Nine different species of exotic giant snakes, released into the wild by irresponsible pet owners, could pose a major threat to U.S. wildlife, according to a new report published today by the U.S. Geological Survey.

Although pet constrictors start out small and cute, the largest snakes can grow up to 20 feet long and weigh as much as 200 pounds. The enormous reptiles end up in the wild when they're abandoned by overwhelmed owners, or when they use their impressive musculature to escape from inadequate enclosures.

Tens of thousands of giant Burmese pythons already inhabit parts of southern Florida, and now scientists say at least eight other species of giant snakes have the potential to breed and thrive in parts of the United States, threatening already-fragile native ecosystems and putting 150 endangered species at risk.

"They will eat almost every vertebrate of the right size, but they mostly prefer birds and mammals," said USGS biologist Gordon Rodda, who co-authored the 350-page study. "We’ve pulled a number of endangered species out of their stomachs."

In addition, Rodda said all nine species are large enough to kill an adult human, although fatalities are rare. For example, despite the large population of captive Burmese pythons in the United States, the first unprovoked fatal attack was recorded earlier this year, when a pet python escaped from its cage and killed a 2-year-old child.

"There have been recorded fatalities from these species," Rodda said. "Personally, I don’t think it’s a big deal, but if I had a small child, I would be mindful of that risk if the child was in an area where there might be pythons."

Individual snakes from all nine species have been found in the United States, but so far only three species — Burmese pythons, boa constrictors and northern African pythons — have established breeding populations in the wild, all currently confined to southern Florida. Based on the snakes' preferred climate range, potential ecological impact and prevalence in trade and commerce, the report classified five species as high risk and the other four as medium risk to native ecosystems.

A preference for warm weather means most of the snakes could only survive in Florida, southern Texas, Hawaii or tropical islands like Guam and Puerto Rico. Still, Rodda said a few species could potentially spread throughout many of the southern states. "The most temperate of the species is the Burmese python," he said. "That’s the one that really goes up both coasts and across the southern U.S."

The hardy animals tolerate urban and suburban environments quite well, and boa constrictors and northern African pythons have both been spotted in the Miami metropolitan area.

Unfortunately, once invasive snakes have taken hold in a particular region, the researchers say they're almost impossible to get rid of, in part because elaborate camouflage makes the snakes very hard to spot. Some progress has been made in terms of radio-tracking and trapping the snakes, but despite several years of effort, Florida's population of Burmese pythons and boa constrictors shows no sign of shrinking.

"At this time, we have no tools that would likely suffice to eradicate a big population of snakes once they had spread," said USGS biologist Robert Reed, the other co-author of the study, who presented the findings today at a congressional briefing. "Instead of looking at the pound of cure," he said, "maybe it’s time to look at the pound of prevention."

The results of the study, along with more than 1,500 public comments solicited by the Department of Interior, will be used by the U.S. Fish and Wildlife Service to decide how to prevent further spread of the giant constrictors. One option would be to place them on a list of injurious species under the federal Lacey Act, which would make it illegal to import the snakes or carry them across state lines.

Of course, reptile enthusiasts don't want to curb the sale of these exotic snakes, and the researchers point out that owning a snake has educational value. "We can testify to these snakes' attraction personally, as we both have kept pet giant constrictors," the scientists wrote. "Thus the social value of protecting native ecosystems must be weighed against the social value of fostering positive attitudes about the protection of nature through giant constrictor ownership."

Regardless of whether these giant snakes are eventually classified as injurious, the Fish and Wildlife Service says they're taking steps to reduce breeding populations in Florida and prevent further snake invasion.

"It's going to take a huge public education and outreach initiative to make people understand the value of being responsible pet owners," said FWS spokesperson Ken Warren. "We don’t pretend that there’s any easy solution, but no action is not an option."

Image 1: Burmese python (Python molurus). Roy Wood/National Park Service.

Image 2: A researcher measures the length of a captured Burmese python. Lori Oberhofer/NPS.

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