Giant Snake Invasion!

Mammal populations in certain areas of Florida are declining, according to one report. The cause? Giant snakes.

The Burmese python (Python molurus bivittatus) is a large constricting snake, native to northeast India, southern China, and southeastern Asia. It doesn’t occur naturally anywhere near the United States, but it’s estimated that more than 300,000 of the snakes have been imported into the U.S. in the last 30 years by the exotic pet trade. When they grow too large to handle, the snakes — known for their docility under normal circumstances — are often released into the wild by pet owners. An adult Burmese python can measure up to 5.5 metres. One individual over 4.9 metres (16 feet) long was captured just last month.

A new report in Proceedings of the National Academy of Sciences (PNAS) shows that mammal populations in the Florida Everglades, as measured by roadside surveys, have shown dramatic declines in the last eight years. The surveys, which covered 56,971 kilometres of roadway in and around the Everglades National Park, observed a decline of 99.3 per cent, 98.9 per cent, and 87.5 per cent in raccoons, opossums, and bobcats, respectively. No rabbits were observed during the recent surveys.

It’s not all because of predation, though. It’s difficult for scientists to be sure which animals are being killed by the pythons and which ones are competing for the same resources. But there’s no doubt that P. molurus is an ambitious species. The United States Geological Survey, which contributed to the PNAS report, has observed the snakes fighting with alligators.

There is even a picture of a python whose belly had burst after eating an alligator. It’s uncertain whether the bursting was due to the alligator attempting to escape the snake’s stomach or a simple buildup of gases, but the image is genuine. Florida’s Burmese python problem has been particularly hard on endangered species such as the Key Largo woodrat. Researchers were tracking down a tagged woodrat in 2007, and found it in the stomach of a seven-foot python. The snake’s stomach also contained a second woodrat.

The pythons are particularly hard to eradicate because they are extremely adaptable creatures. Throughout Asia they live in many different habitats and are capable of living on a wide variety of diets. They move very rarely between hiding spots, which makes them difficult to trap, and they breed at startling rates. They are capable of producing clutches of up to a hundred eggs at a time — as a result pf these factors the python population in the Everglades is estimated to be between 30,000 and 100,000.

Invasive snakes may not be easy to stop, but conservation groups and the U.S. National Parks Service are going to try. The Everglades NPS has a beagle named “Python Pete,” who is trained to sniff out the snakes. In an attempt to prevent the snakes from spreading to the Florida Keys and breeding, the Nature Conservancy has been training FedEx and U.S. Postal Service employees in spotting Burmese pythons, which often warm themselves on the road. There is even a hotline citizens can call to report python sightings.

Trained python responders can then be dispatched to collect the rogue reptiles. There are a number of techniques used to trick the python into tiring itself out so it can be easily captured. One is called “treadmilling,” in which the catchers drag their hands along the snake’s belly to make it think it’s escaping. Since the year 2000, over 1,800 snakes have been removed by the National Parks Service in the Everglades.

The snakes, though, may already be permanently entrenched in the Everglades. A severe freeze in early 2010 failed to do more than put a dent in python populations. Further efforts may consist of making sure the current problem doesn’t get any worse. But at least there’s a bright side: the Burmese python is not known to be aggressive towards humans.

Not yet.

5 Comments on "Giant Snake Invasion!"

  1. Frank Mazzotti- If it Bleeds it Leads

    Laws, like sausages, cease to inspire respect in proportion as we know how they are made. – John Godfrey Saxe

    Sometimes I feel the same way about media coverage. It seems the more I know about a story the less I feel the coverage is accurate and the more sensational a story is the less accurate they seem to be. The recent plethora of stories about pythons consuming prey in the Everglades is a prime example. Stories about large snakes feed directly into an archetypal fear that humans have of snakes, and stories about a feeding frenzy of snakes wiping out wildlife fuels a feeding frenzy of media coverage that wipes out the truth. With great certainty, I predict that the media will make the jump to pythons eating people. Any bets?

    This is a story that I do know something about as I am one of the co-authors. The title of the paper (“Severe mammal declines coincide with proliferation of invasive Burmese pythons in Everglades National Park”, published in the Proceedings of the National Academy of Sciences, suggests that the occurrence of pythons is coincident with a dramatic decline in mammal populations. We were careful not to say “caused” because we don’t know that. With few exceptions, you would get that impression from the media coverage that hoards of rampaging snakes were vacuuming up mammals in the Everglades. We don’t know that and we could be making the right prediction for the wrong reasons.

