Drastic Measures: 8 Wild Ways to Combat Invasive Species

Employing everything from love potion to meat-eating ants, scientists try to stem the influx of new invasive species with some "creative" ideas

By Cassandra Willyard | June 28, 2010 | 13

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Article: Drastic Measures: 8 Wild Ways to Combat Invasive Species » June 28, 2010

Fashionable Fur from Louisiana's Wetlands

Fashionable Fur from Louisiana's Wetlands

Louisiana's wetlands are infested with more than a million large, beady-eyed rodents called nutria. These natives of South America were brought to the U.S....[More]

Fashionable Fur from Louisiana's Wetlands

Louisiana's wetlands are infested with more than a million large, beady-eyed rodents called nutria. These natives of South America were brought to the U.S. in the 1930s to stock fur farms. Soon after, farm escapees and took up residence in Louisiana's bayous, among other places. High demand for fur kept the wild population more or less in check for a few decades. But when the fur market crashed in the 1980s, the nutria population exploded. Now, an artist named Cree McCree is trying to make nutria fur fashionable again to control wild populations and save Louisiana's marshes from nutria noshing.

Nutria are grazers. After their numbers climbed aerial surveys revealed large swaths of wetland that had been eaten bare. Native muskrats graze, too, but they like to nibble the tender leaves of marsh plants, whereas nutria prefer to feast on a plant's base and roots. "The plant dies, and it relinquishes its hold on the soil," says Michael Massimi, invasive species coordinator at Barataria–Terrebonne National Estuary Program (BTNEP), a group set up to protect wetlands affected by nutria.

Land managers have tried several strategies to get rid of the pests, including an unsuccessful state campaign in the late 1990s encouraging locals to eat the rodents (nutria jambalaya, anyone?). What has been more successful is a state program that pays trappers $5 for each nutria tail they deliver. The program brings in 300,000 to 350,000 tails each year. If trappers can sell the fur or meat, they can earn even more. But the bulk of these products go to waste because demand is so low.

So, in 2009 McCree decided to try and reestablish a market for the fur. With a grant from the BTNEP, she challenged local designers to create apparel featuring the rodent's fur. "We're not trying to promote fur so much as we're trying to utilize a wasted resource," Massimi says. The project—Righteous Fur—aims to market nutria fur as a "guilt-free" alternative to traditional fur. McCree has already held two fashion shows in New Orleans, and many of the pieces sold. Even the animal's enormous orange teeth have made it onto the runway as necklaces and earrings. "When they're attached to a nutria they're pretty hideous," Massimi says. "But when you mount them on some Balinese silver, they actually look quite nice." [Less] [Link to this slide]

© Kim Comeaux

Goat Gluttony in Washington State

Goats aren't known for their refined palettes. They'll eat just about anything green. In places such as Hawaii or the Galápagos, where these grazers are unwanted invaders, this mindless munching has caused major damage....[More]

Sniffing for Snakes on Guam

This tenacious terrier isn't searching for illicit drugs or bombs, he's sniffing for stowaway snakes. The tiny island of Guam is infested with them....[More]

Sniffing for Snakes on Guam

This tenacious terrier isn't searching for illicit drugs or bombs, he's sniffing for stowaway snakes. The tiny island of Guam is infested with them. In the past 50 years the invasive snakes have wreaked havoc on the island's native birds and lizards. Now the U.S. Department of Agriculture (USDA) uses dogs to prevent them from sneaking off the island and damaging other islands.

The brown tree snake—a native of Australia, Papua New Guinea and the Solomon Islands—arrived in Guam in the 1940s or 50s, most likely hidden in a load of cargo. Soon it began breeding in the wild. Guam was a brown tree snake's paradise, free of predators and full of defenseless prey. "They populated the whole island in relatively short order," says Daniel Vice, assistant state director of USDA Wildlife Services in Hawaii, Guam and the Pacific Islands.

