Crocodiles are on the prowl in south Florida.
The sharp-toothed cousins of the American alligator are listed as an endangered species. But recent sightings of crocs in the surf off the beach at Boca Raton and among yachts moored in the Intracoastal Waterway at Jupiter have prompted speculation that the once-imperiled reptiles are making a comeback.
If true, it would mark a major victory for conservationists working to reverse the American crocodile's seeming inevitable slide toward extinction in the US. It would also mean that surfers and ocean swimmers in south Florida will have to watch out for more than just sharks.
"They are increasing in numbers, and they are reoccupying areas within their historic range, but now there are people in those areas," says Dawn Jennings, a biologist with the US Fish and Wildlife Service in Vero Beach.
Unlike alligators, which prefer fresh water, crocodiles are generally found in brackish water and can tolerate salt water for limited periods. As a result, crocodiles may show up in places alligators never frequent - like oceanfront beaches.
With as many as 1.5 million alligators in Florida, locals are familiar with the sight of these muck-black denizens in fresh-water lakes, canals, and even golf-course water hazards. But it has been many, many years since Floridians have seen crocodiles lined up like logs on Miami Beach or lurking in the shallows of Lake Worth near the mansions of Palm Beach.
Estimates of the current crocodile population range from 400 to 1,000 adults. "When most of the work with crocodiles began in 1978, we had a total of 20 to 22 crocodile nests annually," says Paul Moler of the Florida Fish and Wildlife Conservation Commission. "Now we are seeing between 40 and 50 nests annually."
Prime crocodile nesting areas are in the mangrove wetlands in protected parks at the southern tip of the Florida Peninsula. A highly productive nesting area has also developed in the 168 miles of man-made cooling canals built for the Turkey Point Nuclear Power Plant, on the southwest shore of Biscayne Bay.
Now, the question is whether these areas are becoming overpopulated, forcing younger animals to migrate in search of new nesting areas. The youngsters have a strong incentive to move away. "Crocodiles will eat crocodiles," says Mr. Moler.
A joint team of federal and state biologists is set to begin an investigation this week to determine what might have lured at least five crocodiles to coastal Palm Beach County in early December.
David Hitzig, of the Busch Wildlife Sanctuary in Jupiter, helped rescue and care for the crocs after they were captured. He says one theory is that someone may have raised the crocodiles illegally in captivity and decided to release them when they grew too big. "It is kind of bizarre to see crocodiles this far north," he says.
The other theory is that the croc population is outgrowing its existing habitat.
If scientists verify that migration is the result of sustained population growth, the Fish and Wildlife Service is prepared to recommend that the American crocodile be reclassified from "endangered" to "threatened" on the Endangered Species List. In terms of regulations, the crocodile would still be afforded all the protections of federal law. The "threatened" classification would simply acknowledge that progress is being made and that continued vigilance is necessary, says Ms. Jennings.
But not all conservationists agree that "down-listing" is the right move right now.
"The animal is faring better than it did 20 years ago," says Joe Wasilewski, a biologist who has spent 13 years studying crocodiles in the Turkey Point canals. "But we really don't know enough about these animals to say that now we should down-list them."
Crocodile experts acknowledge that there is now a greater possibility of crocodile-human encounters. They advise that American crocodiles should be treated the same way knowledgeable Floridians treat alligators - with respect rather than fear.
"Both alligators and crocodiles are dangerous animals," says Mr. Wasilewski. "But American crocodiles are very shy and non-aggressive. There has never been a fatal attack by a crocodile in Florida on a person."
For all the talk of resurgent crocs, however, their comeback faces significant obstacles. Crocodiles are very particular about where they place their nests, and most of the prime mangrove-fringed nesting grounds of an earlier era have since become condos and marinas.
Another limiting factor is cold weather.
"Crocodiles are tropical. So here in the US, they are constrained to live at the southern tip of Florida," says Moler. "There is no room for a major expansion in the number of crocodiles."