Burmese pythons in Florida

Burmese pythons are an invasive species in Florida, where they are a threat to native wildlife. These snakes have few predators in Florida and kill many native birds, reptiles, and small mammals. Burmese pythons were first introduced in the state in the twentieth century and have since had dramatic negative effects on ecosystems in the state. Scientists, government officials, and citizens have tried various methods to stop their spread and their destruction of native species.

Background

An invasive species is a plant, animal, or other organism that is not native to a place and is likely to cause environmental destruction or harm to other living things or people. A species that is an important part of the ecosystem in its native habitat is invasive elsewhere. Humans are responsible for introducing nearly all invasive species to new areas. Humans have introduced some invasive species purposefully without knowing or understanding the potential negative effects. For example, the Japanese plant kudzu was brought to the United States in the late 1800s as part of an effort to maintain soil health. Farmers in the South were paid to plant it as a cover crop. Although the plant did provide benefits such as reducing erosion, it also grew rapidly in warm, moist climates. In the American South, the vine spread beyond where it was planted and pushed out native plant species. It blanketed buildings, telephones poles, and rocks, and choked trees. By the 1950s, scientists no longer recommended planting kudzu, and by the 1970s it was labeled as a weed.

Humans have also unintentionally introduced many invasive species through transportation and travel. For example, in the late 1800s Americans imported Asian chestnut trees to the United States and unwittingly introduced the microorganism Cryphonectria parasitica, which is also known as chestnut blight. The Asian chestnut trees had evolved with the fungus and had developed resistance to it, but native American chestnut trees had never before encountered the microorganism and had no defense against it. By the mid-1900s, nearly all American chestnut trees—which had once been keystone species in many Eastern American forests—had died because of the invasive fungus. Another unplanned introduction is the zebra mussel, which is native to lakes in Russia and Ukraine. The mussels probably arrived in North America in the 1980s when large ships from Europe discharged ballast water, which is held in tanks to provide stability. The species spread through many rivers and into states including Utah, California, and Texas. Whether invasive species are introduced purposefully or mistakenly, they often have negative impacts on the regions where they take hold.

Overview

Burmese pythons are large nonvenomous snakes that kill their prey by constricting, or crushing, them. Like many other members of the python family, Burmese pythons grow to be huge snakes that consume birds and small mammals and reptiles. Most Burmese pythons grow to between 8 and 10 feet long, though some can grow longer than 18 feet. In their native ranges, which include parts of China and Malaysia, Burmese pythons usually live near water. They easily maneuver through water and are skilled climbers. These reptiles also breed quickly, with females laying clutches of between fifty and one hundred eggs.

Humans introduced Burmese pythons in Florida in the twentieth century. Starting in the early 1900s, the snakes were sold legally through the exotic pet trade, a global industry that makes billions of dollars a year. The snakes were relatively inexpensive. After a time, some owners likely lost interest in the pets or felt they could no longer care for them as they grew. Many of these individuals released the snakes into the wild rather than euthanizing or rehoming them. Some pythons escaped during shipping and these animals also went into the Florida wilderness. Florida’s warm climate and the large amount of potential prey helped the invasive species thrive in Florida, especially when the wild population became large enough to breed. Once a breeding population of the species was established, it became an even larger threat because even if humans introduced no new pythons to the environment, the numbers would continue to increase. After the threat that Burmese pythons posed to native species became clear, Florida outlawed ownership or purchase of the reptiles. By the early twenty-first century, Burmese pythons were established in the Everglades, including the protected Everglades National Park.

The Burmese pythons almost eradicated numerous species in and around the Everglades. After the snakes were introduced, the populations of animals such as marsh rabbits, raccoons, foxes, and bobcats declined by more than 90 percent. Bird populations in the Everglades have also been greatly impacted by the snakes. Scientists have observed the snakes killing numerous types of birds, including large herons that usually find food and shelter in the marshes. Scientists have found limited evidence of some native Florida predators killing or injuring Burmese pythons. However, the pythons kill many more native animals each year.

As of the 2020s, Burmese pythons were most prevalent in the Everglades region of Florida. Nevertheless, some scientists and citizens worried about the python’s ability to invade the Florida Keys, which lie to the south of the state. The islands are located just off Florida’s coast, and pythons can swim in saltwater. Some Burmese pythons have been found in the Florida Keys, as of the early 2020s, though the numbers had not reached breeding populations. Nevertheless, scientists could not be sure whether the snakes found on the Keys had traveled there from the mainland or were previously captive animals that had escaped or been released. Because scientists could not be sure of the snakes’ origins, they warned citizens and officials to be vigilant about the threat the snakes pose. It is difficult for scientists to estimate the population size of the Burmese pythons in Florida because the animals easily camouflage themselves in sandy or grassy areas and the marshes are difficult to access. As of the early 2020s, scientists estimated that from tens of thousands to hundreds of thousands of pythons lived in the state.

