Operation: Kill Kermit

Most nights, armed men stomp through the Périgord-Limousin Regional Park in southwestern France with orders to shoot ... frogs. But not just any amphibians. They're after Rana catesbeiana — the North American bullfrog — introduced to France in 1968 by a French aviator who liked the idea of the critters croaking in his garden. They're now an ecological menace.

Weighing up to a kilo, these voracious predators gorge on crustaceans, fish, other frogs, salamanders and even the occasional bird. "It's capable of attacking anything it can swallow," says Tony Dejean, the naturalist at Périgord-Limousin leading the operation. Worse, it was recently discovered that bullfrogs carry chytrid fungus, which kills other amphibians.

Prior attempts to eradicate invasive species have failed in France. But the park service has already killed thousands of the frogs, their tadpoles and eggs, and residents nearby are praying this eradication mission succeeds: "Thousands of bullfrogs croaking all night is unbearable," Dejean says.