Evaluating Multiple Stressors in Loggerhead Sea Turtles: Developing A Two-Sex Spatially Explicit Model

EPA Grant Number: R829094
Title: Evaluating Multiple Stressors in Loggerhead Sea Turtles: Developing A Two-Sex Spatially Explicit Model
Investigators: Wyneken, Jeanette , Crowder, Larry B. , Epperly, Sheryan , Snover, Melissa
Current Investigators: Wyneken, Jeanette , Crowder, Larry B. , Epperly, Sheryan
Institution: Florida Atlantic University - Boca Raton , Duke University , National Marine Fisheries Service
EPA Project Officer: Carleton, James N
Project Period: November 15, 2001 through November 14, 2004 (Extended to November 14, 2005)
Project Amount: $349,421
RFA: Wildlife Risk Assessment (2001) RFA Text |  Recipients Lists
Research Category: Biology/Life Sciences , Ecological Indicators/Assessment/Restoration , Ecosystems


North Atlantic loggerhead sea turtle (Caretta caretta L.) populations respond to the integrated effects of multiple environmental stressors. Environmental stressors often occur in spatially distinct frameworks and affect distinct age classes, sexes, and subpopulations differentially because of differences in habitats utilization. Also, the effects of stressors may not be manifest for years. Loggerheads are long-lived species with spatially and genetically structured as subpopulations, hence threats may be experienced differentially. Maintenance of subpopulation structure may be critical to the survival of the population as a whole. The study aims to restructure wildlife risk assessment models for sea turtles. New information on (i) the spatially distinct subpopulation structure, (ii) anthropogenic stressors that impact turtles at different life stages in different habitats, and (iii) space-based conservation and management options, all call for spatially explicit approaches to loggerhead population dynamics.


Evaluations of the impacts of environmental stressors will be made using updated models that partition current stage-specific mortality estimates. A multifaceted approach will be used that includes:

1. Synthesis of long-term data sets to provide vital rates as well as survivorship values.
2. Spatially and temporally segregation of the mortality associated with well-documented environmental stressors (e.g. trawling, longline, photopollution impacts, etc.).
3. Collection of new data determining actual sex ratios from southeastern US nesting beaches.
4. Documentation of spatial variability in hatchling survivorship following migration from the nesting beach.
5. Production of two-sex, spatially-explicit, models of North Atlantic loggerhead sea turtles.
6. Employment of the models to evaluate and predict the impacts of multiple environmental stressors, test existing management plans, and suggest revisions necessary.

Expected Results:

The combined syntheses and collection of historical and novel empirical data with a new modeling framework will enable the researchers to integrate the effects of multiple stressors as a basis for contemporary management alternatives for species conservation. This approach to wildlife risk assessment for migratory, long-lived species may subsequently be extended to other protected species.

Publications and Presentations:

Publications have been submitted on this project: View all 50 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

animal, reptiles, population biology, habitat degradation, indicators, temperature dependent sex determination, matrix population models, mark-recapture, aquatic, marine sciences, midAtlantic, zoology, toxics, sex, ecological effects., RFA, Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Toxicology, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, wildlife, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Zoology, Environmental Statistics, Ecology and Ecosystems, Ecological Risk Assessment, Ecological Indicators, ecological exposure, risk assessment, predicting risk, spatial distribution, demographic, contaminants, demographic data, stressors, loggerhead sea turtles, multiple stressors, Wildlife Risk Assessment, wildlife populations, stress effects on wildlife populations, two-sex spatially explicit model, spatial demographic model, sensitive population

Progress and Final Reports:

  • 2002 Progress Report
  • 2003
  • 2004 Progress Report
  • Final Report