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Going, Going, Guam: Non-Native Snakes Threaten National Park Ecosystems

Capturing pythons in Everglades National Park takes a group effort. NPS photo.

After World War II, the brown tree snake was accidentally introduced into Guam from its native New Guinea and Australia. Within a few decades these snakes completely devastated the island’s bird life—causing the extinction of nine out of the 11 native species.

Within the last few years, a similar threat posed by the introduction of non-native giant snakes into the United States has become an increasingly large concern.

The American Bird Conservancy (ABC), one of the country’s leading conservation organizations, is joining in the fight to ban importation of several species of such snakes: reticulated pythons, green anacondas, boa constrictors, and two other non-native constrictor species. If ABC is successful, these snakes will be considered “injurious wildlife” and regulated by the Lacey Act.

Implemented in 1900, the Lacey Act is one of the world’s oldest conservation statutes. It made it illegal to transport across state lines any animals or birds killed in violation of state laws. Over the years the Act has been amended several times. If the ABC's effort is successful, it would make importing and transporting these snakes over state lines a federal offense.

Darin Schroder, vice president for conservation advocacy at ABC said, “This bill (H.R. 511 –To Prohibit the Importation of Various Injurious Species of Constrictor Snakes) is necessary to prevent the further spread of these aggressive, invasive predators. It’s well-established that these snakes are highly adaptable to new environments, and that they consume a wide variety of prey, including mammal, amphibian, lizard, and threatened and endangered bird species.”

These snakes have already done sizable damage to Florida’s ecosystem. The Burmese python is estimated to have a Florida population in the tens of thousands. Some of the first in the area were bought as pets and then released in the wild where they rapidly multiplied. Studies have shown that pythons are responsible for a severe decline in the populations of mid-size mammals, such as raccoons, opossums, and bobcats. They’ve even been known to eat alligators—which surely gives human park visitors cause for real concern.

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This big python was captured in the Everlgades this past summer. Photo by Kristen Grace/Florida Museum of Natural History.

The American Bird Conservancy is concerned for all native species, but especially for birds, to which the pythons also pose a threat. Birds from the five-inch-long House Wren to the four-foot-long Great Blue Heron have been found inside of pythons. Birds account for an average of 25 percent of a python’s diet. The snakes not only eat grown birds, but eggs as well.

Invasive snakes pose a threat not just on the United States mainland, but in Hawaii as well where native species are isolated from repopulation by thousands of miles of ocean. Seventy percent of native Hawaiian birds are endangered and they account for one-third of the birds listed under the Endangered Species Act. Many snakes feed largely on birds and if non-native species become established there, native Hawaiian species could face devastation.

“If snakes were to reproduce and proliferate, it quickly may be too late to stop them, and as a result, every measure to keep them out of places like Hawaii needs to be taken,” said Schroder. “The American Bird Conservancy strongly supports H.R. 511 and urges the full committee to take up and pass this important piece of legislation and send it to the floor of the House for full consideration.”

Everywhere you look non-native invasive species are undermining the very ecosystems our national parks are intended to protect. Eradication of these pests in parks consume a growing amount of money. With there being no way to guarantee that “pets” will not be released into the wild, the American Bird Conservancy urges that appropriate measures be taken to prevent ecosystems in the United States from going the way of Guam.

Further Reading: Anyone interested in the invasive species issue, especially the situation in Everglades National Park, should be sure to pick up a copy of Snake in the Grass: An Everglades Invasion, the eye-opening book by Larry Perez.  

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