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USGS defends study that suggests U.S. climate may become accommodating to giant alien snakes

By Dr. Susan Haseltine
Associate Director for Biology, U.S. Geological Survey

This letter is written in response to your blog post of 07 December 2009 [Justification for Congressional python ban unscientific, researchers say] , regarding a press release issued by a reptile-trade organization and an accompanying letter by a group of veterinarians and other scientists.

The article and letter criticized the following recently released report (Reed and Rodda, 2009) U.S. Geological Survey written by  (USGS) scientists: Giant Constrictors: Biological and Management Profiles and an Establishment Risk Assessment for Nine Large Species of Pythons, Anacondas, and the Boa Constrictor.

Some of the information in the letter from Dr. Jacobson and fellow scientists appears to be based on a misunderstanding of the USGS peer review process.
The USGS provides unbiased, objective scientific information upon which other entities may base judgments. To ensure objectivity, independent scientific review is required of every USGS publication. Standards require a minimum of two reviews, and adequacy of the author’s responses to reviews is assessed by both research managers and independent scientists within the USGS.
For the report referred to in the blog, the authors went well beyond the requirements by soliciting reviews from 20 reviewers (18 of them external to the USGS). Reviewers comprised a large portion of the global expertise on both the biology of giant constrictor snakes and the management of invasive snakes.
In addition, the climate-matching methods presented in the report were previously published in the peer-reviewed journal Biological Invasions in early 2009 (Rodda et al., 2009), so these methods have received both USGS peer review and standard journal peer review.
Scientific papers with divergent or competing views on issues are very common and contribute to advancing scientific processes. The Biological Invasions paper had been criticized in a subsequent publication (Pyron et al., 2008).
In the current USGS report, the authors addressed the limitations of the methods utilized in the Pyron et al. (2008) paper.
The USGS report reviewed virtually all of the peer-reviewed literature on giant constrictor biology, as well as much of the literature on snake management (a total of 671 papers and books) and survival in the wild. The report has received favorable review by other invasion biologists including one written by one of the world’s most respected experts in invasive species biology (Dan Simberloff, Ph.D., Univ. Tennessee). The review (Simberloff, 2009) recently appeared in the journal Biological Invasions and can be found here.
With regard to climate-matching in particular, Simberloff praised the “excellent discussion of the differences between and relative merits of climate matching approaches and environmental niche models that would constitute a good introduction to this burgeoning literature for any graduate student and most practicing invasion biologists.
“While allegations have been made that the USGS report is being used as the justification for regulations on the reptile trade, it is important to note that the report offers no recommendations on policy or legislation.
Thank you for the opportunity to offer clarification on these issues.

“National Geographic Explorer: Python Wars” airs in the United States on February 9, at 10 p.m. on National Geographic Channel. Click on the video above to watch an excerpt. Click here to view more excerpts and get additional information.


  1. look_for_the_truth
    January 29, 2010, 2:21 pm

    I wonder if the NatGeo program “Python Wars” will make any attempt to look beyond the superficial spectacle of “large snakes on the loose” and actually consider the true socio-politcal dynamics behind the hype. That’s where the real story is. And that story is really much more interesting. It has everything; US legislators with the help of governmental agencies duping the American people, propaganda machines exposed, money mongering politicians, lies, conspiracy…
    It’d be a great mini-series if it weren’t the sad truth of the state of our current political system.
    Mark P.

