Will Florida Pythons Slither To Rest Of The U.S.?

By Greg Allen

Published November 26, 2012 at 5:57 PM EST

A Burmese python coils around the arm of a hunter during a news conference in 2010 in the Florida Everglades. New research suggests that the pythons won't spread through the American Southeast, as previously believed.

There are several exotic snake species that have become a problem in the Everglades. But for wildlife managers, the biggest headache is the Burmese python.

Earlier this year, researchers with the U.S. Geological Survey captured the largest Burmese python yet in Everglades National Park. Three USGS staffers had to wrestle the snake out of a plastic crate to measure it. The snake was a 17-foot-7-inch female carrying 87 eggs.

Wildlife managers are working to get a handle on the problem of exotic snakes in South Florida; but the snakes have already made a big impact.

One study suggests that in Everglades National Park, pythons have reduced the population of raccoons, opossums, deer and other mammal species by 90 percent.

To help combat the problem, the federal government earlier this year banned the importation and sale of Burmese pythons and three other exotic snake species.

One reason was fears that pythons might spread to other states. A study several years ago by the USGS found pythons could potentially spread up the East Coast and west to California.

But Elliott Jacobson, a professor emeritus of zoological medicine at the University of Florida, says a new study questions how far beyond South Florida pythons could spread.

"These maps give a very false sense of distribution," Jacobson says.

In a study published in the journal Integrative Zoology, Jacobson and other researchers looked closely at the low and high temperatures found along the East Coast in the python's projected habitat range. Freezing temperatures are deadly for pythons. And Jacobson says pythons have trouble eating and digesting food at temperatures below 60 degrees.

"The bottom-line conclusion was the number of freezing days in the winter is going to limit the ability of this animal to spread beyond extreme South Florida," he says.

Jacobson says this new information shows the federal government overreacted when it imposed a national ban on a species that's a problem just in Florida.

And some other well-known scientists are also speaking out against the python ban.

"The press has made this a big deal. The sky is falling — I call it the Chicken Little syndrome — when indeed it isn't," says Brady Barr, the resident herpetologist with the National Geographic Society.

Barr says the new study shows something he and other researchers have maintained for some time — that Burmese pythons can't spread far beyond Florida's three southern-most counties. Barr says that's because, unlike native snakes, pythons can't tolerate cold, and they lack the instinct to hibernate.

"They don't have the innate ability to find hibernacula, to find places to hide or to be warm. They don't know how to do that," Barr says.

That question — whether snakes from tropical climes, like pythons, may take measures to adapt to the cold — is one that divides herpetologists. Gordon Rodda, now retired from the USGS, helped write the report showing that pythons could potentially spread throughout the Southeast U.S. He says there's nothing in this new report to change his thinking, including its doubts about whether pythons may learn to adapt to cold.

"We know that Burmese pythons in the more high altitude portions of their range do in fact hibernate. The question then is: How do they acquire that behavior to do so?" Rodda says.

This is a question that may come up in Congress later this week. A House subcommittee is holding a hearing on whether to extend the ban on Burmese pythons to other exotic snake species.