At the peak of the population explosion, the island may have had more than 30 snakes per acre of forest. Since the snake's arrival, nine native bird species have disappeared from the wild. The two remaining species are "perilously close to extinction," Vice says. The snakes also bite locals and climb on power lines, causing frequent small-scale blackouts.

Naturally, other islands would like to avoid the Guam's fate. In 1993 the USDA set up the Brown Tree Snake Control Plan to keep the secretive snakes from sneaking off Guam. Officials set up traps and laid out toxic bait. They also began inspecting outgoing cargo. But brown tree snakes aren't easy to spot. A meter-long snake can fit inside a soda can with plenty of room to spare, Vice says. The inspectors needed something better than their own eyes to search for snakes. That's when they came up with the idea of snake-sniffing dogs.

Today, the USDA relies on a team of 16 Parson (Jack) Russell terriers. The dogs patrol Guam's ports and cargo warehouses "24 hours a day, seven days a week," Vice says. But because the other snake control measures work so well, they don't find many snakes—maybe half a dozen each year. Still, Vice points out that those are "high-risk snakes"—the ones ready to be shipped off the island. These dogged canines are the last line of defense. [Less] [Link to this slide]

D. Vice, USDA APHIS

Slurping Up Suffocating Algae in Hawaii

Biologists have a new weapon in the battle to save Hawaii's coral reefs from invasive algae—the Super Sucker. Essentially a giant vacuum, the Super Sucker can remove up to 360 kilograms of alien algae from the reef each hour.

Hawaii is home to at least 20 types of nonnative algae. But two kinds, brought to the island for research in the 1970s, are especially noxious—Gracilaria and Eucheuma. They grow rapidly, kill corals and destroy the diversity of the reefs by filling in the nooks and crannies where native sea creatures like to live and hide. "[The algae] takes a healthy diverse system and chops it off right at the knees," says Eric Conklin, the Nature Conservancy's marine science advisor in Hawaii.

The Conservancy has had some success holding community cleanup events where volunteers remove the algae by hand. But no one wants to spend every weekend picking algae off reefs. "We needed something that would basically produce the same effect as these big volunteer events, but that could be operated by a smaller number of people on a very regular basis, and in areas where community cleanups couldn't go," Conklin says.

So, in 2006 Conklin and his colleagues MacGyver-ed an alternative: a giant underwater vacuum. The pump—filched from a gold prospecting machine—sits above water on a floating platform, and the 100-foot hose extends down into the water. "We started off calling it 'The Super Sucker' as a joke," Conklin says. But eventually the name stuck.

The Super Sucker isn't that much faster than hand removal, but it requires a far smaller crew—a couple of divers feed algae into the hose and a few people work on the platform, picking out any by-catch and packing the algae into burlap bags. So far, the Super Sucker has helped restore more than eight hectares of reef.

Removing the algae, however, is only half the battle. To keep it from growing back, Conklin and his colleagues are looking at using native sea urchins, which feed on the algae. "The long-term solution," he says, "is better protection of herbivorous fish." [Less] [Link to this slide]

© Kanako Uchino

Lamprey Love Potion

Sea lampreys earned the alias "vampire fish": After all, they suck blood. These long, parasites are similar to eels and use their suckerlike mouths to latch on to the bodies of other fish....[More]

Snuffing out Smelt in Northern Wisconsin

Snuffing out Smelt in Northern Wisconsin

This giant disk of black rubber may seem harmless, but don't be fooled. This gizmo—called a GELI, short for Gradual Entrainment Lake Inverter—is designed to kill....[More]

Snuffing out Smelt in Northern Wisconsin

This giant disk of black rubber may seem harmless, but don't be fooled. This gizmo—called a GELI, short for Gradual Entrainment Lake Inverter—is designed to kill. It's the newest weapon in the war against invasive rainbow smelt, a native of the North Atlantic states.