    Let me correct two common misconceptions first. This study was not done by the National Academy of Sciences as many stories reported; it was published in the Proceedings of the National Academy of Sciences — big difference. Likewise this was not a nine-year study in that we did not start this study nine years ago. We started this study 1-2 years ago and collected information that was available over a nine-year period (2003-2011) and compared it to similar data collected earlier (1993-1999). And sure enough a very dramatic pattern did exist. I liken what we did to a grand jury investigation. We amassed the available evidence and asked if it was sufficient to demonstrate that a crime had occurred (mammal populations had declined) and to suggest that pythons could be responsible (they had motive, means, and opportunity). An indictment was handed down. That does not mean the pythons are guilty. It does mean we need to go to trial. According to English law the accused should be considered innocent until proven guilty. In science terms we call this a null hypothesis, or a statement of no effect. Of course none of this sells newspapers, draws viewers to a television station, or causes hits on a website.

    What do we do now? We go to trial. In scientific terms, we design a study that evaluates the presence of pythons with the absence of mammals in relation to differences and changes in habitat, hydrology, and other biological components. This study should be a high priority for funding as it critically tests the hypothesis that the presence of pythons is related to the absence of mammals while also quantifying habitats and hydrology. This is important because pythons might not be guilty. If not pythons, what could be causing the decline in mammals?

    I have been thinking about this python-mammal pattern since we assembled the paper and I have been gathering more information. Quite honestly I am seeing other potential patterns emerge. Now let me step back for a moment and comment that it is clear than many people think that a publication is the final complete word on a subject. Not so; many times publications are the first word on a subject and their purpose is to stimulate thinking. I often tell my students that it is okay to be wrong and that in fact you learn more when you are wrong than when you are right. That is also one of the most important reasons that we consider pythons innocent and that we take them to trial. Because, what happens if we are wrong and something else caused mammal populations to decline? We do not want the real guilty party to remain free.

    If we use the period 2000-2002 as the dividing point and ask what other biological responses occurred in the Everglades system before and after that time period, we see that fish communities have changed, location and success of Roseate spoonbill nesting colonies have changed, alligators have gotten skinnier, and the number of young snail kites fledged from nests has plummeted. Are pythons responsible for all of these coincident biological changes? Have other events occurred that could explain these biological changes? Hopefully more science and a better understanding of what is happening to wildlife in the Everglades will emerge from this discussion. Because if it is not pythons (and it might not be), something else is wrong in an ecosystem that we are spending billions of dollars to restore and we need to know what that is.

  2. Eric, Thank you for your response. Sadly every thing you see in media you must divide by a factor of 5 on the threat scale just to realize what the actual threat really is.

    No one has considered, The impact of increased vehicle traffic on these roads. How much has the population in Florida grown in 10 years? Or how much have we as humans filled in to build new and bigger homes? What about illegal poaching. Has it increased?

    I do agree the burmese are an issue for Florida and Florida alone. Florida has taken steps, implemented a ban/license law, giving out hunting permits, and chipping those snakes which remain in captivity. The recent law adding the 4 species to the Lacey act was an over reaction to a threat that had nothing to do with the rest of the USA.
    The original studies submitted tot he USFW were blown up. and designed to implement fear. Sadly even in the scientific community you can basically find or pay someone to agree with or come up with results to prove anything. I bet some out there could still argue the fact the earth is flat if someone lined their pockets enough. To say a Tropical snake which has yet to even move into the northern 2/3 of Florida will be able to take over 1/3-2/3 of the united states within 100 years is absurd.

    Please do some research before posting articles like this. You are simply promoting the fear mongering that every other major news outlet lives and thrives on.

  3. If you are going to Edit my response before posting it. Please delete the response.

    Not only have you changed my words but you do so without reason. Your basically let people respond how you want.

  4. I deleted the first three lines of your response. Which made a baseless accusation against our reporter. The rest of your comment is intact and unedited.

    • I question the integrity of this article. I would like to see the list of references your writer used to come to this factless conclusion.

Comments are closed.