Although loggerhead turtles return to the same beach where they hatched to lay their eggs, a new study finds individual females lay numerous clutches of eggs in locations miles apart from each other to increase the chance that some of their offspring will survive.
The study by Professor Deby L Cassill of the University of South Florida found that some females lay as many as six clutches ranging over six miles during the breeding season.
During their 50-year lifetime, a single female loggerhead will produce around 4,200 eggs and scatter them at 40 different sites on a barrier island off the southern coast of Florida. This strategy helps reduce the risk of complete reproductive failure by hurricanes and thunderstorms that could wash out or flood all clutches.
“Because females diversify reproduction in unpredictable patterns over time and space, nearly two-thirds of loggerhead sea turtle hatchlings made it into the Gulf of Mexico,” said Cassill.
Though the study shows most sea turtle hatchlings reach the Gulf of Mexico, future impacts due to human encroachment and climate change could affect the population. Increased frequency of extreme storms due to warmer waters and sea-level rise may flood or wash away larger portions of clutches, leading to population declines of the threatened species.
The author studied records of nesting loggerhead turtles from from 1988 to 2004. The turtles divided eggs into 40 clutches of variable size (50–165 eggs). To deposit clutches, females migrated to the barrier island 10–12 times at unpredictable intervals of 2–8 years. Each nesting season, females deposited 1–7 clutches over diversified time intervals at diversified locations on the beach. Despite devastating clutch losses caused by ten catastrophic hurricanes, hundreds of erratic thunderstorms and dozens of predation events during this study, 72% of clutches produced by nesting females on this barrier island were undisturbed, with hatching success of an astonishing 92%.
Cassill, D.L. Multiple maternal risk-management adaptations in the loggerhead sea turtle (Caretta caretta) mitigate clutch failure caused by catastrophic storms and predators. Sci Rep 11, 2491 (2021). https://doi.org/10.1038/s41598-021-81968-0