Florida's Python Invasion

Burmese pythons have taken over the Florida Everglades, reducing biodiversity and altering ecosystem functioning.

General overview of the Everglades

The Florida Everglades is a subtropical ecosystem in South Florida and is the largest remaining expanse of subtropical wilderness in the United States. It contains several different riparian habitats that host a wide variety of organisms. A large portion of the Everglades is currently protected in two key areas—Everglades National Park, and Big Cypress National Preserve.

Habitats of the Everglades

Marshland

Mangrove Forests

Cypress Swampland

Animals of the Everglades

The Florida Panther, Snowy Egret, American Alligator, and West Indian Manatee are all found in the Everglades.

Anthropogenic Impact in the Everglades

Human encroachment and development in the Everglades has reduced its size by 50%, reducing biodiversity and changing ecosystem functioning.

Residential development currently occupies a large amount of the Everglades

Humans have also introduced harmful, invasive species into this ecosystem, like the Burmese Python...

What are Burmese pythons, and how did they get to Florida?

Burmese pythons are a non-venomous boa constrictor native to Southeast Asia. The snakes can grow up to 25 feet long and weigh over 200 pounds. They made their way to the United States during the 1970s as exotic pets. The Everglades is close to Miami, Florida, which is infamous for being a hub for the exotic animal trade.

In the 1980s, scientists found several individual specimens in the Everglades. While they initially assumed they were recently-released pets, numerous juvenile specimens found throughout the 1990s and early 2000s led scientists to conclude the species was breeding.

In 1992 when Hurricane Andrew hit Florida, exotic pet breeding facilities were destroyed, releasing scores of pythons into the Everglades. This compounded a python problem that began with humans releasing their unwanted pet snakes into the wild.

Burmese Pythons' Impact on the Ecosystem

Burmese Pythons have led to population reductions in nearly all mammal species within Everglades National Park.

Marsh Rabbit: Extirpated from Everglades National Park

Other mammal species in Everglades National Park that have experienced population reductions between 85-99% (Pitt, et al., 141-143):

Virginia Opossum

Raccoon

Bobcat

Gray Fox

White-Tailed Deer

It is significant to note that not all of these species—namely the predators on this list—are over-consumed by Burmese Pythons. Their reductions in population size are the result of excessive predation on their food supply because of the introduction of Burmese Pythons into the ecosystem. As the Burmese Python has virtually no predators in the Everglades, their population continues expanding because they face no competition from other organisms.

The sole known predator of Burmese Pythons is the American Alligator. However, large pythons are equally capable of killing alligators as well. Both of these species have become apex predators of the Everglades ecosystem.

A Burmese Python explodes after consuming an American Alligator. Both organisms perished.

Python predation rates on mammals have led to a reduction in the available food supply. They are opportunistic hunters and raid the nests of several native wading bird species.

Scientists observed Burmese Pythons consuming both the Great Egret (left) and White Ibis (right)

The data is significant, as the pythons in the study consumed eggs, chicks, and juvenile birds. As scientists found that python predation rates at wading bird nesting sites occurred at five times the normal predation rate, these snakes represent a true threat to the future of wading bird species (Orzechowski, et al. 2338). Additionally, wading bird populations worldwide have declined by 90% since the 1960s ("The Florida Everglades"). Predation by the Burmese Python places more stress on these already fragile population dynamics.

Indirect Ecosystem Impacts

Burmese Pythons' direct predation on native species harms the ecosystem by improving other species' success rates. Soft Shell Turtles, which are not prey to pythons, experience higher nesting success rates in areas where Burmese pythons are well-established. In these areas, fewer mammalian predators eat turtle eggs and young (Willson & Driscoll 1254-1255). The absence of these native predators is because Burmese Pythons eat them.

Florida Softshell Turtle (not python prey)

Though this example of indirect ecosystem alteration of species in the Everglades by the Burmese Python is seemingly minor, researchers discuss how it is a potential example of a trophic cascade. The pythons have limited natural predators of the turtle, which increases turtle survival. The changes in normal predation levels have ramifications that reverberate throughout the lower trophic levels. This ultimately alters nutrient and chemical cycling, which are the foundation of all ecosystems. Though this is well-documented in other areas, research is still underway to examine if this is becoming the case in the Everglades.

Burmese Python Management Challenges and Strategies

Burmese pythons, despite being large, are extremely difficult to detect. The low detectability rate is enough to impede the successful eradication of the snakes from Florida. Once a python is detected in a new area, likely, there is already an established breeding population. In 2012, the Department of the Interior banned the importation of Burmese Pythons, but this move occurred long after the snakes had already been breeding in Florida. However, numerous ways attempt to control the population of these invasive snakes. 

Visually searching for pythons—especially on colder days—has led to moderate yields. The snakes are cold-blooded and flock to warm areas, like asphalt or canal banks, to warm themselves up. Though many pythons have been caught this way, it is largely unsuccessful, as the majority of the Everglades is not easily accessible nor connected by roads.

The Florida Python Challenge is an annual event sponsored by the Florida Fish and Wildlife Commission. It gives out monetary prizes for captured snakes. Though the event gains significant public interest, their success in substantially reducing populations of Burmese Pythons is minor.

A program that trains dogs to detect pythons is currently underway, and is being implemented on a small-scale. The dogs are much more efficient at detecting pythons than humans, but struggle detecting the snakes in the water. Large-scale implementation of this program may help reduce the number of Burmese Pythons.

The "Judas Snakes" python management program tags male snakes and continuously monitor them throughout the mating season, rather than killing them immediately. This has led to scientists successfully finding female snakes that would otherwise mate and reproduce. The program is costly, however, and much of the Everglades is not easily traversable.

Ultimately, there is no easy solution to ridding the ecosystem of these invaders. Additionally, as estimates of the Burmese Python population range from 30,000 to 500,000, it is unlikely that humans will completely eradicate the species. As reports of pythons continue to grow further and further from the Everglades, the need for increased management of the species is essential. There is no one way to approach this issue, so multi-disciplinary strategies that emphasize reducing the impact of this species on the environment must be the approach taken.

Sources

Florida Everglades  Map 

"The Florida Everglades." Exploring Florida. Florida Center for Instructional Technology, College of Education, University of South Florida, 2002, https://fcit.usf.edu/florida/lessons/everglades/everglades.htm#:~:text=The%20Everglades%20is%20a%20unique,%2C%20rare%2C%20and%20exotic%20wildlife. 

Orzechowski, Sophia C. M., et al. “Invasive Burmese Pythons (Python Bivittatus) Are Novel Nest Predators in Wading Bird Colonies of the Florida Everglades.” Biological Invasions, vol. 21, no. 7, Springer International Publishing, 2019, pp. 2333–44, doi:10.1007/s10530-019-01979-x.

Pitt, William C., et al. Ecology and Management of Terrestrial Vertebrate Invasive Species in the United States . CRC Press, Taylor & Francis Group, 2018.

Willson, John D., and Don Driscoll. “Indirect Effects of Invasive Burmese Pythons on Ecosystems in Southern Florida.” The Journal of Applied Ecology, vol. 54, no. 4, WILEY, 2017, pp. 1251–58, doi:10.1111/1365-2664.12844.

Marshland

Mangrove Forests

Cypress Swampland

Residential development currently occupies a large amount of the Everglades

A Burmese Python explodes after consuming an American Alligator. Both organisms perished.

Florida Softshell Turtle (not python prey)