Food habits of the American alligator, Alligator mississippiensis, in the southern Everglades

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Julian Lee - Committee Chair


Food habits of American alligators from Shark River Slough, Everglades National Park, Dade County, Florida were investigated during October and March of two consecutive years, 1994-1996. Larger alligators fed predominately on snakes, aquatic salamanders, and snails. Fish were of minor importance in the diet of larger alligators but were the only vertebrates utilized by smaller alligators. Birds and mammals were not consumed in great numbers by any size class. Apple snails were recovered in large numbers from most size classes. Snails were the most important prey for subadults and juveniles, whereas the smallest alligators preyed almost exclusively on insects.Little seasonal variation existed in prey use, although predation on salamanders was significantly higher in October. There were no sexual differences in the use of any prey. Small alligators fed predominately on invertebrates, and with increasing size, they incorporated vertebrates into the diet.I quantified gastric residence times for seven prey species. Portions of the turtle, bird, and mammal remained in the stomach for at least 10 days after ingestion. In contrast, frogs exited the stomach five times faster than the snake or salamander, and three times faster than the insect. To minimize the biasing effects of differential gastric residence times, a series of standards reflecting recent ingestion were created. These criteria were utilized to reanalyze the stomach content data.Reanalysis revealed that many prey taxa were substantially over-represented by frequency of occurrence and mass. Significant statistical reductions in mass existed for every prey class except crustaceans and fishes when applying the 48 hr residency criterion. These adjustments resulted in a more accurate representation of prey importance in the diet of alligators.I calculated relative condition factors on juvenile alligators to explore the idea that southern Everglades alligators have higher relative body conditions during periods of low water. However, mean body condition was significantly higher during the wet season collection periods, refuting the hypothesis.


Biology, Ecology; Biology, Zoology

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