Smaller longer, larger shorter:: energy budget calculations explain intrapopulation variation in remigration intervals for loggerhead sea turtles (Caretta caretta)

Adult female loggerhead sea turtles (Caretta caretta (L., 1758)) show a size-related behavioural and trophic dichotomy within several populations: oceanic planktivory by small females and neritic benthivory by large females. Within a Japanese population, smaller females have longer remigration intervals (the intervals between Successive nesting years) than larger females. We hypothesized that this is attributed to the size-related foraging dichotomy, and calculated energy budgets and food requirements lot- the small and large females. Total reproductive energy costs for the small and large females were 1003 and 434 MJ, equivalent to 4043 kg of planktonic items and 275 kg of benthic items, respectively. The minimum durations necessary for accumulating the total reproductive energy for the small and large females were 430 and 26 days, equivalent to remigration intervals of 2 years and I year taking into account the nesting and migration durations and seasonal reproduction. Therefore, it was theoretically demonstrated that the intrapopulation variation in remigration intervals for Japanese loggerheads could be caused by the difference in their feeding habits. implying that remigration dynamics in a sea turtle population that shows a foraging dichotomy is regulated by feeding conditions not in a single habitat but in multiple habitats.