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On 25 May 2016, researchers from the Jekyll Island Authority Georgia Sea Turtle Center’s (GSTC) sea turtle patrol team encountered a loggerhead on Jekyll Island, Georgia, USA, which would eventually exhibit sleep-like behavior during her nesting process. The turtle was initially encountered at 23:48 PM. while she was laying eggs. The researchers collected Inconel flipper tag and passive integrated transponder (PIT) tag information, morphometric data, and two biopsy samples (skin) for collaborative research projects. Upon completion of data collection, the nesting female (master (initial) tag YYG497, first tagged in 2010), previously named “Sky” by researchers, had yet to complete the egg-laying process. Due to the turtle’s location in an area commonly occupied by public beach-goers, we remained with Sky as other researchers resumed beach patrol for other potential nesting sea turtles. We soon realized that Sky had ceased contractions and egg-laying, even though there appeared to be relatively few eggs in the chamber compared to a normal clutch. After approximately 60 to 75 minutes of inactivity, we noted this odd behavior and grew mildly concerned about the animal’s state. As part of a series of tests to gauge responsiveness, KMA gently pinched one of Sky’s front flippers which failed to evoke a response. KMA then noted that the animal’s eye was closed, as if she were asleep and proceeded with a palpebral response test (touching the eyelid gently). This test caused Sky to wake up and without laying any additional eggs, she proceeded to cover her egg chamber, disguise the area and crawl back to the ocean. Due to a philosophy of minimizing intervention, the authors made the decision to leave the eggs in situ rather than relocate them to a shallower depth. It was determined upon the nest’s inventory 70 days after deposition that Sky laid just 28 eggs in this nest. The average clutch size for loggerhead sea turtles on Jekyll Island is 104 eggs (GSTC, unpubl. data), which is comparable to the 114 average for the species observed by Brost et al. (2015) at various beaches in Florida, USA. Therefore, Sky’s clutch of 28 eggs is well below the average laid by loggerheads in the southeast US. None of the eggs in this nest hatched, nor did they show any signs of embryological development.

The Jekyll Island Sea Turtle Project is one of many in the southeastern United States working in collaboration with Drs B. Shamblin and C.J. Nairn at the University of Georgia’s Warnell School of Forestry and Natural Resources. Their effort involves creating a genetic catalogue of mtDNA for the entire Northern Recovery Unit for C. caretta using egg and skin samples (Shamblin et al. 2017). Through this collaboration, Sky was matched as being the mother of Jekyll Island’s first nest of 2016, laid on 11 May, at which no turtle had been observed nesting (Shamblin & Nairn pers. comm. 2016). That meant that the nesting event during which she fell asleep was her second detected nest of the season. After the nesting event in which Sky appeared to fall asleep, GSTC researchers encountered her on three additional occasions (Table 1). On 7 June 2016, she was encountered while body pitting (the stage of nesting occurring just before digging an egg chamber and laying eggs). This attempt to nest was ultimately abandoned and she was encountered next on 18 June 2016 during a successful nesting event. Nothing abnormal was noted on this occasion. The final time a GSTC patrol team encountered Sky was on 30 June 2016, during which sleep-like behavior was again witnessed. The patrol team present observed Sky lay one egg and then remain motionless for 20 minutes. The patrollers pinched Sky, at which point she began to cover the nearly empty egg chamber. Once she had left this nesting site, the patrol team dug into the egg chamber to discover that only 2 eggs were in this clutch; this set a new record-low clutch count for Jekyll Island since 1996 (GSTC, unpubl. data). These two eggs were relocated higher up in the original egg chamber, with one of them successfully hatching.

To add another layer of interest to Sky’s story, she had been found in a previous nesting season stranded in the marsh adjacent to Jekyll Island’s Driftwood Beach at 11:30 AM on 30 May 2013. At some point the night before, she nested approximately 0.88 km east of her stranding location, along Driftwood Beach. After being discovered in the marsh, Sky was treated in the field by the GSTC’s veterinarian, Terry Norton, who administered fluids to Sky. Additionally, she had blood drawn and skin biopsies were taken. Soon after this, she was carried back to the beach to be released; Sky then actively crawled back into the ocean and swam away. Sky returned to nest on Jekyll Island three additional times in 2013, although she was not encountered at any of those events (she was instead detected through the genetics project previously discussed; Shamblin & Nairn pers. comm. 2016). The two nests immediately following her stranding event contained a lower-than-average number of eggs (51 and 41, respectively). Only one of Sky’s nests that year produced any hatchlings (the one immediately following her stranding event), although only 2 of the 51 eggs were determined to have hatched (Table 1). This causes us to wonder if her reproductive success that season was compromised either before or because of her stranding event, during which she could have overheated in the daytime sun (the high temperature that day was 28.9 °C).

