Giant pythons could take over America according to the US Geological Survey. Already established in Florida, they could be menacing the west coast by 2020.

Maps showing areas where Burmese pythons would be comfortable reveal the snakes, which can grow to over 6 metres, are already capable of surviving across much of the southern United States. Global warming could even see them expanding their range up to the Capitol by 2100.

“Wildlife managers are concerned that these snakes, which can grow to over 20 feet long and more than 250 pounds, pose a danger to state- and federally-listed threatened and endangered species as well as to humans. Several endangered species have already been found in the snakes’ stomachs,” says Bob Reed, a USGS wildlife biologist (press release).

The snakes are often kept as pets and released into the wild when they get too big. Burmese pythons have already established themselves by this method in south Florida, where they sometimes engage in high profile battles with resident alligators.

Left hand map shows current potential python range. Right hand map shows range under current global warming predictions.

“We were surprised by the map. It was bigger than we thought it was going to be. They are moving northward, there’s no question,” says Gordon Rodda, USGS invasive snake expert (USA Today).

Rodda says in the SF Chronicle that the snakes can slither along at over 30 kilometres a month. In the unlikely event one went constantly in one direction it could reach San Francisco by 2020.

They are already chowing down on threatened species including the Key Largo woodrat and round-tailed muskrats. A tasty trail of beavers could sustain them all the way to Hollywood. “Beavers would be a very tasty treat for them. No beaver would be safe from a python,” Rodda told the Chronicle.

A lack of predators will also help them spread. As the Chronicle dryly notes, “There are few free-roaming African lions and tigers between Florida and San Francisco, the geological survey said.”

However, while the lack of alligators out west can only help the pythons Rodda says one invasive species is enough: “[W]e are not recommending you import alligators into California. That would not be a good idea.”

Photo: this python is an alligator snack but others are coming / Lori Oberhofer, National Park Service.

Maps: USGS