Wednesday, April 15, 2015

1808. Invasive Species: The Snake That’s Eating Florida

By Clyde Haberman, The New York Times, April 5, 2015
Burmese python consuming a deer it killed in Florida
Ever since a serpent enticed Eve to munch on that forbidden fruit in the Garden of Eden, relations between humans and snakes have been at best strained. But at least the gullible Eve and her mate had to cope with just the one snake. In South Florida, wildlife officials have struggled for years with tens of thousands of the creatures: specifically, a species known as the Burmese python, an interloper from Southeast Asia that has taken up what looks like permanent residence in Everglades National Park and other areas of the state.

This is some snake. At full maturity, a Burmese python routinely reaches lengths of 12 feet or more. Twenty-footers weighing 250 pounds are not unheard-of. The pythons are prodigious breeders, with voracious appetites to match. They are believed to have eaten their way through the Everglades, bringing about startling changes in the ecosystem. 

Some mammals native to those marshes, like foxes and rabbits, seem to have disappeared, researchers say. Other species — among them raccoons, deer, opossums and bobcats — are close to being wiped out. Pythons that migrated from the mainland to Key Largo have put indigenous wood rats in mortal peril.

Retro Report, a series of video documentaries exploring major news stories of the past, trains its lens on the dawning realization more than a dozen years ago that the Burmese python had the potential to alter Florida’s environment far more than people realized. But the issue is really greater than one breed of Asian snakes that ran wild after being imported into the country as pets. The United States is awash in invasive species exacting a heavy toll on native wildlife and vegetation. The list of intruders is long. To name but a few, they include Argentine tegus, large lizards that feast on sea turtle eggs; venomous lionfish from Asia, which prey on local varieties of fish; Nile monitor lizards from Africa, which love to eat frogs and crocodile eggs; zebra mussels from Russia, which harm waterways and damage water treatment plants; and Asian carp, which threaten the environmental balance of the Great Lakes.

Florida draws much of the attention because its swamps and tropical climate provide splendid shelter for all sorts of creatures that are not supposed to call this country home. The state, as more than one person has observed, is the Ellis Island of exotic species.
Like many animals previously unknown on the North American continent, the Burmese python arrived through the pet trade. (Language purists might reasonably ask if it is fair to describe these snakes as invasive. It is not as if they barged in on their own. People created the problem.) At least two million constrictor snakes — boas, anacondas and pythons — are believed to have been imported since the 1970s, part of a lucrative market for exotic species. Miami is an important hub for this trafficking.

One issue with Burmese pythons is that people cavalierly bought them when they were maybe a foot long. In short order, those little fellows grew to eight feet, 12 feet, 16 feet. Talk about buyer’s remorse. Unable to deal with these giants, owners often dumped them wherever seemed feasible. One way or another, snakes in South Florida found their way to the Everglades. There, they multiplied, again and again. Recent estimates by the National Park Service put the numbers there as high as 100,000. Walter E. Meshaka Jr. was the supervisory curator for national parks in southern Florida from 1995 to 2000. Even back then, Mr. Meshaka told Retro Report, the question was whether the python population would explode. And, he said, “Lo and behold, it did.”

Quite possibly, some experts in the field suggest, the local wildlife has been slow to appreciate the menace. “It’s probably a safe assumption that things like raccoons and possums probably don’t associate snakes with being something that really is a major threat to them,” Michael E. Dorcas, a herpetologist at Davidson College in North Carolina, said in a 2012 interview with Yale Environment 360, an online publication of the Yale School of Forestry and Environmental Studies. “Because,” Mr. Dorcas continued, “there really hasn’t been a snake big enough to eat a raccoon living in Florida for about 18 million years.”

While the python is more of a direct threat to native birds and animals than to people, attacks on humans are not unknown. One of the more horrifying instances occurred in 2009 when a 2-year-old girl in northern Florida was strangled by a Burmese python that belonged to her mother’s boyfriend. This eight-foot snake, which was later found to have been severely malnourished, broke free, coiled itself around the girl and squeezed her to death. Both the mother and the boyfriend were held responsible — convicted of manslaughter and sentenced to 12 years in prison.

The authorities in Florida have tried getting the unwelcome reptile population under control, but to little avail. A couple of years ago, they organized a Python Challenge, a come-one, come-all snake hunt on state land near Everglades National Park. It put barely a dent in the python population; no more than a few dozen of them were captured. Pythons have shown themselves to be masters of stealth. In a rather glum assessment, the United States Fish and Wildlife Service said in a statement last month that “scientists have not found any way of eradicating invasive constrictor snakes once they become established in the wild.” Some experts say the best hope to kill these creatures en masse may be a deep and prolonged freeze in southern Florida. Of course, everyone would then worry about the devastating effect on the state’s citrus crop.

Should other sections of the country start fretting about possible python incursions of their own? Yes, say some scientists who predict that, in coming decades, the invaders could slither their way across one-third of the United States — perhaps even reaching New York City by 2100. Other experts, however, wave off such fears as overblown.

The Obama administration has chosen to take a stand. Three years ago, the Fish and Wildlife Service banned imports and interstate transport of four species of constrictors: Burmese pythons, yellow anacondas and northern and southern African pythons. Last month, the prohibition was extended to four other species: reticulated pythons, DeSchauensee’s anacondas, green anacondas and Beni anacondas. (Boa constrictors, an important component of the pet snake trade, were spared a ban.) Not surprisingly, reptile sellers and breeders are not happy with the restrictions, with slippery slopesters among them warning that all kinds of animals, including more familiar household pets, could become the next government target.

Effective or not, the import bans are a recognition that some species labeled invaders were invited in by humans. It is a reality reminiscent of a famous line from no less than a swamp creature: the possum Pogo, whose name was the title of Walt Kelly’s long-running comic strip. Referring to unwelcome environmental change, Pogo said, “We have met the enemy and he is us.”

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