Pythons in Florida

Burmese Pythons in Florida - Current Status of the "Florida Python"

by Brandon Cornett, 11/1/09

Burmese pythons are one of the largest snakes in the world. They can be found in the rainforest regions of Southeast Asia, and also in ... the Florida Everglades. Yes, you read that correctly. This massive constrictor is now well established in the Everglades National Park and other parts of the Sunshine State.

This article explains the history of Burmese pythons in Florida, as well as the current status of this invasive / non-native species.

A few months ago, a woman emailed me a picture of a large snake moving across her front lawn. She lived in the suburbs of southern Florida, and the snake was a Burmese python (Python molurus bivittatus). It was a full-grown Burmese too, probably more than twelve feet long based on the photo.

We had a brief discussion about the snake, by way of email, and the woman told me she sees them in her yard and around her neighborhood frequently -- probably twice a month.

My initial reaction was: "What? Burmese pythons are invading Florida neighborhoods! What is going on here?" I had known for years that this non-native snake species was establishing itself in that area, but I had no idea how widespread they had become. So I did some research and read everything I could find on the subject of Burmese pythons in Florida. This document is the result of that research.

History of an Invasion

How did Burmese pythons populate the Florida Everglades, anyway? Where did these snakes come from? How are they thriving in an ecosystem so far from their native habitat?

To answer these questions, we must go back to the early 1990s. Hurricane Andrew devastated Florida in 1992, and it damaged quite a few zoos, pet stores, exotic animal warehouses, and wildlife refuges in the process. Many of the escaped animals -- ranging from monkeys to mountain lions -- were rounded up after the storm. Some, unfortunately, were put down. But many animals eluded capture. It has been documented that a large (but unknown) number of Burmese pythons were "liberated" by Hurricane Andrew, escaping into the Florida Everglades and other parts of the state.

It is also likely that irresponsible pet keepers contributed to this problem, though to what extent I cannot say. We have a snake-care Q&A service on this website, and through it I have spoken to hundreds of snake keepers over the years. On several occasions, I have spoken to Burmese pythons owners who were desperately trying to find new homes for their pet snakes, to no avail. Based on this experience, I believe it's possible that a few pet pythons have been released into the wild over the years, in Florida and elsewhere. And, as you will soon learn, it only takes a single breeding pair to start an "invasion."

Often, people purchase these animals when they are babies, and small enough to be housed in a 10-gallon terrarium. But within a few years, these snakes will be devouring rats like popcorn, and weighing as much (or more) than their owners. I believe that some keepers -- albeit a small minority -- end up releasing their Burmese pythons into the wild, out of sheer desperation. Many in the reptile industry would dispute this belief, and they are certainly entitled to their opinions. But I am convinced that a combinationof Hurricane destruction and irresponsible keepers have contributed to the current state of Burmese pythons in Florida.

Florida Everglades = Ideal Habitat

So what happens when these animals are released into the wild? And why is the problem so isolated to the Florida Everglades and surrounding areas? In a word -- climate.

When a non-native animal is released into the wild, there are two possible outcomes:

• If the local climate is outside the animal's tolerance level, it will soon die.
• But if the climate is sufficient to support the animal, it may establish itself as an invasive species.

This explains why the Burmese python has thrived in the area. The climate and ecosystem of Everglades National Park (and much of southern Florida, for that matter) are ideally suited for the Burmese python. These snakes live in hot and humid areas of Asia. Southern Florida is hot and humid. They eat a wide variety of birds, mammals and reptiles in their native habitat. Here too the Everglades deliver, offering plenty of prey animals to sustain the Burmese python.

In short, there is no better place in the United States for these animals to survive and thrive. That's why southern Florida has become their new "home away from home."

Years went by before anyone knew the full extent of the invasion. It wasn't until 2006 that the first Burmese python "nest" was found in Florida. The females of this species will generally coil around their eggs, using slow muscular twitches to regulate the temperature around the eggs. Such a nest was found in 2006, when a female python was seen with a clutch of more than a dozen healthy eggs. Of course by then, the ecological invasion was already well under way.

How Many Burmese Pythons are in Florida?

There is no way to know with certainty how many Burmese pythons are in the southern Florida area. But they likely number well into the thousands. Some scientists estimate there may hundreds of thousands of these snakes within the state. How could this happen in only 17 years? How could these snakes propagate so quickly? The answer to this question lies within the reproductive characteristics of the Burmese python.

Consider the following. A female Burmese python can lay more than 30 eggs at a time. In fact, a previous sampling of nest sites in the Everglades National Park found an average of 36 eggs per site. Larger females can easily exceed these numbers. One female captured in the Everglades was found to have 85 eggs developing inside her. A well-fed female python will generally reach sexual maturity in a few years. On top of that, these snakes can live for more than 20 years in the wild, and healthy females canreproduce annually for much of that lifespan. Now take that reproductive capacity and spread it over the last 17 years or so, when these snakes are believed to have entered the Everglades in large numbers. Do the math. It's staggering! It seems to me that these snakes are here to stay.

Ecological Impacts of This Invasive Species

Why are scientists alarmed by the propagation of Burmese pythons in the Florida Everglades (and beyond)? What kind of ecological impact do they have? For one thing, these snakes are nearly apex predators when full grown. Aside from the alligators in Florida, there aren't any animals that could attack and kill an adult Burmese python. So they are essentially unchecked in the ecological scheme of things. In nature, there is nothing to keep their populations in balance. Teams of snake hunters (wildlife officials, scientists and volunteers) have tried to round up as many pythons as possible, but that's like plugging your finger into a broken dam.

Image: A Burmese python struggling with a Florida alligator. Click to enlarge

If these snakes continue to propagate and spread, they could cause significant population decline in many native species of animals. Remember when the snakehead fish made national headlines in the early 2000s? This non-native fish began to propagate along the eastern United States. It was a top-level predator, and it quickly decimated other fish populations. Despite the efforts of wildlife biologists, these invasive fish still remain in the United States, and they have spread down the eastern seaboard to Florida (they can actually "walk" outside of water for short distances, spreading from pond to pond).

Scientists have the same level of concern about the Burmese python populations that have bloomed all throughout southern Florida.

How Far Can These Snakes Go?

The Burmese python is well established in the Florida Everglades and other areas in the southern part of the state. That much is undeniable. But how far can these animals spread? Where will they show up next? In general, an invasive species can spread as far as the habitat and climate will support them.

In 2008, scientists from the U.S. Geological Survey released a future range map for the Burmese python. It compared climate data from the snake's native range (in Asia) to climate data in the United States. The report suggested that these snakes could eventually propagate over nearly a third of the United States. But I dispute this aspect of the USGS report. I do not see these snakes spreading beyond the state of Florida, due to weather extremes and unsuitable habitats in neighboring states. Only time will tell.

Updates on the Burmese Python Issue

This page will serve as a living document. We will update this article as needed to provide news and updates about the Burmese Python in the Florida Everglades. Here are some relevant news stories over the years, leading up to the most recent news.

Huge Snakes Pose 'High Risk' to U.S. Ecosystems	New York Times	10/13/09
Lawmakers Start Looking at Python Issue	Jacksonville Observer	10/7/09
Burmese Pythons Expanding Reach in South Florida	The Sun Sentinel	3/6/09
Python Bursts After Eating Gator	National Geographic	9/5/06
Huge, Freed Pet Pythons Invade Florida Everglades	National Geographic	6/3/04