Surprised scientists find deadly Florida pythons have internal GPS

http://www.theguardian.com/environment/2014/mar/20/florida-scientists-deadly-pythons-internal-gps

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They are Florida’s deadliest and most unwelcome visitors, blamed for a massive decades-long decline in the population of native species in the Everglades wetlands even as their own numbers expand at an uncontrollable rate.

Now researchers have discovered one more tool in the Burmese python’s kit of survival mechanisms – a previously unknown homing instinct that enables the giant snakes to travel great distances at speed, right back to any particular spot where the hunting was good.

“We found that Burmese pythons have navigational map and compass senses,” said Shannon Pitman of North Carolina’s Davidson College, the lead researcher of a team of scientists that released six captured snakes back into the wild, then tracked them through the Everglades National Park for up to nine months.

“It wasn’t what we expected. We thought we’d see a kind of aimless, wandering behaviour, but the pythons made their way pretty quickly back to where to where they were captured. It was more sophisticated in terms of movement than we’ve seen in other species of snake.”

What makes the discovery more remarkable is that it was completely accidental. Pitman’s team originally wanted to release the snakes closer to their capture points within the Everglades, as they were more interested in studying the habitat through which they were moving than the actual distances they travelled.

But wildlife officials, whose efforts to eradicate or contain the up to 100,000 non-native snakes estimated to have spread through the park’s 1.5m acres, refused permission.

That led to the team releasing the snakes at more remote locations between 13 and 23 miles away, outside the National Park’s boundaries, and then watching in amazement as one python after another made its way back “home”.

Each snake was fitted with a radio tracker and its position monitored by GPS one to three times per week. All six moved in a near-straight line towards their capture points and five ended up within a couple of miles. The snake with the longest journey took nine months to reach its destination.

Recent studies have exposed the devastating impact pythons have had on native species in the Everglades. In 2012, a National Parks report described the decline in mammal populations in the wetlands as “severe and dramatic”, with marsh rabbits and foxes having completely vanished, along with 99% of the area’s raccoons, in the time since the pythons gained a foothold. Two years earlier, researchers found 25 different bird species, including the endangered wood stork, in the digestive tracts of several snakes.

The Florida Fish and Wildlife Commission (FWC) believes the first pythons, which can grow up to 5.2 metres (17 feet) in length, were probably released into the Everglades as exotic pets that grew too big for their owners, or escaped into the wild from homes or pet shops when Hurricane Andrew devastated a large area of South Florida in 1992. Since then, the agency has been fighting a losing battle to control their numbers.

A well-publicised public “bounty hunt” last year attracted about 1,500 keen hunters but resulted in the capture of only 68 pythons, and FWC has no immediate plans to repeat the exercise, spokesperson Carli Segelson said.

Instead, eradication and control efforts have included an exotic pet amnesty, which has seen 70 Burmese pythons turned in since 2006; the Python Patrol, an educational programme for anyone working in or near the Everglades about how to identify and humanely remove the creatures; an exotic species hotline and those with hunting licences being encouraged to visit a handful of wildlife management areas where pythons are known to be prevalent.

“Pythons are well camouflaged and notoriously difficult to find, so it’s hard to estimate their numbers,” Segelson said. “Any research that helps us better understand them is beneficial.”

Pitman, one of eight scientists who worked on the study, said more research was needed. “It’s impossible to draw a straight line from this to a new management strategy but we hope more information can lead to better efforts to eradicate them,” she said.