At least two Nile crocodiles native to Africa have been found living in the wild in Florida — with more possibly lurking — where they pose a threat to the already fragile Everglades ecosystem and could cause serious injury to people.
How the Nile crocodiles arrived in Florida is not clear, but DNA evidence published in a new study suggests they were likely brought from Africa as part of the exotic pet trade.
"They didn't swim from Africa," University of Florida herpetologist Kenneth Krysko said. "But we really don't know how they got into the wild."
The research published in the peer-reviewed journal Herpetological Conservation and Biology said that DNA from at least two crocodiles captured in Florida were closely related to a Nile crocodile from South Africa.
Samples taken from captive crocodiles in Disney's Animal Kingdom and local zoos did not share similarities with the Nile crocodiles found in the Everglades, further suggesting that someone brought the species illegally into the state as a pet.
The Nile crocodile, which lives mostly in the eastern half of Africa and reaches lengths of up to 20 feet, is a much larger and more aggressive creature than Florida's native species, the American crocodile.
The invasive croc is known to prey upon a large range of animals, including cattle and humans. Nile crocodiles fatally attacked 354 people between 2010 and 2014, while the American crocodile has never been known to kill humans.
The Nile crocodile may also prey on American crocodiles, which are already endangered due to human encroachment on their environment as well as introduced species like the Burmese python. The Nile crocodile could also breed with the American crocodile, resulting in hybrids and changing genetics.
One crocodile in the study was captured, released, and then recaptured two years later, allowing scientists to study its growth. The findings showed that southern Florida's environment provided sufficient prey and temperatures for the creature to grow.
In Mississippi, Nile crocodiles have been released but were recaptured quickly. Still, the scientists noted that much of the Atlantic and Gulf coasts could provide similar conditions as the Everglades, where the Nile crocodiles could also flourish.