Caption-Biologist Ed Metzger with a 18'3" 133 lb Burmese python
Giant snakes in the glades? What's the story?
Burmese pythons are native to Southeast Asia, but are now an invasive species in south Florida. These large snakes were imported by the thousands for the exotic pet trade, many being bought by owners with little knowledge or regard as to how big the snakes grow and the responsibilities and care such an animal requires. People would buy a hatchling python as a harmless baby, but the snake would quickly grow to a large size with an equally large appetite, so that many people were no longer able or comfortable to care for it. They then released the snakes into the everglades. A large snake can be very difficult to handle, properly house, and properly feed. In the past, there was no permit or experience required to buy one; anyone could walk into a pet store and buy a snake that could one day reach 20 ft. in length. While I was in college there were no laws or permits restricting the ownership of large constrictors and I was approached by a student who lived in the same dorm building, wanting to show me a baby anaconda he had just bought. He knew I was knowledgeable about reptiles and asked advice on how to care for the baby anaconda, as he said he had no idea how to care for it and bought it because "it'll impress chicks". I have no doubts that that snake either died from improper care or was released into the everglades.
Another proposed genesis point of pythons is hurricane Andrew, a massive category 5 hurricane that caused immeasurable damage in south Florida and released many exotic animals when caging and housing was destroyed.
Other possible points of introduction include people purposefully releasing snakes to start a colony to create their very own zoo-like landscape in south Florida, or because they like the animal and wanted to see it here. This may sound far-fetched but it is actually the origin story of several introduced species such as European starlings and Brazilian pepper.
Caption-An 8ft python on an everglades levee
How big do they get?
Burmese pythons are often listed as the third longest snake in the world, with reticulated pythons being longest, followed by the green anaconda (although this list is often hotly debated with unverified claims and assertions of huge snakes with little evidence). A quick Google search will often yield varied and contradicting answers, but the longest verified Burmese python was a captive animal which measured 18' 10" named Baby. Most 20 ft. claims can be traced back to this individual. However, there have been a handful of 18 ft. individuals removed from the Everglades so far and I have no doubt that someone soon will make the headlines with a 20 footer.
Caption-Biologist Ed Metzger with a 18'3" 133lb Burmese python
Are they going to eat people? Pets?
Burmese pythons will eat pets, absolutely. People, not so much. There have already been several pets documented as meals for wild pythons, which honestly should not surprise anyone in a state where large reptiles regularly consume our furry friends (dogs and gators don't mix!). As far as the danger to humans extends, it is highly unlikely for a wild python to attack and kill a human that is out minding their own business. You would be more likely to be struck by lightning, multiple times, than to be attacked by a wild python. BUT large pythons are potentially dangerous and there have been several instances of captive pythons killing their owners. This happens when the snake develops what is called a "feeding response". The snake learns that when their enclosure door opens, sometimes food is thrown in. A hungry snake will then begin to anticipate that whatever comes through the open door is likely to be food(yes, they are smart enough to learn patterns and to anticipate things, as are goldfish). Some snakes will even have a feeding response to their owner merely touching the enclosure or walking by in a way that is indicative of possibly opening the door. This is where it is very important to point out that this response is NOT a normal predatory/hunting response but instead a learned behavior. The snake is not hunting the person specifically, but instead it has learned that when the door opens food comes through and so bites at the anticipated "food", which might end up being the person. This is a very important distinction to make. Once the snake is shown that it is not being fed in this moment it can then safely be handled without trying to bite. An example of this is that I once worked with a 20 ft. reticulated python with a very severe feeding response. It was one of the scariest animals I have ever worked with, and would try to feed upon anything that touched the enclosure door, but once taken out it was fine and tame. This is why large snake species should never be kept by novices. Some snake owners also think their snake "likes" them and would never hurt them. Unfortunately, these anthropomorphizing owners are very sadly mistaken. Whether by inexperience, ignorance, or stupidity, the person who puts their hand into the enclosure of a large constrictor with a feeding response could be in for a very unfortunate experience that could potentially even result in death. My point of explaining this process is to illustrate that most deaths from pythons reported in the media are actually due to the folly of captive keepers, not of the snakes hunting people down. To my knowledge there is not a single verified human death from a Burmese python in the wild, although there are a few from reticulated pythons. As for the wild pythons in Florida, I don't think anyone should be worried about being attacked or having giant snakes climbing through their windows. The threat they pose to humans is astronomically small.
