Sea turtle season marked by high nest numbers but also high tides, predation

November 08, 2023

Media contact: Erin Weeks, 843-953-9845, WeeksE@dnr.sc.gov

South Carolina’s sea turtle nesting season officially concluded this week with a total of 6,628 nests for the state – a higher than average year that was tempered by losses from tropical storm Idalia, high tides and predators.

Two loggerhead sea turtle nests kicked off the season on May 2, 2023, and nesting peaked in the first full week of July. Loggerheads lay the vast majority of nests in South Carolina, but 2023 also saw 19 green and two Kemp’s ridley sea turtle nests.

In late August, Idalia moved into South Carolina as a tropical storm and grazed the southern coastline.

"Idalia was a trifecta of water issues," said South Carolina Department of Natural Resources (SCDNR) biologist Michelle Pate, who oversees the agency’s nest protection program. "We had a supermoon, king tide and tropical storm all at once."

The tide, rain and storm surge flooded many coastal beaches, washing away sea turtle nests and habitat in the process. The storm took a particularly heavy toll on Edisto Island and the Cape Romain National Wildlife Refuge, where significant nest losses occurred. All told, SCDNR biologists estimate 600 nests drowned or washed away due to Idalia.

Idalia and king tides (unusually high tides that occur around new and full moons) accounted for two-thirds of 2023’s nest losses, with coyotes, raccoons and armadillos responsible for much of the remainder. Sea turtles have evolved to take some losses in stride; loggerheads nest along a vast stretch of coastline over a long season, limiting the impact of individual storms and predators. But combined with continually eroding beach habitat, these individual threats can become a ‘real issue,’ Pate said.

"The increased number of false crawls showed that nesting mothers had to make multiple attempts to find a good spot on the beach," Pate said. "Then, water issues and increased coyote and armadillo depredation took a toll."

As usual, two islands in the Cape Romain National Wildlife Refuge – Cape and Lighthouse Islands – saw the highest nest density, comprising nearly half (43%) of the state’s total nests. This undeveloped, dark part of the coastline typically sees the greatest nesting activity and is monitored by a small and dedicated team of U.S. Fish and Wildlife Service staff and volunteers.

As usual, two islands in the Cape Romain National Wildlife Refuge – Cape and Lighthouse Islands – saw the highest nest density, comprising nearly half (43%) of the state’s total nests. This undeveloped, dark part of the coastline typically sees the greatest nesting activity and is monitored by a small and dedicated team of U.S. Fish and Wildlife Service staff and volunteers.

Sea turtle nest numbers have been trending upward not just in South Carolina but across the southeastern coast in the past decade. The 2019 season marked an all-time high for our state with 8,792 nests, followed by 5,562 (2020), 5,638 (2021) and 7,968 (2022) nests. High nest numbers are good news, but they’re only part of the equation – the federally threatened loggerhead still has significant milestones to meet before federal officials consider them ‘recovered.’

"If we can’t get hatchlings to emerge and make it to the ocean, then an increase in nest numbers doesn’t help," Pate said.

A tentative estimate of 387,608 hatchlings made it to the ocean from South Carolina beaches in 2023. Only a fraction of sea turtle hatchlings survive to adulthood, but every survivor makes a difference in this protected population.

How to Help Sea Turtles in the Off-Season

Sea turtles don't disappear from our coast after nesting season – some use South Carolina's coastal waters year-round. Here's how you can help in the off-season:

• Boat carefully! Keep an eye out for wildlife while boating, particularly in small tidal creeks where young sea turtles like to feed.
• Report any stranded or dead sea turtles to our 24-hour hotline at 1-800-922-5431.
• Check-Off for Wildlife when completing your state tax returns. Help SCDNR keep wildlife in your life by checking off your contribution to the Endangered Wildlife Fund during the tax season.