Abstract

Alligators are the top aquatic predators of Southern wetlands and, unlike birds, they do not readily migrate. The environmental status of an area is known to affect reproductive parameters of the alligator population.^1,2,3,4,5 Thus, an evaluation of the physiological status of the alligator population in a lake or area of habitat is also an indication of its environmental status. However, capturing and evaluating a sample of adult alligators from a lake or area may not be practical or desirable for an area the size of the Everglades National Park (500,000 acres). Yet, determining reproductive potential and egg parameters for this population can easily be done with a minimum of disturbance. Our laboratory uses reproductive potential,¹ egg parameters,^1,4 yolk fatty acid profiles,⁵ embryonic development,⁶ teratology⁶ and hatchling growth performance^1,4 to evaluate the status of an alligator population. For the present study, egg parameters were determined over a 4-year period for the Everglades National Park, over an 11-year period for Southwest Louisiana (Rockefeller Refuge) and over an 11-year period for Lake Griffin. The Rockefeller Refuge was considered to be a protected, stable, highly productive control area. Lake Griffin in Central Florida is included in the present study because it underwent severe environmental changes in 1996 and 1997.¹ Evidence is presented that reproductive potential and egg parameters are characteristic and relatively constant for a lake or area; however, changes in the environmental status, as occurred on Lake Griffin in 1996 and 1997 will cause readily detectable changes in these values. Data is presented suggesting that the environmental changes on Lake Griffin resulted in the introduction of a hepatic toxin into the alligator population.

Acknowledgements

This research was supported as a part of the ATLSS project of the Dept. of the Interior (USGS) and the National Park Service. The authors wish to thank Dr. Ruth Elsey of the Louisiana Department of Wildlife and Fisheries, the Florida alligator farmers, the Florida Game and Freshwater Fish Commission and especially Mr. Arnold M. Brunell, Mr. Lindsey Hoard and Mr. Allen R. Woodward for providing their information and assistance. Mr. Wayne T. McClellan and Mr. Joseph P. Cardeilhac provided technical assistance.

References

1.  Cardeilhac PT, Winternitz D, Barnett JD, Froelich E, Foster KO, Ashley JD. 1998. Declining Reproductive Potential of the Alligator Population on Lake Griffin in Central Florida. Proceedings International Association for Aquatic Animal Medicine 29:30-37.

2.  Woodward AR, Percival HF, Jennings ML, Moore CL. 1993. Low Clutch Viability of American Alligators on Lake Apopka. Florida Scientist 56:52-63.

3.  Mason GR. 1995. Environmental Influences on Reproductive Potential, Clutch Viability and Embryonic Mortality of the American Alligator in Florida. PhD Dissertation. University of Florida, Gainesville Florida. 123 pp.

4.  Cardeilhac PT. 1987-1991. Diagnosis and Treatment of Infertility in Captive Alligators. Final Reports for the Aquaculture Market Development Aid Program. Vols. I-III. Florida Dept. of Agriculture, Tallahassee, FL 32399-0810.

5.  Millstein SR, Vander Meer RK, Schoenagle EM, Cardeilhac PT. 1994. Dietary Therapy for Egg Fertility in the American Alligator: An Evaluation by Determining Fatty Acid Profiles of Egg Yolk. Proceedings International Association for Aquatic Animal Medicine 25:10-15.

6.  Cardeilhac PT, Hoffingberg ML. Development of the Alligator. 1985. A Color Poster to Grossly Identify Developmental Stages of Normal Embryos Incubated at 88 F (31 C). Aquatic Animal Laboratory, College of Veterinary Medicine Box 100126 HSC University of Florida, Gainesville FL 32610.