Pythons have stranglehold on Florida Everglades ecosystem

ByABC News
January 30, 2012, 8:11 PM

— -- It sounded like a joke when the news first hit in 2000: Giant Burmese pythons were invading the Everglades. But scientists have measured the real impact of the arrival of this voracious species and the news is troubling.

In areas where the pythons have established themselves, marsh rabbits and foxes can no longer be found. Sightings of raccoons are down 99%, opossums 98.9% and white-tailed deer 94%, according to a paper out Monday in the Proceedings of the National Academy of Sciences.

"What if the stock market had declined that much? Think of the adjectives you'd use for that," says Gordon Rodda, an invasive-species specialist with the U.S. Geological Survey (USGS) who published research in 2008 showing that Burmese pythons could conceivably expand across the southern portion of the United States.

"Pythons are wreaking havoc on one of America's most beautiful, treasured and naturally bountiful ecosystems," says USGS Director Marcia McNutt.

Burmese pythons are native to Southeast Asia, but accidental and deliberate release of snakes kept as pets in Florida have allowed them to find a new home there. They can grow up to 16 feet long and weigh up to 150 pounds. The first reports of Burmese pythons in the Florida Everglades began in the 1980s; a breeding population wasn't confirmed there until 2000.

Since then, the numbers of pythons sighted and captured in the Everglades have risen dramatically. According to Linda Friar with Everglades National Park, park personnel have captured or killed 1,825 pythons since 2000.

Now researchers have shown that just as python populations established themselves, the native mammals of the regions began to decline — severely.

People who worked in the Everglades knew they were seeing fewer mammals, but only when the hard numbers came in was it clear just how devastating the decline is.

"These were once very common animals in the Everglades and now they're gone," says Michael Dorcas, a professor of biology at Davidson College in Davidson, N.C., and lead author on the paper.

The pythons aren't a danger to humans. The only known python attacks on humans in Florida have involved snakes kept as at-home pets, says Dorcas, who also authored a recent book, Invasive Pythons in the United States.

Now coyotes and Florida panthers are believed to be affected, as well as birds and alligators.

The decrease in mammals is highest where python populations have been established longest, with more mammals being sighted in areas the pythons have only recently been documented.

Although scientists can't say conclusively that the decline is a result of python activity, there's good anecdotal evidence. "Last October, we found a 15-foot snake with an 80-pound doe inside it," Dorcas says.

The researchers base their findings on systematic nighttime road surveys done in the Everglades that counted both live and road-killed animals. Ten researchers traveled a total of nearly 39,000 miles from 2003 to 2011 and compared their findings with similar surveys conducted in 1996 and 1997.

Mammals in Florida have no natural fear of large snakes because they haven't existed in the area for about 16 million years, when a boa-like snake that used to live there became extinct.