In 2011, researchers in the Florida Everglades found a 15-foot Burmese python that had consumed an 80-pound deer. While alligators are often considered the primary danger in Florida swamps, Burmese pythons have become a significant threat to mammal populations in the region. Since 2000, Florida has removed more than 23,000 of these snakes from the wild, and a single female can lay up to 100 eggs at a time.

The Everglades is a fire-adapted ecosystem, and prescribed burns are part of its management. Fire crews use helicopters to drop small plastic spheres packed with chemicals, which burst into flames shortly after landing. These burns clear dead sawgrass so fresh growth can return and wildlife can move onto the new vegetation. After a burn, the marsh offers something rare: a clear view of the ground for long distances.

What becomes visible on that burned ground is not just the bare limestone and ash. It is also the absence of animals that should be there. Marsh rabbits, raccoons, opossums, foxes, and bobcats would normally be seen moving across an open marsh. In the southern Everglades, scientists have documented how short that list of running animals has become.

The python invasion traces back to pets that escaped or were released by their owners. In 1979, a python more than 12 feet long was found dead on the Tamiami Trail, a highway across the Everglades. Through the 1980s, people reported large snakes in the southwest corner of Everglades National Park, but those sightings were unconfirmed at the time. A 20-year study led by the Florida Museum of Natural History counted 137 non-native species introduced to the state between 1863 and 2010, with the Burmese python among the 56 that established breeding populations.

By 2000, scientists had confirmed a breeding python population inside Everglades National Park. By then, multiple generations were likely spread across a large area.

A study led by biologist Michael Dorcas of Davidson College drove the park’s roads at night between 2003 and 2011, counting every mammal seen, alive or dead. The results were compared with similar surveys from 1996 and 1997, before pythons were established. The findings, published in 2012 in the Proceedings of the National Academy of Sciences, showed raccoon sightings had dropped 99.3%, opossums 98.9%, white-tailed deer 94.1%, and bobcats 87.5%. Marsh rabbits, cottontails, and foxes that had been common on those roads did not appear at all during the survey years.

The study suggested that raccoons and opossums forage at the water’s edge, which is where pythons wait. Larger animals like deer and bobcats may not recognize the danger because nothing in their recent evolutionary history hunted them this way. Bobcats and foxes may have been affected twice: once by the snakes and again when the rabbits they hunted disappeared.

The road counts showed that animals were missing, but they could not confirm what took them. To settle the question, a team led by Robert McClary at the University of Florida fitted marsh rabbits with radio collars and released them into the park. From September 2012 to July 2013, pythons accounted for 77% of the rabbit deaths. The researchers followed the collar signals and found the rabbits inside the pythons. At control sites outside the park, where pythons were rare, no rabbits were killed by pythons.

Python kills increased in hotter, wetter weather, when pythons feed more often and high water lets them swim longer distances to hunt. Researchers noted that inside the park, pythons may have replaced bobcats and coyotes as the dominant predator of rabbits. Marsh rabbits are tough, fast-breeding animals, and their disappearance is considered a strong indicator of how thoroughly pythons have affected the ecosystem.

Prescribed burns are a standard tool in Everglades management. They clear dead sawgrass, knock back invasive plants, and keep the marsh open. In April 2019, Everglades National Park and Big Cypress National Preserve ran a cross-boundary burn covering more than 30,000 acres. Timing matters: lightning fires in the park mostly burn near the start of summer rains, when the ground is still wet and fire skims the surface. Late in the dry season, fires can burn hotter and reach dried-out peat, the marsh’s soil.

Pythons are difficult to find during or after burns. Researchers in southwest Florida have documented pythons sheltering underground, slipping underwater, and climbing into trees, with adults brooding eggs in the branches. The U.S. Geological Survey describes python detection rates as extremely low, citing effective camouflage and secretive behavior. The population size remains unknown.

Researchers have found a partial workaround in the water. Pythons leave traces of their DNA behind, and federal scientists sampling 28 sites across the greater Everglades found python DNA at 25 of them. But a positive water sample only tells crews a python was there recently; someone still has to find it.

