In the 1980s, Burmese pythons released or escaped from Florida’s pet trade began reproducing in the Everglades; scientists linked them to sharp declines in native mammals

Florida's Everglades has become home to an established population of Burmese pythons, a giant constrictor native to Southeast Asia that can grow beyond 17 feet long. Research by the US Geological Survey and its collaborators has documented the snakes' spread across the Greater Everglades Ecosystem alongside severe declines in several native mammal populations. Raccoon observations fell by 99.3%, opossum observations by 98.9%, and bobcat observations by 87.5% between earlier surveys and road surveys conducted from 2003 to 2011. Rabbits were no longer detected during the later surveys.

The population is believed to have originated from a small number of pet pythons that escaped or were released near the southern end of Everglades National Park in the early 1980s. Over the following decades, the snakes found conditions well suited to them. The region's warm, wet landscape provided cover, suitable temperatures, and abundant prey, allowing the species to establish a self-sustaining breeding population. Today, Burmese pythons are established across much of the Greater Everglades, although scientists still cannot reliably determine exactly how many are living there.


Why the python has been so hard to study

One reason the invasion has been difficult to track is the snake's ability to disappear into its surroundings. Its camouflage and secretive behaviour make visual searches challenging, while the dense wetlands provide plenty of places for the animals to hide. As a result, researchers still do not have a reliable estimate of the total python population.

Scientists have used radio transmitters to follow individual pythons and study their movements, survival, and habitat use. Trail cameras and direct observations have also helped researchers investigate reproduction and nesting behaviour. In one documented case, cameras recorded python eggs hatching inside a concrete pipe in the Greater Everglades Ecosystem. Researchers measured temperatures inside the pipe and nest to better understand how the snakes regulate temperature while brooding their eggs.

This work has helped build a clearer picture of how the population grows, moves through the landscape, and reproduces. Understanding these biological patterns is important for developing control methods because removing snakes from the wild is difficult when their numbers and movements cannot be accurately tracked. Research is also examining potential large-scale approaches, including genetic biocontrol.

The toll on native wildlife

The disappearance of native mammals is one of the clearest signs of the python invasion. The dramatic declines observed as the snakes became established raised an important question: were pythons directly responsible for at least some of those losses?

A 2015 study published in Proceedings of the Royal Society B provided stronger experimental evidence. Within 11 months of the rabbits being moved into the study area, Burmese pythons accounted for 77% of recorded rabbit deaths. Rabbit populations failed to persist where pythons were present, while control populations survived in areas where the snakes were absent or rare.

The findings strengthened the evidence that Burmese pythons can directly drive declines in vulnerable native mammals. In the case of marsh rabbits, the experiment showed that python predation could be severe enough to prevent a local population from persisting.