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Nutria Neutralizer: A low-tech solution to the rodent eating Louisiana's coast

Trappers take 400,000 nutria annually through the state's bounty program (John Snell) Trappers take 400,000 nutria annually through the state's bounty program (John Snell)
(WVUE) -

Long before man put up a levee or fired up a pumping station, Louisiana cypress forests acted as natural defenses against hurricanes and tropical storms.

"Swamp forest in one of the best habitats for deflecting storm surge," said Theryn Henkel, PhD., Assistant Director of the Lake Pontchartrain Basin Foundation's coastal program. "They do really, really well in high winds. They don't get destroyed. so, we're protecting the levees that protect our people."

In recent years, LPBF, the Coalition to Restore Coastal Louisiana and other groups have planted 35,000 trees in the Maurepas Swamp south of Hammond and in Big Mar, near the Plaquemines-St. Bernard Parish line. The plantings began modestly several years ago and failed miserably. 

"We planted 200 trees," Henkel said.  "We lost all 200."

At first, they thought it might be shifting land giving way under the trees. However, when another planting failed, they realized the culprit was the ballooning nutria population. Nutria were gobbling up the tiny, defenseless trees.

"They prefer to eat on the basal portion of the plants, the bottom of the plants near the roots, which kills the plant," said Michael Massimi, an invasive species expert for the Barataria-Terrebonne National Estuary Program. 

"The plant releases its hold on the soil and you get more erosion," Massimi said.

Nutria have munched on coastal marshes, barrier islands, levees and canals.

"They're a hassle everywhere they exist," Massimi said.

In the late 1990s, state surveys estimated nutria were damaging 100,000 acres of Louisiana's coast annually. Massimi said the current estimate is less than one-tenth that figure thanks to the state's $5 per head bounty program.

Each year, trappers take about 400,000 nutria. Without the program, it would be difficult to keep up with the South American critters, who have few predators in Louisiana other than alligators.

"They're in the rodent family, so they do reproduce like rodents," Massimi said.  "They average maybe four or five pups per litter, but they can be up to 10 or 12."  Nutria can produce two or three litters in a year.

The population explosion brought the sobering realization that it would be impossible for new cypress forests to grow either naturally or through plantings.

"Even if you get a seedling, if the seed germinates, the nutria just eat the seedlings and you're not going to get any germination," Henkel said.

Coastal groups found solution in a "nutria protector," a $1.50 biodegradable guard that frustrates the rodents trying to munch on the tree. A Lake Pontchartrain Basin Foundation Survey recently found a dramatic increase in the survival rate.

"Since those first plantings, since we started putting nutria protectors on every tree, we are up to 78 percent (survival)," Henkel said.

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