WEST PALM BEACH, Fla. (AP) — A burgeoning population of huge pythons — many of them pets that were turned loose by their owners when they got too big — appears to be wiping out large numbers of raccoons, opossums, bobcats and other mammals in the Everglades, a study says.

The study, published Monday in the Proceedings of the National Academy of Sciences, found that sightings of medium-size mammals are down dramatically — as much as 99 percent, in some cases — in areas where pythons and other large, non-native constrictor snakes are known to be lurking.

Scientists fear the pythons could disrupt the food chain and upset the Everglades’ environmental balance in ways difficult to predict.

“The effects of declining mammal populations on the overall Everglades ecosystem, which extends well beyond the national park boundaries, are likely profound,” said John Willson, a research scientist at Virginia Tech University and co-author of the study.

Tens of thousands of Burmese pythons, which are native to Southeast Asia, are believed to be living in the Everglades, where they thrive in the warm, humid climate. While many were apparently released by their owners, others may have escaped from pet shops during Hurricane Andrew in 1992 and have been reproducing ever since.

Burmese pythons can grow to be 26 feet long and more than 200 pounds, and they have been known to swallow animals as large as alligators.