A major goal for the Comprehensive Everglades Restoration Plan (CERP) is to restore the ecological characteristics of the Everglades including historical abundance and distribution of apex predators including wading birds and alligators. Alligators are important in the Everglades food web as predator, prey, and protector, and are an ecological engineer, creating high (nests) and low (trails and alligator holes) topography within the marsh that is important for biological diversity and ecosystem function. A conceptual ecological model has been developed that describes linkages between alligators and ecosystem stressors such as water depth patterns and salinities, and other ecological attributes such as aquatic fauna and wading birds. We used data from a long-term monitoring program to examine trends in alligator body condition (Fulton’s K) over a15 year period (2000-2014) at seven different wetland areas within the Everglades ecosystem, to assess patterns and trends relative to restoration targets, and relate those trends to hydrologic variables. We developed a series of 17 a priori hypotheses that we tested with an information theoretic approach to identify which hydrologic factors affect alligator body condition.
Results/Conclusions
Alligator body condition was highest throughout the Everglades during the early 2000s and is approximately 5-10% lower now (2014). Values have varied by year, area, and hydrology. Body condition was positively correlated with range in water depth and fall water depth. Our top model was the “Current” model and included variables that describe current year hydrology (spring depth, fall depth, hydroperiod, range, interaction of range and fall depth, interaction of range and hydroperiod). Across all models, interaction between range and fall water depth was the most important variable (1.0) followed by spring and fall water depths (0.99), range (0.96), hydroperiod (0.95) and interaction between range and hydroperiod (0.95). Our work provides additional evidence that restoring a greater range in annual water depths is important for improvement of alligator body condition and ecosystem function. This information can be incorporated into both planning and operations to assist in reaching Everglades restoration goals.