INTRODUCTION

The American alligator (Alligator mississippiensis) is a keystone species of the South Florida Ecosystem. Population growth and survival depends directly on the hydrologic functioning of South Florida watersheds. The American alligator's role as a top predator and its effect on the structuring of plant communities and associated aquatic animals (Mazzotti and Brandt, 1994) make it an ideal indicator of ecosystem health. The response of alligator populations to spatio-temporal changes in hydrological conditions throughout the South Florida ecosystem are integral to the evaluation of any restoration alternative.

Alligators and Water management

Historical trends

• Summer water levels were predictable.
• Nests built at appropriate height to avoid flooding.
• Abundant in prairie habitats of the eastern floodplain.
• Occupancy of the deep water, central sloughs was relatively low.

Current trends

• High and unpredictable rate of nest flooding.
• Natural water level predictability has been lost.
• Marsh alligator densities are now highest in the central sloughs and canals (Kushlan and Jacobsen, 1990; Fleming, 1991) and relatively low in the edge habitats.
• Canal habitats contain high concentrations of adult alligators.
• Nest densities are relatively high on levees and associated spoil islands.
• Low survival of young.
• Decrease in the number of alligator holes or possible brood habitat proximal to canals (F.J. Mazzotti, Univ. of FL pers. comm.).

Future trends with Restoration

• Modified hydrological conditions might be expected to increase nesting effort, nesting success, and abundance of alligators in the aforementioned edge habitats.
• A corresponding increase in the number and occupancy of alligator holes to serve as drought refugia may be seen.

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Acknowledgements

This research was supported in significant part by DOI's Critical Ecosystem Studies Initiative, a special funding initiative for Everglades restoration administered by the National Park Service; and in part by USGS's Florida Caribbean Science Center.

T. Foster assisted with poster formatting.

1 ATLSS The Institute for Environmental Modeling University of Tennessee, Knoxville Knoxville, TN 37996-1610
2 USGS-BRD Everglades National Park Field Station 40001 S. R. 9336 Homestead, FL 33034