we aren’t saying this is a decreasing trend at this point. With science working the way it does, you don’t want to start making assumptions, or trying to say there’s a cause and effect relationship when you don’t have enough data to say for certain.”

Diamondback terrapins are the only truly estuarine reptile in North America. This means they can live in water that is fully salt and fully fresh—and any mixture in between —“a pretty unusual thing to be able to do,” according to Sutton. Found in the narrow strip along the coast from Massachusetts all the way down and around to the Gulf Coast of Texas, these turtles help keep the food web of the salt marsh in balance. They eat periwinkle snails, which, if left unchecked, can devour the Spartina grass essential to almost every living thing in the salt marsh—the same marsh which humanity relies on, not just for recreation or natural beauty, but for its function as a seafood nursery, and for water filtration and storm protection. Terrapins are a priority species and a species of special concern in North Carolina, which means in large part there’s not enough data to tell if they’re in trouble or not.

But if there is something going on, Sutton warns how local extirpation (all of them vanishing from one area) can happen quickly. “They don’t travel far, and it takes them a long time to repopulate an area,” she says.

Around the turn of the 20th century, diamondback terrapins were plentiful enough to act as a food source for the local people. “We know on an anecdotal level [from fisherman’s stories, etc.] the population density is nowhere close to where it had to have been back then,” Sutton says. It is more-than-likely due to overharvesting by humans, and an overall decrease in both area and quality of the turtle’s habitats as more and more humans move to the coast and develop the marshes in which they live.

“Roads are also a big problem for them in areas where females are trying to get from feeding sites to appropriate nesting sites,” Sutton says. Perhaps one of the largest threats to terrapins today comes from the blue-crab fishery: A terrapin will venture into a crab pot in search of an easy meal, become trapped, and, since they are reptiles which need to breathe air, they drown. As Colhoun, Shoemaker and I paddle, we record spots where we see the telltale foam buoy, which denotes a crab trap lurking underwater. We spy far more of these today than terrapins.

The mission of the NC Coastal Reserve and National Estuarine Research Reserve, which Masonboro Island is a component of, is to do research which helps inform management decision-making. That’s why NCCR is working with NC Wildlife on this project: They hope their research will understand and find ways to minimize the impact blue crab fisheries (a large and important one in NC, since we actually produce more crabs yearly than Maryland—maybe a fact Baltimoreans will not admit) have on terrapins. Sutton also hopes protocols they are developing can be applied to collecting terrapin data range-wide, from Massachusetts to Texas. She is currently applying for grant funding to develop an app for tracking terrapins.

“[Our ultimate goal is to] collect long-term data [through monitoring of water quality, meteorologicsal data, and biological data] that allow the research community to have an understanding of how the nation’s estuaries are doing,” Sutton says.

I can’t help to ask the obvious: How are the estuaries doing, exactly? Sutton laughs. “Well, in some places they’re doing quite well, and in other places they’re quite challenged. I would say our sites are in pretty good shape.”

On this morning, under the wide cerulean sky, where ospreys soar and dive for fish, amidst flocks of least terns and red knots basking on sunlit sandbars, as ghost-white Great Egrets stalk fish along the edge of the marsh, even though I didn’t spot a diamondback terrapin, I have to agree with her.

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