Video data from pop-off camera deployments on green sea turtles in San Diego, California

The cryptic and aquatic life histories of sea turtles have made them a
challenging group to directly observe, leaving significant knowledge gaps
regarding social behavior and fine-scale elements of habitat use. Using a
custom-designed animal-borne camera, we observed previously undocumented
behaviors by green turtles (Chelonia mydas) at a foraging area in San
Diego Bay, a highly urbanized ecosystem in California, USA. We deployed a
suction-cup-attached pop-off camera (manufactured by Customized Animal
Tracking Solutions) on 11 turtles (mean straight carapace
length = 84.0 ± 11.2 cm) for between 1 and 30.8 h. Video recordings,
limited to sunlit hours, provided 73 h of total observation time between
May 2022 and June 2023. We observed 32 conspecific interactions; we
classified 18 as active, entailing clear social behaviors, as compared
with 14 passive interactions representing brief, chance encounters. There
was no evidence for agonistic interactions. The camera additionally
revealed that green turtles consistently use metal structures within urban
San Diego Bay. In seven instances, turtles exhibited rubbing behavior
against metal structures, and we observed two examples of turtles
congregating at these structures. High rates of intraspecific interaction
exhibited relatively consistently among individuals provide a compelling
case for sociality for green turtles in San Diego Bay, adding to a growing
research base updating their historical label of “non-social.” The
frequent use of metal structures by the population, in particular the
rubbing of exposed skin, has implications for behavioral adaptations to
urban environments. Our study exemplifies the promise of technological
advances (e.g., underwater and animal-borne cameras) for updating natural
history paradigms, even for well-studied populations.