RENEE MONTAGNE, HOST:
Florida has a snake problem. The Everglades is infested with Burmese pythons. To keep them from spreading, the U.S. Fish & Wildlife Service is making it illegal to import the pythons into the U.S., or transport the snakes across state lines. Now scientists have discovered that the pythons are doing more damage than they ever imagined. NPR's Christopher Joyce reports on pythons gone wild.
CHRISTOPHER JOYCE, BYLINE: Go to YouTube and type in Florida pythons and you can spend hours watching these giants slithering, hatching, and most especially, eating. For these imports from Asia, Florida is the big easy. Biologist Michael Dorcas explains:
MICHAEL DORCAS: There really hasn't been snakes large enough to eat things like possums and raccoons in Florida for, you know, literally millions of years. And so the prey species, such as a raccoon or a rabbit or a possum, may not perceive a python as a predator.
JOYCE: They call them naive because they just don't know enough to run away. Just how naive became clear after Dorcas drove thousands of miles through the Everglades, counting mammals. Compared to the 1990s, well over 90 percent of the raccoons, possums, white-tailed deer, and bobcats in the Everglades are now gone.
Dorcas, a snake expert from Davidson College in North Carolina, says there's no evidence that disease did them in. He blames the pythons. Other biologists agree. Susan Jewell of the U.S. Fish and Wildlife Service says some invasive species take over when they find a new place.
SUSAN JEWELL: Certain ones have all the right characteristics that make them the perfect invasive species. They have all the right stuff. Super species.
JOYCE: Burmese pythons fit that category. They eat everything, they like water, and they can live a year without eating. And Jewell says their potential range is huge.
JEWELL: It's basically the southern third of the United States and our island territories. And that's pretty enlightening.
JOYCE: That's one reason the Fish and Wildlife Service, this month, made it illegal to import Burmese pythons and three other species of constrictors. Starting next March, you can't transport them across state lines either. You can still own them, however, or buy and sell them within a state.
Pet owners take a lot of blame here, for letting pythons loose when they get too big. Marshall Meyers, with the Pet Industry Joint Advisory Council, says that may or may not be true. But, he says, the ban is overkill.
MARSHALL MEYERS: I think for those people that are dealing in the Burmese python, it's going to have some significant financial impact.
JOYCE: Meyers says the government should, instead, set up a permit system to allow inter-state trade. And also to make sure people who buy the snakes know what they're in for. Meyers says, increasingly, people do not.
MEYERS: A significant number of the reptiles today are traded over the Internet or at reptile shows. These are not going through traditional bricks and mortar type pet stores, where they have care sheets they give out, they explain the information about the animals.
JOYCE: In any case, it's too late for the Everglades. Dorcas and Jewell say there's no clear way to get rid of the pythons. And they're likely to get hardier over time. As for the damage, Dorcas says it's never good to lose a big chunk of the animals in any habitat.
DORCAS: Any time you have, you know, a large percentage of your mammals that suffer severe declines like this, it's pretty safe to assume there's going to be some major ecosystem impacts.
JOYCE: Dorcas published his research in the journal Proceedings of the National Academy of Sciences.
Christopher Joyce, NPR News.