Alien Giant Snakes Threaten to Invade Up to 1/3 of U.S.

October 14, 2009

Nine species of giant snakes—none of them native to North America and all popular pets among reptile lovers—could wreak havoc on U.S. ecosystems if the snakes become established in the wild, according to a new study by the U.S. Geological Survey (USGS) (pictures of giant snakes mentioned in the study).

Two of the giant snakes are already at home in Florida. One of them, the Burmese python, has the potential to infiltrate the entire lower third of the U.S., the study says.

(Related: "Python 'Nightmare': New Giant Species Invading Florida.")

Mature individuals of the largest of the nine giant snake species—the Burmese, reticulated, and northern and southern African pythons—have been known to attack and kill people. But attacks on humans are rare, and scientists think the snakes pose minimal risks to humans.

Some of the snakes can grow longer than 20 feet (6 meters) and weigh more than 200 pounds (90 kilograms).

All nine giant snakes are considered invasive or potentially invasive, meaning they could live and reproduce in parts of the U.S. The snakes mature rapidly, produce large numbers of offspring, are not picky eaters, and can survive in a variety of environments.

The report names five giant snake species as high risk, saying they "put larger portions of the U.S. mainland at risk, constitute a greater ecological threat, or are more common in trade and commerce": the Burmese python, northern and southern African pythons, boa constrictor, and yellow anaconda.

The other four species—the reticulated python, Deschauensee's anaconda, the green anaconda, and the Beni anaconda—are considered medium risk.

Thousands of Giant Snakes Already in U.S.?

The giant snakes are native to a variety of countries in Africa, South America, and Asia.

For the study, USGS scientists examined the potential for each of the nine species to thrive in regions of the U.S. that match the reptiles' native habitats.

Two of the species—the Burmese python and the boa constrictor—have been confirmed to be breeding in parts of Florida. The other seven species are not as established but are considered potential threats.

While the possible ranges for some of the giant snakes are limited to parts of Florida and Texas, other species could spread more widely. The Burmese python, for example, could spread across the lower third of the country, the study concludes.

Scientists estimate that there could be tens of thousands or even hundreds of thousands of these giant snakes already living wild in the United States. However, due to the snakes' camouflage, humans rarely notice them.

"For every snake that you see," said study co-author and USGS biologist Bob Reed, "there could be a thousand snakes that you didn't see."

Giant Snakes Spell Death Sentence?

Most of the giant snakes found in the wild were once pets that either escaped or were released by humans after they had proved too difficult to care for, the report says.

While humans may think they are doing their pets a favor by releasing them, freedom for the snakes could be a death sentence for many North American ecosystems.

"If you want to be good to Mother Nature, do not under any circumstances let [your snake] go," said study co-author and USGS zoologist Gordon Rodda. "You'd be better off euthanizing it than releasing it."

And though some of the species occasionally attack humans, Rodda added, "the main damage that we see from these snakes is ecological."

For example, the post-World War II invasion of brown tree snakes on the U.S. territory of Guam has decimated the South Pacific island's native wildlife populations.

Many of the mammals, birds, and lizards that the tree snake—a native of Australia, Papua New Guinea, and the Solomon Islands—preys on pollinate the island's trees and flowers, so Guam's native plants are also on the decline.

A similar loss of species diversity is possible in parts of North America, where many small animals are unaccustomed to the hunting styles of huge predatory snakes, the scientists warn.

"Our native animals don't have an evolutionary history with giant sit-and-wait snakes," Reed said.

Freeing Giant Snakes: Antisocial Act

The authors of the new study "didn't leave anything unturned," said Ken Krysko, a senior herpetologist at the Florida Museum of Natural History in Gainesville, who was not involved in the study.

"No one can dispute anything they wrote down in there."

The new study will be reviewed by the U.S. Fish and Wildlife Service (FWS) and National Park Service. The findings will be taken into consideration when determining options for controlling the snakes' spread, said FWS spokesperson Ken Warren.

One possible action, Warren said, is to declare the snakes as injurious to humans and the environment. This would prohibit importing the snakes into the United States and transporting them across state lines.

However, such an action would not make it illegal to own or sell the snakes.

It will also be important to educate the public on the ecological dangers posed by freeing giant snakes, said USGS's Rodda.

"It has to be understood as an antisocial act," Rodda said. "Just as friends don't let their friends drive drunk, friends don't let their friends release giant snakes."

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