The Burmese python has conquered the Florida Everglades, raising concerns about the effects to endangered species as well as overall shifts in the ecological balance of the area due to climate change.

"Nothing gets people's attention like a 20-foot snake," said Gordon Rodda, a U.S. Geological Survey expert on invasive snakes.

An American alligator and a Burmese python locked in a struggle to prevail in Everglades National Park. This python appears to be losing, but snakes in similar situations have apparently escaped unharmed, and in other situations pythons have eaten alligators. Photo by Lori Oberhofer. Courtesy of the National Park Service.

The Burmese python, a species native to South Asia, was likely introduced to the area when pet snakes were released into the wild. Today, Rodda estimates that there are at least 30,000 pythons slithering through the Everglades. Given that a nest of hatchlings was found in 2002, that number is expected to continue growing.

In Florida, the large and growing Burmese python population is bad news for the Key Largo woodrat and other endangered species. The snake preys heavily on the woodrat, which is endemic to the area, and scientists have already pulled 1 percent of the global woodrat population from the stomachs of Burmese pythons.

The snakes also threaten the round-tailed muskrat, a species that is not currently listed as endangered but is being considered for the designation. The muskrat appears to have disappeared entirely from the areas now occupied by pythons, and its only remaining habitat lies only slightly to the north of the snake's current reach. The muskrat could be driven to extinction if the snake's habitat continues creeping northward.

Climate change could cause the habitat to do exactly that. Rodda and other USGS researchers recently compared the climate of the snake's native habitat in South Asia with projections for the U.S. climate through 2100 to create a map of where the snake could potentially survive now and in the future. The projections of the Community Climate System Model 3, a computer program for predicting climate created by the National Center for Atmospheric Research with help from scientists worldwide, indicate that the United States' climate of 2100 could host snakes as far west as California and as far north as Oklahoma and Virginia.

USGS has done climate maps for other invasive species, according to Rodda, and is looking for a way to "systematically do them all."

Rodda emphasized that the snake's spread would take several decades but that it could proceed more quickly if captive pythons are released into the wild in areas other than Florida.

One purpose of the habitat maps is to identify where wildlife officials should be most wary of releases of captive snakes. "We want to know where we have to worry about releases. A released snake in Texas is a lot scarier than one in Kansas, because snakes won't survive in Kansas," Rodda said.

A small number of captive releases may grow into a self-sustaining breeding population under a variety of scenarios, including when snakes released from captivity of opposite sex find each other in the wild and mate or when a pregnant snake is released. A third, bizarre possibility, according to Rodda, is a population growing because of facultative parthenogenesis, a process in which female snakes, when facing a shortage of males, produce and fertilize their own eggs.

The pythons have gained a solid foothold in the southern part of Florida and appear poised to expand, according to Elizabeth Fleming, a Florida representative for Defenders of Wildlife. "The pythons are thriving in the current climate and multiplying like crazy," Fleming said. "I'm sure they'll do well in the next one."

Disturbing lessons from Guam

Invasive snakes have the potential to decimate local populations. The brown tree snake arrived on Guam in the 1950s, probably aboard cargo ships from New Guinea. With no natural predators or competition, its population exploded, and today is a common pest on the once snake-free island.

The results have been catastrophic for native birds, reptiles and mammals. Twelve of Guam's native bird species, some of which were found nowhere else, have vanished from the isle, as have half of the island's lizards. The island's last native mammal, a large fruit bat, is expected to vanish this year, said Rodda.