Using DNA analysis, scientists have confirmed the capture of Nile crocodiles (Crocodylus niloticus) in South Florida.
A Nile crocodile (Crocodylus niloticus). Image credit: Tambako the Jaguar.
The Nile crocodile is a large species native to the rivers, lakes and swamps of Africa. It can reach up to 7 m in length and up to 730 kg in weight and is known to prey upon crustaceans, arachnids, insects, fishes, amphibians, reptiles, birds, and mammals.
Now three juveniles of this African species have been found in South Florida, swimming in the Everglades and relaxing on a house porch in Miami.
“The invasive crocodiles were captured between 2000 and 2014, leading us to analyze their DNA, study their diet and one of the animal’s growth,” said co-author Dr. Kenneth Krysko, a researcher with the Florida Museum of Natural History.
“We verified the animals were Nile crocodiles linked to native populations in South Africa, and confirmed the species can survive in Florida — and potentially thrive.”
Dr. Krysko and his colleagues found one juvenile grew nearly 28% faster than wild Nile crocodile juveniles from some parts of their native range.
“DNA analysis revealed the three similar-size Nile crocodiles were genetically identical, suggesting they were introduced via the same source, but the source has not been confirmed,” Dr. Krysko said.
According to the team, over the last decade, large groups of Nile crocodiles have been imported from South Africa and Madagascar for display at places like Disney’s Animal Kingdom and to supply Florida’s flourishing pet trade, with the latter being the most likely introduction pathway.
While there is currently no evidence of an established population, the scientists recommend a scientific risk assessment to evaluate the potential for Nile crocodiles to breed and spread across the state.
“Florida’s Atlantic coast and the entire Gulf of Mexico coastline provide favorable climate for Nile crocodiles,” they said.
“Florida’s subtropical climate is one reason the state has the world’s largest number of invasive species — from the Burmese python that has invested the Everglades to the Cuban tree frog, which has been found as far north as Jacksonville on the East Coast and as far north as Cedar Key on the Gulf Coast.”
“My hope as a biologist is that the introduction of Nile crocodiles in Florida opens everyone’s eyes to the problem of invasive species that we have here in our state. Now here’s another one, but this time it isn’t just a tiny house gecko from Africa,” Dr. Krysko said.
The team’s findings were published in the April 2016 issue of the journal Herpetological Conservation and Biology.
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Michael R. Rochford et al. 2016. Molecular Analyses Confirming the Introduction of Nile Crocodiles, Crocodylus niloticus Laurenti 1768 (Crocodylidae), in Southern Florida, with an Assessment of Potential for Establishment, Spread, and Impacts. Herpetological Conservation and Biology 11 (1): 80-89
