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NEW YORK TIMES (New York) 09 January 11 A Snake Invasion? Debating the Risks (Leslie Kaufman)
In Sunday’s paper, I write about the controversy over the federal government’s move to ban imports of nine species of snake and their transport across state lines. Its decision was based largely on a risk assessment by two government scientists of the impact those snakes could have on native ecosystems.
As I explain in the article, snake breeders and other snake enthusiasts have widely criticized one aspect of the report in particular: the suggestion that pythons could be suited to a range of climates across a band of the American South.
The two scientists behind the report, Gordon Rodda and Bob Reed, are eager to answer their critics. In fact, they will have a peer-reviewed rebuttal in print by the end of the month.
First, they point out that climate was only one part of the risk assessment. Had they focused solely on the impact that invasive snakes like the Burmese python have already had on places like the Everglades, for example, that would have been enough to produce an assessment of significant risk.
They cited brown tree snakes in particular as a harbinger of havoc. They were accidently transported to Guam about 50 years ago, and for decades they appeared harmless. Now they are uncontrolled pests that have decimated populations of birds and other small vertebrates native to the island’s forests.
But the scientists also defend their climate models. They emphasize that the models are not meant to factor in every variable that would affect the ability of the species to thrive, like the availability of prey and human development of the land. In other words, a climate model is not a prediction that the animal will spread to those areas, but an outline of the limits of the areas where they can survive the cold and dryness.
They also argue that scientists who did the alternative climate model incorporated too many variables, far more than standard practice would dictate was necessary, in assessing risk — and that this led them to underestimate the area through which the snake species might spread.
While some pythons have died in winters to the north of the Everglades, Dr. Rodda and Dr. Reddy say, their fate does not necessarily reflect the survival capacity of the species as a whole. Pythons learn adaptive behaviors early in their life cycle, they note, whereas the ones taken from the Everglades had matured without exposure to the cold and therefore may not have known how to protect themselves.
Finally, they point out that many of the wild pythons in the Everglades survived the cold snap of January 2010 just fine. They note that hatchling counts in the summer of 2010 were equivalent to those of the previous year, which indicates that the Burmese python population is still expanding — enough to make a grown alligator shudder.
Snake Invasion? Debating the Risks

NEW YORK TIMES (New York) 10 January 11 In Snake Wars, the Cudgel Is a Century-Old Law (Leslie Kaufman)
In my article on Sunday about a dispute over a federal decision to ban the import and interstate transportation of nine species of snake, I mentioned that the Lacey Act provides for a range of civil and criminal penalties for violators.
Though it is more than a century old, the Lacey Act is neither a well-known nor a well-liked statute. It was passed in 1900 mainly to preserve the native species and plants from overfishing and excessive hunting, but it has since been amended to address imports of non-native species that are either endangered in their own countries or would prove invasive here.
To some critics, the Lacey Act is hopelessly reactive. Others fault it because it has failed to prevent a spectacular number of exotic plants and animals from entering the United States, including the large and hungry Asian carp, which poses a threat to the Great Lakes ecosystem.
Kristina Serbesoff-King, invasive species program manager for the Nature Conservancy, an environmental group that preserves and restores wild lands, is among those hoping for the adoption of better laws and tighter regulation of imported animals. “Right now imported species are innocent until proven guilty,” she said. But recent research on invasive species suggests that newly arrived plants and animals can seem to pose no problem for a time but then suddenly explode. “By the time you detect the problem, it is too late,” she said. “The Burmese python is a perfect example.”
Andrew Wyatt, president of the United States Association of Reptile Keepers, was quoted in my article as warning that environmental groups are looking to expand the Lacey Act in ways that will have broad implications for all non-native animals, even hogs and cats.
Ms. Serbesoff-King says that such critics are only half right.
“We are not looking to ban all non-native species, but we do want risk assessment being done on them to see if they pose a threat,” before they enter this country, she said.
In Snake Wars, the Cudgel Is a Century-Old Law