Why Burmese Pythons Are So Dangerous to Florida's Ecosystems

Burmese pythons have established themselves as a successful invasive species in southern Florida and experts say they pose a significant risk to the state's ecosystems. But why is this the case?

The non-venomous, constrictors are among the largest snakes in the world, capable of growing to around 20 feet in length—with the Florida record being a specimen that measured 18 feet, 9 inches.

As the name suggests, Burmese pythons are native to parts of Southeast Asia, but they were introduced to the Sunshine State by humans decades ago.

A Burmese python in the Everglades
Burmese pythons pose a significant risk to the ecosystems of southern Florida. One of the large constrictor snakes is photographed above. FWC/Andy Wraithmell

How Did the Burmese Python Get to Florida?

Burmese pythons were introduced to the state in the 1970s and 1980s when thousands of the animals were imported to be sold as exotic pets.

"Burmese pythons were introduced to Florida through accidental and intentional releases through the pet trade," Lisa Thompson, a spokesperson for the Florida Fish and Wildlife Conservation Commission, told Newsweek.

"A misconception exists regarding how pythons became established in Florida. Some believe Hurricane Andrew in 1992 caused the python problem, but pythons had been detected prior to that hurricane, as early as 1979. Several introduction events likely occurred in multiple locations across south Florida," she said.

The species is now considered to be invasive in the state, where they are living across more than 1,000 square miles of the south, primarily in the Everglades ecosystem but also in some of the surrounding areas, according to the U.S. Geological Survey.

It is virtually impossible to estimate the size of the Burmese python population in Florida because they are so hard to detect.

"Pythons have cryptic coloration and can hide well, and even expert searchers may find only 1 percent of the pythons that are in the area they are searching," Bryan Falk, a program analyst at the National Invasive Species Council, told Newsweek. "This low probability of detection remains the biggest challenge to control and research of invasive pythons in Florida."

But based on the numbers of Burmese pythons that have been removed from Florida's ecosystems, experts say there are likely tens of thousands in the state, perhaps up to 100,000 or potentially even more.

What Does a Burmese Python Eat? And How Is the Burmese Python Impacting the Everglades Ecosystem?

Burmese pythons have no natural predators in Florida and are thriving in the south of the state, where they are growing to large sizes, meaning they can eat a large variety of animals.

According to Falk, Burmese pythons eat more than 70 species in Florida, and they even occasionally consume alligators.

"Burmese pythons are large, invasive constrictors causing negative effects to Florida's ecosystems," Thompson said. "These invasive pythons are dietary generalists, preying upon native mammals, reptiles and birds, including some Endangered or Threatened species such as the Endangered Key Largo woodrat."

Not only do the pythons eat native wildlife, but they also compete with them for limited food resources. In fact, severe declines in some small mammal populations in Florida have been linked to invasive pythons.

One 2012 study from the Proceedings of the National Academy of Sciences of the United States of America (PNAS) based on animal road surveys reported "severe apparent declines" in mammal populations that coincided with the proliferation of pythons within the Everglades.

"Before 2000, mammals were encountered frequently during nocturnal road surveys within the Everglades National Park," the authors of the PNAS study wrote. "In contrast, road surveys...from 2003–2011 documented a 99.3 percent decrease in the frequency of raccoon observations, decreases of 98.9 percent and 87.5 percent for opossum and bobcat observations, respectively, and failed to detect rabbits."

"Road surveys also revealed that these species are more common in areas where pythons have been discovered only recently and are most abundant outside the python's current introduced range. These findings suggest that predation by pythons has resulted in dramatic declines in mammals within Everglades National Park."

A Burmese python in the Everglades
Burmese pythons prey on a variety of native wildlife in the Florida Everglades. One of the invasive snakes is shown above. FWC/Andy Wraithmell

The mammals that had experienced the worst declines have often been found in the stomachs of the pythons. The introduction of the pythons has had other negative effects on Florida's ecosystems, according to experts.

"We are just beginning to understand the cascading effects of these and other, less obvious impacts to the Florida ecosystem," Falk said. "One example is disease transmission. Because pythons have reduced the number of mammal species, mammal-feeding mosquitoes are now feeding more often on rodents, and rodents are hosts to Everglades virus, which the mosquito can then transmit to humans."

The implication is that in areas where pythons occur, a person may be more likely to become sick from a mosquito-borne mammal virus, which underscores the complexity of impacts that invasive species can have."

It is also known that pythons brought a non-native parasitic Asian species of pentastome (a type of crustacean) to Florida.

"This parasite lives in the lungs and can be passed to native species of snakes," Thompson said. "Recent research indicates that the parasitic pentastomes are now spreading independently of pythons and have been found from Key Largo to Volusia County. Other emerging disease risks, including nidovirus, may impact native species of snakes, but the extent or impacts of this virus on Florida's wildlife are not fully understood."