Who ate all the animals?

Nearly all the mammals in Florida's Everglades are gone. More than 99 per cent of raccoons that were there 15 years ago have disappeared, as have 98.9 per cent of opossums and 94.1 per cent of white-tailed deer. Scientists think they know who's responsible: a large snake that doesn't belong there.

Burmese pythons kept as pets have either escaped or been let loose when they grew too big. And they do get big: four metres in length, with a weight of up to 70 kilograms.

The snakes will eat almost anything: roosters, geese, birds, even large animals. "Last October, we found a 15-foot snake with an 80-pound doe inside it," biology professor Michael Dorcas told USA Today. Dorcas is the lead author of a paper published in late January in Proceedings of the National Academy of Sciences.

Since 2000, staff in the Everglades National Park have captured or killed 1,825 pythons. It's difficult work, because the snakes are very hard to find.

Their activity, however, has far-reaching effects: because the snakes have eaten all the small animals, there is no food left for larger predators like coyotes, panthers and alligators.

Gordon Rodda, an invasive-species specialist, says people should be alarmed at how fast the animals are disappearing. "What if the stock market had declined that much? Think of the adjectives you'd use for that."

Rodda says that once the mammals are gone, the snakes might continue to search for food. Dorcas agrees: "All of Florida and much of the coastal plain of the southeastern United States is suitable habitat."

The positive news — if there is any — is that the pythons almost never attack humans.