Nine species of giant, exotic snakes will face new import and transportation restrictions if regulations under consideration by the Interior Department are enacted.

The snakes would be listed as "injurious species" under the Lacey Act, a law first established in 1900 that gives the Interior Department the ability to restrict some aspects of commercial distribution of potentially harmful plants and animals.

"The Burmese python and these other alien snakes are destroying some of our nation’s most treasured – and most fragile – ecosystems,” Interior Secretary Ken Salazar said in a statement. “The Interior Department and states such as Florida are taking swift and common-sense action to control and eliminate the populations of these snakes, but it is an uphill battle in ecosystems where they have no natural predators. If we are going to succeed, we must shut down the importation of the snakes and end the interstate commerce and transportation of them.”

The new regulations come after the the U.S. Geological Survey published an assessment of the risk posed by exotic snakes to native ecosystems. That 300-page study found that the snakes could put 150 endangered species at further risk if they continued to be released into the wild.

While not an outright ban on the snakes — pet owners could still keep them and buy them from in-state sources — they could reduce the number of snakes on the market. That will likely drive up the prices for the snakes. And that's exactly the point, said USGS zoologist Gordon Rodda, who co-led the study.

"It probably will have the effect of driving up the price somewhat. From the standpoint of unwanted pets being released, that's actually a very good thing," Rodda told Wired.com. "People are dumping the animals because they are not worth anything, so if you make them more valuable, then they are less inclined to be released."

In other words, by restricting cheap foreign snake imports, the Interior Department hopes to raise price of "used" snakes. It's a market-based mechanism for changing the behavior of pet owners.

But, Rodda noted, the new regulations won't do anything to address the populations of snakes that are already established.

"This really only addresses the prevention of future problems, it's certainly not air tight," he said. "There are still going to be tens of thousands of these animals around, some of which will escape or be released."

Individual animals can be a nuisance, but it's reproducing populations that are the big problem. Three species have established breeding populations in the United States: Burmese pythons, boa constrictors and Northern African pythons. All the known populations are in south Florida.

How a few scattered individuals released far from each other in time and space find each other and begin to breed is a major outstanding research question. Indeed, it seems downright improbable.

"It takes an unusual confluence of events, and because it's a rare event, it makes the science a little complicated," Rodda said.

Establishing a new population of non-native animals can be difficult even when humans are trying to do it. In the early 1890s, a group called the American Acclimatization Society engaged in a project to introduce every bird mentioned by Shakespeare into New York. The starlings they released had colonized the entire American continent by 1950, but it took several releases to get the original colony established.

"They brought them over many times before it actually worked," Rodda said. "It wasn't just one or two birds, either; they brought a whole bunch."

Nonetheless, we know that humans have somehow created populations of snakes accidentally. The key may be that it doesn't actually take many animals to create a new population. After World War II, the brown tree snake was accidentally introduced into Guam. Over the last 50 years, the species has overrun the island, killing off native species and seriously damaging the native ecosystem. Mitochondrial DNA analysis has found that all those rampaging snakes are the offspring of a single female, Rodda said.

*Image: Burmese python (Python molurus). Roy Wood/National Park Service.

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