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Should the federal government be in the business of banning exotic snakes? Take Burmese pythons, for instance. The threat they pose to the Everglades is well documented. Pythons have been breeding in South Florida since the 1990s, and some studies have indicated they're spreading. Concerns that pythons could move into other states led to a nationwide prohibition on their importation and sale. But as NPR's Greg Allen reports from Miami, some researchers now argue that such a far-reaching ban was unnecessary.

GREG ALLEN, BYLINE: 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.

(SOUNDBITE OF VIDEOTAPE)

UNIDENTIFIED MAN: (Groan) P-52 folks, and she's angrier and stronger.

ALLEN: Earlier this year, researchers with the U.S. Geological Survey captured the largest Burmese python yet in Everglades National Park. In a videotape, three USGS staffers wrestle the snake out of a plastic crate to measure it.

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UNIDENTIFIED WOMAN: Wow. You're having to use all your muscle, aren't you?

UNIDENTIFIED MAN: Yep.

UNIDENTIFIED WOMAN: To hold her head.

UNIDENTIFIED MAN: Yeah. And she's still stronger than me.

UNIDENTIFIED WOMAN: Do you know where her...

ALLEN: This snake was 17 feet, seven inches long and a 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 in Everglades National Park pythons have reduced the population of raccoon, possums, deer and other mammal species by 90 percent. To help combat the problem, the federal government earlier this year banned importation and sale of Burmese pythons. A study several years ago by USGS found pythons could potentially spread up the East Coast and west to California. But Elliott Jacobson, an emeritus professor of zoological medicine at the University of Florida, says a new study questions how far beyond South Florida pythons could spread.

ELLIOTT JACOBSON: These maps give a very false sense of distribution.

ALLEN: 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.

JACOBSON: 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.

ALLEN: 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. Brady Barr agrees. He's resident herpetologist with the National Geographic Society. He 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.

BRADY BARR: They don't have the innate ability to find hibernacula, to find places to hide or to be warm. They just - they don't know how to do that.

ALLEN: 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 USGS, helped write the report showing pythons could potentially spread throughout the southeast U.S. He says there's nothing in this new report to change his thinking.

GORDON RODDA: 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?

ALLEN: Later this week, this is a question that may come up in Congress. A House committee is holding a hearing on whether to extend the ban on Burmese pythons to other exotic snake species. Greg Allen, NPR News, Miami.

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