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Encore: 40-Year UF/IFAS Study Connects Health of American Crocodiles to Salinity Levels in Florida Everglades

Nest hatching by Jemeema Carrigan (57).jpg
Jemeema Carrigan
American crocodile hatchling.

This episode originally aired on May 25, 2021.

While Florida might best be known for an abundance of American alligators, it’s also the only place in the world where gators coexist with American crocodiles — particularly the southern Everglades. A new study led by scientists with University of Florida's Institute of Food and Agricultural Sciences maps out the status of crocodile populations in south Florida over the past 40 years to learn how they’ve responded to changes in the Everglades ecosystem. "American Crocodiles as restoration bioindicators in the Florida Everglades" was published in PLOS ONE on May 19.

For the study, UF/IFAS scientists conducted a long-term capture-recapture assessment on the South Florida population of American crocodiles from 1978 to 2015. They studied an area spanning 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 during which they mark the crocodiles so they could monitor them over time. As they recaptured them scientists could then measure growth, survival and body condition. The study used salinity levels from nearby monitoring stations where crocodiles were in their natural habitats whether in freshwater estuaries, brackish waterways or in sea water along the coastal shoreline.

Data indicates that increased salinity in the water that crocodiles navigate negatively influences their health, breeding behavior and ultimately, their survival. This research also helps to inform researchers about the success of Everglades restoration efforts because American crocodiles are considered a key wildlife indicator.

We spoke with the study’s lead author, Dr. Venetia Briggs-Gonzalez. She's a research biologist who works at the Croc Docs Laboratory at the UF/IFAS Fort Lauderdale Research and Education Center.