Malcolm Brabant in Miami: The crocodile nesting sites were all but wiped out

The reptiles joined the list of endangered species in 1975 when there were just 20 nesting females left in two havens, the Everglades National Park and north Key Largo.

But biologists at the University of Florida now say that crocodile nests have been found as far afield as Florida's southern Gulf Coast and at the Marco Island Airport.

Nuclear breeder

They have also discovered nests in an area called Biscayne Bay for the first time in 100 years.

Researchers estimate that between 500 and 800 crocodiles are thriving in the state.

Florida: Uniquely home to crocs and alligators

In fact, the reptile's comeback has been so vigorous that the Florida Game and Fresh Water Fish Commission receives more complaints about nuisance American crocodiles than any other endangered species.

Frank Mazzotti, professor of wildlife ecology and conservation at the University of Florida, said: "We have more crocodiles, in more places, doing more things than we have had for a long time."

He attributes the success of the reptiles to the Endangered Species Act and to the efforts made to clean up and preserve the crocodiles' natural habitat.

Unusually, a nuclear power plant also comes in for some praise in the story of the species' recovery.

Cooling canals at the Turkey Point Nuclear Plant near Miami provided ideal crocodile nesting conditions, allowing them to reproduce at a rate three or four times the average.

The American crocodile only occurs in South Florida - the only place in the world where crocodiles and alligators co-exist.

'Associate humans with food'

This may have something to do with the American crocodile's passive disposition, which is in marked contrast to the highly aggressive character of other species of the reptile.

Prof Mazzotti said that although the crocodiles regularly turned up in public places as they looked for new areas to inhabit, they were only dangerous when fed.

"They not only become used to humans, they associate humans with food," he said.

"Unfortunately, they don't know where the hand-out ends and the hand begins."