Burmese pythons are eating their way through the Everglades, leaving a dramatic decline in mammal populations in their slithering wake in just a decade, according to a study released today.
Researchers kept track of animals — like raccoons, opossums and rabbits — they saw alive or found as roadkill during nighttime road surveys in Everglades National Park before and after 2000, when pythons were recognized to be established in the park.
“The numbers, even to us, were astonishing,” said Michael Dorcas, biologist at Davidson College in North Carolina and the study’s lead author with scientists from eight other institutions, including the U.S. Geological Survey.
No rabbits or foxes were spotted along 35,000 miles of surveys between 2003 and 2011, and the frequency of sightings of raccoons declined by 99 percent compared to surveys along the same routes in 1996 and 1997; sightings of opossums and bobcats declined by 99 percent and 88 percent, respectively, according to the study published online in Proceedings of the National Academy of Sciences.
The findings, the first to document the pythons’ effect on the South Florida ecosystem, stress the importance of stopping the spread of the nonnative predator and raise big questions about the havoc they are wreaking, Dorcas said.
“We need to know more about what’s going on here,” he said.
Just how many pythons are roaming the Everglades is unknown, but scientists say they number at least in the tens of thousands _ and are spreading.
The study found mammal populations were more healthy at spots where pythons have only recently been found compared to spots in Everglades National Park where pythons have been established the longest.
That pattern gave researchers confidence that the pythons were the culprit for the mammal decline. They dismissed disease because so many different species showed decline.
Other than changes in water flows, the park has not seen man-made changes in the past 20 years that could cause such a drop-off in mammals, researchers concluded.
They also pointed out that pythons hunt for food in the same habitats along the water’s edge where unsuspecting raccoons and opossums go for a meal.
Endangered species also could be vulnerable, the study says. Scientists already know that pythons eat wood storks and Key Largo wood rats.
Measuring a decline in a rare species, such as the Florida panther, is more difficult because they are more difficult to find, Dorcas said.
“It could be happening and we haven’t detected it yet,” he said.
Today’s report puts a scientific exclamation point on a trend that has captured imaginations around the world.
In 2006, images of a burst python with an alligator sticking out of it helped focus public attention on the Everglades python invasion as did news last year that hunters captured a python that had eaten a 76-pound deer.
Earlier this month, the U.S. government banned the importation and interstate transportation of four nonnative constrictors, including the Burmese python.
“Right now the only hope to halt further python invasion into new areas is swift, decisive and deliberate human action,” U.S. Geological Survey Director Marcia McNutt said in a written statement today.
At Everglades National Park, spokeswoman Linda Friar worries that the python is single-handedly changing the public’s perception of what they can see at the park.
She said python sightings by visitors to the 1.5-million acre park are extremely rare, and pythons do not pose a safety hazard to park visitors.
The National Park Service is spending about $1 million on several projects to try to corral the python problem, she said. They include a study with Auburn University to use trained dogs to root out pythons and working with the University of Georgia to design a smartphone application to report pythons and monitor them on the web.
“We’re watching it and doing what we can with the resources we have to determine what the impacts might be,” Friar said.
Since 2005, The Nature Conservancy has trained everybody from park rangers at Big Cypress National Preserve to meter readers in the Florida Keys to capture pythons.
Nothing short of a volunteer army of python watchers is needed to keep the python menace from spreading with consequences that are largely still not understood, Nature Conservancy biologist Cheryl Millett said.
“We need all those eyes and ears out there,” she said.