In an article published in the Proceedings of the National Academy of Sciences, the group said nocturnal road surveys along the main road in Everglades National Park show steep declines in the number of animals spotted. In surveys between 2003 and 2011, no rabbits were observed and the number of raccoon sightings was down 99.3 percent while the number of opossums fell 98.9 percent.
While there could be other reasons, the authors said pythons, constrictive snakes that can grow to be 20 feet or more in length, are the main suspects. The decline in mammal populations coincides with the spread of the snakes and is most severe in the southern Everglades, where they first became established.
Water levels have changed during the years involved, but the area has otherwise been stable during the time.
The snakes are known to eat those particular mammals.
"There aren't many native mammals that pythons can't choke down," Robert N. Reed, a research wildlife biologist at the U.S. Geological Survey's Fort Collins Science Center and one of the authors of the study, told The Washington Post.