BARTON, B. T.*; ROTH, J. D.; Yale University; University of Central Florida: Sea turtle nest predators: Implications for community ecology

All four species of marine turtle that nest in Florida are listed as threatened or endangered under the Endangered Species Act of 1973, requiring actions to protect and restore these species. Raccoon (Procyon lotor) predation is among the highest causes of egg mortality for marine turtles, and raccoon removal programs have been implemented on some Florida beaches for >25 years. We examined the cascading effects of raccoon removal on sea turtle nesting beach communities in east-central Florida. Interestingly, raccoons consume ghost crabs (Ocypode quadrata), the second most common marine turtle nest predator on these beaches. We compared the diet and demography of a raccoon population that had experienced two decades of raccoon removal to a previously unmanaged population. The sex ratio of the historically managed population was significantly male-biased (10.5:1) in comparison to the unmanaged population (1:1), which is probably due to male-biased natal dispersal. Stable isotope analysis of raccoon and ghost crab tissue suggests marine turtle eggs are not a critical aspect of either predator�s diet, a finding that has been speculated by other authors. We also compared the abundances of raccoons and ghost crabs at four study sites using passive tracking plots to determine the numerical relationship between these two species. Our data suggest intraguild predation by raccoons limits ghost crab abundance and that reduced raccoon abundance allowed ghost crab abundance to increase, resulting in a net increase in sea turtle egg predation. These results support our hypothesis that intraguild predation of ghost crabs by raccoons is an influential interaction on sea turtle nesting beach community dynamics.