By Mary Pringle for Island Eye News
This is the tenth year that the Island Turtle Team has participated in a multi-state genetics research project by collecting a DNA sample from every nest that is laid in our project area. This is happening all along the coast from North Carolina to Georgia and now even in many areas of Florida as well. This is known as the Northern Recovery Unit, and there is cautious optimism that the population of this species of sea turtle is beginning to rebound after a long period of decline.
Since our loggerheads are part of a distinct subpopulation and do not interbreed with those in Florida, it is vital that they be protected.
The list of questions from SC Department of Natural Resources this project might answer includes:
- How many clutches of eggs does each nesting female lay in a year?
- Is the female nesting on more than one beach?
- How far apart are her nests?
- How many turtles are nesting in more than one state?
- Most individual females do not nest every year. How often does each turtle nest: every two years, three years, four or more years?
- How precisely does a daughter return to her hatching site to lay her eggs?
Since the Turtle Team began, we have seen amazing advances in the way we report nesting results. I remember sending in a handwritten sheet by snail mail to DNR on James Island with our nesting report at the very end of the season. Now we submit data online to seaturtle.org immediately giving every detail about each nest including the GPS location. The results of each nest are compiled by the end of the season in the fall. This happens with every nesting beach from North Carolina to Georgia and is updated daily.
In previous decades the only methods for scientists to track turtles was to tag them with metal flipper tags, imbedded chips and occasionally very expensive satellite transmitters. But these turtles were seldom seen again, tags were lost and transmitters stopped working. Our samples are sent to the University of Georgia where our samples are analyzed. A maternal nuclear DNA sample is found between layers of the inner shell of each egg. This means that even turtles nesting on remote uninhabited barrier islands can be identified.
The first nineteen of our 47 Isle of Palms nests laid by July 10 have already been analyzed. We don’t have results from any of the ten Sullivan’s Island nests at this time.
Here are some highlights with the numbers assigned to these nesting females:
#1415 is a regular visitor to the Isle of Palms laying Nest #5 at 33rd Ave on May 18 and Nest #19 on June 1 fourteen days later. She has visited us 20 times either 4 or 5 times a year in 2010, 2012, 2014, 2016, 2018 and now in 2019. It is unusual for one to lay eggs in consecutive years as she is doing this year. Normally after laying so many nests in a season, they take a year off to rebuild their nutritional condition.
#2992 really prefers the north end of the island near Dewees Inlet. This season she laid Nest #3 at the 17th tee and Nest #14 at Ocean Point two weeks apart. She previously nested up there always in odd numbered years in 2011, 2013, 2015, and 2017. She did visit Sullivan’s once in 2016 but not again before or after for all of her18 nests.
#5608 nested for the first time on the Isle of Palms at Ocean Club Villas in Wild Dunes on May 21.
She usually nests either in North Carolina or in the Cape Romain area near McClellanville on even numbered years. We wonder if she will return.
#3023 laid Nest #10 on May 25 at the 3A Access Path. She had not been seen since 2011 when she nested on the Isle of Palms and on Debordieu Beach. It’s unusual for a turtle to skip six years before nesting again. Usually this means something has happened to her, but we are glad that she survived and is back again.
We have had 18 sea turtles of four different species wash up or “strand” on our two beaches. If an adult female loggerhead that exceeds 80 cms in shell length dies, we send a keratin sample from her shell to be analyzed so she can be identified by her DNA. Fortunately, we rarely see stranded adult females, and we have only done this twice in 2019. Most of them are juveniles and other species. It is exciting when we see that a new loggerhead is nesting for the first time and as the population is beginning to rebound. None of our first samples have showed a new mother coming ashore in 2019, but it might happen. To learn more about this study you can go to http://www.dnr.sc.gov/seaturtle/volres/genetics.pdf.