Spatial and Age-Structured Population Model of the American Crocodile for Comparisons of CERP Restoration Alternatives

Project Investigators: Daniel Slone, Kenneth G. Rice, Frank J. Mazzotti Project Personnel: Timothy W. Green Project Start Date: 2007 End Date: 2008 Recent Funding: (FY07) USGS GE PES Work Plans Project Summaries

Summary

To adequately understand crocodile populations and model population growth, existing data must be assembled and model parameters estimated. A simulation model can then be constructed and validated both with existing data and through expert opinion.

Restoration efforts in the Comprehensive Everglades Restoration Plan (CERP) will likely cause changes to salinity levels throughout the habitat of the American crocodile. Changes in salinity were seen after previous hydrologic changes in the area, when reduced freshwater flow was associated with increased salinity levels in Florida Bay estuaries, including one of the core nesting areas of the American crocodile. Large crocodiles are not significantly affected by high salinity, but previous work has shown that high salinity levels may reduce survival of hatchlings and juveniles. The detrimental effects of high salinity on hatchling and juvenile crocodiles has led to the hypothesis that increased freshwater flow to the estuaries will increase the animals' distribution, abundance, and growth.

To adequately understand crocodile populations and model population growth, existing data must be assembled and model parameters estimated. A simulation model can then be constructed and validated both with existing data and through expert opinion. A crocodile population model to simulate the south Florida ecosystem under varying management strategies is vital to evaluating and assessing restoration success under CERP.

The objectives of this project are to:

1. Build an age and spatially structured crocodile population model suitable for comparison of CERP restoration alternatives.
2. Couple the local age-structured models into a spatial dispersal model incorporating crocodile movement behavior.
3. Use spatial parameter maps from the Florida Everglades as driving functions on the spatially structured model and to construct crocodile finite rate of increase maps under different management regimes.
4. Perform sensitivity analysis on the model parameters, and release model concept and code for peer-review.

Work Plans

• 2007

Project Summaries

• 2007