A new study finds that massive pythons in the Everglades appear to be wiping out large numbers of raccoons, opossums, bobcats and other mammals.

The report was published Monday in the Proceedings of the National Academy of Sciences. It finds roadside sightings of certain mammals are down sharply in areas where pythons and other large constrictor snakes are lurking.

The snakes are not native to the Everglades. Many are believed to have been pets that were turned loose once they grew too big. Others may have escaped from pet shops during a hurricane in 1992 and have been reproducing ever since.

Scientists are afraid the snakes will disrupt the food chain and upset the ecosystem in the Everglades.