By Mary Pringle for The Island Eye News
How a loggerhead sea turtle chooses a place to nest is sometimes a mystery.
We do know that they can wait in the ocean and scan the shore for lights and other deterrents before crawling onto the beach to lay eggs. But sometimes the beach where they crawl is not the ideal place for their nests to incubate for other reasons, such as the topography of the shoreline.
When a nest is repeatedly washed over by the surf or when groundwater rises into the egg chamber, the embryos that require oxygen will die before hatching begins.
We are told that before groups like the Island Turtle Team started relocating and protecting nests that only about 10% of nests in South Carolina survived. This was discovered by aerial surveys conducted by the South Carolina Department of Natural Resources years ago. Now survival can be as high as 80% or 90%. Last season, every one of our 72 nests produced hatchlings.
This would not have happened if we were not allowed to move them. This season we have relocated the majority of nests.
There are so many ideal spots in the middle sections of the Isle of Palms, and we wish the turtles would find those. Could it be that some are returning to Wild Dunes because 30 years ago when they hatched this area was undeveloped and a better spot for nests?
On the Ocean Boulevard section of the Isle of Palms, south of the pier, the primary dune was lost to Hurricane Matthew in 2016. An emergency scraping of sand at low tide created a berm to protect houses and property there. Since then the berm/ primary dune has been damaged by storms and rebuilt several times. If turtles do not make it up onto this dune but lay on the flat beach or at the foot of an eroded section of the berm, nests are not in a safe place. Tall houses looming over this section of the beach can also create lighting problems for hatchlings from inside lights or recessed lights even if outside lights are turned off.
In Wild Dunes, parts of the north end were severely eroded and covered with sandbags until the most recent major renourishment project was completed in 2018. Turtles will not nest in the wet sand of a narrow beach and cannot nest on sandbags. They instinctively know that they should find an elevated spot and will stop digging if they encounter sand that is too wet. The project that pumped sand onshore created a very wide beach, but there are no elevated dunes there yet. Some years they do not nest much in this flat area, but this season they seem to be using it more. It is too far for them to make it to an elevated spot several hundred yards from the water, and this would be a difficult or impossible trek for the hatchlings anyway.
Sullivan’s Island has historically had fewer nests than the Isle of Palms. The reason for this could be that because of the Charleston jetties, Sullivan’s has always gained sand, making it a very wide beach in some sections where turtles need to crawl for a long time to find a proper nesting spot. The sandbars and gullies at the north end have also been a problem at times. We have always wondered if these features, along with fewer miles of beach than the Isle of Palms, have influenced nest numbers.
This is the eleventh year we have participated in the genetics research project than encompasses the four major Atlantic states where loggerhead turtles nest. Nest location information has been amazingly enhanced by the results of our gathering genetic material from one eggshell from every nest that is laid. We have learned that some loggerheads are very faithful to the area where they hatched and nest there regularly. But people are surprised to know that some do not show this kind of site fidelity. About eight years ago, we had one nesting female who laid her first nest on the Isle of Palms, two weeks later nested on Hatteras Island in North Carolina and two weeks after that on Cumberland Island in Georgia. This location information would never have been known before scientists started identifying every female whose nests were sampled.