Sea turtles--Nests--Florida

The beaches of Boca Raton, Florida serve as a rookery site for three species of sea turtles, all of whom are considered either federally threatened (loggerhead) or endangered (green turtle, leatherback). At this beach, nest security was though to be compromised by both human visitors and increasing mammalian predators populations. Since 1988, the City has employed the use of square wire cages to protect the nests from both factors. Cage effectiveness was questioned due to high predation rates, despite caging. Evaluations to determine the effectiveness of this method were conducted. Pairs of caged (control) and uncaged (experimental) nests were established in zones reflecting high/low traffic and high/low predator attacks and monitored on a daily basis. Following emergence, nest fate comparisons were made. Decoy cages were used to determine predator efficiency. Data suggest that cages are not needed in areas of low traffic or predator attacks. Additional data suggest that cages actually attract, rather than deter, mammalian predators.

Studies of loggerhead, leatherback and green turtle nest distribution across beaches (between water and dune) have revealed conflicting random versus non-random patterns of nest placement. I examined nest placement on a southeast Florida beach (Juno and Jupiter) with average beach widths of 30 (natural) and 90 m (nourished beach) and tested slope as a proximal cue for nesting using long-term data sets and GPS technology. All three species had similar species-specific crawl lengths and nest sites relative to distance from water, regardless of beach width. Loggerheads and leatherbacks crawled and nested significantly shorter median distances (8--14 m) relative to the water compared to greens (15 m), corresponding to sites of maximum productivity measured as percent hatchling success. The observed consistencies of crawl distance across all beach profiles suggest a strong evolutionary selection for a non-random crawl length at this study site, regardless of beach width and slight shifts in slope.