In southwest Florida, one team has taken a different approach. Since 2013, biologist Ian Bartoszek and his team at the Conservancy of Southwest Florida have surgically implanted radio transmitters in male pythons and followed them. They call these males scout snakes and keep about 40 of them in the field. From November through April, breeding season, a male python goes looking for the largest female he can find. The scouts lead the team to breeding females, sometimes to large tangles of males wrapped around one female.

One scout led the team to a female weighing 215 pounds and measuring nearly 18 feet, with 122 developing eggs inside her. The conservancy estimates its program has kept around 20,000 python eggs from hatching. In the November 2024 to April 2025 season alone, the team removed 6,300 pounds of pythons, pushing its total past 40,000 pounds from a 200-square-mile area between Naples and the western Everglades.

In areas the team has worked the longest, the scouts are struggling to find mates, and the females they find are smaller. Local suppression appears to be working where people show up week after week.

The U.S. Geological Survey released a synthesis of python research in 2023. Its conclusion: with the tools that exist today, eradicating Burmese pythons across South Florida is not possible. The report says there may be tens of thousands of pythons across the known invasion area, though even that number is uncertain.

There was a moment when cold weather seemed to intervene. In January 2010, a record cold spell hit South Florida. Researchers reported 40 to 90% of pythons dying in the field. Of 10 radio-tagged pythons, only one survived. But the survivors passed on their genes, and a team at the University of Texas at Arlington found evidence of natural selection in genes tied to temperature sensing, behavior, and physiology. The Florida population shifted in a matter of years, a rare documented case of genome-wide adaptation on a short time scale. Researchers suggested the snakes may not stay bound to South Florida’s heat.

A second genetic finding involves interbreeding. A study of about 400 pythons caught between 2001 and 2012 found that at least 13 carried DNA from the Indian python, a separate species that prefers higher, drier ground. Researchers think the interbreeding most likely happened before the snakes became established in South Florida. The mixed ancestry suggests a population with more genetic variety to work with, which gives natural selection more to choose from.

The pythons have continued to spread north. At the Arthur R. Marshall Loxahatchee National Wildlife Refuge in Palm Beach County, staff caught the refuge’s first python hatchling in July 2025. In February 2026, they found its first confirmed nest with 31 eggs already hatched, and python DNA has been detected beyond Loxahatchee.

The ecological effects extend beyond the snakes themselves. When pythons reduced populations of raccoons, foxes, and bobcats, they also removed animals that kept rats in check. A study in the Journal of Mammalogy found mammal communities in python-invaded parts of the Everglades are increasingly dominated by cotton rats and other rodents. These rats can carry diseases, including hantavirus.

Nathan Burkett-Cadena, an entomologist at the University of Florida, led a team that caught a mosquito species called Culex cedecei in Everglades National Park and tested the blood in its gut. In 1979, before the pythons arrived, hispid cotton rats made up about 15% of this mosquito’s meals. By 2016, cotton rats made up 77%. The hispid cotton rat is one of the only known hosts of Everglades virus, which can cause fever, headache, and in rare cases, inflammation of the brain. Burkett-Cadena said it is unclear whether more bites on rats raise the risk to people, and this mosquito tends to stay in the wild away from towns. His team believes it is the first time anyone has shown an invasive predator increasing contact between mosquitoes and the hosts of a human disease.

The pythons also brought an Asian lung parasite that has jumped into Florida’s native snakes. A 2020 study found it in 13 native snake species, and those native snakes turned out to be better hosts for it than the pythons. Infected native snakes carried heavier loads of the parasite, and the parasites inside them grew larger. Researchers found an infected native snake more than 200 miles north of the northernmost infected python.

Pythons also carry elevated mercury levels. One study of park pythons measured up to 3.5 parts per million, and the Florida Department of Health advises against consuming python meat.

Researchers are studying genetic biocontrol that might someday suppress pythons on a large scale. For now, the proven tools are scouts, hunters, and patience. At Loxahatchee, refuge biologists run real-time camera traps on tree islands, watching for native mammals as well as pythons.

The real measure of success, researchers say, will be whether the native animals return. After a burn clears the sawgrass, the ground shows who is missing. When marsh rabbits can live in the southern Everglades again, the marsh will be recovering.