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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES) Initiative

Fiscal Year 2005 Study Summary Report

Study Title: American Alligator Ecology and Monitoring for CERP
Study Start Date: 2003 Study End Date: 2006
Web Sites: sofia.usgs.gov, www.atlss.org
Location (Subregions, Counties, Park or Refuge): Total System
Principal Investigator(s): Kenneth G. Rice, Frank J. Mazzotti, H. Franklin Percival
Study Personnel: Eliza Gilbert, Danielle Ogurcak, Chris Bugbee
Supporting Organizations: University of Florida
Associated / Linked Studies: MAP study: American Alligator Distribution, Size, and Hole Occupancy and American Crocodile Juvenile Growth & Survival, CESI study: Relative Distribution, Abundance, and Demographic Structure of the American Alligator in Relation to Habitat, Water Level, and Salinity.

Overview & Objective(s): Many important questions concerning the effects of Everglades restoration on alligator populations remain unanswered such as the impacts of decompartmentalization, the role of alligator holes as aquatic refugia, and the effects of hydrology on population growth and condition. Further, the methods for monitoring and evaluating restoration success are not clear or have not been adapted for use during CERP. Also, we need to continue to update and validate restoration tools such as population models for use in alternative selection, performance measure development, and prediction. This project will directly address the questions outlined above, develop monitoring methods, and validate restoration tools for use in CERP.

  • Develop monitoring methods necessary for evaluation of restoration success in alligator populations.
  • Understand the effects of decompartmentalization and other CERP projects on restoration of alligator populations.
  • Identify and quantify the extent of aquatic refugia maintained by alligators throughout the system and develop relationships necessary to predict restoration of refugia.
  • Validate and update ecological models for use in prediction of the effects of restoration.

Status: We are continuing to provide parameter information to the ATLSS alligator population model. We are adding to our information concerning the impacts of canals on alligator populations with investigations into alligator production. We have established monitoring of alligator population growth, condition, and size distribution throughout the Greater Everglades. We are investigating quantitative and field methods to improve the precision and accuracy of our monitoring through the use of double-observer surveys, artificial surrogates, radio telemetry, and mark recapture. We are currently mapping alligator holes and aquatic refugia within Everglades National Park. The ATLSS Alligator Production Index is now available for use in the restoration process but is also undergoing further calibration, validation, and updating with new data. The ATLSS Alligator Population Model has been completed and has undergone expert review, calibration, and some validation. Both models are fully functional and available for use in comparison of restoration alternatives.

Recent & Planned Products:
Through the first 3 quarters of FY05, 2 peer-reviewed journal articles, 3 major technical reports, and 1 book chapter were published. We also gave several presentations at National and International Meetings and 2 additional manuscripts were submitted to peer-reviewed journals.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan) [See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]:

  • The role of alligator holes in providing dry season refugia was identified specifically as a science need for the Ten Mile Creek Reservoir — Assisted Stormwater Treatment Area Project (p. 35), the Water Preserve Area Projects (p. 45), and the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement Project (p. 65, 69).
  • The study supports the L-31N Seepage Management Pilot and Everglades National Park Seepage Management Projects (p. 48) and Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement Project (p. 65, 69) by providing ecological monitoring and assessment of restoration impacts on the alligator.
  • Both models developed in this study (habitat suitability model and spatially explicit demographic model) are identified as Landscape-scale Science Needed to Support Multiple CERP Projects (p. 83).
  • The study supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structures project as it (1) provides monitoring and assessment of responses of aquatic communities and habitats (p. 37) and (2) helps understand the ecological effects of hydrology and water quality on refuge resources (p. 40).
  • The study support the Southwest Florida Feasibility Study Project by providing modeling to predict species-level responses to habitat change (p. 50) and monitoring of key indicators (p. 51).
  • The study provides improvement of ecological model to make them more suitable for application and analysis as identified in the Combined Structural and Operational Plan Project (p. 64).
  • Further, this study establishes the system-wide monitoring program for alligators as outlined in CESI-MAP.

Key Findings:

  1. We have been able to document the effects of canals and hydropattern on alligator production, movement, and body condition. This information has been incorporated into a population model that can be used for simulation of the effects of restoration including decompartmentalization.
  2. We have produced, calibrated, and validated 2 simulation models that can be used to compare the restoration alternatives throughout the Greater Everglades Ecosystem.
  3. We have developed a monitoring program for alligator populations that can be used to evaluate the effects of restoration throughout the Greater Everglades Ecosystem. This program includes a comprehensive set of performance measures that can evaluate short (body condition), medium (population density, alligator hole occupancy), and long-term (nesting) effects of restoration on alligator populations.
  4. We have mapped alligator holes throughout the Everglades system for monitoring of alligator populations and use as the aquatic refugia data layer in other ecological models.
  5. We have documented an overall decline in alligator body condition throughout the Everglades over the last 5 years. We are now performing analysis to investigate the relationship between this decline and hydrologic variables.

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