Researchers tracking invasive Burmese pythons in the Florida Everglades made an unexpected discovery in 2021: the pythons were being killed and eaten by a predator that had been overlooked for decades.
Dr. Ian Bartoszek and his team at the Conservancy of Southwest Florida had spent years building a tracking network to study python behavior. They surgically implanted radio transmitters in captured pythons and released them back into the wetlands, mapping their movements, hunting routes, and resting patterns.
The study, based in Naples and active since 2013, was one of the longest continuous python tracking projects in existence.
Then one of the tracked pythons stopped moving.
The transmitter still worked, sending location signals every few seconds. But the movement data told a different story. Three weeks of regular activity had collapsed into absolute stillness. The team knew what that usually meant.
They went into the field, heading toward the coordinates through waist-deep black water and sawgrass. When they reached the location, they found nothing. No carcass, no blood, no drag marks in the mud. The 13-foot, 50-pound python had simply vanished.
The transmitter was still signaling, but it was moving. Something alive was carrying it steadily through the swamp. Whatever had consumed the python had done so in one meal, transmitter included.
Over the following weeks, two more tracked pythons disappeared under the same circumstances. The team recovered the transmitters they could locate and took X-rays. The images showed a python spine, still coiled in its distinctive S-shape, inside the stomach of another animal. There were no break marks, no scattering patterns, no bite marks on the bone. The predator was still digesting its meal somewhere in the Everglades.
The team had no idea what it could be.
To understand why these disappearances mattered, it helps to understand what Burmese pythons have done to South Florida. Native to Southeast Asia, these constrictors arrived in Florida through two converging paths. The exotic pet trade sold them legally throughout the 1970s and 1980s, and owners who could not handle their rapid growth often released them into the Everglades. Hurricane Andrew also destroyed commercial snake breeding facilities in 1992, releasing hundreds of animals into the wetlands in a single night.
The pythons found an ecosystem with no predators that recognized them as prey. Native mammals had evolved alongside different predators and had no behavioral response to a 15-foot ambush constrictor hiding in the grass. They walked toward the snakes. The snakes ate them. Then the snakes reproduced.
Research published in 2012 documented the collapse of mammal populations in Everglades National Park. Raccoon numbers dropped by 99.3 percent in the most affected areas. Opossums declined by 98.9 percent. Marsh rabbits, river otters, foxes, and bobcats disappeared entirely from whole sections of the park. Dissections of captured pythons revealed remains from 58 different bird species.
Dr. Frank Mazzotti, a wildlife ecologist at the University of Florida, has studied the invasion for over two decades. His estimate, refined through years of field research, is that tens of thousands of pythons currently inhabit South Florida wetlands, with realistic upper estimates reaching hundreds of thousands. For years, the consensus among researchers was grim: the pythons had essentially won. Human removal programs extracted thousands of snakes annually, but Mazzotti’s assessment remained steady. They were barely scratching the surface.
Then Bartoszek’s signals started disappearing.
The team worked through the list of possible predators. An alligator was the obvious first guess, but alligators leave unmistakable evidence. Their bite force, measured at over 2,900 pounds per square inch, crushes bone. Their death rolls scatter debris across meters. The consumed pythons showed none of this. No crushed vertebrae, no torn tissue, no signs of trauma at all.
Florida panthers were ruled out quickly. Panther kills carry consistent physical markers: claw punctures at specific anatomical points, bite wounds on the skull or cervical spine, partially consumed carcasses. There was no carcass.
Black bears had the same problem. Terrestrial mammals leave drag marks, disturbed vegetation, scattered remains, and footprints. The swamp floor around each disappearance site was perfectly intact.
The team ruled out eagles, great horned owls, snapping turtles, and even cannibalism among snakes. Every candidate failed based on the physical evidence, or rather, the complete lack of it. Whatever was responsible had consumed a 13-foot python without leaving a trace.
They set up motion-activated infrared cameras across the study area and waited.
When they reviewed the footage, the room went silent. The predator was not an alligator, panther, bear, or bird. It was a snake, thick-bodied, dark-scaled, coiled in perfect ambush posture at the base of a cypress tree. It was a Florida cottonmouth.
