Extreme predation of eggs and hatchlings for loggerhead turtles in eastern Indian Ocean

• Published in: Biodiversity and conservation 2024-01, Vol.33 (1), p.135-159
• Main Authors: Avenant, Casper, Whiting, Scott, Fossette, Sabrina, Barnes, Peter, Hyndes, Glenn A.
• Format: Article
• Language: English
• Subjects: Accelerometers; Aquatic reptiles; Beaches; Biodiversity; Biomedical and Life Sciences; Breeding success; Climate Change/Climate Change Impacts; Conservation Biology/Ecology; Crustaceans; Ecology; Eggs; Interspecific relationships; Juveniles; Life Sciences; Marine crustaceans; Nesting; Nests; Original Research; Predation; Predator prey relations; Predator-prey interactions; Predators; Prey; Reproduction; Sea turtles; Seabirds; Shellfish; Threatened species; Turtles; Videography
• ISSN: 0960-3115; 1572-9710
• DOI: 10.1007/s10531-023-02739-z

Understanding predator-prey interactions at the vulnerable egg and hatchling stage of sea turtles is crucial to effectively manage these threatened marine species. Our research quantified ghost crab predation on loggerhead turtles Caretta caretta at Gnaraloo Bay and Bungelup Beach, two of the four principal nesting sites for this species in the Southeast Indian Ocean. We counted ghost crab burrows along belt transects as a proxy for crab densities. We used start- and end-of-season nesting inventories to determine egg predation rates, in-situ accelerometers to measure predation activity in nests, and infrared videography to assess predation rates on emerging hatchlings. Ghost crab densities and egg predation rates at Gnaraloo Bay were almost twice those at Bungelup Beach. Egg predation was most prevalent at night and in the first and third trimesters of incubation. We did not observe any hatchlings emerging from nests at Gnaraloo Bay, while we observed predation, mainly by ghost crabs and to a lesser extent by seagulls, on 43% of hatchlings at Bungelup Beach. The alarmingly high rate of mortality due to native predators highlights a need for immediate management actions to mitigate this threat to a globally important loggerhead turtle stock. Our multi-method approach provides a holistic estimation of reproductive success from when eggs were laid to when hatchlings reached the relative safety of the ocean.