How Burmese Pythons Took Over the Florida Everglades

Starting in the 1980s, the swamps of the South Florida Everglades have been overrun by one of the most damaging invasive species the region has ever seen: the Burmese python. These massive snakes, which can grow to 20 feet long or more, with telephone-pole-sized girths, have all but decimated the region’s small- and medium-sized mammal population, wreaking havoc within the area’s ecosystem.

That ecosystem, the Florida Everglades, commands some 1.5 million acres—or about one-and-a-half times the size of Rhode Island. Save for a few bisecting roadways (US 41 and I-75), these desolate subtropical swamps are detached from the grid of American civilization. It’s hard to fathom that downtown Miami sits just 30 miles away from the vast wetlands that have become an adopted home for (at least) tens of thousands of huge snakes.

Because female pythons can lay 50-100 eggs per year—and the creatures have no natural predator in the region—their threat continues to escalate.

Native to Southeast Asia, pythons were first brought to the United States as exotic pets. When the exotic pet trade boomed in the 1980s, Miami became host to thousands of such snakes.

Because pythons can grow to such unmanageable sizes, it was inevitable that some irresponsible owners would release the snakes into the wild. But most experts believe the pythons established a reproducing population in the Everglades sometime after Hurricane Andrew—a category 5 storm that devastated the state in August 1992. It was during that storm that a python breeding facility was destroyed, releasing countless snakes into the nearby swamps.

Today, authorities have no idea how many pythons occupy the area, in large part because the Everglades—in their vast inaccessibility—are so hard to conduct surveys in. And the mottled brown snakes blend well into the scrubby environment.

“It could be tens of thousands, or it could be hundreds of thousands,” says Rory Feeney, the bureau chief of land resources at the South Florida Water Management District (SFWMD)—a federal agency that helps spearhead Everglades conservation efforts. The agency, Feeney adds, has been actively “dealing with invasive pythons for over a decade.”

While only in South Florida for an ecological blink of an eye, the Burmese python has already devastated the mammal population of the Everglades, severely threatening its biodiversity. According to one study, between 1997 and 2012 the Everglades’ raccoon, opossum and bobcat populations dropped 99.3, 98.9, and 87.5 percent respectively. Meanwhile “marsh rabbits, cottontail rabbits and foxes effectively disappeared,” the study said.

Another study, which fitted rabbits with radio transmitters and released them into the Everglades, found that 77 percent of those who died within the year met their fate at the deathly squeeze of the invasive serpent.

“We’ve found wading birds in the bellies of these pythons. We’ve found deer,” says Feeney.

Daniel Simberloff, a biologist and ecologist at the University of Tennessee, Knoxville and the editor-in-chief of Biological Invasions, succinctly described the Burmese python’s brutal efficiency in South Florida:

“The habitat of the Everglades—it’s perfect. It’s warm; they do really well in muddy, marshy habitats…and of course, there’s this huge food base that was totally unadapted to deal with them. There was nothing to keep them from doing very well.”

As evidence of the python’s damaging spread became clearer, state and federal authorities began working together in an attempt to eradicate the python population. In 2010, the state made python pet ownership illegal.

Then in 2017, the Florida Fish and Wildlife Conservation Commission and the SFWMD introduced the Python Elimination Program, which hires people to hunt the swamps for snakes. These “python removal agents” are generally paid minimum wage, plus additional fees per foot—sometimes up to hundreds of dollars per snake. State and federal agencies are also upping the ante by hosting occasional competitive "python challenges," complete with cash prizes.

Feeney says the elimination program has removed almost 4,000 pythons from the wild, likely a small fraction of the estimated number of pythons still lurking the Everglades. But he has some cause for optimism since half those snakes have been females—which are capable of laying 50-100 eggs per year. Every female snake removed from the wild, he says, ”is a step in the right direction.”

The agency is also exploring more aggressive tactics, from canine detection to genetic warfare, which involves editing the genomes of snakes that are then released into the wild.

Simberloff says that scientists could theoretically “put a gene in there that causes all the offspring of a male that carries the gene to be male. Or causes all the female offspring to die. And these driven genes could really knock back the population.”

But until such technology is developed, the Burmese python will likely continue to squeeze life out of the great Florida wild.