Man-eating crocodiles found in Florida

DNA tests have con­firmed that three man-eating Nile crocodiles have been found living in Florida’s swamps.

Unlike local alligators, the species preys on hu­mans and is thought to be responsible for up to 200 deaths a year at home in sub-Saharan Africa.

It is possible more of the beasts are at large in the state, experts say.

It is not known for cer­tain how they reached the US. “They didn’t swim from Africa,” said University of Florida herpetologist Ken­neth Krysko.

One likely possibility was that they were brought in illegally by unlicensed col­lectors, who then failed to keep them secured or inten­tionally released them, Mr Krysko told the Associated Press news agency.

The animals were found in 2009, 2011 and 2014 and were confirmed as Nile crocodiles by a recent DNA test.

The Nile species can grow to up to 6m (20ft), signifi­cantly larger than local al­ligators, which commonly grow up to 4m.

They are known to prey on shrimp, fish, insects, birds and mammals, in­cluding humans. They are also known to attack live­stock.

Florida wildlife experts are concerned that the Af­rican species could pose a threat to the state’s ecosys­tem if they breed in the Ev­erglades wetlands.

The Burmese python was first sighted in the Ev­erglades in the 1980s and there is now an established population of the snake.

“I have two words: Bur­mese python,” wildlife bi­ologist Joe Wasilewski said. “If you would have told me 15 years ago we would have an established population in the Everglades, I wouldn’t have believed you.”

Alien wildlife can wreak havoc in an unprepared ecosystem. When the Bur­mese python turned up far from home in the Florida Everglades in the 1980s it bred fast, sustaining its re­production by feasting on endangered local wildlife, including alligators. There are now thought to be about 30,000 of the formidable snakes in the area.

But invading species don’t always come in large packag­es. The Indian Silverleaf - or Sweetpotato - whitefly, just a millimetre long, is estimated to have caused more than $100m worth of damage at­tacking crops across Califor­nia, Texas and Arizona in the 1980s.

Sometimes the species don’t even have to invade, they are invited. Cane toads, native to South and Central America, were introduced to Australia in the 1930s in an attempt to control the grey-backed cane beetle, which was destroying cane crops. But with no natural predator, the poisonous toads spread like wildfire, killing native species as they went.

And invasive species aren’t always obviously menac­ing either. In 1859, Thomas Austin had 24 ordinary rab­bits shipped to Australia for hunting purposes. “The in­troduction of a few rabbits could do little harm,” he re­portedly said at the time. But Austin underestimated the habit of rabbits to reproduce like, well, rabbits. Soon there were tens of millions and they killed off local plant spe­cies, having a devastating ef­fect on Australia’s ecosystem.

• One of the three crocodiles