What are nutria? The invasive species affecting California’s waterways – KTXL FOX 40 Sacramento


(KTXL) — In California wetlands, there could be possible sightings of rodents that are considered an invasive species. 

The rodents are called nutria, which are large, semi-aquatic creatures that feed on plants that hold wetland soil together, according to the United States Department of Agriculture. 


Federal officials said the nutria consume weeds and overabundant vegetation.

They also destroy native aquatic vegetation, crops and wetland areas. 

The nutria can grow more than 20 pounds and can destroy wetlands by eating up to 25% of their body weight each day, according to the California Department of Fish and Wildlife. 

The USDA said nutria have been found in at least 20 states with California being the most recent state where they were discovered. 

In California, DFW officials said Nutria have recently been found in the Delta and have been discovered in Merced, Stanislaus, Fresno, San Joaquin, Fresno, Mariposa, Sacramento, Madera and Tuolumne counties. 

What do nutria look like? 

Nutria sometimes gets mistaken for beavers and muskrats, but the invasive rodents have features that are different than those creatures. 

The invasive rodents have round, sparsely haired tails, white whiskers and large front teeth that are yellow to orange. Other than growing up to 20 pounds, nutria are approximately two-feet long with a large head, short legs and are typically dark brown, the USDA said.

Compared to nutria, the DFW said beavers have flat tails while muskrats have dark whiskers and grow to only to five pounds. 

Photo courtesy of the California Department of Fish and Wildlife

What is their habitat?

Nutria can be found anywhere in or near freshwater or estuaries and have been discovered in cattail and Tule marshes, ponds, canals, sloughs and rivers, according to DFW. Those types of habitats are known locations along the Sacramento-San Joaquin Delta, which provide an ideal habitat for nutria. 

State officials said the public should look for signs of nutria in wetlands, canals, rivers, and creeks, along levees and riparian areas. 

“The nutria’s relatively high reproductive rate, combined with a lack of population controls, helped the species to spread. In many regions, they cause severe damage,” the USDA said.

What is their impact in California?

Due to nutria feeding habits, they can destroy 10 times the amount of plant material they consume, “causing extensive damage” to native plants, soil structure, and nearby agricultural crops. 

“The loss of plant cover and soil organic matter results in severe erosion of soils, in some cases converting marsh to open water,” DFW’s website reads. “Further, nutria burrow into banks and levees, creating complex dens that span as far as 6 meters deep and 50 meters into the bank and often cause severe streambank erosion, increased sedimentation, levee failures, and roadbed collapses.”


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