Growth dynamics in the American alligator (Alligator mississippiensis)

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Abstract

The growth dynamics of the American alligator (Alligator mississippiensis) were studied in the subtropical Florida Everglades using extensive mark-recapture data from over 2000 recaptures of known-aged and unknown-aged animals. A model based on the power curve best describes growth of Everglades alligators. The nonasymptotic character of this curve leads to rejection of the hypothesis that alligator growth is determinate. A model consisting of piece-wise linear equations better described growth in the first year, and suggested a period of arrested growth occurred in the first winter. A comparison of predictions from growth models derived from several populations indicated that Everglades alligators grew more slowly than did those in more temperate areas, leading to the rejection of the hypothesis that growth rates in subtropical Florida would be elevated because of the long growing season. We attribute this result to a combination of increased maintenance costs and a limited resource base in the Everglades.

Analyses considered the extent to which growth model evaluation and use can be affected by data selection. Mathematical constraints posed by negative growth data can be alleviated by including growth records over combined recapture intervals to achieve a positive growth increment. However, periods of no to negative growth may be real, and such deviations are obscured by fitting growth data to monotonically increasing models.

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