Sea turtle recovery not as certain as it seems
The numbers are staggering — more than 4,600 sea turtle nests in 2012, the nests doubling in two years, three straight years of thousands of nests laid along the coast.
But the numbers are deceptive.
Nesting by the beloved, threatened loggerhead and other sea turtle species might well be increasing along the South Carolina coast. But more beaches than ever are monitored for nests, adding to the count in recent years. The experts pay closer attention to the “index beaches,” six of the densest nesting spots along the coast, where data has been recorded consistently since 1982 and the increases are spottier.
Now investigators are looking for better answers, CSI-style, with DNA turtleprints.
The S.C. Department of Natural Resources just released its 2012 sea turtle nest numbers indicating another year of what appears to be steadily climbing totals; the index beach nest numbers show an unprecedented high of about 2,000 nests. But that comes after an unprecedented low of fewer than 400 in 2004. From 2004 to 2012 the index beach numbers have increased and declined in the same range as the 20 years before 2004.
“There are definitely more turtles out there,”said DuBose Griffin, DNR sea turtle program coordinator. But “there’s nothing to say we won’t see (2004 numbers) next year.” For now, the assessment of the species’ recovery remains “cautiously optimistic,” she said.
For creatures that have been managed as endangered species for more than 30 years, sea turtles remain a mysterious species that spends most of its life unseen in the ocean.
Nobody can really estimate how many are out there — critical information for managers trying to judge decline or improvement. The only real data comes from the nest counts. Nobody really knows why the nesting numbers can vary so widely — literally by the thousands — year to year.
Until now, researchers could do little more than speculate how often females come ashore to lay eggs and whether they lay eggs at more than one spot. They could only tag females they caught coming ashore at night, maybe 100 per year in a good year.
For the most part, researchers couldn’t say what turtle laid what nest. In fact, though it’s considered a given that mature females return to nest along the beaches where they were hatched, nobody could really say precisely how they do.
All those unknowns are big questions when you’re trying to manage the recovery of a species.
Since the turtles were put on the federal endangered species list in the 1970s, the numbers of Atlantic nesting turtles generally were thought to be in severe decline in Florida, where the overwhelming bulk of nests are laid, and a more gradual decline in South Carolina, where the most nests outside Florida are laid. The states are the two largest-by-numbers nesting grounds in the world for loggerhead turtles, which lay the overwhelming bulk of the nests.
Protections were put in place one by one. Maybe the most significant one: In 1988, South Carolina became the first state to mandate turtle excluder devices on shrimp boats. It takes two to three decades for the long-lived loggerheads to mature sexually, so the nest increase now should be reflecting a better-survived generation of hatchlings.
To get a surer read on that, genetic testing samples are being pulled from egg shells in South Carolina, Georgia and North Carolina. So far, more than 21,000 samples have been taken and more than 5,500 individual females identified.
“It’s unprecedented work being done nowhere else,” Griffin said.
Joe Nairn, conservation genetics professor at the University of Georgia, can say confidently that females lay more than one nest and some individuals as many as seven during egg-laying years. But they don’t lay eggs every year.
One female has laid five nests on the same beach within a third of a mile; another laid nests on adjacent islands.
“We can tell each turtle apart,” Nairn said. “We can tell which turtle laid what nest.”
And the data base ought to be able to identify from which mother came individual nest-laying females when they flipper ashore for the next generation of laying.
“We have generated an enormous data set,” said Nairn, who is working with Brian Shamblin, a post-doctoral student who adapted the technique from ornithology.
The bottom line is that turtle conservation managers might soon have answers to questions such as where turtles tend to go to lay eggs if their nesting beach is lost — critical to know along a coast of eroding barrier islands.
“More information so they can make better decisions,” Nairn said.Reach Bo Petersen at 937-5744, @bopete on Twitter or Bo Petersen Reporting on Facebook.