MIAMI While Burmese pythons boomed in the Everglades, populations of key native animals headed in the opposite direction - their numbers crashing to near zero in the case of bite-sized creatures such as raccoons, opossums and marsh rabbits.

Those are the findings of a sobering study published Monday, the first by scientists to assess the impact the giant constrictors have had on the complex food web of the Everglades. One word sums it up: carnage.

Scientists have firmly established what pythons eat, pulling the remains of just about everything that walks, crawls or flies in the Everglades from the bellies of captured snakes over the last decade. But just how much a snake population of unknown size has been eating has largely been a guess until now.

According to the study published in the science journal Proceedings of the National Academy of Science, the probable answer is, once again, just about everything.

"When we actually did the calculations, we were astonished by the magnitude of the declines," said Michael Dorcas, a biology professor at Davidson College and the study's lead author.

The peer-reviewed study, based on nocturnal field surveys conducted before and after the python invasion, suggests a collapse of the park's mid-sized mammal populations since the mid-1990s and points to the exotic snake as prime suspect.

Raccoons - once so abundant that park managers had to post signs warning campers to safeguard food from roaming hoards of the wily thieves - dropped 99.3 percent. Opossum sightings fell 98.9 percent. Observations of bobcats, foxes and deer also all fell steeply.

And marsh rabbits - small brown bunnies frequently seen foraging along roads in the park's pre-python past - didn't appear at all during the surveys.

Pythons indicted

Frank Mazzotti, a wildlife ecology professor at the University of Florida, likened the study to a grand jury investigation - a damning initial finding that needs more research to refine and confirm.

"We examined all the evidence and there is enough to indict pythons, but we haven't gone to trial yet," said Mazzotti, one of 11 university and federal government researchers who co-authored the study.

Other factors may have contributed to the decline, he said. For predators, the declines could be less from snakes eating them than from the reduced amount of prey to go around.

Still, the Obama administration pointed to the findings as more justification for the decision earlier this month to ban the import and interstate sale of Burmese pythons, two types of African rock pythons and yellow anacondas. The decision to declare them "injurious species" had been criticized by reptile breeders and collectors, as well as some GOP lawmakers who contend the measure would kill jobs in the cottage industry of constrictor breeding.

The study suggests a strong link between the rise of the snake and the fall of the bunnies and other mammals, and finds little support for other possible causes.

Between 2000 and 2010, a period when python captures soared from two to nearly 400 a year, no diseases swept the mammal population and there were no big losses of habitat or other major environmental changes that might explain the declines, the study found.

Besides the coincidental timing, researchers also found a pattern across the landscape, with the greatest losses in the southern portion of the park in and around Flamingo, where the python infestation has been heaviest. Mammal populations are strong on the park's fringes or in adjacent areas.