On a steamy August day, Frank Ridgely stands inside a chilly surgical suite at Zoo Miami, preparing to slice into a seven-and-a-half foot-long Burmese python.
The snake was captured at the Big Cypress National Preserve, one of an estimated thousands roaming South Florida, devouring small mammals and helping wreck the balance of the ecosystem.
After the python is gassed and knocked out, Ridgley makes an incision between its scales and opens a hole in its body cavity big enough to fit a fist-size receiver and battery. There’s a faint pop as he pries open the ribs.
This is step one in a complex and grueling project that will take scientists deep into South Florida’s formidable marshes and swamps, searching for a better way to hunt pythons. Since late 2017, a team with the U.S. Geological Survey and National Park Service has been tracking pythons using transmitters in the Big Cypress National Preserve and Everglades National Park. They’re studying the python habits - what kind of habitat they prefer and how they move around - to help hunters who only have a one percent chance of spotting a snake in the wild.
They’re also looking for ways to build a better Judas snake - where one snake is used to lure other snakes - with a new twist: sex pheromones. They know they have their work cut out for them.
“You could you could send out thousands of people to wander around Big Cypress and you still wouldn't catch enough snakes to get rid of the Burmese pythons,” said Jill Josimovich, a U.S. Geological Survey biologists in charge of the study. “There are many times we tracked our snake and we know we're virtually standing on top of it, within a meter, and we cannot see a single scale that animal.”
But scrutinizing their behavior and using Judas snakes could lead to designing a strategy to, at the very least, better manage the snakes in the wild.
Once Ridgley secures the receiver inside the python, he uses the shaft from a crossbow arrow to thread a thick flexible antenna between the python’s ribs and skin. He used to use a surgical cannula, but researchers decided to use a thicker antenna after it became clear the muscular snakes were wearing out and breaking the antennas, reducing the receiver’s transmission power. Because they need to be able to locate the snakes by plane, they need a reliable signal.
In recent years, Ridgley has planted trackers in about 50 snakes at the zoo, becoming so adroit that he now teaches it to students, some of whom wander in today’s surgery.
Throughout the hour-long procedure, a Doppler ultrasound monitor attached near the python’s heart maintains a constant whooshing sound. While comforting, Ridgely says it’s no guarantee the snake remains alive.
“I had the University of Florida bring me a python once that had been frozen for two weeks,” Ridgley says. “When we thawed it out to do the necropsy, the heart started beating again.”
Once the snake is stitched up and oxygen squeezed into its lungs, Big Cypress biologist Matthew McCollister, who drove the snake over in a locked box for the surgery, carries it outside to a concrete loading pad. After a few minutes stretched out in the 90-plus degree heat, the cold-blooded reptile revives quickly.
“If they were very combative when you first got them out of the bag, now it's the exact opposite,” Ridgely says. “They're so nice and calm and slow.”
Two weeks later, McCollister is at the wheel of a swamp buggy, driving Josimovich and Andrea Currylow, a newly hired USGS biologist, down a bumpy trail near the Monument Lake campground. They’re tracking snake C-5, or Charlie, the first snake they began monitoring.
Josimovich and Currylow are part of the USGS’s Fort Collins Science Center, where the agency keeps its rapid response team for invasive species. While using radio telemetry to track snakes is not new, implanting sex pheromones is. The Fort Collins station helped fund pheromone research by James Madison University chemical ecologist Rocky Parker, who has been using the method to manage invasive brown tree snakes in Guam.
Josimovich is hoping that might hold the key for managing pythons, too.
“The idea is that this hormone could feminize the scent profile of the snakes, hopefully putting a slight twist on the traditional Judas snake method,” Josimovich says.
Last year, her team of researchers set up an experiment in Everglades National Park using a Y-shaped maze that held both a female python and a male implanted with the sex hormone. Males released into the maze showed equal preference for both, a signal that the brown tree snake method could work with pythons. Because the study got delayed until after the start of the December to April python breeding season, Josimovich said the team is repeating it this year to confirm the findings.
“It's like okay, the hormonal manipulation might elicit interest in other snakes,” she said. “So we’re going to be continuing that work next breeding season.”
In Big Cypress, the work is a little more straightforward: figuring out what characteristics in the pythons make them the best snake bait for other pythons.
