August 12,  2008

Sea turtles are nesting on the seashore in record numbers

By JORDAN TOMBERLIN



Late one August evening, just a little north of ramp 43 in Buxton, 15 baby loggerhead sea turtles, each one smaller than the palm of your hand, patiently awaited nightfall, when they could finally begin a long and harrowing journey to maturity—a journey that few, if any of them, would survive. 

 The hatchlings were found earlier that day, during routine excavations of two hatched sea turtle nests, one in Avon village, and one in Buxton, just south of Cape Point.

“You hope you don’t find these,” said Michelle Baker Bogardus, lead sea turtle biologist at the Cape Hatteras National Seashore, as she removed a live hatchling from the Avon nest during excavation. “It usually means that they’re weak, but this little guy is really energetic, so that’s a good sign.”

The Avon hatchling was joined by 14 other hatchlings from the much larger Buxton nest, and just after the last rays of sunlight had disappeared, the hatchlings were placed on the sand, one by one, and began making their way toward the water.

Just minutes after hitting the sand, the turtles had to fend off one of their most relentless predators—ghost crabs—which swarmed the site in spite of the human presence, attempting to attack the hatchlings at every opportunity. And they had to battle the surf, which kept pushing them back on shore just as they were making progress.

Releasing the turtles directly to the water would seem like the nicest way to let them go, but because turtles return to nest on the same beaches they were born, they have to imprint the sand.
And as it turns out, getting to the water is the easy part. They have twice as much to worry about when they start swimming.

Their ultimate destination is the Sargasso Sea—an area miles out in the Atlantic that has an abundance of sargassum, a kind of sea grass that doubles as a place for the turtles to feed and a place for them to hide. Turtles will spend years hiding out in the sargassum, ostensibly growing and gaining strength, though, according to Bogardus, we don’t really know what they’re doing out there.  

“Their whole ability to survive really depends on them swimming as far and as fast as they can,” says Bogardus. So, rather than absorbing their yolk at a consistent, steady rate during their incubation, sea turtles wait, absorbing the majority of the yolk a few days before they hatch.

Then they use all that energy to hatch, crawl out of the nest, fight off predators, and swim about 48 hours straight, until they reach relative safety. 

“Only about one in 1,000 hatchlings survive to maturity, when they are able to give back to the population,” says Bogardus. “And that’s putting it low.”

Loggerhead turtles are biologically designed to offset the low survival rate. They generally nest every two years, and during a single nesting season, each turtle comes to the shore every two weeks, laying and average of four to five nests per season, each of which contains about 100-120 eggs.

Still, that means that, even if all of the estimated 600 eggs that a nesting turtle lays per year were to hatch, which is highly unlikely, there might be one hatchling that will survive to replace it. 
Given the difficulty of keeping a stable sea turtle population, it’s not hard to understand why people are so excited about the record number of sea turtle nests that have been laid on the Outer Banks this year. 

As of Aug. 9, on Cape Hatteras National Seashore alone (which includes Ocracoke, but excludes the Pea Island Wildlife Refuge or Cape Lookout National Seashore), there were 106 confirmed nests and one dig—a site where a turtle has almost certainly nested, but park rangers are not 100 percent sure. Almost all were loggerhead nests.  Three were green sea turtle nests. 

That’s the highest number of turtle nests on record for Cape Hatteras, besting the previous record by seven or eight nests, and far exceeding the 2007 nesting season, which, with 82 nests, was considered a very good year.  And because nesting season continues through the end of August, it is entirely conceivable that the number of nests could keep rising.  

Not only are there more nests this year, they have, so far, all been very successful nests.

“Biologically, it’s just wonderful,” says Bogardus, who, in spite of her expertise in the field, admits that no one really knows what has caused the recent spike in nests and that it’s far too early to begin picking out variables.  

“There are so many things that affect sea turtles. So many variables go into their nesting, that it would be premature to credit just one thing,” she says. 

Those eager to use record number of nests as evidence for the success of the April 30 consent decree should consider that Pea Island Wildlife Refuge, where beach driving, day or night, has been banned for decades, is also having a banner year.

Last year, Pea Island produced 14 nests.  This year, as of Aug. 4, there were 23 confirmed nests on Pea Island, and, like Hatteras, the distinct possibility of even more.

Cape Lookout National Seashore is reporting 92 nests and 13 digs, as of Aug. 7, and several of the digs will probably turn out to be nests. Seashore biologist Michael Rickard says he expect the year will turn out to be close to average, which is about 125 nests.

And the entire state of North Carolina is doing really well.

