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Briefing: Invasive Species

Invasive species are wreaking havoc on some communities

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The Burmese python is one of many invasive species threatening North America.

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While strolling across her Florida backyard, Sue Nulman spied a dead bird on the grass near some leaves. Then something else caught her eye: the scales of a large reptile, which presumably was about to make a quick lunch of the bird.

"I saw maybe three to five inches of this python under the leaves," she said. "It was coiled up. I had no idea how long it was." But she could tell by its girth -- about the thickness of her fist -- that this was no ordinary snake in the grass.

Burmese Pythons Invade Florida -- and Elsewhere

Nulman wasted no time in taking care of the snake, a Burmese python. "I pounded the hell out of it," she said, using a piece of metal rebar as a weapon. Her next weapon was the telephone, which she used to call the Python Hotline. Established by Everglades National Park, the Python Hotline was created to monitor the spread of invasive species like pythons across Florida, which has seen an explosive growth in exotic animals run amok.

The Burmese python can grow to be larger than 20 feet long, weigh over 250 pounds, and usually lives on a diet of birds, rabbits and rats, which they kill by constricting (the pythons are non-poisonous). But researchers have found that the snakes will also eat larger prey like bobcats, deer and alligators. In one well-documented case, a python measuring 13 feet long swallowed a six-foot alligator -- until the gator gashed a hole in the snake's gut from the inside out. Neither animal survived the encounter.

And, according to a report released this year by the U.S. Geological Survey, the pythons have the potential to spread across one-third of the United States, from the southeast to central California.

Meet the Invaders

The Burmese pythons now slithering across Florida are only one of many exotic species that are invading North America. Because of increased trade from developing countries, the popularity of exotic pets that escape or are set free, and a climate that's growing warmer every year, North America is seeing a wave of invasive species that are threatening to wipe out many of the continent's native plants and animals.

The red lionfish, a colorful but venomous fish native to the western Pacific Ocean, has been found from Florida to North Carolina. The fish has no natural predators in the waters off the southeastern coast of the United States. Divers are warned to avoid the lionfish's feathery spines -- they cause extremely painful stings that can spread over an entire limb and require expert medical attention.

The Chinese mitten crab, which can live in both freshwater and saltwater and can travel overland, has been established along the West Coast of the United States for many years. It is now established in East Coast waterways like the Hudson River as far as 100 miles inland, where its voracious eating habits may starve-out native wildlife.

Another unwelcome aquatic invasive species that can walk across land is the northern snakehead, a ghoulish-looking fish that can grow up to three feet in length and has been sighted from California to Massachusetts. The snakehead is sometimes referred to as "Frankenfish" for an ugly face that sports rows of sharp teeth, which it uses to eat everything in sight. Fishermen finding this species are advised to kill it on the spot, since it can survive several days out of water and walks on its front fins.

Florida: Exotic Species Hotspot

But many of the animals that Americans take for granted are in fact introduced species. The wild boar, a native of Europe and Asia, was first introduced in the 1500s by colonists. The nine-banded armadillo has moved north from the deserts and chaparral of Mexico and Central America, and is now well established as far east as Georgia. The European starling was set free in a well-intentioned but disastrous effort to introduce into this country all the birds mentioned in the writings of William Shakespeare.

For many invasive species, warm-weather areas like Hawaii and Florida are ground zero for their expansion into new habitats. "A great many of the species we have are tropical and sub-tropical. It's a climate match," said Scott Hardin, exotic species coordinator with the Florida Fish and Wildlife Conservation Commission.

The trade in exotic pets -- both legal and illegal -- is also well-established in Florida. "The port of Miami is the port of entry for a lot of exotic plants and animals," said Hardin. "It's a long-established industry in Florida."

But Hardin does not discourage all exotic pet ownership. "If it's done responsibly, owning exotic pets can be a gateway for learning more about nature," he said, adding that his agency does not seek to drive the trade underground by making it illegal or tightly regulated. "We try to promote responsible pet ownership."

Part of the mission of Hardin's agency is public education, at the consumer level as well as the retail level. "We're trying to encourage people to understand what's native and what's not," he said.

Invasive Species vs Native Animals

One of the non-natives that's become a particular concern to folks like Hardin is the Nile monitor lizard, a monstrous reptile native to Africa. "It's the largest of the African monitors; they get up to seven feet long," he said. Monitor lizards like those found in southwest Florida are notoriously aggressive and will dine on everything from crayfish to small mammals, including domestic cats.

While many invasive species are a threat because they can out-compete many native animals for scarce food supplies, Hardin notes that some carnivorous invaders like the Nile monitor lizard are a problem because they eat native animals themselves, some of which are endangered species. Monitor lizards, for example, will eat the eggs and hatchlings of the American crocodile, the gopher tortoise, sea turtles and the burrowing owl, all of which are listed as endangered or threatened species.

Another warm-climate invasive pest is the green iguana, which eats plants and can quickly denude a landscaped yard. "The population has exploded," said Hardin. "They started in the Miami area and have moved north and south from there."

Sue Nulman has her own experiences with iguanas. "I've never killed animals in my life, but I've had to kill these iguanas - they're all over my garden," she said. And if she ever sees another Burmese python, she's ready: "I've got sticks and shovels stationed all over my yard."

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