Pythons and anacondas worked their way to the top of the Everglades food chain through vicious fighting and voracious eating, but they have a weakness. “It’s real simple. When it gets cold, they die,” said Andrew Wyatt, president of the U.S. Association of Reptile Keepers, which supports the trade and trafficking of pet snakes for profit.

View Photo Gallery: Rabbits, raccoons, opossum and bobcats have all but disappeared from Everglades National Park, after giant pythons were introduced to the ecosystem.

But snakes appear to be adapting in a way that will allow them to expand to colder climates, wildlife biologists said.

Research shows that pet owners released pythons into the Florida Everglades, where the snakes began to breed and kill off the local animal populations. Though Obama banned the importation of Burmese pythons, researchers are worried that the species may migrate farther north.

When Michael F. Dorcas took 10 big snakes from the Everglades to a colder climate in South Carolina, he was surprised at how long they lived before finally succumbing to frost.

“Lots of questions remain . . . about whether they would be able to survive or not,” said Dorcas, a Davidson College professor who studies snakes in the wild and their impact on ecosystems. “Thermal patterns can change. They might have an ability to evolve.”

As the climate changes, and temperatures warm, snakes can go on the move. During two cold snaps that hit Florida in winters that started in 2009 and 2010, many pythons survived by burrowing into the earth and by finding deeper, warmer water to ride out the low temperatures. Dozens of snakes perished and were disposed of by the U.S. Fish and Wildlife Service, but what didn’t kill those that survived might have made them stronger, Dorcas said.

“We just had a major selection event for cold-tolerant pythons,” Dorcas said. Fish and Wildlife predicted that a new generations of Burmese pythons on the edge of their non-native range can adapt and “expand to colder climates.”

Wyatt remains doubtful. Although he has fought bans on the import and commerce of constrictor snakes, Wyatt admits that pythons and anacondas are a problem in the Everglades. But the problem will stay there, he said, because the snakes are built for the tropics.