February 22, 2008
Python ‘Invaders’ Spreading Beyond the Everglades
The Everglades apparently isn't big enough for the giant invaders, who have grown fat, happy and increasingly numerous on a diet of unsuspecting natives. Over the last year, pythons have been found in the wild from Key Largo to Glades County -- and a new study suggests the exotic predators could spread beyond South Florida.
The Burmese, or Indian, python -- at least theoretically -- would feel right at home from California to Delaware in an array of habitats from scrub deserts to mountain forests, according to a study by federal scientists. In 100 years, global warming might even extend the range for the big snakes as far north as the Big Apple.
The results, said lead author Gordon Rodda, a zoologist with the United States Geological Survey, will probably even surprise many biologists.
'Many people get their image of where pythons live from 'The Jungle Book,' " said Rodda, one of a number of scientists working with Everglades National Park on eradication efforts. "Pythons don't just occur in tropical areas."
The study, soon to be published in the journal Biological Invasions -- the exotic-species threat is serious enough to merit its own academic publication -- doesn't point to places pythons definitely will spread, but presents maps showing where the climate could allow migrating or illegally released pythons to survive.
The suitable habitat, which stretches from coast to coast, underlines an all-terrain capability that scientists say has allowed one of the world's largest snakes to thrive in the Everglades.
"It's a pretty hardy animal," said Skip Snow, a biologist with Everglades National Park who leads a multiagency effort to eradicate fast-spreading and formidable invaders that threaten native wildlife.
Pythons, which can top 20 feet in length, potentially could upset the natural balance of the Everglades or other wild places -- a concern memorably illustrated in 2005 by now-famous photos of a 13-foot python that exploded after attempting to swallow a six-foot alligator.
In 2002, when python numbers first started climbing in the park, the conventional wisdom was that nature would control them, Snow said -- fire ants would eat their eggs, gators would eat them or maybe a deep freeze would kill them all.
Now, they're breeding and the population appears to be booming. The number of captures in the park hit nearly 250 in 2007, Snow said, more than a 50 percent jump. While that may not sound like much in so vast a park, the captures represent only a fraction of the actual population.
Last year, pythons also showed evidence of pushing beyond the Everglades, with more than a half-dozen captures in Key Largo, including one snake found because it swallowed an endangered wood rat equipped with a radio tracking device. Another snake was found as far north as the Brighton Seminole Reservation in Glades County, where it revealed itself, freshly chopped, under a roadside mower.
To assess the potential threat of the python nationally, Rodda and two colleagues in the USGS Invasive Species Science Branch -- ecologist Catherine Jarnevich and wildlife biologist Robert Reed -- looked at weather patterns in its native Southeast Asia.
There the snake is found in 11 countries, from Bangladesh to Vietnam, and survives not just in swamps but forests, scrub deserts and the foothills of the Himalayas. Hibernation, which can last for four months, allows the snakes to survive extended chills in some areas.
Rodda stressed that the study was intended only as a broad survey of suitable areas and did not take into account critical factors like the availability of prey or burrowing areas. But similar climate-based assessments are frequently used to evaluate the threats of exotic plants, weeds and pests, the study said.
The scientists found that the snakes could adapt to climates in 11 states across the southern border as well as Mexico. Under a global warming model, it could make a go of it as far north as New York and New Jersey.
For scientists and state wildlife managers, the continuing spread of the snake on its own is a real concern.
"The evidence from Florida is that they are spreading northward at a rapid rate," Rodda said.
Last year, the Florida Fish and Wildlife Conservation Commission adopted tougher restrictions, including snake registration, in an effort to confine the python to south of Lake Okeechobee and deter illegal releases, considered the source of the problem. The agency is also sponsoring exotic-pet amnesty days for owners to turn in unwanted creatures, with the third set for Saturday at Metrozoo.
But Rodda said the study underlines a bigger threat that released pets could take hold elsewhere, as they have in the Everglades. He and Snow hope wildlife managers in other states deemed "suitable" for the big snakes pay attention and begin to adopt restrictions, like Florida.
"The most direct use of this map is for managers who are concerned about where something could get released and survive," Rodda said. 'If somebody in Corpus Christi, Texas, says, 'I have a bunch of pythons and I want to release them,' then worry about that dude. It could be a big problem."