  2. Jim S.
    January 28, 2010, 6:54 pm

    Thanks Jonathan…Here’s some additional information for review and consideration…The “python issue in the ENP (as it is in many other locations), is about tax payer MONEY and they’ll need a lot in the DECADES to come…There are studies to write, experts to hire, scholarships and fellowships, etc to fund. Of course none of these will be biased in any manner or form and of course none of them will be beneficiaries of any tax payer dollars via public laws authorizing appropriated expenditures nor will there be any grant money from the tax payers or private foundation. Got to maintain that “non-partisan” status for the news media and “scientific journals” to cite their peer reviewed papers and studies after all…
    In short, this is another example of a “green” money pit to support the Biosphere Reserve Program (and World Heritage Program)…The pythons in the ENP, will be another Brown Tree Snake money pit…
    From the NPS…
    Speaking of the Brown Tree Snake, they’ve been studying this invasive species for how long now? Have held how many congressional hearings? Have spent how much of the tax payers money on this issue? Paid for how much infrastructure, computers, government agency scientists, university experts, etc? And for what? Is the Brown Tree Snake still a problem? Why yes it is…In fact, it’s one of the poster children of the agencies of the department of the interior regarding invasive species. By poster child I mean, it’s a propaganda banner to approach congress for tax payer dollars…After all, no problem equals NO MONEY!
    Well, in 2004 things got serious as congress passed Public Law 108-384 (October 30, 2004) entitled the “Brown Tree Snake control and Eradication Act of 2004”…However a reading of the law indicates that most of the money is being spent on infrastructure and not on eradicating the Brown tree Snake on the ISLAND of Guam!
    If all the kings’ men and women of several of the kings departments and agencies have not been able to solve the problem of an invasive species on an ISLAND, what is the likelihood that they’ll ever solve the problem of pythons in the ENP? That’s the point, it is not about solving problems, it’s all about MONEY…To keep a “program” going…The “success” on the ISLAND of Guam is something you departments of the government should be VERY proud of…We, the tax payers of America really are getting our money’s worth!!!!
    For you NPS folks reading this blog, I thought that after the country saw that map of the United States divided up into “core areas”, “buffer zones” and “transition zones” back in 1996 (that resulted in congressional hearings regarding Land Sovereignty Bills)…Remember that? Looks like the NPS is back into this again…I thought you folks worked for the US tax payer…
    News Release, Office of the Secretary, U.S. Department of the Interior, “Secretary Kempthorne Announces World Heritage Nominations for Mount Vernon in Virginia and Papahanaumokuakea in Hawaii, January 12, 2008
    Jim S.

  3. Jonathan Brady
    January 27, 2010, 10:30 pm

    You asked for it, you got it!
    There’s a year by year total of how many burms have been removed from the Everglades. A startling number, right? haha! Basically, it’s one per day.
    Senator Nelson, with the help of the dept of the interior, has suggested as many as 150,000 burms live in the Everglades (or 10 per acre – they’re EVERYWHERE!!! Even though they only capture one per day). If that estimate is correct (as we know ALL of the science is coming out of the dept of the interior), this problem has no solution. It is futile to fight… Controlling populations may be an option, but eradication is impossible.

  4. Steve
    January 27, 2010, 2:31 pm

    Hey America….particularly those that cherish our rights to keep the pets we were guaranteed to keep! What is going on in the SREL study? Mr. Brady and others…..can any “SCIENTIST” of any substance or merit be serious in stating that the pythons released in their outdoor enclosure at the Savannah River Ecology Lab has survived this arctic winter period in the deep south? The Miami Herald has stated that iguanas froze to death and were falling out of the trees by the dozens, if not hundreds. MIAMI! I have kept large constrictors and say those animals at SREL were dead after the first night of 20 degree weather. But guess what? Dr. Dorcas of Davidson U. who is contributing to the study says no info can be released about the experiment till June of this year! I say again…June of 2010. Do you think legislation will wait till then to be passed? This whole thing is a travesty of American Legislation and is a perfect example of bullying and “Buying” of the American people. Wake up everyone in political office, remember what Yamamoto said after bombing Pearl on Dec. 7th? He told his officers that despite the huge victory his fear was that the Japanese military/govrnment had awakened a “Sleeping Giant”. Self centered politics will get you out of office quickly.
    One other thing…ask the USGS and the state of Florida and/or USFWS how many pythons have been collected to this point? Obviously if there are “hundreds of thousands” there should be records of vast numbers being collected by the state appointed/licensed trappers. What are the real numbers Florida? Where is the data to prove the numbers? WE WANT TO KNOW AND DEMAND TO KNOW!!!

  5. eddie_indigo
    January 27, 2010, 10:22 am

    “The USGS provides unbiased, objective scientific information…”
    I disagree. Just look at the title of this article – ” USGS defends study that *suggests* U.S. climate *may* become accommodating to giant alien snakes” “Suggests?” “May?” Like Larry said above, is that real science?
    In addition to what was already said above, the Dept. of Interior (USGS, NPS, USFWS) has no credibility. How can any organizations under the DOI be unbiased, it’s already been decided (even when there is NO scientific evidence to support it) that Burmese pythons are “destroying some of the nation’s most treasured — and most fragile — ecosystems.”
    The fact that the USGS released two Burmese python range maps (with the second being base on a 100 year climate prediction) makes it biased. The fact that the USGS released the map BEFORE doing any “real life” experiment to support its far fetched theoretical model makes it biased. The fact that USGS and other DOI scientists have already decided the pythons are destroying ecosystems makes it biased. There is NO evidence to support the claim that the burmese pythons have a negative overall effect on the Everglades. The fact that USGS and other DOI funded scientists hand picked a few anecdotes of the stomach contents of a few pythons to “prove” they are “invasive” makes the USGS biased. The fact that no mention of natural and man-made barriers (cities, highways) to northerly migrations, if they are even possible, makes the USGS biased.

