How exactly DID Burmese Pythons get so numerous in the Everglades?  Were they released by owners who didn't want them and they found they liked the ecosystem?Nearly 80 percent of radio-tracked marsh rabbits that died in Everglades National Park in a recent study were eaten by Burmese pythons, according to a new publication by University of Florida and U.S. Geological Survey researchers.  A year later, there was no sign of a rabbit population in the study area.  The study demonstrates that Burmese pythons are now the dominant predator of marsh rabbits, and likely other mid-sized animals in the park, potentially upsetting the balance of a valuable ecosystem.