The American Alligator (Alligator mississippiensis) was abundant in the pre-drainage Everglades. Alligators once occupied all wetland habitats in south Florida, from sinkholes and ponds in pinelands to mangrove estuaries during periods of freshwater discharge (Craighead, 1968; Simmons and Ogden, 1998). Nearly all aquatic life in the Everglades is affected by alligators (Beard, 1938). As a top predator in their ecosystem, alligators undergo an extraordinary change in body size, consuming different prey items as they grow (Mazzotti and Brandt, 1994). As ecosystem engineers, alligators create trails and holes that provide aquatic refugia during the dry season and concentrate food items for larger predators. Alligator nests provide elevated areas for nests of turtles and snakes, and for germination of plants less tolerant of flooding (Craighead, 1971; Kushlan and Kushlan, 1980; Enge et al., 2000). Alligator activity also keeps many small creeks in the freshwater mangrove zone, gator hole sites, and areas around tree islands from becoming overgrown with vegetation. It is possible the activity creates firebreaks that provide refuge to woody vegetation and various animal species (Craighead, 1968; Simmons and Ogden, 1998). The water present in holes during the dry season provides critical habitat for nesting female and juvenile alligators (Mazzotti, 1989; Kushlan and Jacobsen, 1990) and provides open water necessary for alligator mating (Garrick and Lang, 1975).

In Everglades National Park, the largest historical alligator populations occurred in broad marl prairies to the east and west of the ridge and slough habitats, and in the freshwater mangrove zone. Land development and water management practices have reduced the spatial extent and changed the hydropatterns of these habitats (Mazzotti and Brandt, 1994). As a result of these habitat alterations, alligators are now less numerous in the marl prairie, rocky glades, and mangrove fringe areas. For alligators, an important alteration was the construction of canals. Alligators initially displaced by development or drainage now reside in canals. The effects of artificial habitats such as canals on creation and maintenance of alligator holes had not been studied until recently. Everglades canals serve as alligator refugia throughout the Greater Everglades ecosystem. Adult alligator density (especially of males) is higher in canal habitats than in the natural marsh interior (FFWCC, unpub. data; Morea, 1999). The canals may provide suitable habitat for large alligators, but unlike alligator holes, they are not suitable for smaller alligators, smaller marsh fish, or foraging wading birds. Though this trend may be remedied by proper management practices, characteristics of alligator habitats have changed with the creation of canal systems now present in the Florida Everglades (Kushlan, 1974).

Restoration of hydrologic patterns and ecological function in the Everglades is now underway. The relations among dry season refuge, aquatic fauna, wading birds, and alligators have been identified as key uncertainties in the Comprehensive Everglades Restoration Plan (CERP; U.S. Army Corps of Engineers, 1999). Due to the alligator's ecological importance and known sensitivity to hydrology, salinity, habitat productivity, and total system productivity, the species was chosen as an indicator of restoration success. A number of biological attributes (relative density, relative body condition, nesting effort, and nesting success) can be measured, standardized methods for monitoring have been developed, and historical information exists for alligator populations in the Everglades. These attributes can be used to determine success at different spatial and temporal scales, and are instrumental for constructing ecological models used to predict restoration effects. The relative abundance of alligators is expected to increase as hydrologic conditions improve in over-drained marshes and freshwater tributaries. As canals are removed, densities of alligators in adjacent marshes and occupancy of alligator holes is expected to increase. As hydroperiods and depths approach more natural patterns, nesting success, alligator growth, and condition are all expected to increase in areas where they are currently below historic values.

REFERENCES

Beard, D.B. 1938. Everglades National Park Project: Wildlife Reconnaissance.U.S. Department of Interior, National Park Service. Washington, D.C.

Craighead, F.C., Sr. 1968. The role of the alligator in shaping plant communities and maintaining wildlife in the Southern Everglades. Florida Naturalist. 41:2-7, 69-74, 94.

Craighead, F. C. Sr. 1971. The Trees of South Florida: The Natural Environmentsand Their Succession. University of Miami Press, Miami, FL.

Enge, K.M., H.F. Percival, K.G. Rice, M.L. Jennings, G.R. Masson, and A.R.Woodward. 2000. Summer nesting of turtles in alligator nests in Florida. J.Herp. 34: 497-503.

Garrick, L.D. and J.W. Lang. 1975. Alligator courtship. American Zoologist 15: 813.

Kushlan, J.A. 1974. Observations of the role of the American alligator in the southern Florida wetlands. Copeia 993-996.

Kushlan, J.A. and M.S. Kushlan. 1980. Everglades alligator nests: nesting sites for marsh reptiles. Copeia 1930-1932.

Kushlan, J. A. and T. Jacobsen. 1990. Environmental variability and the reproductive success of Everglades alligators. J. Herpetol. 24(2):176-184.

Mazzotti, F.J. 1989. Structure and function. Pages 42-57 in C.A. Ross and S. Garnett, editors. Crocodiles and Alligators. Weldon Owen Pty. Ltd., Australia.

Mazzotti, F. J. and L. A. Brandt. 1994. Ecology of the American alligator in a seasonally fluctuating environment. pp. 485-505 in S. Davis and J. Ogden, (eds.), Everglades: The Ecosystem and its Restoration. St. Lucie Press, Delray Beach, Florida.

Morea, C. R. 1999. Home range, movement, and the habitat use of the American alligator in the Everglades. Unpublished Thesis, Univ. Florida, Gainesville, Florida.

Simmons, G., and L. Ogden. 1998. Gladesmen. University Press of Florida, Gainesville, FL.

U.S. Army Corps of Engineers. 1999. Final Integrated Feasibility Report and Programmatic Environmental Impact Statement. Central and Southern Florida Project Comprehensive Review Study. U.S. Army Corps of Engineers. Jacksonville District.

Contact: Frank J. Mazzotti, University of Florida Fort Lauderdale Research and Education Center, 3205 College Ave., Ft. Lauderdale, Florida, 33314; Phone: 954-577-6304, FAX: 954-475-4125, e-mail: fjma@mail.ifas.ufl.edu

(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report 03-54)

Back to Project Homepage