By Kale Williams

Oregon’s natural beauty is one of our great state’s hallmarks. Waterfalls cast off sheets of mist as they cascade hundreds of feet through our forests. Snow-capped peaks stretch toward the sky and cast shadows over lush valleys below. The desert highlands stretch endlessly east, providing a stark contrast to the coast, buffeted by storms and waves.

And all of it home to a rich tapestry of wildlife. But some of it doesn’t belong.

Below you’ll find Oregon’s invasive species, the hitchhikers and stowaways that have come to our state through no fault of their own, but wreak havoc once they’re here.

There are steps you can take, however, to stop the spread of these insidious pests. The Oregon Department of Fish and Wildlife has a number to call, 1-866-INVADER, if you spot one of these critters.

Rick Boatner, invasive species coordinator for the state, said an ounce of prevention is worth a pound of cure.

“For a lot of these species, it’s a lot easier to prevent them from getting here than it is to control or remove them once they’re here,” he said.

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American Bullfrog

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How they got here: Native to the American Southeast, these bulbous bullfrogs were first brought to Oregon in the early 1900s for their legs, which are considered a delicacy by some. Since then, they have proliferated as critters purchased as pets, or for science classes, have made their way into the wild.

How they impact the environment: These are big and hungry frogs, reaching widths of up to 8 inches. To sustain their amphibious girth, American bullfrogs eat many native species, including other frogs and turtles. Their appetites mean they often out-compete other species for food and can transmit disease to native species.

They also reproduce. A lot.

While native species, like the red-legged frog, lay about 5,000 eggs each season, the American bullfrog can lay up to 20,000.

What you can do: According to the Oregon Department of Fish and Wildlife, if you see a wild American bullfrog, you should kill it. "If you see bullfrogs in the wild, remove them to eat or kill them. One accepted method is stunning the frog with a sharp blow to the head, followed by decapitation."

If you see them for sale in a pet store, you should report them to the agency.

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Asian and silver carp

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How they got here: Introduced in the 1970s, these fish were brought over from Eastern Asia for aquaculture and phytoplankton control.

How they impact the environment: Phytoplankton, microscopic plants that serve as food for a wide range of species. Asian and silver carp, which can grow up to 50 pounds, devour this important resource leaving little for larval fish and native mussels.

What you can do: Carp are ubiquitous in Oregon, but the bighead and silver varieties are the most destructive. If you spot one, note its exact location and report it immediately to ODFW. I possible, keep the fish as a sample so it can be tested and positively identified.

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Chinese and Japanese mystery snails

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Courtesy/Rick Boatner/ODFW

How they got here: These mysterious gastropods were likely imported to Oregon as pets in household aquariums.

How they impact the environment: Mystery snails can carry diseases and parasites that can impact human health. Like the carp mentioned above, they also prey on algae, zooplankton and phytoplankton. They make their homes in lakes, ponds and irrigation ditches and their shells can clog up intake pipes.

What you can do: Make sure to clean, dry and drain boats before transferring them to different bodies of water. If you have a mystery snail in an aquarium you no longer want, they should be euthanized and discarded, never released into the wild.

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Chinese mitten crab

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Wikimedia Commons/Christian Fletcher

How they got here: Native to China and Korea, the mitten crab is so named for the hairy tufts it sports on its claws. It's unclear how they ended up in Oregon.

How they impact the environment: Much like the iconic salmon of the Pacific Northwest, these crabs easily transition between fresh and saltwater. They breed in saltwater estuaries, then migrate upstream, sometimes as far as 100 miles, to mature into adults. They've been known to climb over small dams and can disrupt fish migration as well as competing with native species for food. They can carry the Oriental lung fluke, a parasite that can afflict humans, and their frequent burrowing has been known to compromise the integrity of river banks and stream beds.

What you can do: If you catch a mitten crab while crabbing, don't throw it back. Freeze it if you can and get in touch with ODFW.

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Common snapping turtle

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How they got here: The common snapping turtle likely came to Oregon as a refugee of the pet trade.

How they impact the environment: These rapacious testudines feed on aquatic vegetation, amphibians, crayfish, worms, birds, small mammals, carrion and even other turtles.

"Snapping turtles will eat about anything that will fit between their jaws," according to ODFW and often out-compete native turtle species for food.

What you can do: If you have a snapping turtle, never release it into the wild. If you see one out and about, contact state officials.

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Crayfish

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How they got here: There are at least three invasive species of crayfish in Oregon — the rusty crayfish, native to the Ohio River Valley; the red swamp crayfish, which hails from the southwestern U.S. and northern Mexico; and the ringed crayfish, which comes from the midwest. Each of them likely came to the state destined for a dinner plate, but somehow made their way into our lakes and rivers.