When a young Burmese python moved through the frame, the cottonmouth struck in a flash. The bite was quick and clean. The python tried to coil, but the venom was already working through its tissues. The cottonmouth retreated and waited. Once the python’s resistance faded, the cottonmouth began the slow process of swallowing it whole.
Florida cottonmouths have inhabited these wetlands for thousands of years, long before humans reached the peninsula. The species, classified separately from the broader cottonmouth group in 2015, is the only pit viper in the world that lives a fully semiaquatic life. They can hold their breath for nearly an hour. They hunt underwater as comfortably as on land. They swim with only the top of their head exposed, leaving no trace on the surface.
Adults typically reach 30 to 48 inches in length, but they are exceptionally heavy-bodied for their size. Their heat-sensing pits, located between eye and nostril, can detect temperature differences as small as 0.003 degrees Celsius. This makes them effective hunters even in complete darkness. A python basking in daylight or digesting a meal is warmer than the surrounding water, making it a detectable target.
Their venom is cytotoxic and hemotoxic, destroying tissue and breaking down red blood cells. For prey animals, the outcome is almost always fatal regardless of size, because cottonmouths do not need to overpower their prey physically. They bite, deliver a maximum venom dose, and withdraw immediately. Then they wait.
Cottonmouths eat other snakes. This is not incidental or opportunistic behavior. Research has documented at least 27 different snake species in their diet, including members of their own family. They are born snake hunters, a behavioral pattern refined over millennia in these specific wetlands.
When young Burmese pythons, ranging from 18 inches to 3 feet and rich in protein, began appearing in cottonmouth hunting range, they were simply added to a menu that had existed for thousands of years.
Three confirmed kills in one study area within a few months constituted a pattern. And the cottonmouth was not working alone.
Five of the 19 pythons under observation were killed by American alligators. One was killed by a 9-foot alligator, not a giant, but an adult that considered the python ordinary prey. Contrary to the popular narrative of pythons overpowering alligators, the tracking data showed alligators continuing to defend their territory and eliminate competitors.
In June 2021, cameras captured an adult bobcat, a species whose numbers had dropped by 87.5 percent in invaded areas, walking directly toward an active python nest. The bobcat intimidated the defending female into retreat, then raided the nest egg by egg, methodically and efficiently. This was the first photographic documentation of a native Florida mammal deliberately raiding an active Burmese python nest.
Tracking data added another dimension. Barred owls and red-shouldered hawks were hunting juvenile pythons from exposed positions at dusk and dawn. Each individual kill seemed small, but multiplied across thousands of square miles over a Florida winter, the cumulative effect could be significant. Florida panthers and black bears were also documented taking pythons opportunistically.
Taken together, the data suggested something rarely observed in real time: an ecosystem pushed toward collapse was generating organized resistance, with predators at every level of the food chain turning on the species that had displaced them.
The numbers still do not favor the ecosystem’s response alone. A female python lays 12 to 36 eggs per clutch and defends the nest aggressively. Hatchlings emerge at over two feet long and begin hunting within days. Females mature at 3 to 5 years and reproduce annually for two decades or more.
Humans have removed more than 5,000 pythons from South Florida since organized efforts began. The 2024 Python Challenge alone removed nearly 200 snakes. Mazzotti has long maintained that these numbers represent only a fraction of the true population, because pythons are extremely difficult to find. They blend into sawgrass, submerge under root tangles, and remain motionless for days without a thermal signature.
But the data shows the calculations have changed. Every cottonmouth bite, every bobcat nest raid, every alligator or raptor kill, and every removal by contractors is a permanent subtraction from a population that must outpace the pressure against it. When pythons arrived and found no natural predators, their growth curve was steep and unrestricted. That is no longer the case.
The question is not whether the counterattack is happening. The data answers that. The question is whether it is happening quickly enough before the python’s reproductive advantage becomes insurmountable. No one knows yet. The study is still ongoing. The transmitters are still signaling.
