Reptiles adapt to the changing Everglades
DAVIE – A study by University of Florida scientists that focused on the endangered American crocodile is mapping its population status over the past 40 years in response to changes in the Florida Everglades.
Key findings demonstrate that increased salinity in the water in which crocodiles navigate influences their health, reproductive behavior and ultimately survival.
Considered a key wildlife indicator, the health of the American crocodile will continue to tell us whether water restoration efforts that began in the late 1980s are benefiting crocodiles. These restoration efforts began as part of a comprehensive $14.8 billion Everglades Restoration Project aimed at restoring more natural conditions to the Florida Everglades.
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“Crocodiles may appear tough and resilient, and we consider them ancient dinosaurs, but they are vulnerable to environmental changes, including human-caused changes to their natural ecosystem,” Venetia Briggs said. Gonzalez, a research biologist who works at the Croc Docs Laboratory at the Institute of Food and Agricultural Sciences at the University of Florida Research and Education Center in Fort Lauderdale.
Briggs-Gonzalez is lead author of American Crocodiles as restore bioindicators in the Florida Everglades, a study published in PLOS ONE on May 19. The study draws on nearly 40 years of capture data and sheds light on how increasing salinity levels in Florida Bay over time influence the health of the American crocodile population.
“As designated bio-indicator species telling us how restoration efforts are working in the Everglades, our results show that hypersaline conditions in the waterways in which they live, breed and navigate negatively affect how a crocodile behaves in its environment. Where a crocodile is captured is important to its overall condition, rate of growth, and ultimately to its survival,” Briggs-Gonzalez said.
For the study, UF/IFAS scientists conducted a long-term capture-recapture assessment on the American crocodile population in South Florida from 1978 to 2015. Through the study, the researchers estimated annual survival of the species and assessed efforts to restore more historic hydrological conditions. in South Florida.
Scientists surveyed an area stretching 341 miles from Biscayne Bay west to Cape Sable. The study area included Northeast Florida Bay, Crocodile Lake National Wildlife Refuge, and the Flamingo Area in Everglades National Park.
Scientists conducted 10,040 crocodile capture and release events. Over 90% of what they captured were hatchlings. To assess the status of American crocodiles in Florida, they measured growth, survival, and body condition. The study used salinity levels recorded at nearby monitoring stations where the crocodiles were found in their natural habitat, whether in freshwater estuaries, brackish waterways or in seawater along of the coastal coastline.
“Overall there’s a good sign of improvement, and they’re doing better here than other parts of the world in their lineup,” Briggs-Gonzalez said. “However, with increasing freshwater flow and decreasing salinity, we expect further improvement in crocodile growth, body condition and survival.”
Among the study’s critical findings is how American crocodiles in South Florida showed signs of moving from their traditional nesting grounds to avoid areas of high salinity. Scientists have found that there are areas of high salinity mostly concentrated in northeast Florida Bay, where water has been diverted to accommodate development.
“Historically, crocodile nesting has occurred in the Crocodile Lake National Wildlife Refuge and northeast Florida Bay in Everglades National Park, with no known nesting in the Cape Sable or Flamingo area until now. until a canal was blocked in 1986 and the first nest was discovered the next morning,” Gonzalez-Briggs said.
Since then, the majority of nesting in Everglades National Park has moved to the Cape Sable and Flamingo areas. The study reports that nests in northeast Florida Bay are increasing at a slower rate.
“High salinity is not good for wildlife, especially those that need fresh water,” Briggs-Gonzalez said. “Now they have to endure salt water, and baby crocodiles need fresh water to survive. High salinity also threatens a crocodile’s growth and fitness. It’s a cascading effect that impacts on all aspects of their lives.
A crocodile’s survival and growth are long-term measurements, while body condition is a short-term measurement. With continued monitoring by the Croc Docs, up-to-date data will illustrate the progress of crocodiles in the Everglades.
“Crocodiles show us that fresh water is important,” Briggs-Gonzalez said. “How much and when matters because it affects their survival. It’s not just about whether they will live or die, but how healthy they will be during their lifetime. By getting the right water in the Everglades, everything else will fall into place.
Lourdes Mederos is a public relations specialist at the University of Florida’s Institute of Food and Agricultural Sciences. His email is [email protected]