Caption- A wild python striking out.
What makes them so successful here?
Pythons are very successful in south Florida for a variety of reasons. A female python can lay over a hundred eggs per clutch and the young hatch out just under 2 ft. in length, which is the adult size of some of our native snakes here in Florida. They can grow to a large size rapidly, up to 6 ft. in their first two years of life, allowing them to outgrow most of our native snake predators and opening a much wider selection of large prey. With a lack of predators, an abundance of prey, and a high reproductive rate, python numbers were able to explode in Florida.
Caption- A clutch of wild python eggs in a culvert pipe in the everglades.
Pythons are also habitat generalists and make themselves at home in marshes, pine rocklands, mangroves, and other Florida habitats. They can be very aquatic and are adept swimmers, seeming to use canal systems to help in their spread.
Caption- A young python swimming in the everglades.
Caption- A python is at home in the aquatic everglades.
How real is the threat to the environment?
The threat of wild pythons to people is highly exaggerated and sensationalized by most media outlets, but the threat this invasive species poses to the surrounding environment is very real. The effects of the presence of an apex predator can be wide ranging, diverse, and unpredictable. An incredible and well studied example of just how extensive the effect one species can have on an environment is the story of wolf reintroduction in Yellowstone, where the presence of wolves influenced grazing behavior and altered the course of rivers and changed habitats. You can learn about the Yellowstone wolf story here https://blog.ted.com/video-how-wolves-can-alter-the-course-of-rivers/
But what do wolves have to do with snakes? The wolves are an example of how one top predator can influence the behavior of prey and literally change the habitat and landscape. We currently have no idea if or how pythons are influencing the behavior of alligators, birds, or any of their other prey, and may not be able to see the cascading effects for decades. In a hypothetical situation pythons could cause major changes to how the everglades functions, or could have no effect, but due to how complex ecosystems are there is no way to know.
Caption- A hatchling burmese python
So let's leave the hypotheticals behind and explore what we DO know- pythons have been recorded to eat an extremely long and varied list of native wildlife, ranging from 6ft alligators(reread that- SIX FOOT long gators, not just little babies!), adult deer, bobcats, raccoons, opossums, and a wide variety of wading birds. The list goes on and on to include just about anything smaller than deer and gators. This list also includes many protected or endangered animals such as the Key Largo woodrat, wood stork, mangrove fox squirrel, and others.
Some comparative studies show a 90% decrease in mammal populations due to pythons. The loss of these animals is not only detrimental for the population of that species, but for other species that rely on them as prey, such as the critically endangered and iconic Florida panther. Panthers could even be on the menu themselves, with records of pythons consuming leopards in their native range.
There is a little good news about python diet though, and that is that they do not eat often. Being ectothermic reptiles, pythons may only eat once a week or once a month depending on conditions and prey size. This low metabolic need also helps the pythons in that a large individual can survive over a year without eating.
Caption- A python striking
Can't we just send out a bunch of hunters? Make an open season bounty for everyone?
This idea is repeated a million times over online and seems like a great idea to anyone who hasn't tried hunting snakes themselves, but if you have ever tried you'll know it can be extremely difficult to locate snakes in habitat. A testament to this is the fact that over 90% of python records and sightings are from roads, levees, and peripheral areas that have been cleared of brush--basically areas that are not real everglades habitat but mowed or otherwise unvegetated areas. The reason for this is that pythons have incredible camouflage and once they enter into dense habitat they completely disappear. A 10 ft. snake can very easily disappear in only knee high grass and be completely unnoticeable. A quick look at any python record map will show a preponderance of sightings along every road and levee, but records just a few hundred feet off these paths are relatively nonexistent due to our inability to spot snakes in this habitat and the difficulty and time required to traverse such terrain.
