Nesting ecology of olive ridley (Lepidochelys olivacea) turtles on arribada nesting beaches

Historically, the olive ridley (Lepidochelys olivacea) arribada at Playa Nancite, Costa Rica, was one of the largest arribadas in the eastern Pacific with 70,000 nesting females in a year. Recently that arribada drastically declined. We hypothesized that the decline at Playa Nancite could be due to low hatching success as a result of the high density of nests on the beach, such that recruitment to the population was insufficient to balance losses. To test this hypothesis, we examined density-dependent effects on hatching success and their underlying mechanisms by experimentally manipulating nest densities on the nesting beach. Experimental nest densities affected hatching success with highest density having lowest hatching success. Higher nest density led to lower O2 levels and higher CO₂ levels in the nest, with greater changes in the latter part of the incubation. Highest temperatures occurred in high nest density areas. Bacterial diversity and richness were higher in the high zone of the beach on Playa Nancite. Bacterial diversity and richness were also studied at another arribada beach, Playa La Flor in Nicaragua. Bacterial diversity and richness were higher in the high zone of the beach on Playa La Flor. Bacterial abundance was not different in different zones of the beach or in different nest densities at both Playa Nancite and Playa La Flor. Bacterial diversity and richness may be important in affecting hatching success of olive ridley eggs. Long term failure in production of hatchlings due to historically high densities probably contributed to the decline of arribadas on Playa Nancite. The effects of egg harvest on olive ridley sea turtle nesting beaches have been debated for decades. In order to more effectively manage the beach at Playa La Flor, Nicaragua, and potentially other nesting beaches, we developed an experimental protocol to measure the impact of egg harvest on this beach. Management strategies have traditionally involved the removal of eggs that are predicted to have less chance of survival, despite a lack of experimental data supporting this approach. Our findings indicate that even controlled egg harvest has a negative effect on nest hatching success and total hatchling production.