Turtle Statistics on Seabrook Island

Judy Morr, whose many duties at the Seabrook Island Turtle Patrol include statistician extraordinaire, compiled some interesting data on the turtles that nest on our island. The South Carolina Department of Natural Resources has tracked the nesting patterns of loggerhead sea turtles for the past several years by sampling DNA. The Seabrook Island Turtle Patrol assists this study by providing a sample from each nest on our beaches. Judy took the information provided by DNR to put together the information.

As you may know, loggerhead turtles typically nest every other year or every third year. They lay several nests a season year (averaging 4) with about 120 ping pong ball-sized eggs in each nest. The 2018 Sea Turtle Nesting season begins in early to mid-May with the first nests hatching in July.
Most noteworthy are:

  • Mother CC000343 really loves our island! Last year she laid 5 nests on Seabrook. All 19 of her nests since 2010 were on Seabrook and all at the southern end of the island. She had an 89% hatch rate in 2015 and 93% in 2017. This compares favorably with our overall average of about 75%.
  • Mother CC000530 laid 2 nests on Seabrook in 2017 and one on Kiawah; 19 of her 22 nests laid since 2010 having been on Seabrook. The other 3 were on Kiawah. Her average clutch count is 138 eggs with a hatch rate of 74%. There were a total of 2,236 hatchlings in those 22 nests.
  • Mother CC006108 laid 4 nests on Seabrook in 2017. All 16 of her nests since 2011 have been on Seabrook with 12 being between the Club and Boardwalk 6.

Judy’s review of last year’s nests produced some other interesting results:

  • 66 of the 70 nests have DNA mapped.
  • These 66 nests were laid by 43 unique mothers.
  • 10 of those 43 mothers had never before been identified in the system, regardless of the beach.
  • Those 43 mothers laid a total of 158 nests on 29 different beaches in 2017.
  • Of those 158 nests, 66 were on Seabrook Island with an additional 47 nests on Kiawah.

Some other fun facts:

  • Mother CC001594 must call Cape Island (north of McClellanville) “home” as she laid 11 nests there since 2010. Her first nest of 2017 was on Seabrook Island before she laid 4 additional ones on Cape Island. I guess she just couldn’t get home before it was time to lay those eggs.
  • Mother CC003703 also prefers Cape Island. She has laid 17 nests there since 2011. In 2013, she laid her first nest of the year on Kiawah and this year she laid a nest on Seabrook in mid-May. Her first 2017 nest on Cape Island was on 5/21.
  • Mother CC002034 has laid 15 nests on Harbor Island (off St. Helena ) since 2011. This year she took a vacation and laid her fourth of six nests on Seabrook.
  • New mother CC010751 laid her only nest on Seabrook. All the other new mothers laid multiple nests in 2017 but only one on Seabrook.
  • Of the 247 mothers who have laid on Seabrook Island to date, 75 of those laid somewhere in 2017. Since Seabrook had 43 mothers, that means 32 prior Seabrook mothers chose to lay somewhere else in 2017.
  • Theoretically, mothers who laid in 2014 or prior would have nested again by 2017. 57 of the 201 mothers who laid in 2014 or prior have not laid since 2014. Hope they’re OK.

If all that isn’t “turtle-nerdy” enough for you, here’s a link to a New York Times article on the same subject.


-Submitted by Gary Fansler





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