Which sea turtle nested on the beach?

By Caitlin Calabrese

Beachgoers can use more than just tracks to tell what sea turtle species have been on the beach. Our Brevard nesting sea turtles also exhibit differences in nesting behaviors. Observing clues like depth of body pit, amount of camouflage sand, and crawl pattern can help indicate species.

Before we discuss how these species differ, let’s talk similarities. Loggerhead (Caretta caretta), Atlantic green (Chelonia mydas), and leatherback (Dermochelys coriacae) sea turtles are all nocturnal nesters, waiting for the safety and cool of the dark to emerge from the ocean and nest. Additionally, due to the physically taxing nature of the nesting process, these girls will all take periodic breaks or even sleep during nesting. Although there are species-specific behaviors, the general nesting procedure remains the same for all three species: ocean emergence, traversing the sand until optimal nesting site is found, digging the body pit, digging the egg chamber, covering the egg chamber, camouflaging the nest, and returning to the ocean.

Let’s begin with our most common Brevard nester, the loggerhead. Loggerhead turtles are slower on their ascendance from the ocean compared to their return. Loggerheads will nest anywhere from the tide line to the dune. When the loggerhead reaches her nesting site of choice, she will begin to slow her front flippers and continue her nose push. To body pit, the loggerhead will forego her alternating gait to begin simultaneously pushing back sand with both front flippers, begin to dig with her hind flippers, and pivot her body to sink lower into the sand. After her body pit is complete, she will dig her egg chamber exclusively using her hind flippers in a scooping motion. Upon completion of her egg chamber, the loggerhead will cover her egg chamber with her hind flippers. Once the egg chamber is covered, she will use her front flippers to throw sand behind her in order to camouflage the nest. Loggerhead nests can exhibit considerable variation in camouflaging sand, or “spray,” ranging from a more compact and organized mound to one with a lot of sand thrown. Compared to greens and leatherbacks, however, loggerhead nests will have the least amount of camouflaging sand thrown.

The green sea turtles will display observable variations in nesting compared to loggerheads. It is characteristic of green sea turtles to traverse the width of the beach to reach the dunes, however, this is not absolutely true for every green nest. Once the green has found her ideal nesting site, she will begin her body pitting process in a more aggressive fashion than the loggerhead, alternating front flipper and hind flipper sand sweeping resulting in a laborious and highly energy consuming process that results in a very deep, obvious, circular body pit. It is reported that green sea turtles will use ten times their resting metabolic rate while nesting. Green turtles will dig their egg chamber in a process very similar to the loggerhead, just slightly deeper due to the longer flipper length. Greens will employ the same egg-chamber-covering procedure as loggerheads, just in a more vigorous fashion. Once the egg chamber is covered, a green turtle will camouflage her nesting site with large front flipper sweeps throwing sand at great distances, resulting in a considerably larger nesting site than the loggerhead. In addition to the energy expenditure of the rapid digging, once nested, the green turtle will have to crawl out of her deep body pit before crawling back to sea.

Our biggest nesters, the leatherbacks, will emerge from the ocean and traverse the beach with frequent resting stops. Leatherbacks can also make an “orientation circle” on their ascending or descending journey, which presents as one or a few large circular swirls with pushed sand collecting in the center.  Leatherbacks also rarely false crawl, so indications of leatherback presence usually indicate a nest. Another interesting species trait of the leatherback is the release of spacer eggs. These infertile eggs may be released during the nesting process as well as in the egg chamber. A leatherback body pitting process is marked by alternating front and hind flipper sweeps, with the front flippers pivoting outward, the pivoting motion contributes to the size and disorganization of the body pit. Leatherbacks have the same chamber-digging procedure, using the hind flippers in a scooping motion. The chamber, however, will be deeper due to the length of hind flippers (really, really big turtle).  Once the egg chamber is covered, the leatherback turtle will begin to camouflage by throwing sand from simultaneous front flipper strokes.  Leatherbacks uniquely will take pauses, pivots, or crawls during this process, leaving multiple “mounds” of camouflage. On her way back to the ocean, the leatherback usually will make an “orientation circle” where she rotates completely before heading home. 

Piecing together turtle tracks with nesting behavior patterns provides a holistic perspective of identifying the species of a nesting event.

References:

“Leatherback sea turtle.” Gumbo Limbo Nature Center. (2019). Retrieved from: https://www.gumbolimbonaturecenter.org

Smith, L. (2010). Fasting physiology of the loggerhead sea turtle, Caretta caretta, throughout the

            nesting and pre-nesting seasons. Southeastern Louisiana University, ProQuest

            dissertations publishing.

Witherington, B., Witherington, D. (2015). Our Sea Turtles: a practical guide for the Atlantic and

            Gulf, from Canada to Mexico. Pineapple Press Inc.: Sarasota, Florida.