Environment

Merced County’s invasive rodents are a problem for Valley farms. Can they be stopped?

Massive invasive rodents are chewing up wetlands in Merced and other counties. Area leaders say the problem needs more money to eradicate the animals, before they are out of control.

South American rodents called “nutria” were found in Merced County in March 2017. That alarmed California wildlife officials because of the rodents’ potential to harm agriculture and water infrastructure that’s vital for San Joaquin Valley farms.

Nearly 700 nutria have been caught and killed since then, including 580 in Merced County alone, according to Valerie Cook, the manager of the Nutria Eradication Program for the state Department of Fish and Wildlife.

“We’ve been in really an emergency response, but everything we have done to date is to suppress that population just to keep it from hitting (an) explosion,” she said on Friday.

The rodents are an invasive species in several states, including Louisiana, Maryland and Oregon.

Nutria can give birth to litters of a dozen about three times a year, and become pregnant again within 48 hours of giving birth. They live in marshland and feed heavily on vegetation. Where they appear, they can be a scourge on the environment, according to the state.

In contrast, native beavers, which are larger than nutria, but can also be destructive, only breed once a year to produce three to six offspring, according to Greg Gerstenberg, operation chief of the eradication program.

On top of that, beavers make their homes in one area of a waterway and generally stick to it. “Nutria are colonial. They actually live in big groups,” Gerstenberg said. “So their damage becomes widespread.”

Nutria males leave the place they were born, making new homes up to 50 miles away. They eat just about any vegetation.

The primary concern in keeping nutria out of the San Joaquin River Delta is because they burrow in irrigation canals and levees. That poses a risk to drinking water, and could expose downstream communities and farm fields to flooding.

As of May 2019, in addition to Merced, nutria have been confirmed in San Joaquin, Stanislaus, Fresno, Mariposa, and Tuolumne counties, according to the state.

The state Legislature appropriated about $1.9 million for the 2019-20 fiscal year to eradicate nutria, and set up continuing funding for the next three years. Some say that’s not enough.

The state estimates within five years there could be nearly 250,000 nutria wreaking havoc on California’s endangered wetlands.

California Rep. Josh Harder, D-Turlock, is pushing for legislation that would add another $7 million in federal funding towards the eradication.

“The way we nip it in the bud is we take it seriously and we educate our population,” he said on Friday. “Let’s make sure we put the resources toward the program that are going to help it.”

He said officials in Maryland are only now getting a handle on their invasion after fighting it for two decades.

Officials said the proposed funding could be enough to put a team of 40 people on the eradication effort, doubling the current crew.

The money would help implement “Judas nutria” — animals that are caught, sterilized and outfitted with trackers to help wildlife officials find the more sneaky animals. Nutria-tracking dogs are also part of the new efforts.

It’s not clear how the nutria got into California. The massive rodents were brought to the U.S. in the 19th century for their fur, according to wildlife experts.

What is clear is the rodents must go, according to Harder

“People have seen what happened in Louisiana, 400,000 nutria caught every single year,” he said. “We don’t want that to be us. If that becomes us that will be a risk to (our) way of life, all the ag water infrastructure.”

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Reporter Thaddeus Miller has covered cities in the central San Joaquin Valley since 2010, writing about everything from breaking news to government and police accountability. A native of Fresno, he joined The Fresno Bee in 2019 after time in Merced and Los Banos.
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