First it was the Burmese python. Now scientists believe as many as nine non-native snakes representing five species could become established in portions of the United States.

The outcome of such an ecological invasion could include unforeseen impacts on native reptiles and threaten birds and other species, according to a study released last week by the U.S. Geological Survey, whose earlier conclusions on the Burmese python are being tested at Savannah River Ecology Laboratory in Aiken County.

"This new report has some differences from the earlier paper, which was just on Burmese pythons," said post-doctoral research scientist J.D. Willson, who is studying Burmese pythons in a specially designed enclosure within Savannah River Site. "The new document basically does the same thing for the other giant constrictors."

In June, following predictions that climates throughout most of the Southeast could support populations of Burmese pythons, Savannah River Ecology Lab launched a yearlong study to gauge their ability to survive during colder weather.

"They are all still alive at this point," said Dr. Willson.

Colleagues and Dr. Willson are monitoring 10 pythons captured in south Florida, where the exotic snakes have already created a breeding population numbering in the tens of thousands. The test snakes at SREL range up to 11 feet in length, although the giant constrictors can reach 20 feet and weigh more than 200 pounds.

According to the new report, high-risk species -- Burmese pythons, northern and southern African pythons, boa constrictors and yellow anacondas -- all put larger portions of the U.S. mainland at risk than previously thought. Medium-risk species -- reticulated python, Deschauensee's anaconda, green anaconda and Beni anaconda -- constitute lesser threats.

"This report clearly reveals that these giant snakes threaten to destabilize some of our most precious ecosystems and parks, primarily through predation on vulnerable native species," said Dr. Robert Reed, co-author of the report and a USGS invasive species scientist and herpetologist.

Although the new list of potential exotic invaders includes more snakes than the Burmese python, most of them would remain confined to the warmer climates, the report said. "Based on climate alone, many of the species would be limited to the warmest areas of the United States, including parts of Florida, extreme south Texas, Hawaii, and America's tropical islands, such as Puerto Rico, Guam, and other Pacific islands," the authors concluded.

The Burmese python remains one of the most adaptable of the giant constrictors, as evidenced by its ability to establish itself in south Florida, where it continues to spread. Scientists determined they can travel 40 kilometers in a month and documented a clutch of 107 eggs.

Although they rarely kill or attack humans, they do pose a "small potential for contribution to traffic accidents," the USGS authors wrote, because they can occasionally block roads and contribute to "bystander accumulation."

The project at SREL is a joint effort that also involves the National Park Service, University of Florida and Davidson College. UGA professor emeritus Whit Gibbons and Davidson College professor Mike Dorcas are also involved in the studies.