Report Documents the Risks of Giant Invasive Snakes in the U.S.
Released: 10/13/2009 12:00:00 PM
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Five giant non-native snake species would pose high risks to the health of
ecosystems in the United States should they become established here,
according to a U.S. Geological Survey (USGS) report released today.
The USGS report details the risks of nine non-native boa, anaconda and
python species that are invasive or potentially invasive in the United
States. Because all nine species share characteristics associated with
greater risks, none was found to be a low ecological risk. Two of these
species are documented as reproducing in the wild in South Florida, with
population estimates for Burmese pythons in the tens of thousands.
Based on the biology and known natural history of the giant constrictors,
individuals of some species may also pose a small risk to people, although
most snakes would not be large enough to consider a person as suitable prey.
Mature individuals of the largest speciesBurmese, reticulated, and northern
and southern African pythonshave been documented as attacking and killing
people in the wild in their native range, though such unprovoked attacks
appear to be quite rare, the report authors wrote. The snake most associated
with unprovoked human fatalities in the wild is the reticulated python. The
situation with human risk is similar to that experienced with alligators:
attacks in the wild are improbable but possible.
This report clearly reveals that these giant snakes threaten to destabilize
some of our most precious ecosystems and parks, primarily through predation
on vulnerable native species, said Dr. Robert Reed, a coauthor of the
report and a USGS invasive species scientist and herpetologist.
High-risk speciesBurmese pythons, northern and southern African pythons,
boa constrictors and yellow anacondasput larger portions of the U.S.
mainland at risk, constitute a greater ecological threat, or are more common
in trade and commerce. Medium-risk speciesreticulated python,
Deschauensees anaconda, green anaconda and Beni anacondaconstitute lesser
threats in these areas, but still are potentially serious threats.
The USGS scientists who authored the report emphasized that native U.S.
birds, mammals, and reptiles in areas of potential invasion have never had
to deal with huge predatory snakes beforeindividuals of the largest three
species reach lengths of more than 20 feet and upwards of 200 pounds. The
reticulated python is the worlds longest snake, and the green anaconda is
the heaviest snake. Both species have been found in the wild in South
Florida, although breeding populations are not yet confirmed for either.
Breeding populations have been confirmed in South Florida for Burmese
pythons and the boa constrictor, and there is strong evidence that the
northern African python may have a breeding population in the wild as well.
Compounding their risk to native species and ecosystems is that these
snakes mature early, produce large numbers of offspring, travel long
distances, and have broad diets that allow them to eat most native birds and
mammals, said Dr. Gordon Rodda, a USGS scientist at the Fort Collins
Science Center and the other coauthor of the report.
In addition, he said, most of these snakes can inhabit a variety of habitats
and are quite tolerant of urban or suburban areas. Boa constrictors and
northern African pythons, for example, already live wild in the Miami
metropolitan area.
The report notes that there are no control tools yet that seem adequate for
eradicating an established population of giant snakes once they have spread
over a large area. Making the task of eradication more difficult is that in
the wild these snakes are extremely difficult to find since their
camouflaged coloration enables them to blend in well with their surroundings.
We have a cautionary tale with the American island of Guam and the brown
treesnake, said Reed. Within 40 years of its arrival, this invasive snake
has decimated the islands native wildlife10 of Guams 12 native forest
birds, one of its two bat species, and about half of its native lizards are
gone. The python introduction to Florida is so recent that the tally of
ecological damage cannot yet be made.
USGS researchers used the best available science to forecast areas of the
country most at risk of invasion by these giant snakes. Based on climate
alone, many of the species would be limited to the warmest areas of the
United States, including parts of Florida, extreme south Texas, Hawaii, and
Americas tropical islands, such as Puerto Rico, Guam, and other Pacific
islands. For a few species, however, larger areas of the continental United
States appear to exhibit suitable climatic conditions. For example, much of
the southern U.S. climatic conditions are similar to those experienced by
the Burmese python in its native range. However, many factors other than
climate alone can influence whether a species can establish a population in
a particular location, the report notes.
The Fish and Wildlife Service and the National Park Service will use the
report to assist in further development of management actions concerning the
snakes when and where these species appear in the wild. In addition, the
risk assessment will provide current, science-based information for
management authorities to evaluate prospective regulations that might
prevent further colonization of the U.S. by these snakes. The 300-page
report provides a comprehensive review of the biology of these species as
well as the risk assessment.
Resources
* View the risk-assessment report
* Questions and Answers about this report
* View b-roll video and image gallery (below)
* Read U.S. Fish and Wildlife Service information on injurious wildlife
* Everglade National Park web page for the Burmese Python species profile.
Scientific Names
* 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 Schauensees Anaconda (Eunectes deschauenseei)
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