According to Matthew Godfrey, senior turtle biologist with the North Carolina Wildlife Resource Commission, the average number of North Carolina nests, based on data from the past 13 years, is about 715. As of now, he estimates a total of about 785 nests across the state.

Though the reasons behind the nest boom remain hazy for now, the importance of North Carolina’s nests to the sea turtle population are crystal clear.

While excavating the Avon nest, just a couple hundred yards south of the pier, Bogardus pulled out a temperature gauge, which had been placed in the nest to document the temperature during incubation.

“The sex of a sea turtle is determined by the temperature at which they incubate,” she explained. Nests laid in cooler temperatures will produce more males, while nests that incubate in warmer temperatures will yield more females.

Because Cape Hatteras, located in a temperate climate zone, is the northernmost boundary for nesting sea turtles, the nests here generally yield more males, and since 90 percent of loggerheads nest on the subtropical beaches of Florida, the success of the 10 percent laid on other, cooler beaches to the north is crucial to the health of the species. 

“Most people don’t know how important our nests are. Without the male population produced here, the whole North Atlantic population could be ruined,” Bogardus says.

It would be almost impossible to overestimate the fragility of sea turtle eggs, and with so much riding on the success of these delicate nests, the Park Service adheres to strict, often unpopular, management practices to ensure the health and safety of every nest on the beach.

Each morning during nesting season, around 5 or 5:30, teams of park rangers patrol the beaches looking for evidence of turtle activity. When a nest is found, the site is carefully examined, roped off, and closely monitored until it hatches—usually anywhere from 50 to 90 days after it’s been laid. 

In the event that a nest must be moved, usually because it has been laid close to the high tide line and is in danger of being washed over, it’s done with the utmost care and precision.

“We measure the dimensions of the original nest, and then we bury the eggs at the exact same width and depth that the mother laid them,” Bogardus explained, as she continued to excavate the Avon nest, which had been relocated closer to the dunes. “We try to keep everything as natural as possible.”

The closures remain small until the nests reach day 50 of incubation, which is the earliest date that the eggs could possibly hatch. At day 50, the Park Service expands the closure, roping off 175 feet on either side of the nest and extending the closure all the way to the water.

Unfortunately, in the case of nests laid close to the dunes, which is actually the best place for them to be, this results in an almost complete beach closure.

The park also puts up a “filter fence” at day 50—black tarpaulin material, about two feet high, that surrounds the nest and helps block out artificial lights, including bonfires, which can disorient the turtles and jeopardize their survival.

Bogardus recently related the story of visitors to Avon, who were in touch with her after they had a legal bonfire on the beach about 300 feet from a full beach closure for a turtle nest that had reached the hatch window.

The filter fence extended to the high-tide line, but the turtles hatched at low tide, and as they headed to the water and got beyond the fencing, they were attracted to the bonfire and headed into the fire pit.  The visitors, Bogardus said, did the correct thing, scooping up the hatchlings before they got to the pit and carrying them to the ocean.

The closures remain as such until three of four days after the nest has hatched, when park rangers excavate the site to determine the outcome of the nest and, perhaps most importantly, to rescue any live hatchlings that, for whatever reason, didn’t make it out.
 
Until Sept. 15, beachgoers are permitted to walk or drive, in areas where ORV use is allowed, behind these closures.  

However, under the consent decree, any nest still in the ground that has reached 50 days of incubation after Sept. 15 will automatically become a full-beach closure—175 feet on either side of the nest, from the dunes to the water—until the nest has hatched and been excavated, which could take up to 90 days, though according to Bogardus, most of the nests this year have hatched around day 60.  

As of Aug. 11, there are 14 nests that will reach day 50 on or after Sept. 15, as well as 25 nests that will reach day 50 by Sept. 1 and so will possibly still be in the ground by the Sept. 15.

According to Bogardus, a lot of these closures will not significantly impact ORV access—some are in villages and others are in protected areas— but several of them will affect access, mostly on Hatteras Island.  And several of the nests are near Cape Point and could bring another closure of that area during the fall fishing season.

“The concern now is how many more nests are we going to get from here on out. Those are going to be the problem nests for access,” says Bogardus. 

It will be a while before we know if the stricter requirements of the consent decree will have any impact on the remaining nests. As Bogardus has frequently pointed out, the survival of sea turtles and the success of their nests depend on a mind-boggling number of variables.

“They’re mysterious,” she says. “Here’s a creature that’s been around for 100 million years. They survived whatever killed the dinosaurs…and it’s amazing to me that we know so little about them.”

What Bogardus and others do know is that they will keep doing everything they can to protect these ancient, enigmatic animals.
And for now, at least, it seems that whatever they’re doing is working.





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