  6. flustercluck
    January 27, 2010, 8:11 am

    The crocodiles in South Florida have had a thousand years to advance as far north as temperatures will allow. They are incapable of surviving much north of where they are right now. As comparable as they might be to alligators, they are not. As comparable as subtropical pythons might be to native North American colubrids, they are not. They can not survive any further north than the crocodiles.

  7. dangles
    January 26, 2010, 4:22 pm

    well-stated, guys…

  8. Jonathan Brady
    January 26, 2010, 4:17 pm

    Nepotism – noun – favoritism (as in appointment to a job) based on kinship.
    Why did I define “nepotism”? Because I think it’s the single most important reason that the USGS (United States Geological Survey) is called on to “create science” for the USFWS (United States Fish & Wildlife Service) and NPS (National Park Service [the Everglades National Park, or ENP, is part of the NPS umbrella]). All three of these organizations are divisions of the US Department of the Interior.
    All three organizations, the USGS, the USFWS, and the ENP, have a stake in hyping up the Burmese python situation in the ENP.
    A little history; in 1993, the ENP was added to the “World Heritage in Danger” by UNESCO (a United Nations organization). This designation was given due to rampant pollution, as well as destruction caused by Hurricane Andrew in 1992. Due to this designation, the State of Florida entered into an agreement with the Federal government to restore the Everglades to the tune of 20 billion dollars. The Federal government agreed to pick up 10 billion dollars of the tab to restore the ENP.
    To illustrate how important 10 billion dollars can be to the ENP (which again, is part of the Department of the Interior via the NPS), you should know that the annual budget for the ENP is approximately 15 million dollars (not including land purchases). That means the Federal government promised 666 times the annual budget of the ENP, to the State of Florida for restoration purposes.
    In 2007, UNESCO came back and checked out the Everglades, gave them a pat on the back for their efforts and said, congratulations, this site no longer belongs on the list of “World Heritage in Danger”. This immediately ceased the funding from the US government, which had only paid out a small portion of the 10 billion dollars so far. This obviously impacted the State of Florida, as well as the Department of the Interior, and by proxy, the USGS and USFWS.
    So, the ENP needed an excuse to reinstate this funding. After all, all government entities operate based on funding (via taxes). They needed a villain, a poster child if you will.
    The Everglades are now home to over 300 plant and animal species that are not native to the area. Some pose no threat to the indigenous plant and wildlife. Some pose a medium threat, and some a high threat. The single most destructive animal affecting the Everglades is the common housecat. This comes in the form of pet populations that are outside cats, as well as the feral cat population. These cats absolutely decimate native populations of birds and rodents. Cats are closely followed by feral hogs which dig up native plants and destroy the root systems. Either of these animals would have been an excellent target, er… poster child, for Everglades restoration.
    But who in their right mind would create a campaign to fight cats? It would be political suicide! Feral hogs? Hunting groups and the NRA would be ALL OVER that, and nothing would be done. So what else is there?
    2 years prior in 2005, headlines across the world read: “Python explodes after eating alligator”. How’s that for garnering attention? Pythons exploding! WOW! That inspires awe! And who’s going to argue against fighting pythons?
    So, the stage was already set, the news media was already paving the road, and it was apparently decided that the Burmese python would be the new poster child to demonstrate the need for Everglades restoration, despite the fact that there is little to no credible evidence to suggest that Burmese pythons have had any appreciable effect on native plants and animals, or waterways.
    In 2007 (the same year that the ENP lost its designation as a World Heritage Site in Danger and the Federal funding ceased), the NPS and USFWS (again, both are part of the Dept of the Interior) asked the USGS (another part of the Dept of the Interior) to write a paper about the danger that Burmese pythons pose to the ENP. Coincidence? You decide.
    This study would cost money, of course, but it’s merely a changing of money from one hand of the Dept of the Interior, to another. Net effect is that no money is lost paying scientists from another organization, especially any that would be impartial. Additionally, and this of course would be refuted by the organizations but anyone who’s ever worked for a company will know it’s true, the results of the study can be closely “monitored”, due to the familial (or, nepotistic) ties through the Dept of the Interior.
    The initial study was entitled: What parts of the US mainland are climatically suitable for invasive alien pythons spreading from Everglades National Park?
    The study has been extensively refuted by Pyron et al, so I will leave my criticisms out except for one important point, which Pyron et al, graciously omitted from their study.
    No one can explain why the Indian python was included in the initial study when they are already illegal to import into the US, none have ever been found in the wild, there are likely fewer than 100 within the borders of the US in captivity meaning each likely has tremendous value (minimal chance for release), it requires a permit to move them across state lines, and they’re smaller and FAR more cold-tolerant than the Burmese python. To us as keepers of reptiles, it’s obvious. If Burms can’t survive prolonged or repeated temperatures below 50 degrees, but Indian pythons can survive prolonged and/or repeated temperatures below 35 degrees, the average now becomes 42.5 degrees and the threat from the Burmese pythons seems larger. Obviously the threat from Indian pythons becomes less, but as I stated, there are none in the wild so there’s no real risk in diluting their temperature range. The authors of the report wanted to skew the temperature data sets to a lower temperature threshold to allow for the inclusion of more states than are truly at risk for “INVASION” by Burmese pythons, via “averaging”. (note: these are not the actual minimum temperatures of tolerance, these are just examples to illustrate a point)
    Then another study was commissioned by the NPS and USFWS and again the USGS was tapped to provide the “science”. This paper is entitled: Giant Constrictors: Biological and Management Profiles and an Establishment Risk Assessment for Nine Large Species of Pythons, Anacondas, and the Boa Constrictor. This study criticized the paper by Pyron et al, and their methods to prove that the Burmese python was not a threat to the rest of the US. However, upon closer inspection of the criticisms, it is apparent that even the USGS knows their study has serious flaws. Here are a few excerpts from the second paper by the USGS:
    The criticism of Pyron et al, cited in the USGS report goes like this:
    To try to justify the use of their climate modeling, the USGS report says that it’s ok to use mean monthly temperature instead of highs and lows because:
    Most species can probably aestivate for months to minimize exposure to seasonally inclement weather or food unavailability,… but this is not known with assurance.
    Just to be clear, that says: “probably” and “not known with assurance”. Very scientific!
    To further justify their methods, they espouse their methods as being reliable because they are “a priori” methods. For those like me that don’t know what “a priori” means, I looked it up. One definition for “a priori” is this:
    Not based on prior study or examination; nonanalytic.
    Does a method that is NOT based on the examination or analysis of the home range of these pythons sound like a very good way to determine whether these species can survive in other places?
    In the paper, they say this in regards to their “a priori” method:
    A priori methods, in which the metrics are chosen for a biological reason in advance, without knowledge of the statistical outcome, are valuable because they offer statistical protection against spurious correlation, but they do not ordinarily discover the best possible fit between climate conditions and a species’ native range boundary.
    Just so we’re clear, “yes”, they did just say they wanted to protect against spurious correlation by choosing something that was not likely to give the best results. I’m curious though, how do the two differ? In both cases, the results are unreliable. Very scientific, again!
    Perhaps I should point something out to be re-read, they just said; “but they do not ordinarily discover the BEST POSSIBLE FIT BETWEEN CLIMATE CONDITIONS AND A SPECIES’ NATIVE RANGE BOUNDARY.”
    To reiterate, they PREFER a method that doesn’t ensure the most accuracy.
    The paper then goes on to provide a criticism for the ecological niche modeling employed by Pyron. The quote is as follows:
    A popular alternative to a priori identification of climate metrics is the use of automated programs that select the climate metrics on the basis of which metric gives the best fit to the native range distribution.
    It goes on to say:
    This localized use is relatively robust against overfitting and lack of statistical independence among points, in that nearby sites are likely to have the same suite of statistical confounds and collinearity as did the original plots.
    If all of that scientific over-talk is too confusing, I’ll sum up their statement. They just said that ecological niche modeling is too precise. Please re-read this: “select the climate metrics on the basis of which metric gives the best fit” and “relatively robust against overfitting”. Summarized as; “too precise”.
    So the USGS would prefer that we use models that do not ordinarily discover the best possible fit between climate conditions and a species’ native range boundary (which has been skewed by the inclusion of the Indian python) instead of modeling that is too precise. I’m going to say it again, VERY scientific!
    While Dr. Haseltine is correct in saying the report makes no recommendations regarding regulation. I would like to know why there has been no mention of how the USGS is related to the USFWS and/or ENP/wildlife park services. All entities stand to gain an enormous amount of money should the ENP be reinstated on the “world heritage in danger” list, and the non-native snakes would be the perfect “poster child” to ensure that happens. All entities stand to gain because there will certainly be additional studies commissioned to evaluate how best to deal with the “problem”. Cushy jobs for everyone until retirement! Because these snakes aren’t going away.
    Why aren’t they going away? There are no methods currently known to eradicate non-native populations of snakes, once established. One only need to look at Guam, and it’s non-native brown tree snake. That snake has had an appreciable impact on the native bird population. Millions upon millions of dollars have been filtered into a project to eradicate the brown tree snake with absolutely no positive results to show for it. There is no “bar” for success in this field because there’s been no success. By the way, we can thank Gordon Rodda of the USGS for his abysmal failure of this project. Incidently, he’s the lead author or co-author of the two studies cited above.
    Dr. Hazeltine’s final sentence reads as follows: “While allegations have been made that the USGS report is being used as the justification for regulations on the reptile trade, it is important to note that the report offers no recommendations on policy or legislation.”
    I would like to reiterate that the report offers no insight into the relationship between the USGS, USFWS, and the NPS (and therefore the ENP). Disclosure of this nepotistic relationship would be damning at best, and suicidal at worst.
    Dr. Hazeltine, please do not think for a moment that the citizens of the world will tolerate the lies and deceit perpetuated by your agency any longer. Pet owners are fighting back against ridiculous legislation and the baseless, nepotistic science behind it.
    Jonathan Brady

  9. LevelHead
    January 25, 2010, 7:24 pm

    Yes my Name is Larry Micklevitz. I may not have as advanced of an education as you Dr. Haseltine, Rodda or Reed,or Dr Skip Snow. What I do know is that the species of Python (Python molurus -Burmese Python -Asian variety) in the “ENP” is different than the Python species that fits the parameters addressed in the USGS report (Python molurus -Indian Rock Python -smaller Indian variety). The Indian Rock Python is already covered/Banned under CITES and the Lacy act . Only that Indian Rock Python species can survive in some of the parameters set by the USGS report.
    As recognized by Rodda & reed (McDiarmid et al. 1999)
    Here is that above info covered in another article
    (Rodda and Reed’s true motivation and objective can be seen clearly in one simple but damming sentence.
    Rodda and Reed wrote, “The Burmese Python is a questionable subspecies of the Indian Python, Python molurus” (McDiarmid et al. 1999).
    Here is the significance of that singularly damning statement.
    1. The USFWS does not agree with that statement. The USFWS knows that Burmese and Indians Pythons are completely different animals. The Indian Python is already federally regulated. Import and export are illegal. Interstate sales are illegal as well without a Permit granted by the USFWS. Permits for commercial interstate shipping are only granted to individuals who pass through a rigorous application process. If the USFWS believed that the problem Burmese Python is actually the Indian Python, as Rodda and Reed claim in that single sentence, USFWS could end the trade in Burmese Pythons overnight. However, the USFWS leadership is after much more than just that problem species. They never mention the fact that the USFWS disagrees.)
    That info taken from Axcess News this Article titled
    “The inside story on the proposed snake ban; U.S. Fish and Wildlife Ignore Science”
    On Monday, 25 January 2010
    written by Brandon Piddington.
    Found at this Link:
    Comparing Apples & Oranges or making assumptions do not lead sound justifiable science.
    A search of the manuscript for 11 grammatical qualifiers, including may, might, maybe, could, appears to, and others, found
    a total of 1369 uses. More than one in every hundred words is a qualifier. On average there are 5.3 qualifiers per page.
    That information found here A Review of the Reed & Rodda Paper
    You also can read that review at this address:
    I also know the Burmese Python Asian species cannot survive weather conditions much further north than the “ENP”. They will not survive north of Tampa Bay much less any other State.
    I can agree on one thing there is an unwanted Feral Burmese Python issue in the “ENP”. I can only guess the estimated numbers to be 5000 or less but certainly no where near 150,000. I doubt they are nearly as destructive as the Feral Domestic Cat Population or Feral Boars/Hogs are.
    My guess is that Alligators and American Crocs feed on those same species endangered wading birds as well as any mammal that comes to the waters edge to drink. Much same as the Burmese Python’s do.
    The Pythons do not belong there in the “ENP” but certainly is wrong and far over kill to impose a Far reaching Ban in every state on the other species such as 4 species of Anaconda or certainly not Boa Constrictors. Boa Constrictors that for about the last few million years have and do live just 120 miles South of Texas border in Mexico. IF they could live in the U.S., they already be.
    So please get the correct science in place first. So another segment of the American economy isn’t destroyed. Putting thousands and thousands more American families out of income and work.
    Please stop this unwarranted attack on this segment of the American population. Using this corrupted agenda to form policy.