A new USGS report with a long name has this short take-away message: All nine giant constrictor species capable of colonizing parts of the United States pose a moderate to severe ecological risk, and several species pose a small but credible risk to humans.

The just-released open-file scientific report at the center of attention here is a 302-pager authored by Robert N. Reed and G.H. Rodda and bearing the ungainly title Giant Constrictors: Biological and Management Profiles and an Establishment Risk Assessment for Nine Large Species of Pythons, Anacondas, and the Boa Constrictor. Rapidly growing concern about giant snakes already on the loose and reproducing in parts of the southeastern U.S. -- including at least two national parks (Everglades National Park and Big Cypress National Preserve) – insures that this report will be heavily publicized, frequently cited in scientific publications, and perhaps used to justify a “call to arms” in what some alarmed people characterize as a looming war against giant reptile invaders.

Scientists rightly worry about the damage that Burmese pythons and other giant constrictors might do in vulnerable ecosystems like the Everglades. But that’s not all. Pet owners fear for their dogs and cats, parents fear for their children, and elected officials and government agencies fear they’ll catch hell from constituents/taxpayers if they don’t “do something about” this giant snake problem. In such an atmosphere, having sound science on which to base policies, strategies, and tactics is absolutely vital, and that’s what makes studies like this one so welcome.

If you’d like to see the whole report, which reviews the biology of the giant constrictors as well as their ecological risk potential, visit this site. Be warned that this 302-pager is a more than routinely large file (just under 15 MB).Here is the gist of it.

Nine non-native boa, anaconda, and python species are invasive or potentially invasive in the United States, including:

• Indian or Burmese Python (Python molurus)
• Northern African Python (Python sebae)
• Southern African Python (Python natalensis)
• Reticulated Python (Python [or Broghammerus] reticulatus)
• Boa Constrictor (Boa constrictor)
• Green Anaconda (Eunectes murinus)
• Yellow Anaconda (Eunectes notaeus)
• Beni or Bolivian Anaconda (Eunectes beniensis)
• De Schauensee’s Anaconda (Eunectes deschauenseei)

The report presents these salient facts and conclusions regarding these giant constrictors:

• Due to their invasiveness potential and characteristics that impede control, all nine species pose risks to ecosystems in the United States. All nine species mature early, produce numerous offspring, travel widely, and will eat most birds and animals they encounter. Our native birds, mammals, and reptiles haven’t encountered constrictors before and haven’t learned how to deal with them.

• Five species -- Burmese pythons, northern and southern African pythons, boa constrictors, and yellow anacondas -- pose a severe ecological risk because they are more commonly brought into this country (mostly via the pet trade) and are more capable of inhabiting diverse habitats and dealing with different climate conditions. Their potential to destabilize colonized ecosystems (primarily by preying on indigenous wildlife) is very high. Though classified “medium risk,” the remaining four species -- reticulated python, Deschauensee’s anaconda, green anaconda, and Beni anaconda -- are potentially serious threats.

• Two of the high risk species -- the Burmese python and the boa constrictor -- are known to be reproducing already in the wilds of South Florida. The Burmese python has been particularly successful in this colonization effort, with its wild population now numbering in the tens of thousands. It’s likely (though not yet proven) that the northern African python may have a breeding population in the wild as well.

• The warmest areas – Florida, extreme south Texas, Hawaii, Puerto Rico, Guam, and other Pacific islands -- are most vulnerable to colonization by the giant constrictors. Since climate is not the only determinant of distribution, the Burmese python and a few other species may be able to colonize a larger area.

• There is a very small, but credible risk to humans. Although individuals of the three largest species can grow to 20+ feet in length and weigh over 200 pounds, most constrictors that people encounter in the wild would be too small to be lethally dangerous. It remains that mature members of the largest species -- Burmese, reticulated, and northern and southern African pythons -- have attacked and killed people in their native range. Unprovoked attacks are likely to be rare in the United States, with an incidence similar to alligator attacks.

Given the seriousness of the giant constrictors threat, it’s unfortunate that there are no adequate tools for eradicating established populations of giant constrictors once they’ve colonized a large area. Hunting them is problematic because their excellent camouflage makes them very difficult to spot, even from just a few feet away. Trapping and other control methods are being investigated, but there’s no assurance that effective mechanical or chemical controls will be developed.