DNA Study

by Karen Johnson

Since 2010 N.E.S.T. has participated in a multi-state genetics research project to answer several basic sea turtle nesting questions. By collecting an egg from every single nest, biologists are able to use DNA genetic fingerprinting (CSI for sea turtles) to identify individual sea turtle females, to gather information about sea turtle nesting behavior and habits, and to provide a census of the actual nesting population.

 

This data gives us a good idea of:

  • The species of the turtle – Loggerhead (our most common), Green, Kemp’s Ridley, Leatherback, or even a Hawksbill
  • How many clutches of eggs (nests) each nesting female lays in a year
  • Whether the turtle is nesting on more than one beach
  • How close together or far apart each individual turtle lays her nests
  • The number of turtles nesting in more than one state
  • How often each turtle nests; every two years, three, more, less?
  • How precisely a daughter returns to her hatching beach to lay her own eggs

VDNA sample vial with DNA (turtle egg shell) sample inside. Photo by S. Westheiden

 

Cool facts we have learned about turtles in our nesting population:

  • Some turtles have been very site specific, nesting in a very limited range.
    • Five females (so far) have nested exclusively in the Northern Outer Banks (N.E.S.T.). One new mom in 2016 laid three nests that were all located in Nags Head.
  • Some turtles are far less site specific, nesting up and down the coast in multiple states.
    • The maximum distance between nests by any of our turtles was 492 miles.  In 2011 she nested in Corolla and in 2013 in Cumberland, GA.
    • In 2016, one female laid two nests. The first was in Wassaw, GA and the second was 420 miles north in Nags Head.
  • Previous studies suggest that individual loggerheads average nesting three to four nests every two years.  Results from our data show interesting variations.
    • The average number of nests laid by turtles on our nesting beaches is two. For the entire study area, the average is 4.5 nests.
    • One turtle laid nests in 2012 and again in 2013. She waited three years before nesting again in 2016.
    • In 2016, we had thirty-two nesting females, twenty were new moms.
    • A turtle in Georgia laid the most nests in a single year of any turtle studied in the multi-state project.  In 2011 she laid a total of eight nests. In 2015, she laid six nests, and in 2017 she has been identified as laying four nests with more DNA samples waiting to be processed. Perhaps as impressive as her high productivity is her high site specificity.  All of the nests have been within seven miles of each other!