Dipteran larvae infestation of leatherback turtle (Dermochelys coriacea) nests on Gandoca beach, Costa Rica

We examined the ecological characteristics of dipteran larvae infesting Leatherback nests on Gandoca Beach, Costa Rica in 2005-2006. Fly infestation exceeded 75% of nests, but levels were much lower when evaluated as the percent of the clutch infested. Fly larvae seemed to act mostly as scavengers, but a few live hatchlings were attacked indicating that flies also act opportunistically as predators. Several dipteran species were recorded with the sarcophagid Eumacronychia sternalis being dominant. Back-calculations from the development timeframe for E. sternalis showed that infestation happened shortly after hatchling emergence, suggesting that flies are attracted to the nest because of emanating odours of decomposing material brought to the surface by emerging hatchlings. Sampling year, bacteria or fungus invasion, and the interaction between nest depth and the number of dead hatchlings best predicted the incidence of larvae within nests. Infestation levels in egg hatcheries were not higher, possibly because of protective baskets. Our results suggest that flies do not seriously threaten Leatherback turtle populations in Gandoca, but they can cause incidental mortality and measures should be taken to protect nests against larval infestation.