Daniel H. Slone¹ and Kenneth G. Rice^2
1USGS Florida Integrated Science Center, Gainesville, FL, USA
²USGS Florida Integrated Science Center, Fort Lauderdale, FL, USA

The Comprehensive Everglades Restoration Plan (CERP, www.evergladesplan.org) requires ecological models to assist in evaluation of restoration project alternatives, formation of restoration targets, and evaluation of restoration success. The American alligator is considered a keystone predator in the Everglades system that creates important habitat features such as mounds and water holes that are used by plants and other animals. Furthermore, they are an important component of the Everglades restoration plan because they are both highly dependent on the success of restoration efforts and indicative of the restoration's effect upon other species. They depend on a predictable and even water flow free from drought, and from flooding that often destroys nests: conditions integral for the health of other Everglades residents as well.

Historically, alligators were more abundant in prairie habitats of the eastern floodplain than in deep-water central sloughs. They are now concentrated in these deep central sloughs and canals, with relatively few individuals residing in the edge habitats due to the extremely short hydroperiod under managed conditions. Within the framework of CERP, plans are being laid to restore a more natural water flow to the Everglades ecosystem. In support of this, the largest ecological restoration project ever attempted in the United States, USGS and its cooperators are using a system of empirical data collection and simulation modeling to apply information on wildlife community patterns for guiding the Everglades restoration process, known as the ATLSS (Across Trophic Levels System Simulation, coordinated by Donald DeAngelis, USGS) Project. The alligator model is part of the ATLSS system of models, but with an intuitive GUI interface, it is useful also as a stand-alone simulation of alligator population densities and health, and accepts arbitrary hydrological models as a driver, either for the entire CERP geographic scope and work plan, or over a smaller area with only one or few CERP projects modeled. By applying the alligator model to proposed restoration alternatives and predicting population responses, we can choose the alternatives that result in biotic characteristics that approximate historical conditions, and identify future research needs.

Using the historical Calibration water set, which simulates actual water management through the years 1979-2000, the model output of population density was compared to historical counts of alligators conducted along airboat trails at night with a spotlight. Simulation results of alligator nesting were compared to nesting site surveys, and a body condition index in the model was compared to body condition data collected from the region. Validation results from these comparisons are presented to show the accuracy of the model in several diverse locations throughout their range. Implications for restoration and management decisions are discussed.

Contact Information: Daniel H. Slone, USGS Florida Integrated Science Center, 2201 NW 40th Terrace, Gainesville, FL 32605 USA, Phone: 352-264-3551, Fax: 352-374-8080, Email: dslone@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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