'Swamp rats' on the move as winters warm

Caged nutria-768

A captured nutria, waiting to be weighed, in Tualatin, Ore. Warming winters mean the invasive water-loving rodent is likely to expand its range beyond the Pacific Northwest, the Mississippi Valley and the Eastern Seaboard. Photo by Tess McBride/U.S. Fish and Wildlife Service.

Aug. 12, 2013

An invasive rodent with a bounty on its tail in Louisiana is set to introduce itself to the rest of the country.

by Brett Israel
The Daily Climate

As fans of "Duck Dynasty" can attest, hunting for nutria – big, water-loving rodents with bright orange front teeth – is hugely popular in Louisiana. This might not be exclusive to the bayou for long. As winters warm, nutria could migrate across the country, according to new research.

In the year 2050 ... almost all of the states are suitable for nutria.
- Catherine Jarnevich, USGS

Researchers at the U.S. Geological Survey found that during a recent string of mild winters, nutria populations expanded northward in the United States. Left uncontrolled, that trend could continue over the next 40 years, the data show. Climate change models predict milder winter temperatures across the country, and the new study suggests that could lead to nutria extending their range big time in the Pacific Northwest, the Mississippi Valley and the Eastern Seaboard.

Nutria-400Nutria shot-400"In the year 2050 we show that almost all of the states are suitable for nutria," said study author Catherine Jarnevich, a research ecologist with the USGS. The research, not yet published, was presented at the recent meeting of the Ecological Society of America in Minneapolis.

Introduced for the fur

Nutria are large (weighing 10 pounds), water-loving invasive rodents. They reproduce quickly and have hunkered down in many parts of the world after being introduced for the fur industry. The Southeast, Pacific Northwest and Chesapeake Bay are nutria hotspots. Nutria can destroy coastal marshes and bald cypress swamps by eating the roots and developing plants, wiping out vegetation. 

Nutria expand their range north or scurry south depending on winter temperatures. Historically nutria ranges have expanded northward following milder winters and contracted southward following more severe winters. 

Preventing the spread

The USGS study focused on the current and potential distribution of nutria in the Pacific Northwest. Here, nutria have been confirmed only west of the Cascade Mountains in Oregon and Washington. Researchers are already thinking about how to prevent these rodents from spreading.

"Monitoring the primary routes of potential dispersal, such as the Columbia River, will be important for limiting expansion eastward," said Trevor Sheffels, a research ecologist at Portland State University.

Louisiana pays trappers $5 for each nutria tail turned in.

In Louisiana, wildlife managers have taken a more aggressive approach. Due to a relatively stable climate, nutria in Louisiana don't expand and contract like in other states. Here, the water rodents run wild year-round. The rodents are so widespread that there literally is a bounty on their tails. 

Louisiana's Coastwide Nutria Control Program, now in its 11th year, pays trappers $5 for each nutria tail turned in. So far, the program appears to be paying off, said Edmond Mouton, a biologist program manager with the Louisiana Department of Wildlife and Fisheries.

"It's been successful," Mouton said. "In the beginning we had close to 100,000 acres impacted [by nutria], down to 600 acres now. It's a dramatic decrease."

Brett Israel is a staff writer at the Daily Climate an independent, foundation-funded news service covering the environment, energy and climate change. Follow him on Twitter: @btiatl

Photos: Close-up of nutria (top) by madmonk111/flickr. Nutria being given a sedative so it can be measured by Tess McBride/U.S. Fish and Wildlife Service.

The Daily Climate is an independent, foundation-funded news service that covers climate change. Find us on Twitter @TheDailyClimate or email editor Douglas Fischer at dfischer [at] DailyClimate.org

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