Action | Student News

Diamondback Terrapins:
Working Toward a PhD at the Duke Marine Lab

Story and photos by Julia Connors T'04

"Dead fish, dead fish, dead fish..." graduate student Kristen Hart reminds herself as she walks around the corridor to a freezer storing the bait for today's outing. She takes out a garbage bag full of menhaden. "It's what the crab fisherman around here use in their crab pots, and it attracts terrapins, so that's what we use, too." She hands me a bag of frozen fish to carry out to the truck and turns back to the freezer, grabbing another for herself. The sunglasses resting on the top of her head, her flip-flops, old-shirt and quick-dry shorts confirm that she's ready to go back into the field for another day of research.

We load up all of the rest of the gear in our arms-buckets, water bottles, sunscreen, rubber boots and a GPS (Global Positioning System) receiver-and navigate the stairs down to the waiting lab truck, its flatbed already filled with 14 red crab pots and several large buckets.

Kristen and I hop in the truck painted with the Duke University Marine Lab ensignia, as Erin McLaughlin, Kristen's field assistant, goes to retrieve two turtles that have spent the weekend in captivity and need to be returned to the location of their capture. She brings them over to give me my first glimpse at live diamondback terrapins, Malaclemys terrapin, the species of turtle that Kristen has been studying since she was an undergraduate at Boston College. Both turtles have breathtaking black and white skin patterns and varied carapace patterns. The female is much larger than the male, which is typical in the adults of the species. She places the bucket in the bed of the truck and jumps into the cramped cab with Kristen and me.

As the houses grow fewer and we grow closer to the salt marsh where much of Kristen's research is based, she explains why she is studying terrapins. Diamondback terrapins are listed by the U.S. Fish and Wildlife Service as a "Species of Special Concern," and were once extensively harvested. But when their populations began to decline, so did the harvesting. Populations of such turtles appear not to have recovered in the last several decades and remain subject to some harvesting. In North Carolina, there are no real restrictions on size or season for harvesting terrapins.

"They call this road Terrapin Alley because there is so much roadkill of terrapins," Kristen tells me as we cross over the North River on Highway 70 near Beaufort, N.C., home of the Duke Marine Lab. But exposure to car and motorboat hits are only one obstacle that terrapins face in this region today. In North Carolina, the major threat to terrapins is the commercial blue crab fishing industry. Terrapins, which can stay underwater for up to five hours before needing to the surface for air, swim into crab pots and are unable to find their way back out. The majority of turtles caught in commercial crab pots drown.

For her dissertation, Kristen is examining demographics and genetics of terrapins, attempting to better understand their population dynamics and structure in hopes that her research will contribute to future conservation efforts. She gives me an outline of the work she has completed and hopes to complete in the next three years before her intended graduation in May 2004. I'm surprised by the variety of the fieldwork, analysis, conferences, classes, and seminars that she lists as part of the long process toward earning her doctorate in ecology. She explains, "It's a lot of work, but I'm on top of things. I came in with a masters [in Environmental Management in 1999] and that helped a ton to get the fieldwork rolling."

In the plan, Kristen details the five potential chapters of her dissertation, each taking a different approach toward her main goals. Entitled, "Behavior ecology of terrapins in NC and FL," the first chapter concentrates on determining home range, habitat use, and interactions with other species. Other chapters include, "Population genetics in NC and FL," "Mark-recapture studies of terrapins in NC and FL," "Specific conservation application: Bycatch reduction devices (BRDs), terrapins, and blue crabs in NC," and "Diamondback terrapin population modeling."

"I hope to be a research scientist who teaches one course a year. I'd love to have graduate students eventually," Kristen tells me.

Kristen pulls off the highway onto the side of the road and stops the truck. Several small man-made creeks weave through the tall green and brown grasses, creating a viable habitat for terrapins and blue crabs. This area is one of the five sites where Kristen conducts her research in North Carolina.

Climbing into the flatbed, she unloads the crab pots, then jumps down with a bag of baitfish, loads the bait compartment of each pot with two fish and shows me how to set the pots in the creek.

After we set the pots, Kristen tells me, "Now we wait. We'll come back in about three or four hours and see what we caught."

Not a single pot comes up empty; each is filled with several blue crabs, various sizes of flounder and other fish. Only two come up with turtles: two large females, one a recapture from the previous year. We take the GPS location of the turtles, put them in buckets and load them into the truck, then shake all of the large, edible crabs into a bucket, releasing the rest.

I spend a morning in the lab with Kristen and Erin as they do a lab workup on four large turtles. Three are recaptures. Kristen begins her work on the new turtle by taking several body measurements. She then draws blood for genetic testing from the back of the squirming turtle's leg. Afterwards, she takes out a passive integrated transponder (PIT) tag syringe and shows me the massive hollow needle, then injects it deeply into the skin of the turtle under its carapace, pushing the tag into the body in the process. PIT tags contain microchips that give each turtle a nine- to 10-digit bar code. Using this system is an efficient way to keep tabs on individuals within a population. Putting the turtle back in the bucket, Kristen takes measurements and weights of the three recaptures, and then declares that they are ready to be sent back home.

Kristen has decided that I need to learn a little something about the local sentiment towards turtles. So she takes me to C & S Seafood when she goes to pick up her bait, where anti-turtle paraphernalia lines the walls in the cramped office of a crab building.

"Did she tell ya' that we put a bumper sticker on her truck?" the owner asks me as she pipes away on her cigarette. She laughs deeply and reads me the quotation from the sticker, "We like to see turtles swim too-in potatoes and onions."

Getting back into the truck, Kristen explains that not only do terrapins eat the crabs inside the pots, but sea turtles eat the crabs from the outside, often times ripping and ruining the pots in the process. "The crab fishery is a $50 million business in North Carolina-the biggest fishery. I have learned that management options MUST consider impact on local economy and values of individuals in the community. Fishermen are pretty much into conserving resources too. They don't want dead turtles in their pots. They do want better crab catches."

Julia Connors T'04, attended Summer Session II at the Duke Marine Lab in 2001, where she met Kristen Hart.