Cracking the Code: How Lowcountry Turtle Teams Are Using DNA to Save Loggerheads

Lowcountry turtle teams join in loggerhead studies

Story + Photography by Carol Weir

A partnership between Sea Turtle Patrol Hilton Head Island, a genetics researcher at the University of South Carolina Beaufort and a University of Georgia scientist is unlocking the hidden lives of loggerhead sea turtles — without tagging the turtles.

Kim Ritchie, USCB’s director of research at Pritchards Island, leads student interns and volunteers who locate nests on the USCB-owned barrier island near Fripp. Amber Kuehn heads Hilton Head Island’s Sea Turtle Patrol, a nonprofit supported by The Town of Hilton Head Island. They’re both collaborating with Brian Shamblin of the University of Georgia on DNA studies intended to deepen scientific understanding of loggerheads and guide conservation efforts.

Eggshell forensics

Shamblin, a researcher at UGA’s Warnell School of Forestry and Natural Resources, began his study on loggerhead maternal DNA in 2008 after his team isolated microsatellite markers — short DNA sequences unique to loggerheads. Using a technique similar to human forensic identification, he made a breakthrough when he matched an eggshell to a previously tagged mother.

Hilton Head Island joined the study in 2010. Since then, turtle patrols in South Carolina, North Carolina and Georgia have collected a single eggshell from each new loggerhead nest, preserved it in ethanol and sent it to Shamblin’s lab. But starting this year, the first steps in this process will now take place in the Lowcountry.

A lab of their own

Thanks to fundraising by Sea Turtle Patrol HHI and a grant from the Palmetto Dunes Cares Foundation, Kuehn recently purchased genetics lab equipment. Ritchie, a trained geneticist, will teach Kuehn, lab manager Skyler Griffin and volunteers how to use the DNA thermocycler (also called a PCR machine) and other tools. With this equipment the scientists will create many copies of a target DNA sequence, allowing for further analysis. Ritchie is buying similar equipment for her work with USCB students on Pritchards Island. Using this technology, the teams will extract DNA from the eggshell’s inner layers, which hold the mother’s identity.

When funding ebbs

Shamblin welcomes the assistance. Analyzing samples is costly, and his federal funding was cut when loggerheads in the population he studies were downgraded from endangered to threatened under the Endangered Species Act.

“We depend on donations to continue this research,” he said. “Everything the folks on Hilton Head can do on the front end relieves pressure on us.”

His study has already identified nearly 16,000 unique nesting loggerhead females in the region.

Why DNA beats guesswork

“Sea turtles spend most of their lives in the ocean, so it’s hard to observe them directly or track them with tags,” he said. “DNA from eggshells gives us a way to build a census of nesting females and track long-term population trends.”

His lab now receives over 8,000 samples annually. DNA is extracted, and the data is uploaded to seaturtle.org, where it informs models that predict how turtles will respond to threats like climate change or coastal development.

Traditionally, scientists around the world estimated turtle population health by counting nests. But since females lay multiple nests in different areas each season, genetic fingerprinting offers more accuracy.

Born to return

Sea turtles nest in the same magnetic zone where they were born — South Carolina, Georgia and North Carolina share one. Like birds, they use Earth’s magnetic fields to guide migration and nesting.

“Many older turtles hone in on a specific area over time,” Kuehn said. “We have one female that only nests on the north end of Hilton Head, within 300 feet of her previous nests. Another nests up and down the coast. They are all over the board.”

In 2024 Kuehn’s team collected DNA from 204 Hilton Head nests. Results revealed 62 nesting females, including 16 first-timers. Five were daughters of known turtles, and three were the first “grand-turtles” recorded returning to the area. Pritchards Island began DNA collection two years ago. Since loggerheads take about 30 years to mature, turtle research requires long-term commitment.

What the data shows

The study is answering questions such as: How many nests does a female lay? How often does she return? Ritchie sees it as a rare teaching opportunity.

“It’s exciting to involve USCB students in nationally impactful field research,” she said. “Comparing Hilton Head and Pritchards islands can help us understand more about sea turtle behavior and conservation. It’s also a fantastic training tool for students in lab and field methods.”

Looking for loggerhead dads

Last year Shamblin began a new study about loggerhead paternity, and Hilton Head Island was invited to join the effort. To learn about the fathers, Kuehn’s team collects flippers from dead hatchlings.

“We don’t know much about loggerhead males,” Kuehn said. “They are a mystery.”

A single female can mate with multiple males before laying her first nest. Their sperm fertilizes different eggs in the clutch. The paternity study explores critical unknowns including:

• Mating frequency and the order in which sperm is used

• Male breeding behavior and how many nests they fertilize

• Overall male population size

“The majority of nests have just one dad,” Shamblin said. “But some have two, three or even four.”

Hot topic: Nest temps

Ritchie and Kuehn are also collaborating on a nest temperature study. Temperature determines hatchling gender — warmer nests produce more females; cooler ones, more males. With climate change in mind, scientists want to monitor gender balance and assess nest survival and health. In nests on Pritchards and Hilton Head islands, Ritchie places devices that send a constant stream of temperature readings. Kuehn’s team retrieves the devices on Hilton Head Island after the hatchlings emerge.

Team turtle

Behind all the turtle science are thousands of people getting up every day before sunrise and spending hours on beaches searching for sea turtle tracks in the sand. Shamblin, Kuehn and Ritchie agree that these volunteers are vital to both the research and the species’ survival.

“We couldn’t do this without beach cooperators,” Shamblin said. “It’s a true team effort—science, community and conservation coming together to protect an ancient species.”