The American crocodile (Crocodylus acutus) is a federally listed species that occurs along the coast of southern Florida and the Florida Keys. American crocodiles can be found in natural and man-made water bodies ranging from fresh to hypersaline. American crocodiles in the USA were reclassified from endangered to threatened in 2007 in part because of a nesting colony at the Florida Power and Light Turkey Point Power Plant (TP). A major threat to continued recovery of American crocodiles is habitat degradation due to a growing human population.
The first American crocodile reported at TP was in 1976 and the population there has since flourished. A program was implemented in 2009 to monitor distribution, abundance, and body condition through spotlight and capture surveys. In 2013, system-wide changes in temperature and salinity were detected, and a trend of decline in both crocodile abundance and overall body condition was observed. From May 2015 to February 2016 we investigated the potential causes of these declines at the clinical level. Blood was collected from C. acutus at TP and compared to samples from crocodiles in nearby Everglades National Park (ENP). These samples were analyzed for 16 parameters related to stress and health.
Results/Conclusions:
From 2013-2015, water temperature at TP fluctuated between 24 – 45 degrees centigrade but did not increase, and salinity increased from 60 - 84 ppt. In correlation with these increases, both the number of individuals observed and the body condition of crocodiles decreased. Blood panels showed that American crocodiles had elevated sodium and chlorine levels, as well as elevated corticosterone compared to crocodiles in ENP. Elevated levels of sodium and chloride are commonly associated with dehydration, and elevated corticosterone in cooling canal animals suggests that TP crocodiles exhibited higher stress relative to ENP individuals.
TP is a completely man-made landscape that has proven suitable for crocodiles. Recent changes in environmental conditions have been associated with population and individual responses of crocodiles. This underscores the value of crocodiles as ecological indicators. We hypothesize that management efforts to lower salinities in the TP cooling canal system will increase relative density and improve body condition and overall health of crocodiles.