ShareThisNAPLES, Fla. - Thousands of 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 published Monday.
Researchers discovered the effects of the snakes when they compared the 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.
No rabbits or foxes were spotted between 2003 and 2011, and the frequency of sightings of raccoons declined by 99 percent compared to 1996 and 1997. Views of opossums and bobcats declined by 99 percent and 88 percent, respectively, according to the study in the 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.
It was only earlier this month, that the U.S. government banned the importation and interstate transportation of four nonnative constrictors, including the Burmese python.
The new study found mammal populations were healthier at spots where pythons have only recently been found, compared to areas 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.
Monday'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 100-pound deer.
Python sightings in the 1.5-million acre park are extremely rare, and pythons do not pose a safety hazard to park visitors, park spokeswoman Linda Friar said.
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 detector 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.
The Nature Conservancy is heading up a program to train everybody from park rangers to meter readers to capture pythons.
Nothing short of a volunteer army of python hunters is needed to keep the python menace from spreading with consequences that are largely still not understood, said Nature Conservancy biologist Cheryl Millett.
"We need all those eyes and ears out there," she said.
(Eric Staats is a reporter for the Naples Daily News in Florida. Email him at emstaats(at)naplesnews.com.)
