Normally, what a snake eats for breakfast isn’t worth a headline. But this is no normal snake. And this was no normal meal.
The Burmese python is a massive snake native to Southeast Asia that arrived in South Florida in the 1980s, possibly released into the wild by careless pet owners. There are now as many as 300,000 of these invasive creatures slithering through the state, and they’ve been known to eat alligators, bobcats, rabbits, and birds.
Now scientists have discovered that Burmese pythons — which can reach 18 feet in length and swallow a bobcat whole — are even more ravenous than they realized. In a new paper in Bioinvasions Records, a team of researchers describe slitting open the intestine of a dead 14-foot python and finding the remains of three different white-tailed deer. The snake appears to have gobbled them up, an adult and two fawns, in just 90 days.
The implications are disturbing. “If this was just one snake that ate three deer in isolation, that’d be one thing” says Scott Boback, a biologist at Dickinson College and lead author of the study. But the incident comes alongside growing evidence that the Burmese pythons are ravaging native wildlife in South Florida’s Everglades. “When you put that all together, you’ve got to say, okay, something serious is going on here.”
There’s growing evidence that Burmese pythons are devastating the Everglades
Something disturbing is definitely happening in Everglades National Park, South Florida’s most famous natural wonder. In a 2012 study, scientists showed that sightings of raccoons, opossums, bobcats, rabbits, foxes, and other mammals in the region have declined more than 80 percent since the mid-1990s.
These observed declines were strongly correlated with the Burmese python’s known habitat, and the researchers couldn’t find any other plausible explanations for the mammals’ disappearance. Hunting, for instance, has long been banned in the Everglades park.
Of course, correlation isn’t causation. But in 2015, a team led by Bob McCleery of the University of Florida conducted a follow-up experiment. The researchers took 100 marsh rabbits (which have seen a precipitous decline), tagged them with radio collars, and released some of the rabbits into two sites where pythons were known to exist and the rest into a region where there were no snakes. Lo and behold, the rabbit populations crashed in the python regions — with three-quarters of them eaten by the snakes.
“All these studies are putting together a story that we just can’t ignore anymore,” says Boback.
This latest discovery adds to that picture. There have been isolated reports of pythons consuming deer before. And that 2012 study suggested that white-tailed deer populations have fallen 94 percent in Everglades National Park since pythons became established. Now, for the first time, a python has been found eating multiple deer in a short time period.
I asked Boback if he knew how the python had managed to catch and eat three deer. “This has been keeping me up at night,” he says. “It’s possible that the deer were all snoozing. But it also could have been an ambush.”
It’s thought that pythons use their olfactory senses to figure out where mammals tend to travel, and then lie in wait for one to pass. “It drives me crazy to think how a single snake was able to hide,” says Boback, “so that not just one deer but three deer walked within a meter of it — and then how it was able to strike from a low position … or grab a leg. … It’s fascinating to figure out.”
However it happened, the notion that pythons may be gobbling up lots and lots of white-tailed deer is troubling. For one, deer are a major revenue source in South Florida, thanks to the sale of hunting licenses. There are also ecological implications — the elimination of deer could rearrange the region’s ecosystem in unpredictable ways.
But what’s even more worrisome, says Boback, is that it suggests there’s little limit to what pythons can devour. “They’re eating pretty much every vertebrate in the Everglades,” he says. “They’re basically taking all that diverse biomass and replacing it with python biomass. And we’ve seen this story before.”
One huge worry is that the Everglades will see a repeat of what happened in Guam
The nightmare scenario is what happened on the island of Guam. During World War II, heavy ship traffic brought the non-native brown tree snake to the island. There had never been a snake species on that island before, and the local birds had no idea how to evade it. In the decades since, 12 native bird species have gone extinct.
“That really shows how we’ve underestimated these animals in the past,” Boback says. “It took literally 20 years for scientists to admit that the brown tree snake was established and was causing population declines of these birds.”
Eventually, officials did figure out how to deal with the brown tree snake in Guam. They devised clever traps, baited with live mice, that the snakes could squirm into but couldn’t easily escape. More recently, people have injected dead mice with acetaminophen (Tylenol) — which is deadly to snakes — and fired the mice out of a helicopter into trees to bait and kill the snakes. (Yes, really.) Once an area is cleared of snakes, they can reintroduce bird species.
The problem is that these strategies won’t work easily in the Everglades. For one, the region has all sorts of other native snakes besides the python that are already endangered — it’s tough to devise a trap that only kills pythons without wiping out a lot of other wildlife.
So at the moment, South Florida is struggling to figure out how to respond. The state has held hunting contests in some years to raise awareness, but people usually manage to kill a few dozen snakes or so — barely a dent in the population. Meanwhile, areas at the edge of the python’s habitat like the Florida Keys have had some success in fending off invasions with rapid response teams: Locals are encouraged to report python sightings, and a team immediately comes in to take care of it.
The biggest challenge, however, is that Everglades National Park is so vast, stretching hundreds of miles across, and the pythons can easily hide in the park’s endless sea of grass. The snakes are rarely ever spotted unless they happen to cross over roads. “Roads are really the only place we can reliably detect them,” says Boback.
No one’s quite sure where these Burmese pythons are going next
What we do know is that the pythons are extraordinarily efficient predators. Boback notes that the pythons convert about 80 percent of the food they consume into biomass — that is, into either growing bigger or producing babies. For mammals, by contrast, that efficiency is usually around 20 percent. That simple formula helps explain why pythons will continue to dominate.
They’re also incredibly well-suited to the warm climate of South Florida. And one big question is whether they might eventually travel north of Lake Okeechobee, which sits in the middle of the state, as the planet warms.
This turns out to be incredibly contentious. Some early studies looked at climate conditions in the snake’s current habitat, projected how climates in other states might change with global warming, and suggested that Burmese pythons could eventually establish themselves as far north as New Jersey. Other studies argued that these early studies missed important factors — like sharp swings in weather that could limit their range. (Among herpetologists who study the python, Boback says, this debate can quickly degenerate into angry shouting at conferences.)
So there’s a lot more to figure out here: how the snakes reproduce, where they’re likely to go next, and, most importantly, how to stop them.
“Mostly,” says Boback, “I think we need to start taking these snakes more seriously. We tend to be biased as humans — our imagination only takes us so far as to what these snakes can do. And if we continue to underestimate them, that will get us in trouble.”