Standardized data collection for the Jekyll Island Sea Turtle Project dates back as far as 1991. With the exception of 2000-2006, the project has conducted nighttime tagging of nesting females (Ondich & Andrews 2013). Only two occurrences (apart from Sky) in this dataset could be found in which the word “sleep” was written in the comments (other search terms such as “rest” and “trance” yielded no results). The most recent observation occurred on 27 June 2014 when a turtle (“Josie,” master tag UUF121, first tagged in 2011) was encountered during her ascent of the beach. Researchers used a night vision monocular to observe her movement from a distance so as to not spook her from nesting. As the turtle ascended, her path went through a runnel (tidal pool) that ran parallel to the ocean. It is not uncommon for sea turtles to abandon a nesting attempt when they approach or enter the water in a runnel (GSTC,unpubl. data). On this attempt, Josie clearly became confused by the water in the runnel and began swimming and crawling through it. After a few minutes, she remained motionless. The patrol team present estimated that Josie’s entire time spent in the runnel (including the time she swam around it and sat motionless near the edge) was approximately 60 minutes. When the patrol team approached her, Josie appeared to be sleeping. She did not respond to the team’s approach, nor when they turned on their red headlamps. Josie only regained awareness of the situation upon the responsiveness test of a slight pinch of her flipper, at which she resumed her confused path through the runnel. The patrol team guided her out of the runnel and toward the ocean. The patrol members present (including KAM) noted that she appeared to be sleeping; however, they could not be sure given that they spent a great deal of the time far away from her, not wanting to cause her to abandon her nesting attempt should she decide to head back toward the dunes.

The only other documented event of a loggerhead apparently sleeping on Jekyll Island was witnessed on 16 June 2009 during a failed nesting attempt (master tag YYG258, first tagged on this emergence). The patrol team present noted that she had fallen asleep in a tidal pool with a steep embankment that prevented her from crawling out on her own. The comments do not specify how the turtle was awakened, but the patrol team did assist the turtle out of the tidal pool. Of the 474 eggs this female laid between 4 clutches that year, only 6 eggs hatched (1.3%). This turtle has not been detected via tag or genetic identification since 2009.

This “sleeping” behavior is also not specific to C. caretta. One author (KAM) witnessed a similar occurrence in an olive ridley sea turtle (Lepidochelys olivacea) on one occasion in 2010 on Corozalito Beach, Guanacaste Province, Costa Rica. That turtle received Inconel flipper tags and was measured while she laid an apparently full clutch of eggs. KAM left the turtle in order to resume her patrol of the beach, but upon returning to the same area approximately 30 minutes later, the turtle continued to remain still over her uncovered egg chamber, evidently sleeping. KAM noted this behavior as peculiar, but was unsure of its rarity, as it was only her second season working with sea turtles. Uncertain of what to do, she left the turtle undisturbed. Upon her next pass of that area some unknown time later in the night, the turtle had covered the egg chamber and returned to the ocean.

From these few observed events, it is entirely possible that this sleep-like behavior is not uncommon or even species-specific, but has simply gone unpublished to date. Literature searches on the topic of sea turtles resting or sleeping for extended periods during nesting yielded no articles on behavior similar to that described above. We need to learn whether this behavior is truly common as part of sea turtle physiology and if it is indicative of underlying health issues. It is therefore important to understand whether these behaviors are a means of some turtles resting during the exhausting nesting process (i.e., voluntary behavior), or if it is an involuntary physiological occurrence, perhaps the sea turtle equivalent of narcolepsy. We hope that by publishing this note of this behavior we can begin a conversation within the sea turtle research community regarding the commonality and potential causes behind a sea turtle apparently sleeping while nesting.

Table 1. Nesting history of the loggerhead sea turtle Sky (master tag YYG497), including the date of emergence, activity type (nest or false crawl, i.e., abandoned nesting attempt), whether Sky was encountered by the patrol team (a nest at which she was not encountered was linked to Sky by genetic identification), the nest’s clutch size, hatch success, and any comments related to the activity.

Acknowledgments. We thank all of the individuals who have worked on the Jekyll Island Sea Turtle Project since 1972, and specifically those researchers who were present at the nesting events described above: Alison Ballard, Zachary Butler, Simon Dilts, Ray Emerson, John Lyons, Elissa Monahan, Breanna Ondich, Katie Parson, Lindsay Partymiller, Lauren Schaale, Gregory Skupien, Rachel Sommer, Stephanie Sowa, Norah Stevens-Kittner, Kim Tomczak, Nicole White, Katrina Woods, and Kristen Zemaitis. Additionally, we thank Brian Shamblin and C. Joe Nairn for their work on the C. caretta genetics project, which allows us to match individual sea turtles to nests at which a turtle was not encountered. Our sincere thanks also go to Terry Norton of the GSTC and Mark Dodd of the Georgia Department of Natural Resources. This publication is supported in part by an Institutional Grant (NA10OAR4170084) to the Georgia Sea Grant College Program from the National Sea Grant Office, National Oceanic and Atmospheric Administration, United States Department of Commerce. All 2016 Jekyll Island research was carried out under the Georgia DNR Scientific Collecting Special Purpose Permit CN:27067.

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