Trends in American Alligator Pods in Arthur R. Marshall Loxahatchee National Wildlife Refuge

Abstract

Alligators are an important component of the Greater Everglades serving as ecosystem engineers, predator, prey, and are tightly tied to water depth patterns. Because of their importance to ecosystem function and link to hydrology, alligators are an ecological indicator for Everglades restoration. I used data from fall night-time spotlight surveys of alligators in the Arthur R. Marshall Loxahatchee National Wildlife Refuge to describe the trend in number of hatchling pods from 1998 to 2021 and relate that trend to hydrologic parameters hypothesized to influence alligator production. I used an information-theoretic approach to evaluate 14 models created from combinations of year of observation and three hydrologic variables: average and range in water depth from 16 April of the previous year to 15 April of the nesting year (breeding potential window) and average water depth from 16 April to 31 May of the nesting year (courtship and mating window). Number of pods ranged from 16 in 1998 to 0 in 2011. Each of the four top models included year and one or more of the hydrologic variables as predictors and explained 26-34% (D-squared) of the variation in number of pods. Year was the predictor for which the 95% confidence interval did not contain zero and indicated a declining trend (-3% to -8%; 95% confidence interval). All hydrologic variables were included in the top models indicating they contribute some information toexplaining the trend; however, contrary to my hypotheses, there was not a clear relationship between any of the hydrologic variables and number of alligator pods. My hypotheses were based on information synthesized in the Alligator Production Suitability Index model being used in Everglades restoration planning and my results suggest that additional refinement of that model is warranted.