Katrina Weakened, But Didn't Wipe Out, Invasive Rodents

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With the vegetation removed, fragile organic soils are exposed to erosion through the action of the tides. Unless the damaged areas are quickly revegetated, the eroded soils sink below sea level and the area becomes open water.

The degree to which nutria-caused wetland loss heightened the affects of Hurricane Katrina is unknown, but it's something the USGS's Carter plans to investigate.

"The state flew flights to assess nutria impacts along the coast," the ecologist said. "It would be interesting to see if the areas they marked as heavily impacted by nutria suffered more storm damage than areas that were nearby but not noted as heavily impacted by nutria."

Meanwhile, Baker said the control program will continue. The trapping season runs from November 20 through March 31, and applications for trappers are currently available from the Louisiana Department of Wildlife and Fisheries.

The control program demonstrates the ability of wetlands to recover, already halving the damaged acreage since 1998. Baker hopes participation will remain steady, allowing more wetlands to recover.

"As long as the wetland is not totally destroyed and converted to open water, which is the most severe case of wetland damage here, the wetland can come back," he said.

New Threats

While Hurricane Katrina likely reduced nutria populations in Louisiana, Mississippi, and Alabama, the storm also brought new threats, Carter said.

Exotic pets were "more than likely" left behind in evacuated homes and may have escaped into the environment. As an example, Carter pointed to the Cuban treefrog (Osteopilus septentrionalis).

"This has become an important pest in Florida," he said. "It looks similar to our native green treefrog and occupies similar habitats. However, it is larger, poisonous, and it eats native treefrog species with abandon."

If the invasive frogs become established in the wild, they could have a devastating impact on frog populations in New Orleans as well as the nearby Jean Lafitte National Historical Park and Preserve.

"The Cuban treefrog is just one example," Carter said. "This is a situation that bears close monitoring and perhaps action, if resources allow."

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