Collector and Arrow 100 Successfully Aid Monitoring of Sea Turtle Nesting on Hilton Head Island

Sea Turtle Patrol Hilton Head Island

The Endangered Species Act has federally protected sea turtles since its inception in December of 1973.  State governments have the authority to monitor nesting beaches on US coastlines.  Officially starting in 1985, the South Carolina Department of Natural Resources manages and trains volunteers on Hilton Head Island to mark loggerhead sea turtle nests, monitor for hatching activity, and inventory the results.  Of the six species of sea turtles in U.S. waters, the island also sees small numbers of green sea turtles, leatherback sea turtles and Kemp’s Ridley sea turtles.  The Sea Turtle Patrol Hilton Head Island (Sea Turtle Patrol HHI) has 16 volunteers with a wide range of ages and backgrounds that monitor 17 miles of beach for sea turtle nesting.  

Twenty years of Sea Turtle Nest Activity

There are 14 miles of main ocean facing beach and a couple of small beaches on the north end that face Port Royal Sound that make up the difference.  Every stretch of beach is patrolled annually from May 1st – October 31st or until the last nest hatches.  Overall, Hilton Head Beaches average 325 nests, but up to 463 nests have been laid in one season.  The patrol starts at 5am and lasts as long as it takes to mark all nests laid the night before.  Hilton Head Island is a large tourist destination and it is important to keep beach goers off of the nest site.  The egg chamber is approximately 6 inches in diameter,  2ft – 3ft deep, and is positioned in the center of the triangle.  An average of 120 eggs are laid and incubate for about 60 days.

With this system of marking nests, what could possibly go wrong?  So many things….

Hurricane season is officially June 1st – November 30th in South Carolina, with a peak period between Mid-August – Mid-October.  This is the same timeframe as sea turtle hatching season!  

Sea Turtle Patrol HHI has always used a GPS to mark sea turtle nests, but the accuracy was generally 6 feet off the mark.  This became an issue when Hurricane Matthew struck Hilton Head in 2016, but a more serious issue when storm surge from Hurricane Irma affected the island the following year.  Hurricane Matthew hit Hilton Head on October 8, 2016.  After emergency measures, there were only 2 nests left on the beach as it was nearing the end of the hatching season. Both nests were lost due to the storm.  On September 11, 2017, Hurricane Irma blew by leaving significant flooding in her path while the island was still recovering from Hurricane Matthew.  Irma was earlier in the season than Matthew and there were 54 sea turtle nests still incubating on the beach.  Irma’s waves removed all of the remaining nest marker poles and Sea Turtle Patrol HHI was expected to find 54 nests to determine their status.  As you can imagine, a GPS that only gets you within 6 feet of a 6 inch hole was not very helpful.  Only 8 nests were found.  

The Town of Hilton Head had already worked with the mapping experts at Anatum GeoMobile Solutions to implement their mapping workflow with the Eos Arrow 100 submeter receiver and the Esri Collector for ArcGIS system to document facilities and storm damage.  The municipality already had the Collector app setup for mapping, so the municipality provided Sea Turtle Patrol HHI with access to an appropriate map in Collector and funds were raised to purchase an Eos Arrow 100 GNSS to mark sea turtle nests.  Each nest was documented for the first time using the new Arrow GPS during the 2019 sea turtle nesting season and it was a record breaking year with 463 nests!  This is how we use it…  

After identifying a potential nest, patrol volunteers probe for soft sand to find the area where the mother turtle dug the nest cavity, dropped her eggs, and covered them up with about a foot of sand.  She disguises the nest to make it difficult, but once the egg chamber is located, the Arrow GPS attached to a survey pole is gently placed over the center of the nest to capture latitude and longitude via Bluetooth connection to the Collector application running on an iPad.  Then, 3 poles are inserted in a triangular formation with a 1ft margin around the nest to mark the area.   Keeping track of these nests with the new system was wildly successful in 2019 and again in 2020!  The Collector app generated a map with visual marks and amazing accuracy based on the lat/long from the Arrow GPS.  The overview of the nest sites came in very handy as the Jeep drove down the beach with the Arrow device attached to the roof of the vehicle with a magnetic mount.  

There hasn’t been a hurricane to contend with since we got the equipment, but when many nest marker poles were removed around July 4th, presumably used as bottle rocket launching devices, the positional accuracy of the nests mapped with the Arrow 100 GPS allowed us to pinpoint the egg chamber and poles were easily replaced.  Sometimes, people will simply remove the poles if they are “in the way” or if they feel like being mischievous.  From now on, we will always be able to find our hatchlings with the Arrow 100 on board, whether it’s due to Mother Nature, or crazy humans.

Amber Kuehn
A South Carolina based marine biologist, Amber is the volunteer permit holder for South Carolina Department of Natural Resources on Hilton Head Island. Captain Amber also provides marine education tours through Spartina Marine Education Charters.