Even breeding like bunnies can’t save some mammals in Everglades National Park from invading Burmese pythons.
When the heat of summer revved up snake activity, the pythons ate up to a fifth of a study population of marsh rabbits each week, researchers report March 18 in Proceedings of the Royal Society B. That rate of predation over the long term is “not even close to sustainable” for the once-abundant rabbit population, says mammal ecologist and study coauthor Robert McCleery of the University of Florida in Gainesville. It’s the best evidence yet — contrary to what a mammal ecologist might predict — that the pythons really could wipe out populations of a famously fast-breeding mammal, he says.
McCleery had been skeptical that pythons by themselves could do so much damage. Marsh rabbits (Sylvilagus palustris) can produce six litters a year of multiple young, he says, and biologists have long expected that in rich habitats, fast-reproducing little animals rebound faster than predators can gobble them.
McCleery and colleagues monitored the fates of 80 marsh rabbits, some introduced into the snakiest locales and some in snake-poor zones. Examining the carcasses revealed mammals as the top predators in python-poor zones. But pythons killed more than two-thirds of the dead rabbits in the high-snake zone. “We’re talking about a total switch of predators,” McCleery says. Pythons, which don’t limit their diet to rabbits, may also be a major cause of dwindling populations of slower-breeding mammals, the study says.