Long lives and high invariant reproductive costs: why do sea turtles not nest every year?

While many verte brates breed annually, there are a few that do not. Female sea turtles are a classic example of a generally non-annual nester, with often intervals between breeding seasons (termed the remigration interval) of 2-4 years. Non-annual nesting in sea turtles is believed to be due to long migration distances. While this hypothesis holds for populations where females migrate large distances (e.g. sometimes several 1000 km), it is harder to reconcile with cases where migration distances are short (e.g. sometimes <50 km). We show that even with very short breeding migrations, there are invariant time and energy costs to breeding. The time involved in the breeding process (migration, mating, nesting, internesting and returning to the foraging grounds) also comes with the opportunity cost of an individual being away from its foraging grounds and so lost foraging time. We show that this strategy of non-annual nesting is linked to high survival rates for adult sea turtles, a feature that is common across other non-annual breeders such as albatrosses and southern right whales.