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. In the area monitored by N.E.S.T., over 200 DNA samples have been analyzed with 130 unique individual female “fingerprints”.

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 surprise 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, both within the same summer and from year-to-year
  • 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

The viral DNA vial shown above uses alcohol as a preservative.  The eggshell from the egg contains maternal DNA.  The embryo is sacrificed and shell is placed in the vial for shipment to the lab.

Cool facts we have learned about turtles in our nesting population (turtles laying at least one nest between Nags Head and the VA/NC state line:

Some turtles have been very site specific, nesting in a very limited range.

  • Eight turtles have nested exclusively in N.E.S.T.’s monitoring area and returned more than one season.
  • One turtle laid two nests within a third of a mile of each other in Kitty Hawk in 2012. In 2019, she again laid 2 nests one-half mile apart in Kitty Hawk in the same area as in 2012!
  • A 2016 mom laid three nests that were all located in Nags Head within 3 miles of each other.

Some turtles are far less site specific, nesting up and down the coast in multiple states. In North Carolina the average distance between nests for a loggerhead turtle mom is 81.9 km (51.7 miles) which is more traveling between nests than in other states which show the average distance is only 31.8 km (19.6 miles).

  • The maximum distance between nests by any of N.E.S.T.’s turtles is 556 miles. In 2017, a turtle began her nesting in Florida laying two nests. She then traveled to North Carolina laying 3 (possibly 4) more nests as far north as Corolla.
  • In 2018, a turtle began her nesting in Florida, traveling up almost to the North Carolina/Virginia border to lay a nest in Carova – 546 miles from her first nest.
  • It is not as though the turtles just keep moving up the coast laying nests. They tend to jump north and south throughout the nesting season. In 2019, two first-time nesting moms were long distance travelers. One laid her first nest in Vilano Beach, FL, traveled to Corolla for her next nest, and then finished south in Fort Fisher, NC. Another mom had an impressive nesting season laying at least 5 (and estimated up to 7) nests. She began in Holden Beach, NC, went south to Cumberland, GA, then back even further north to Southern Shores, winding up her first nesting season.

Previous studies suggest that individual loggerheads average three to four nests every two years. Results from our data show interesting variations.

  • To date, turtles have laid one to eight nests in a season in North Carolina; the average number of nests laid by turtles is 3.5. For the entire study area (NC-SC-GA-FL-VA-MD), the average is over 6 nests.
  • One turtle laid nests in 2012 and 2013! She waited three years before nesting again in 2016. She returned in 2018 when she laid four, maybe even five, nests.
  • A turtle who loves Cape Hatteras National Seashore goes beyond the average in productivity. In 2012, she laid seven nests, in 2015, eight nests and in 2017, six nests! Another turtle mom, who also lays her nests exclusively on beaches in Cape Hatteras National Seashore, laid 5 nests in 2013, 8 nests in 2016 and 9 nests in 2019.
  • As impressive as the high productivity of a turtle is, some also have a high site specificity. In 2017, a turtle in South Carolina laid nine nests within eight miles! A Georgia turtle is known for laying all of her nests within a seven-mile stretch!

Interesting facts learned in the 2019 nesting season

In North Carolina

  • The first nest laid in North Carolina was May 4 at Cape Lookout National Seashore; the first nest laid in the Northern Outer Banks was May 22.
  • The last nest laid in 2019 in North Carolina was September 17 at Cape Hatteras National Seashore; the last nest laid in the Northern Outer Banks was August 11.
  • The total number of nests in 2019:
    Loggerhead: NC: 2293   OBX: 27
    Green: NC: 63 (the most ever in NC!)   OBX: 0
    Kemp’s Ridley :NC: 2   OBX: 1

Interesting nesting behaviors of turtles who nested in the Northern Outer Banks in 2019

  • 5 turtles together laid 11 of our 28 nests
  • Nesting histories show that 5 turtles lay nests exclusively in the Northern Outer Banks; one turtle has been nesting since 2012!
  • 4 turtles lay nests only on three beaches – the Northern Outer Banks, Pea Island or Cape Hatteras National Seashore
  • 4 turtles laid only one nest in 2019, their first season

Interesting nesting behaviors of turtles who have nested in the Northern Outer Banks in the past but nested on other beaches in 2019

  • A turtle who laid a nest in 2010 in Nags Head returned to lay a nest in Deveaux Bank, SC in 2019 after a 9-year hiatus!
  • Two Loggerhead turtles whose very first nests were laid in the Northern Outer Banks have now relocated south. One turtle had 2 nests in NC in 2015. In 2019, she laid her 5 nests on beaches in SC. The other turtle traveled to the Cape Romain National Wildlife Refuge in SC for the remainder of her first season in 2011. 3 years later in 2014, she nested in Cumberland, GA, returning in 2019, after a 5-year nesting gap, to Cumberland.
  • In 2013, a Green sea turtle first-time nesting mom laid one nest in Duck. She disappears for 6 years. In 2019, she laid, once again, only one nest, on Sand Island, SC