“Whether they're hormonally manipulated or not, is it the big snakes?” Josimovich said. “Is it the ones with the largest home-range sizes or the ones closer to roads.”
What becomes quickly clear during the outing, on a day where the ground temperature in the shade measured 91-degrees, is just how difficult the work is.
The day before, researchers flew over the preserve, located Charlie and passed those coordinates along to Josimovich. The coordinates put Charlie deep in the preserve, beyond the trail.So after an hourlong ride in the swamp buggy, Josimovich, McCollister and Currylow hop out where a fence separates the preserve from private property. Josimovich takes the lead, holding a radio antenna and monitoring her receiver.
Beyond the trail, the landscape alternates between dark swamp waters and hardwood hammock. Inside the hammock, ferns grow head high and so thick it’s hard to see just five feet ahead. At one point, McCollister ducks under a tree branch and vanishes.
“We're trying to essentially bushwhack through a very dense wall of vegetation in the direction where the signal is strongest to try to get to Charlie,” Josimovich explains. “Sometimes he is in places that are very easy to walk to. And other times...in hardwood hammocks or habitats that are just a lot more challenging.”
This is part of the reason pythons have been able to flourish. The first python was captured in Everglades National Park 40 years ago in October. Researchers believe early on owners dumped snake pets. When numbers spiked in the 1990s, a breeding facility damaged by Hurricane Andrew likely became a source.
Either way, the snakes found an ideal new home. They are perfectly camouflaged and found a bountiful buffet of raccoons, marsh rabbits, deer and even alligators. As the pythons spread, the number of small mammals nearly vanished.
Making their way from the ferns back onto the trail, the team comes across a hunting camp, posted with numerous no-trespassing signs. Either a real or fake handgun hangs from the front gate, near a sign that reads “shaky gun.”
The trio wades into the swamp, where the water can be waist deep and even deeper in holes. A canopy of cypress and the cool water provide some relief from the ferns’ claustrophobic heat. After about an hour, listening to the persistent chirp of the transmitter, Josimovich stops. She’s narrowed in on Charlie.
But finding him in the head-high ferns is difficult. For a good three minutes, she hunts around, trying to zero in with the transmitter.
“He’s right near me,” Josimovich said. “He’s in these ferns.”
Five seconds later, Currylow spots him, sliding silently by in brush about two feet away. The only thing visible is about a two-inch patch of scales.
Just as quickly as they see him, he vanishes.
In a field report, Josimovich and Currylow record temperature, wind speed, cloud cover and habitat type. When compared to data collected from other tracked snakes, they hope to figure out what kinds of conditions pythons prefer. Other research has already found the snakes behave differently than in their native ranges, swimming in water and congregating around tree islands where they may be drawn by wading birds.
It takes just five minutes to collect the data and they head back. This time, when they near the hunting camp, McCollister spots a mound sticking out of the swamp. It’s an alligator nest, littered with broken egg shells. McCollister thinks the nest is empty, and the eggs likely gobbled up by a hungry predator since it’s a little early for hatchlings.
But a few minutes later, Josimovich spots dozens of yellow and black-striped baby gators swimming in the swamp.
“Just be careful,” McCollister warns. The gators’ mom is likely close by. “If one gets to squeaking, she’ll come around.”
To avoid bumping into the mom, the team ignores the no-trespassing signs around the hunt camp and cuts through, scrambling over the barbed wire fence.
On the ride back, the swamp offers one last adventure when a thunderstorm rolls in. The rain comes down so hard that they stash cell phones, radios and transmitters in a cooler. As the lighting becomes more fierce, Josimovich suggests they jump out of the metal swamp buggy and wait out the storm in the brush. She’s from West Virginia, where her grandfather got hit by lightning - twice.
Josimovich has everyone space themselves 50-feet apart and hunch as close to the ground as possible, just to be safe. With each burst of lightning, she grabs her ears and hunches lower.
In the months ahead, biologists monitoring the snakes will be back again and again as they struggle to crack the code in building a better python trap. What complicates the effort is how little is known about their behavior, not just here, but in their native range, Josimovich said.
“There's no other habitat on Earth like the Everglades, so I would love to be able to go and actually compare,” she said.
For now, she thinks the pheromone research may hold the most promise.
“If we could develop an actual tool where we had, in theory, this like bottled pheromone that you could create trails to pheromonal attractant traps or maybe put it on roads and, you know, draw more in. But that's several years away.”
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