“We’re bringing them into the county under the idea that they’re all innocent until proven guilty. But we have historically had such a high standard of guilt, if you will, that it requires these animals to first of all escape, establish, get out in the wild, breed, and do something egregious like eat something that someone likes,” Snow said. “By then it’s way too late.”

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Burmese pythons have been crawling amok in South Florida since at least the mid-1990s. The population's forerunners were probably released by pet owners daunted by the prospect of maintaining a predator that can grow to 20 feet (6 meters) long and weigh 200 pounds (90 kilograms).

No one knows exactly how many there are now, but estimates put their numbers in the thousands or tens of thousands. The pythons have been devouring local wildlife, indulging in mega-meals like deer, bobcats and alligators, as well as endangered species like the woodstork and the Key Largo woodrat.

All 10 pythons did well through the summer and fall, and even survived 12 December nights that were no warmer than 41 degrees Fahrenheit (5 degrees Celsius). Then, in January, the region was plunged into an extremely unusual cold spell. With temperatures dipping below freezing at night for long stretches, the 10 snakes died, according to a paper published in September online in the journal Biological Invasions.

Still, said study leader Michael Dorcas of Davidson College in North Carolina, "there certainly is a possibility that pythons could survive in South Carolina and possibly even farther north."

[....]

Finally, the pythons that survived the longest were the ones that crawled into underground cavities at night, and Dorcas wonders whether they might have fared even better outside the enclosure.

"There are certainly in South Carolina much deeper retreats that they could have found if they were out in the wild, such as armadillo burrows," Dorcas said. “If we provided deeper refugia, well, would they have survived? We certainly had snakes that survived a long time and were finally killed by the extreme cold snap we had in January. But snakes had survived many nights where it got below freezing.”