As if killer bees and kudzu weren't enough, the southern United States may soon have another invasive species to contend with — giant Burmese pythons capable of swallowing deer and alligators whole.
Approximately 30,000 of the big snakes, which can reach 30 feet and 200 pounds, already live wild in Florida's Everglades, thanks to thick-headed pet owners who've released them into the swamps when they've grown too large to keep at home.
But now the U.S. Geological Survey says Florida is not the only place the Burmese python can thrive.
In fact, the big beasts, which are not poisonous and rarely attack humans, could live happily in the entire southern third of the country, from Southern California to Texas and the Lower Mississippi Valley and up the Eastern Seaboard to Chesapeake Bay.
All it would take would be enough pet releases in various locations to create a breeding population.
A few years ago, captains Al Cruz and Ernie Jillson of the Miami-Dade Fire Rescue department pulled up in front of an apartment building.
A crowd gathered on the grass was watching a 10-foot Burmese python slowly squeeze a large Muscovy duck to death. But the lanky juvenile snake then struggled to get the 12-pound duck down its throat.
Cruz and Jillson, members of Miami-Dade Rescue's specialized Venom 1 unit, wrestled the snake under control as feathers flew. They carted the python away, not to be euthanized but to make sure it ended up where it wouldn't kill native animals or pets.
"Lately it's getting worse," Jillson said. "We're going to find even more of these animals."
In 2004, wildlife researchers found a gory tableau in the Everglades — a 13-foot python had swallowed a six-foot alligator whole. Then the snake's abdomen burst open, killing it and leaving both animals forever conjoined in reptilian mutually assured destruction.
In April of this year, a Eugene, Ore., police officer had to pry a pet-store owner's hand, which may have smelled like mice, from a 12-foot python's mouth. The snake even made a dash for the exit before being wrangled back into its cage.
Slithering Across America
The Oregon snake probably couldn't have survived in the Northwestern wilderness, but officials worry that pet Burmese pythons released into warmer areas could establish new populations. It would take about 50 individuals to ensure a viable community.
The U.S. Fish and Wildlife Service is considering listing the snakes as injurious wildlife under the Lacey Act, which would prohibit them from being imported or carried across state lines.
Unfortunately, the horse has already left the barn. One million live Burmese pythons were legally imported into the U.S. between 2001 and 2006, according to Fish and Wildlife. Almost all of them ended up as pets, and half of them came in through Miami.
"We don't have tools that are sufficient to control them on a continental scale," says Gordon Rodda, an invasive snake expert at the Fort Collins Science Center in Colorado, and lead author of the USGS study determining the extent of the snake's possible range.
Climate is the key factor in whether a snake can live or die in any given area. The USGS study, published in the February issue of the scientific journal Biological Invasions, found that conditions — including temperature and rainfall — in the lower third of the continental U.S. match those where pythons live in Southeast Asia, India and China.
The northern limits of the hypothetical U.S. range are open to some interpretation among snake experts, but most agree that the maps accurately predict where the pythons could survive. And since closely related Indian pythons live in the foothills of the Himalayas, where temperatures can dip to 40 degrees Fahrenheit, there's some wiggle room.
When the thermometer gets that low, or seasonal conditions get too dry, snakes aren't up for doing much and will simply hibernate, possibly for as long as four months.
A 10-foot snake ideally requires a fairly large, empty cavity to crawl into, but a hole under a tree stump or a rock pile will suffice.
Getting enough food isn't a big problem for Burmese pythons — they seem to prefer birds and rats, but will eat almost anything.
"If you're a sit-and-wait predator, you're probably going to grab it if it goes by," Rodda said. "You're not going to say, 'I don't feel like bluebirds today, I'd rather wait for a quail.'"
Top of the Food Chain
In 2003, when park rangers first confirmed that the pythons were breeding in the Everglades, some experts figured the abundant alligators would keep them in check. No such luck.
"This indicates to me it's going to be an even draw," University of Florida wildlife professor Frank Mazzotti told the Associated Press in 2005 after the famed conjoined-in-death carcasses were found. "Sometimes alligators are going to win, and sometimes the python will win."
Kenney Krysko, a herpetologist at the Florida Museum of Natural History in Gainesville who performs necropsies on every Burmese python caught by the National Park Service, has seen a couple of cases of the snake coming out on top.
"We just found our second alligator," says Krysko, referring to a recent snake examination. "We found them eating lots of wading birds. We found at least one bobcat, and at least one white-tailed deer."
Krysko stopped to correct himself. "It was mostly just some hair remnants and four hooves."
The pythons have extended their range down into the Florida Keys, where they lunch on the endangered Key Largo wood rat.
"Look at the end of the mainland to Key Largo — it's kind of a long way," says Paul T. Andreadis, a herpetologist at Denison University in Granville, Ohio.
But food may not be the only reason to traverse salty waters. Most of the snakes captured in Key Largo have been males who could be looking for mates.
"How far would they go for a date could potentially be a long distance," speculates Andreadis.
On the other hand, the mainland snakes don't seem to be taking food off any rival predator's table.
"There's no indication prey are in short supply," says Andreadis.
Others think the snakes are just getting started in a relentless, if slow-moving, slither across Florida and then into the rest of the Southeast.
"Once they hit the sugar cane fields [around Lake Okeechobee], it's definitely a lost cause," due to the large rat population there, Krysko said. "It's already a lost cause."
Even more alarmingly, Krysko said that the snakes he's received from up near Naples, Fla., are probably not transient Everglades snakes, but rather more released pets.
Some herpetologists argue there's still one highly efficient, dominant predator that could stop the pythons — us.
"When these things reach major urbanized areas, are they going to want to go across a Wal-Mart parking lot?" wonders Michael Dorcas, a biologist at Davidson College in North Carolina who tracks pythons using radio transmitters.
The answer could be yes. Ernie Jillson of Miami-Dade Rescue says most of his unit's Burmese python removals are from the heart of suburbia — curled up next to air-conditioning units, in swimming pools, under garages.
Rodda thinks residents of the southern U.S. need to be vigilant about not releasing pet pythons. He stresses that the authorities no longer consider their efforts a removal campaign for the invasive species, but simply a management campaign.
"The longer it takes, the harder it gets," Rodda says. "That is certainly the case here. It's getting harder with every passing day."