Changed reproductive schedule of eastern Pacific leatherback turtles Dermochelys coriacea following the 1997–98 El Niño to La Niña transition

Abstract

We used a long term tagging dataset to investigate alterations in the reproductive ecol- ogy of leatherback turtles Dermochelys coriacea in Pacific Costa Rica in response to changes in cli- matic conditions. We calculated the remigration interval (RI) and reproductive output of individual turtles to determine whether these variables changed after a transition from El Nino dominated to La Nina dominated conditions. The reproductive schedule of turtles changed after the end of El Nino conditions, such that the number of turtles nesting with short RIs increased, but their reproductive output did not change. In addition, RIs of individuals that nested before, during and after the transi- tion altered coincident with the oceanic productivity changes caused by the climatic events. We mod- elled this data to show that a dominance of 'bad' El Nino conditions reduces population feasibility through increases in the age at maturity and RI, while a dominance of 'good' La Nina conditions causes the reverse. We propose that changes in climate may similarly manifest in changes in the reproduction and migration of individual animals of other Pacific vertebrate predators, affecting their population feasibility.