Burmese pythons in the Florida Everglades have caused a major decline in native mammal populations, and researchers have identified a parasitic worm as an additional threat to the ecosystem. The pythons, introduced decades ago through the exotic pet trade, now number in the hundreds of thousands and have reduced raccoon populations by over 99 percent in core areas. Other mammals, including opossums and marsh rabbits, have seen comparable or total declines.

Trail camera data shows that surviving animals have changed their behavior significantly. Raccoons stay in their dens for extended periods, and some prey species have stopped breeding or foraging normally. The presence of pythons has created such intense fear that animals are dying without direct contact with the snakes.

A separate discovery involves a parasite called Rileyella orientalis, the Asian snake lungworm. This worm evolved with Burmese pythons in Southeast Asia, where it causes no symptoms in them. The pythons shed the parasite’s eggs into the environment, where they move through insects, frogs, and native snakes. Native Florida snakes have no immunity to the parasite. Infected snakes eventually die from lung damage caused by the worms.

The parasite has now established itself in Florida’s native food web and no longer depends on pythons to spread. Infected snakes have been found as far north as Jacksonville. Internal reports suggest that several native snake species could face regional extinction within the next two decades. One native species, the cottonmouth, appears to handle the infection better than others, though the reason is not yet known.

The pythons originally entered the Everglades through two main routes. Some escaped from a breeding facility during Hurricane Andrew in 1992. Many others were released by pet owners who had bought young snakes cheaply and later found them too large to keep.

Efforts to control the python population have had limited success. Bounties, professional hunters, and tracking programs have removed thousands of snakes, but the population continues to reproduce at a pace that outruns removal efforts.

In northern Florida, a separate program has been reintroducing the Eastern Indigo snake, a native species that feeds primarily on other snakes. The Indigo snake is immune to pit viper venom and grows to nearly nine feet in length. A captive breeding program has released snakes into the Apalachicola region, and recent evidence shows they are breeding in the wild. The Indigo snake cannot take down an adult python, but it may prey on juvenile pythons, potentially limiting their spread northward.

Trail cameras have also documented native predators adapting to the invasion. Bobcats have been recorded killing juvenile pythons and destroying python nests. Some recordings show bobcats caching python carcasses, suggesting they now treat pythons as a regular food source. Alligators have also been observed eating young pythons near the water’s edge.

The situation remains unresolved. The parasite is expected to continue spreading through the native snake population, while the pythons continue their slow movement northward, limited in part by cold winter temperatures. Researchers monitoring the area describe the core python zones as having far less wildlife activity than in previous years. At the same time, the documented behavior of native predators suggests some species are adapting to the presence of the invasive snakes. The long-term outcome for the Everglades is not yet clear.