Rainbow smelt were brought to the Midwest in 1912 as food for fish farm salmon. But the tiny fish soon escaped into Lake Michigan and then moved into Wisconsin's inland lakes, perhaps by hitchhiking in fishermen's bait buckets. In Wisconsin alone smelt have already invaded about 25 lakes, "and every year they tend to pop up in another lake," says Jake Vander Zanden, a biologist at the University of Wisconsin–Madison's (U.W.) Center for Limnology. Smelt compete with other species for food and feed on baby fish, including trout, walleye, yellow perch and cisco.

How will the GELI help to get rid of smelt? The goal, says Jordan Read, an environmental engineering graduate student at U.W.–Madison, is to "flip the lake on its head." Temperate lakes tend to stratify, with cold water sinking to the bottom and warm water floating on top. Smelt like the cold water. If the cold water disappears, so will the smelt—or at least that's the hope.

The researchers plan to test this idea out in Crystal Lake, an 84-acre lake in northern Wisconsin. In 2011 they will put about a dozen of these devices in the middle of the lake. Each disc has an inflatable tube running around the rim that is connected to an air compressor. Once the device has sunk to the bottom of the lake, the researchers can start the compressor, fill the tube, and the GELI will rise slowly to the surface, bringing up a large volume of cold water from the lake bottom. Once the GELI hits the surface, the tube will deflate and the GELI will sink again, bringing warm surface water to the bottom. "Eventually we erode that stratification," Read says.

The baby smelt don't mind warm water, so to wipe out the entire smelt population the researchers will have to mix the lake for several years. According to Vander Zanden and Read, the mixing shouldn't have an impact on native fish, which can tolerate warmer waters. The hope is that once the smelt are gone, native fish like yellow perch will rebound. "One of the big ideas here," Vander Zanden says, "is to test of whether the ecosystem can really be brought back to something resembling its original state after eliminating this nasty invasive." [Less] [Link to this slide]

© UW-Madison University Communications / Bryce Richter

Blocking Asian Carp from the Great Lakes

Blocking Asian Carp from the Great Lakes

They're big, they're ugly, and they're making their way inexorably north.

Asian carp—which can reach a hefty 45 kilograms—are voracious eaters....[More]

Blocking Asian Carp from the Great Lakes

They're big, they're ugly, and they're making their way inexorably north.

Asian carp—which can reach a hefty 45 kilograms—are voracious eaters. Two species—the bighead and the silver carp—are of particular concern. Catfish farmers brought these fish to the U.S. in the 1970s to clean ponds. But the carp escaped into the Mississippi River Basin during massive flooding in the 1990s. They have been migrating north ever since. The fear is that they will eventually make their way into the Great Lakes and out-compete native fish for food.

Skittish silver carp are reviled for more than their voracious appetites. Boat motors can startle the fish, causing them to leap from the water. Occasionally they collide with a surprised boater.

In 2002 the U.S. Army Corps of Engineers erected a $4-million temporary underwater electric barrier in the Chicago Sanitary and Ship Canal, which connects the Mississippi River system with Lake Michigan. Two years later they began constructing a permanent electric barrier. A second barrier was activated in April 2009 and a third is set to be erected this fall.

Last November, scientists found carp DNA on the Great Lakes side of the barrier, possibly indicating that the electric fence had already been breached. Lynne Whelan, a spokesperson for the Corps, points out that the presence of carp DNA does not necessarily mean the presence of live carp. Now, however, there is even more compelling proof: In June a fisherman reeled in a nine-kilogram bighead carp in Lake Calumet, just six miles from Lake Michigan. Researchers are in the process of trying to determine whether the fish came from the wild or a fish farm, and whether he is a loner or part of a larger population.

