WATCH: The giant, rat-sized snails devouring South Florida

South Florida is under attack, and the non-native species threatening to wreak havoc seems innocent enough: It's not the giant Burmese pythons that made a home in the Everglades in 2000, nor a ravenous, land-walking fish like the Asian carp that have been eating through waterways farther up north.

No, this foreign invader is a snail.

But what a snail it is. The giant African land snail "can grow as big as a rat and gnaw through stucco and plaster," says Reuters' Barbara Liston. Since the monstrous mollusks were first noticed in the Miami-Dade County area in September 2011, researchers and vigilant homeowners have caught at least 117,000 of them, or about 1,000 a week. And "residents will soon likely begin encountering them more often, crunching them underfoot as the snails emerge from underground hibernation at the start of the state's rainy season in just seven weeks."

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Just how big and bad are these slow-moving menaces? "The largest stretch 8 inches," says Zack Peterson in the Ocala StarBanner. "The oldest live nine years. The busiest lay up to 1,200 eggs" a year. They eat at least 500 species of plants, plus the stucco and plaster that provide calcium for their shells. And if that's not disturbing enough, the snails "even carry a parasitic nematode that can lead to meningitis in humans" — though no cases of the pathogen, rat lungworm, have been found among humans in the U.S. yet. (Watch raw footage of the snails below.)

They sound like "monsters from hell sent to punish us," or at least Florida, says Michael Ballaban at Jalopnik. But "perhaps the worst part of the invading monster snails is that if you hit one on the highway their shells are hard enough to cause a blowout." They can also turn deadly when a lawnmower hits one, flinging the shell out at high velocity. And then there's the slime trails they leave everywhere. "It becomes a slick mess," Denise Feiber, a spokeswoman for the Florida Department of Agriculture and Consumer Services, tells Reuters.

This isn't Florida's first battle with the giant African land snail. The Sunshine State won the last war — in the 1960s, after a boy brought three snails home from Hawaii — but it wasn't cheap or easy. Those three snails turned to 17,000 in seven years, and beating them took 10 years and $1 million. "Feiber said she doesn't want this eradication project to last that long," reports the StarBanner's Peterson. So last week, her department held a strategy roundtable with experts from across the U.S. and Canada.

How did this invasion start? "One possibility being examined is a Miami Santeria group, a religion with West African and Caribbean roots, which was found in 2010 to be using the large snails in its rituals," says Retuers' Liston. Or somebody could have brought them in as pets, like in 1966. Or it could have just been an accident, like this decidedly unsavory possibility:

Miami-Dade is ground zero, but "unfortunately, the invasion is not limited to Florida," says Josh Mogerman in the Chicagoist. These "ticking environmental time bombs" have been found in upper Midwestern schools, pet shops, and even one private breeder's operation. And it would only take one escaped or released snail to spark a new infestation, Feiber tells Reuters: