In the 1970s and ’80s, a few dollars could buy you an exotic pet. It could get you a Burmese python. But those pets get big, fast. Growing up to ten feet in its first year, a Burmese python can go from a distraction to a danger. Sometime in the 1980s, enough regretful owners in South Florida had abandoned their pets, deciding to deposit them in the Everglades, ostensibly thinking that it would be a better home. It was. By the time biologists noticed what was happening, the snakes had eaten everything.
The mammal population in Everglades National Park is crashing. Alligators and birds native to the region aren’t faring much better, but mammal populations — raccoons, opossums, and rabbits — have been reduced by as much as 99 percent since Burmese pythons were introduced to the area. Not even fast-breeding rabbits are making it out of this flood of flicking tongues.
According to a new study published this week in the Proceedings of the Royal Society B, the rabbit population in South Florida might actually get wiped out by Burmese pythons. The findings also suggest that the burgeoning Burmese are also the key suspects in the declining numbers of other mammals in the area.
To find out just how voracious the population of pythons in the Everglades National Park had become, lead authors Robert Robert A. McCleery and Adia Sovie from the Department of Wildlife Ecology and Conservation at the University of Florida released 80 marsh rabbits with tracking devices from donor populations randomly into two areas of the park — one where Burmese pythons were established and one where they were not. Over the course of 11 months, the researchers tracked how many rabbits were killed by predators and what predators did the killing.
Over the course of the study, researchers cataloged how the rabbits stopped hopping. If they found a carcass with removed organs, they attributed it to a mammalian predator. If there were feathers and “fecal sprays” at a site, they figured a bird took it. Reptile predations were less messy, but obvious. The researchers could visually confirm that a tracking device was inside a python or alligator, as those reptiles eat prey whole.
The difference in deaths between sites was clear, and alarming. As shown in the chart above, in areas where the pythons were established (left graph), pythons represented the majority of killers. Beyond 250 days, there was little chance there was a rabbit who hadn’t been constricted.
In stark contrast, in areas where there were few pythons (or none), no rabbits were killed by pythons. 77 percent of kills in the python area were from pythons, while 71 percent of kills in the non-python area were from mammals like bobcats. In other words, in areas that pythons populated, the snakes easily out-competed other predators.
The difference was so huge that even the dry language of the scientific study showed surprise. “It seems unlikely that marsh rabbits and other mammal populations will rebound without action to manage pythons,” the team concludes.
Like another invasive species released in Florida, the “living oil spill” that is the lionfish, Burmese pythons are taking over because of the snakes’ ability to resist environmental pressure. They can survive long periods without any food, eat almost anything they can fit in their mouth, are hard to track, have few natural predators, and produce a lot of eggs.
There could be tens or hundreds of thousands of Burmese pythons now slithering around the Everglades. Everything done to stop them has failed — snake-sniffing dogs, trapping, pheromones. As of now, our best bet is to prevent the spread of these snakes and track the extent of their influence.
“Without effective tools and a strategy for reducing the prevalence of these invasive snakes,” the new paper finishes, “the dire state of mammals in the Everglades will probably remain unchanged, and even spread if python populations expand northward or become established elsewhere in the USA.”
MORE INFORMATION: The Snake That Ate Florida
IMAGES: by Florida Fish and Wildlife; Robert A. McCleery, Adia Sovie, Robert N. Reed, Mark W. Cunningham, Margaret E. Hunter, Kristen M. Hart