Scientists and wildlife conservationists have tried numerous programs and strategies to limit the population of Burmese pythons. One of the most popular and most successful enlists the help of Florida citizens. Each August, people hunt pythons in a contest that awards cash prizes for the largest specimens. This program is effective not only because it removes hundreds of snakes at one time, but also because it raises awareness about the threat that Burmese pythons represent and because it helps encourage public participation in trying to solve the problem. Furthermore, scientists have studied the program, and they have not identified any unintended consequences, such as a reduction in native species. Scientists have found that citizens can also help eradication efforts by reporting sightings of Burmese pythons in the wild. Burmese pythons can be hunted or killed on private property and some public lands without a permit, although people must have permits to capture live pythons for eradication.

Scientists have also conducted targeted eradication efforts that focus on reducing the python population in certain areas. Some researchers have focused their efforts on removing large females, who are capable of breeding and producing many offspring, from the environment. To locate such females, scientists will capture male pythons and implant radio transmitters into the animals. They then release the males into the wild and let the pythons find females of the species for them. Also, conservationists have developed programs through which people can drop off unwanted Burmese pythons (or other exotic animals) in safe locations without being questioned or facing repercussions. Local and state government programs including the Python Action Team Removing Invasive Constrictors (PATRIC) and the Python Elimination Program have been responsible for most of the python removals in the twenty-first century in Florida.

As of 2022, the largest Burmese python found in the Florida Everglades was 18 feet long and weighed 215 pounds. The previous record was a 140-pound snake found in 2016. The dramatically larger snake found in 2022 suggested that the pythons were becoming an even more significant threat because they were becoming larger. The snake found in 2022 was a female in which one hundred and twenty-two eggs were developing. Scientists believe that the snake’s large size and its reproductive potential indicate Burmese pythons might be even more harmful to Florida ecosystems and even more difficult to eradicate than they had earlier thought.

Bibliography

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Beckmann, Sean, Paloma Avila, and Terence Farrell. “Effect of Native and Non-Native Snake Scents on Foraging Activity of Native Rodents in Florida.” Journal of Mammalogy, vol. 103, no. 1, 2022, pp. 136 – 145. DOI: 10.1093/jmammal/gyab124. Accessed 22 July 2022.

Falk, Bryan G., et al. “Prospects and Limitations of Citizen Science in Invasive Species Management: A Case Study with Burmese Pythons in Everglades National Park.” Southeastern Naturalist, vol. 15, Oct. 2016, p. 89. EBSCOhost, doi.org/10.1656/058.015.sp806.

“How Have Invasive Pythons Impacted Florida Ecosystems?” US Geological Survey, www.usgs.gov/faqs/how-have-invasive-pythons-impacted-florida-ecosystems. Accessed 21 July 2022.

Kuta, Sarah. “Florida Biologists Capture Record-Breaking 215-Pound Python.” Smithsonian Magazine, 5 July 2022, www.smithsonianmag.com/smart-news/florida-biologists-capture-record-breaking-215-pound-python-180980363/. Accessed 21 July 2022.

Mazzotti, Frank J., et al. “Implications of the 2013 Python Challenge for Ecology and Management of Python Molorus Bivittatus (Burmese Python) in Florida.” Southeastern Naturalist, vol. 15, Oct. 2016, p. 63. EBSCOhost, doi.org/10.1656/058.015.sp807.

McCollister, Matthew F., et al. “Native Mammalian Predators Can Depredate Adult Burmese Pythons in Florida.” Southeastern Naturalist, vol. 20, no. 2, Apr. 2021, p. N55. EBSCOhost, doi.org/10.1656/058.020.0205.

Sweeney, Chris. “Invasion of the Bird Snatchers.” Audubon, vol. 120, no. 4, Winter 2018, p. 34. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=sch&AN=133356249&site=ehost-live.

Tarshis, Lauren. “Monsters of the Everglades.” Scholastic Scope, vol. 59, no. 6, 2010, p. 4. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=sch&AN=55538643&site=ehost-live.

“What Are Invasive Species?” National Invasive Species Information Center, 2021, www.invasivespeciesinfo.gov/what-are-invasive-species. Accessed 21 July 2022.