The greater Everglades of south Florida are characterized by complex patterns of spatial heterogeneity and temporal variability. Spatial and temporal hydrologic patterns (hydropattern), which result from the distribution, volume, and timing of water flow, are a major driving force controlling the trophic dynamics of these systems. After many decades of intense adverse water management impacts, hydrologic restoration alternatives are now being developed and proposed. Thus, there is a need to predict and to compare the future effects of alternative hydrologic restoration scenarios on the biotic components of these systems. The American alligator is not only a top consumer and a keystone species in the Everglades, but also physically influences the system through construction and maintenance of alligator holes and trails. The existence of this species is important to the faunal and floral character of the Everglades as it has evolved. Despite its prominence biologically and publicly in the system, many important questions about basic behavioral and population parameters of alligators remain unanswered.

Although many assumptions can be made, there is no reasonable certainty in estimates of movements or survival of varying size classes of alligators under either stable or fluctuating water levels. The reproductive contribution of an individual animal or of different size/age classes in a given year has been a principal stumbling block for attempts at modeling any crocodilian population. This study is focused on both field experiments and statistical models to obtain estimates of the aforementioned parameters. Further, the broad project goals include end products of ecologically based ecosystem models (under the model integration framework, "Across Trophic Level System Simulation" (ATLSS) program), including predictive population model(s) for alligators to be used in evaluating restoration scenarios for the Everglades/Big Cypress ecosystems. The project incorporates the expertise of many collaborators, including Clarence L. Abercrombie of Wofford College; Timothy S. Gross of the U.S. Geological Survey; Frank Mazzotti of the University of Florida; and several biologists from the Florida Game and Fresh Water Fish Commission and the Everglades National Park.

The project includes several interrelated component studies designed to address the questions outlined above:

1. Alligator movement, habitat use and preference, survival, and breeding potential: This study uses radiotelemetry technology to monitor the movement patterns of alligators in Everglades National Park (Shark River Slough) and Water Conservation Area 3A. Over the course of the study, approximately 80 animals (partitioned into area, habitat, sex, and size classes) have been implanted with transmitters and monitored for 1-3 years. Preliminary analyses are available including estimates of home-range size, habitat preferences, nesting parameters, and movement patterns. This study is scheduled to terminate in Summer 1999.

2. Alligator Thermoregulation: Of the 80 telemetered animals discussed above, approximately 30 additionally were implanted with temperature data recorders. The recorders logged internal body temperatures every hour for 1 year. After recapture, the loggers were removed and coupled with corresponding environmental temperatures, we now have an excellent data base to address questions concerning metabolic costs of surviving in various thermal environments. This data, in conjunction with the telemetry results outlined above and further measurements of alligator holes and canals discussed below, will allow us to explore the relative role of canals and other landscape features and hydrological impacts on alligator populations. This study is scheduled for completion in Fall 1999.

3. Alligator Holes: During the course of the telemetry study, it became apparent that animals existing in natural slough habitats used the landscape in very different ways from animals living in canal systems. Marsh animals use 1 to 5 alligator holes for thermoregulation, cover, and, presumably, feeding. To better understand the role of alligator holes and canals in the life history of the alligator, we have undertaken to catalog the physical attributes of the holes or canals used by each telemetered alligator. This information will be important for the simulation models discussed below, as well as, determining the relative importance of these landscape features. This study will conclude in 2000.

4. Breeding Potential Index: As a component of ATLSS, the alligator breeding potential index provides an estimate of the relative rate of successful offspring production under varying hydrological conditions in south Florida. The model uses index estimates for nesting potential, habitat conditions, and nest-flooding potential to construct an index value for each 500-meter cell in the greater Everglades ecosystem. When fully functional, the index will provide comparisons of each alternative and base condition under the Central and Southern Florida Comprehensive Project Review Study (RESTUDY). We hope to have a verified index in place on the ATLSS website by Spring 1999.

5. Population Model: A matrix-based population simulation model for the alligator in south Florida will be constructed during 1999-2000. This model, although having the same underlying goals of the above index (to explore the effects of varying hydrological alternatives on alligator populations), will investigate other life-history parameters. In concert with this model, historical data sets will be located, and a data base of alligator ecology studies will be produced. When coupled with the outputs from other existing models, the alligator population model will provide estimates of survival, fecundity, and growth (both individual and population) under each Restudy alternative and will be incorporated into the ATLSS program.

A significant part of the funding for this research was provided from the U.S. Department of the Interior, South Florida Ecosystem Restoration Program "Critical Ecosystems Studies Initiative" (administered through the National Park Service) and from the U.S. Geological Survey, Florida Caribbean Science Center.

(This abstract was taken from the Proceedings of the South Florida Restoration Science Forum Open File Report)