How they impact the environment: All of the above compete with Oregon's lone native species, the signal crayfish, which can't compete with larger, more aggressive out-of-state crustaceans. The red swamp variety burrows into lake bottoms and stream beds, often destabilizing the soil and causing erosion. If one body of water dries up, they can travel over dry land to find a new home. The rusty crayfish is an aggressive grazer, consuming up to twice as much plant material as other species and destroying aquatic plant beds in the process.

What you can do: It can be hard to distinguish invasive crayfish form their native counterparts, so make sure you know what kind of animal you're dealing with before you take any action. Once you've made sure you're dealing with a crayfish that shouldn't be here, remove it from the water and kill it humanely. There are very specific rules and regulations regarding importation of crayfish for consumption, laid out here.

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New Zealand mud snail

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How they got here: This tiny, spiral-shelled snail was likely brought to the U.S. in the late 1980s in the ballast water of a ship or importation of game fish.

How they impact the environment: Though they are very small, only 3 to 6 millimeters long, these diminutive critters can mass in large numbers and squeeze native invertebrates out of the food chain, disrupting food sources for trout and other fish species. They also degrade water quality, according to ODFW, with potentially dramatic repercussions for recreational fishing.

What you can do: The mud snail expands its range by hitchhiking on watercraft and fishing gear. Once the snail is established, it's nearly impossible to get rid of it without damaging other parts of the ecosystem. ODFW has posted a comprehensive guide on the best ways to treat your gear to make sure you don't transport these invasive snails from one body of water to another.

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Japanese weatherfish

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How they got here: These small, eel-like fish, which are native to East Asia, were originally introduced in Hawaii in the late 1800s primarily as bait fish by Asian immigrants. On the mainland, they are thought to have escaped from a California goldfish farm in the 1930s and have spread far and wide since.

How they impact the environment: So named because they get more active ahead of storms, the weatherfish feed on native species, transmit disease and compete with trout, coho and chinook juveniles for food and habitat.

What you can do: If found, report the weatherfish to ODFW and, if caught, never return them to the wild.

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Red-eared slider

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Wikimedia Commons/Greg Hume

How they got here: Native to the eastern part of the country, these turtles have invaded many habitats in the west after being purchased as pets and released into the wild.

How they impact the environment: These terrapins compete with local turtles for food and habitat, especially nesting sites. The sliders lay eggs about a month earlier than our native species, often alerting predators to nest sites long before the local turtles get a chance to lay eggs there. Red-eared sliders also carry diseases and parasites to which native animals have no immunity.

What you can do: Consider your purchase carefully before you get a red-eared slider as a pet. They can live up to 20 years and grow to be the size of a dinner plate. If you have one of these adorable, but problematic, animals and want to get rid of it, call ODFW for advice.

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Zebra mussel and quagga mussel

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How they got here: These little striped mollusks, which are native to the waters of Eastern Europe, likely came to the U.S. attached to the hull of a boat. They haven't made Oregon their home yet, but their destructive capabilities are such that wildlife officials have put in preemptive measures to make sure they never get here/

How they impact the environment: As highly efficient filter feeders, both the zebra and the quagga mussel can disrupt entire food chains. They can strip a body of water of nearly all the microscopic food necessary for the development of fish larvae and other small organisms. These mussels also reproduce rapidly in mats that blanket river and lake beds.

They can clog intake pipes for power plants, irrigation systems and boat motors. Once they get settled in a body of water, they are extremely difficult, if not impossible, to remove.

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Wikimedia Commons/M. McCormick

What you can do: Similar to the mudsnail, these critters find new homes by hitching rides on boats and fishing gear. Boaters are required to obtain a Aquatic Invasive Species Prevention Permit. Make sure you clean and treat everything that comes into contact with water where these mussels live and if you see any of these invasive critters, contact ODFW.

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Feral swine

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How they got here: These wild versions of domesticated pigs were likely released from farms and homes, sometimes unintentionally. They reproduce at such a fast rate that 70 percent of their population in Oregon, estimated at 2,000 to 5,000, would need to be culled every year just to keep them at current levels.

How they impact the environment: Their reputation as voracious eaters holds true as these foragers will consume just about anything including: acorns, grasses, fungus, leaves, berries, fruits, roots, corn and other agricultural crops, insects, crayfish, frogs, salamanders, snakes, mice, eggs of ground nesting birds, small mammals, fawns, lambs, calves, kid goats and carrion.

They suppress timber growth and rooting around in the dirt with their snouts has been shown to cause erosion, as evidenced in the picture below. They also compete with, and consume, other native wildlife for food and habitat.

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What you can do: If you spot a feral swine on public land, contact ODFW.

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-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale