Sea Turtle Research in Florida

USGS Cooperative Research Unit Corner

Sea Turtle Research in Florida

Florida's coast and surrounding waters provide nesting, developmental, and foraging habitats to five species of sea turtles, all of which are listed under the Endangered Species Act. The leatherback (Dermochelys coriacea), hawksbill (Eretmochelys imbricata), Kemp's ridley (Lepidochelys kempi), and green (Chelonia mydas) are designated as Endangered (the green in Florida and Pacific Mexico only, Threatened elsewhere), and the loggerhead (Caretta caretta) is listed as Threatened. The Florida Cooperative Fish and Wildlife Research Unit has undertaken a number of studies on sea turtles that directly address specific needs listed in the Recovery Plans for the respective species. Unit scientists and students collaborate directly with personnel from the National Oceanographic and Atmospheric Administration, the U.S. Fish and Wildlife Service, the Florida Fish and Wildlife Conservation Commission, and multiple other agencies to answer biological and management-oriented questions. Results from the research are published in peer-reviewed journals, technical reports, theses and dissertations, and communicated to the agencies to assist in their sea turtle conservation efforts.

Since 1994 the Unit has conducted research at Cape San Blas/St. Joseph Peninsula in the Florida Panhandle with a focus on loggerhead nesting ecology. The Cape has one of the most dynamic and fastest eroding shorelines in Florida: the program has documented normal inter-annual beach losses of 10m and much greater losses during active hurricane years. Despite the instability of this beach, the Cape and Peninsula support one of the highest densities of the genetically-distinct northwest Florida nesting loggerhead subpopulation. Site fidelity (natal homing) is a known life-history trait of sea turtles that if strictly adhered to in this environment could be counter-adaptive in maximizing reproductive success. An intensive saturation-tagging program for nesting turtles was started in 1998 and in conjunction with more recent information obtained from satellite tagging, has elucidated the scatter-nesting strategy the turtles use to ensure that some of their nests survive. The tagging program is among the longest running in the southeastern U.S. and continues to provide information on vital rates for the population.

Besides the high natural background erosion rates on the barrier beaches, nesting turtles must contend with major anthropogenic habitat alterations. Beach nourishment (re-profiling of the shoreline with sand dredged from offshore or trucked in) and coastal armoring (placement of rock, steel, fabric tube or hybrid revetments) projects have been carried out along the Peninsula to protect homes and roadways from erosion, and have afforded an opportunity to examine how sea turtles respond to these perturbations in their nesting habitat. Findings indicate that there may be latency in response to habitat degradation and nest losses may occur while animals adjust to sub-optimal beach conditions. In addition, when climate change (severe weather events) and sea level rise are factored in ? both as natural changes and as stimuli for humans to act to protect coastal infrastructure ? the resulting higher rate of nesting habitat loss may exceed the population's ability to compensate.

The Coop Unit is involved in other nesting beach studies, including the effects of beach driving, beach furniture, and debris fields on nesting turtles and on hatchlings, and the efficacy of conservation-oriented public education efforts. Recent work on lighting and orientation responses in sea turtle hatchlings directly addresses the effects of coastal development (introduction of point sources of light as well as sky-shine) and the methods used to mitigate them. Findings included identification of alternative lighting products, and recommendations for improved practices in assessing wildlife-friendly lighting.

The variety of habitats used by sea turtles from egg to adulthood makes their study compelling, yet logistically challenging. In 2001, Unit scientists and students initiated an in-water study of sea turtles in St. Joe Bay, Florida. Various netting methods were used in a mark-recapture study aimed at characterizing species composition, size classes, growth rates and residence times for turtles in this area. The long-term effort has resulted in identification of St. Joe Bay as an important developmental habitat for juvenile turtles in the northeastern Gulf of Mexico. The significance of the finding has been reinforced by subsequent large cold-stunning events (2001, 2004, 2010, 2014) where thousands of turtles were rendered torpid by rapid temperature declines and were removed from the Bay for rehabilitation in massive rescue efforts. Recent work includes diet characterization of juvenile green turtles in the Bay, and evaluation of their diet consistency and feeding patterns using gastric lavage and stable isotope techniques. Rather than transitioning to a diet of strictly seagrass, the animals are more opportunistic than previously thought and expand their foraging habitat and prey base to match seasonal availability of resources.

Following the 2010 Deepwater Horizon oil spill, the Florida Coop Sea Turtle Research Program played an important role in the response and assessment monitoring for the Natural Resource Damage Assessment (NRDA) process. Ongoing activities include providing technical assistance to the NRDA Trustees, collection of tissue and biological samples for contaminant assays, and satellite tracking of sea turtle movements in the Gulf of Mexico.

Marine turtles have an important role in coastal and marine systems as predators, grazers and ecosystem architects. The overall goal of the research program at the Florida Cooperative Fish and Wildlife Research Unit is to address questions that will help resource managers restore historically depleted sea turtle populations so that they may fulfill their ecological functions.

Each month, the ONB features articles from Cooperative Fish and Wildlife Research Units across the country. Working with key cooperators, including WMI, Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about.

July 14, 2014