Twice Michigan has sued to force Illinois and the Corps to close the man-made locks that lie between the Mississippi River Basin and the Great Lakes, but the U.S. Supreme Court rejected its petitions. This latest fish find has prompted Michigan legislators to once again demand that the Corps close the locks until the two watersheds can be permanently separated. At this time, the U.S. Army Corps of Engineers says it has no plans to alter its operations. [Less] [Link to this slide]

Courtesy of T. Lawrence / Great Lakes Fishery Commission

Combating Cane Toads in Australia

In the 1930s farmers released thousands of poisonous cane toads native to Central and South America into sugar plantations around Cairns, Australia, in the hope that they would rid the fields of beetles. Big mistake. The plan failed, and the toad spread across northeastern Australia, gobbling up native insects and poisoning predators that mistakenly fed on them.

Rick Shine, an evolutionary biologist at the University of Sydney, has been studying the ecology of the invasive cane toad since 2004. "We kept finding all these vulnerabilities," Shine says. For example, the frogs that are native to Australia know how to avoid large, carnivorous ants because they've evolved with them for millions of years. The toads, on the other hand, "have all the wrong responses," Shine says. The baby toads come out of their ponds when the ants are most active. And, when they encounter an ant, rather than hopping away, they freeze.

The researchers found that they could attract meat-eating ants to the ponds where cane toads breed by setting out cat food. When the toads emerge, the slaughter begins: The ants attacked 98 percent of the toads in the first two minutes. Of those, 70 percent died. "Their poison doesn't affect the ants, so they just get creamed in huge numbers."

Shine's lab is also looking at ways to train large predators to avoid eating the toads. Big animals are more likely to grab big toads, which contain the most poison and can cause an instant heart attack. In a recent experiment the researchers laced cane toad meat with a drug that induces severe nausea and fed it northern quolls, cat-size marsupials that sometimes feed on the toads. The tainted meat doesn't kill the quolls, but it makes them very ill. In the field "the ones that have been educated survive very well, the ones that haven't been educated die almost immediately," Shine says. The researchers have seen quoll populations bounce back in some study areas as a result of the training. Shine and his colleagues say the strategy may work for other large predators such as monitor lizards as well. [Less] [Link to this slide]

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1. ormondotvos 05:01 PM 6/28/10

Goats v. Kudzu?
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2. ormondotvos 05:12 PM 6/28/10

Flying food fish?
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3. ssm1959 06:26 PM 6/28/10

My family has been fighting this battle for 45 years on a timber farm in southern Wisconsin. There are many hard earned lessons over those years that need to be kept in mind. First, what is the natural history of the species in the new environment. Many species present with an initial invasive flush which fades over a few years leaving the new species in an equilibrium. You cannot win against these not do you have to. The environment will control them. Those species that experience an unrelenting release phenomenon is where you have to throw the limited resources. This group is made up of both native and non-native species. before you declare war on them be sure to assess ALL!!!!!!! contributors to the problem. For example: Eurasian buckthorn did not take off until deer populations exceed 35 per square mile. As the deer mowed down the native species that competed it left buckthorn an uncontested niche. Our efforts in controlling this infestation were wasted until we brought the deer numbers down to a more reasonable level.

In all instances, consider the use of fire and /or mowing prior to herbicide. Fire is far more effective in its cost and application than paying people to runaround spraying chemicals that will only work at the spot applied and only for the phase of growth targeted. Timely mowing will reduce seed production but is must be done after the plant has set and has no chance of flowering again. Fire, my personal fav, works wonders. It targets all phases of growth and may have inhibitory effects in the soil as well.

In all cases read, scrutinize and analyze before committing. You can help stem the tide locally which is the best you can do in most cases.
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4. hankroberts 11:08 PM 6/30/10

http://scholarsarchive.library.oregonstate.edu/jspui/handle/1957/2885

Sucrose and sawdust application on cheatgrass removal

I tried spraying sugar water after a recent fire on a restoration site I've been poking at for a few decades -- the idea is to feed the soil microbes so they take up all the excess minerals left near the surface by the fire, and then the next spring the cheatgrass starves while the deep-rooted native plants get a chance to recover.

