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Cold Weather Python Studies

Another new cold weather python study by the SREL furthers evidence that pythons cannot live outside the Everglades.

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The newly released python cold weather study, “Can invasive Burmese pythons inhabit temperate regions of the southeastern United States?,” Dorcas et al. 2010, now brings a total of four independent sources (three studies and one anecdotal report) reinforcing that pythons cannot endure temperatures normal to the temperate southern third of the United States.

The question posed in the title of this latest study can now be conclusively answered, “NO.” Only in the southernmost tip of Florida, around the Everglades National Park, have pythons shown an ability to survive for any length of time. The new information presented in the study continues to shed light on the failings of the U.S. Geological Survey (USGS) Climate Match, Rodda & Reed 2008, and that of its authors who appear to be standing by their grossly misrepresented conclusions. Such an unjustified position in light of the series of proceeding reports and studies has left many amongst the scientific community with a perception that the USGS authors may be intentionally attempting to influence policy by artificially creating a perceived need for an Injurious Wildlife Listing under federal law.


As predicted by Barker 2008, tropical pythons have no way of judging fatally cold temperatures and essentially don’t know when to come out of the cold. Although the new Dorcas et al. 2010 study goes to great lengths to explain away the deaths of 100 percent of their study animals as the result of an anomaly, or “poor decision making” by the pythons, the bottom line is that all of the pythons in their study succumbed to fatally cold temperatures last winter. That is consistent with the results of the two Florida cold python studies where 16 of 19 pythons died. The study group in the Everglades experienced 90 percent mortality. When Dorcas et al. 2010 was published the Aiken Standard proclaimed, “…there will be no python invasion in South Carolina any time soon.”

This is the fourth paper to convincingly describe how pythons exposed to critically low temperatures die. Barker 2008 related how pythons left heated refugia to crawl into snow and die, and concluded that pythons and boas do not have the instincts and inclination to seek shelter from low temperatures. Seven of nine pythons in the U.S. Department of Agriculture study of Avery et al 2010 left heated refugia to die in cold temperatures in central Florida. Nine of 10 radio-tagged pythons in the study of Mazzotti et al. 2010 died in the Everglades (the tenth animal had to be rescued or it likely would have died, as well). Now it is finally revealed that 100 percent of the pythons in the study of Dorcas et al. 2010 conducted at the Savannah River Ecological Lab (SREL) in Aiken, SC, died despite living in a large enclosure with a human-enriched habitat and numerous refugia.

This new study paper is replete with unfounded speculation, explanation and rationalization. For example, it is stated that the two surviving snakes in Avery et al. 2010 “adopted” a survival strategy, implying that these two snakes somehow experienced a flash of ingenuity and changed their behavior. This is no more than idle speculation. It’s far more realistic to admit that the two survivors simply didn’t do anything, which is not surprising considering the near-freezing temperatures. The fact is that if the snakes had not been in heated refugia, they would have died.

In Dorcas et al. 2010, it is repeatedly stressed that the winter temperatures in South Carolina were colder than average, however, it’s never mentioned that this was just a winter cold snap. This was not record cold weather, it happens with regularity. In fact, eight of the 10 pythons were dead even before the unusual cold snap hit in early January, and the two last survivors died in the underground refugia.

The paper implies that it is surprising that necropsies of the snakes didn’t reveal respiratory illnesses. But, the fact is that the snakes froze so quickly that they did not have time to develop the respiratory complications that sometimes result from long-term chronically low temperatures. For Burmese pythons, winter temperatures in South Carolina and throughout the Southeast are not unpleasant suboptimal temperatures, they are fatally cold temperatures.


In a recent memo dated September 29, 2010, U.S. Department of the Interior (DOI) Secretary Ken Salazar cautioned agencies in regards to the integrity of science used to make policy. It should be interesting to see if U.S. Fish & Wildlife Service (FWS) and USGS pay only lip service to the mandate and continue to push for an Injurious Wildlife listing regarding nine constrictor snakes without credible science to support the listing. And in the case of Rodda & Reed 2009, the climate matching data that is the underlying justification for the proposed listing has been demonstrated to be either completely inept, or an intentional attempt at deception, according to Barker & Barker 2010. Either way this process has not been what Secretary Salazar has described as restoring scientific integrity at DOI.

What many in the animal interest world need to realize is that this proposed rule regarding constrictor snakes has implications far beyond just Herpetoculture or pets. If enacted it would set precedent for an ideological shift in the way animals are looked at in the United States. Never before have so many animals been proposed for addition to the Injurious Wildlife list of the Lacey Act.

Remember, this is all at once, and without sound science to back the listing. Never before have animals so widely held by the general public been proposed for listing. It could create a whole new class of criminal. Organizations like Defenders of Wildlife, Humane Society of the United States and The Nature Conservancy have been the main proponents of the rulemaking, seeking all nonnative animals be added to the Injurious Wildlife list. Once the precedent is set and a million Americans are in possession of Injurious Wildlife (boas and pythons), and potentially subject to felony prosecution, what will be next? Horses, hogs, cats and fish would be at the top of the list for addition. Under the current criteria anything nonnative to the U.S. could be listed as Injurious Wildlife.

The United States Association of Reptile Keepers (USARK) has filed a formal challenge of the USGS constrictor report, Rodda & Reed 2009, under the Information Quality Act in the form of a 36 page, 16 point Request for Correction. The official government response to it was written by Gordon Rodda, the USGS report author, and summarily dismissed as “no corrections necessary.” USARK has subsequently filed an 86 page appeal in an effort to hold the federal government accountable to its own rules and standards. As of today more than 30 days have passed without anything more than an acknowledgement of receipt of the appeal. A subsequent request for a response has gone unanswered.


USARK has laid the groundwork for legal action, if necessary. Extensive Freedom Of Information Act requests filed by USARK have uncovered documents that seem to point at a policy decision made by staff at FWS and USGS at the behest of powerful special interest groups. This apparently was followed by a coordinated effort to manufacture the “science” necessary to support that decision after the fact. This certainly does not appear to be a template for the standard of integrity mandated by Secretary Salazar. If judged on the facts and merits, we are confident that we have a solid and sound foundation for a successful lawsuit.

For more information about USARK, click here .

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