Caption- A well camouflaged python.
Another issue with allowing an open bounty for just anyone to claim is that snake hunting is a very specialized skill that requires specific knowledge and experience to be effective and do properly. Knowing how to hunt one animal does not translate directly to another; being a great pheasant hunter does not make you a great elk hunter, and neither translates into a great snake hunter on your first day. There may be similarities of course but you must learn the specifics of your quarry, and when it comes to snakes that means learning habits unlike any other animals and memorizing a variety of species. A problem encountered by would-be python hunters is proper identification, leading to the capture and destruction of non-target species. This has resulted in rare species being killed, and in major health hazards as novices try to capture venomous snakes that they think are pythons. I was told of one individual capturing a venomous water moccasin and attempting close its jaws with a vice grip, and of another individual capturing a large eastern diamondback rattlesnake in a cardboard box, both thinking it was a python. Amazingly, and surprisingly, neither ended up in the hospital or morgue.
This shows the need for properly trained and vetted expert hunters, not just an open bounty. Thankfully several agencies have done this with very successful programs of properly trained and well-selected hunters that are compensated for their time, resulting in over 800 pythons captured in 2017 managed by the South Florida Water Management District. The University of Florida also conducted a fascinating study where Irula tribesmen from India were brought to south Florida to share python hunting strategies. The Irula tribe is considered to have the best snake hunters in the world and have made their living capturing snakes for generations.
Caption- Irula tribesmen with a recently captured python
But what about feral cats? Aren't they worse?
It seems that every time I make an online post about pythons I will have a misguided reptile lover comment saying we should focus more about cats and less about pythons. One problem does not negate another, both exist, and just because feral cats deserve an amount of attention does not mean pythons should be overlooked. Unfortunately some people take the discussion of python facts as a direct affront to the pet trade and people's ability to own snakes and so try to use cats to take attention away from pythons. (this strategy of false equivalencies and distraction is also called "whataboutism", a logical fallacy associated with Russian propaganda but now heavily used in American politics, especially by Trump).
People often compare burms to cats but this really does not make any sense in the everglades; worldwide, cats are the most destructive invasive species and do require attention, but in the everglades they exist peripheral to human habitation or roads where people dump them. In the context of the everglades, once you move a mile or so away from any roads or human disturbance, cats drop off the radar and essentially cease to exist. Pythons on the other hand are true ecosystem invaders and can be found in the deepest reaches of the everglades wilderness. They are a major everglades issue across the entire system from the pine rocklands to the mangroves and every habitat in between. One can take a helicopter ride into the deep and inaccessible everglades and still encounter pythons, but no cats. This is why when discussing invasive species in the everglades cats are not really an issue, but pythons are. So although cats are incredibly destructive and the worst invasive species in the world, they are not really part of the everglades conversation.
Caption- A large python on the roadside.
So how many are really out there?
Several thousand Burmese pythons have been removed from the everglades, but as stated above almost all those captures were made along roads and levees. These roads and levees make up a miniscule percentage of the total land currently inhabited by pythons in their large range from Ft Lauderdale to Key Largo, so logically this should lead us to believe there are man, many more pythons in south Florida than what has been seen thus far. Currently there are no reliable population estimates. Some speculate that there are over 100,000 individuals, a number many scoff at until you really start to look at the data of how such an extremely small amount of land is searchable across this vast landscape of wilderness. The reality is that we will likely never know how many pythons are out there, but considering the small amount of data we have and given the amount of habitat I believe there are more than most think.
Caption-These three pythons were caught in a twenty minute span.
Can they be eradicated?
No. Given the large amount of inaccessible land they inhabit and their elusive nature there is no foreseeable way to eradicate pythons from Florida with current technology and methodology. Then what is the point? We try to learn as much as we can about python biology and habits to improve removal numbers and limit the spread as best we can. It is also important to remove every individual we can. Every single python removed makes a major difference. This apex predator can have a tremendous impact at the individual level; every individual removed saves thousands of prey animals.
The only known predator of an adult python in the everglades is an alligator.