The result for this amateur trial looked quite good. Other studies on this idea have been coming out recently.
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5. sparcboy 10:25 AM 7/1/10

Surprising no mention of an invasive species that affects much of the southern U.S.: Feral Hogs.
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6. rhinoguy 02:52 PM 7/1/10

I don't see how hunting nutria for their fur would be an effective way of managing/controling/removing an exotic species. What, when the nutria hear how cruel we are to the ones we've caught the rest will get scared and leave? Aren't there alternatives to this? If there is no more humane or sensible way of removing the nutria from Louisiana than convencing hunters that they would make great jackets, aren't we still working with or at the level of the mentality that has caused so much trouble with wildlife management to begin with? Wouldn't live trapping, sterilization, and returning the animal to the exotic habitat to mate unsuccessfully be a more realistic and humane way of doing this? It goes back to the old idea that it's probably not the best idea to put animal management in the hands of people who get such a kick out of slaughtering them.
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7. jar2353 01:35 PM 7/2/10

We have certainly handled the "Invasive Species" infecting our border states.
Why not apply the same method: Do Nothing!
(except when we need votes)
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8. J. Howard 06:13 PM 7/2/10

In Rochester, New York, a coalition formed by the Sierra Club and other community organizations and individuals has begun a project to control invasives, primarily Norway maple, in a unique hardwood grove in the City. We welcome ideas and contact with other groups trying to do similar projects in a city. We have found that many people in the community resist removal of the Norway maples and have a limited understanding of the potential for change in native ecosystems that can be effected by invasive plants.
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9. prachitripathi 11:48 PM 7/2/10

this so called artist is promoting fur, no matter how much she denies it. once it catches public fancy there will be huge demand and not only nutrias but other furry native species will also suffer. nutrias did not swim across the oceans from south america to invade the wetlands of united states. a more humane way to control them should be thought of and the fur lobby who bring in these exotics and are responsible for their escape into the wild should pay. and by the way, is there no risk analysis worked out before a new species crosses borders? i think thats where we need to put a check.......its stupid to slaughter them for no fault of theirs.
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10. prachitripathi 11:49 PM 7/2/10

Even the animal's enormous orange teeth have made it onto the runway as necklaces and earrings. "When they're attached to a nutria they're pretty hideous," Massimi says. "But when you mount them on some Balinese silver, they actually look quite nice.".......................THE LAST LINE BEATS IT ALL. SO INHUMAN.
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11. bucketofsquid 09:56 AM 7/6/10

jar2353 - you are a racist pig and no one likes you. Take your hate mongering over to Fox News where it belongs.

Rhinoguy and Prachitripathi - Predators kill and eat things all of the time. It is the natural way. These nutria are a threat to the survival of huge numbers of species so yes they are at fault just by existing. The people that brought them in have been dead for decades. How are dead people going to pay for anything? How many nutria can be captured and sterilized each year? 400,000? A million? Any less than this is meaningless.

Personally, I think nutria hunting should be encouraged as a good recreational "green" sport. Boy Scouts could have community service nutria kills. It is a winning solution.

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12. bucketofsquid 09:58 AM 7/6/10

The forum software used by SciAm is terrible.
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13. macadamia man 10:37 PM 7/8/10

@prachitripathi

"THE LAST LINE BEATS IT ALL. SO INHUMAN."

I'd say your line should read so inhumane. All too human . .
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Drastic Measures: 8 Wild Ways to Combat Invasive Species

Fashionable Fur from Louisiana's Wetlands

Fashionable Fur from Louisiana's Wetlands

Goat Gluttony in Washington State

Goat Gluttony in Washington State

Sniffing for Snakes on Guam

Sniffing for Snakes on Guam

Slurping Up Suffocating Algae in Hawaii

Slurping Up Suffocating Algae in Hawaii

Lamprey Love Potion

Lamprey Love Potion

Snuffing out Smelt in Northern Wisconsin

Snuffing out Smelt in Northern Wisconsin

Blocking Asian Carp from the Great Lakes

Blocking Asian Carp from the Great Lakes

Combating Cane Toads in Australia

Combating Cane Toads in Australia

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