According to a new study, the introduction of non-native snakes into southern Florida swamps has devastated the population of small mammals, almost completely wiping out some vulnerable species. According to the U.S. Geological Survey, the number raccoon and possums spotted in the Everglades has dropped more than 98%, bobcat sightings are down 87%, and rabbits and foxes have not been seen at all in years.

Large snakes, like boa constrictors, anacondas, and pythons, are not native to North America, but are popular among reptile collectors and traders who — inadvertently or not — re-introduced them to the Florida swamps about a decade ago. Since that time they caused a huge disruption to the already fragile ecosystem, threatening wildlife and even some humans. They grow fast, breed rapidly, adapt well to their environments, and prey on small animals that don't recognize them as a threat. They're also great at hiding, which makes them both deadly hunters and difficult to catch.

They will also eat just about anything, even birds, deer, and alligators. (The 162-pound Burmese python pictured above had recently swallowed a gator.) That's why the government banned the import of Burmese and other pythons last year, although (thanks to lobbying by the U.S. Association of Reptile Keepers) the reticulated python and the boa constrictor are still allowed to be traded.

Biologists say that with anywhere from 30,000 to 100,000 snakes now on the loose, it's impossible to wipe out the pythons entirely, though they may still be able to contain their damage — and keep them out of other states, provided the cold weather cooperates. The weather and careless pet owners, who have established 56 non-indigenous reptile and amphibian species in the state of Florida alone. In other words, when you get bored with your exotic pets, don't just throw them out.