Nutria – invasive species found in San Joaquin Valley

Need a fashion fur? Look no further than to the San Joaquin Valley. Nutria, an invasive species, are on the loose there according to the California Department of Fish and Wildlife (CDFW).

CDFW announced the discovery of a small reproducing population of nutria in the San Joaquin Valley­. Nutria, (Myocastor coypus), is native to South America. Nutri fur is used as a fashion accessory for fancy clothing. In California, they are an invasive species brought here from  Louisiana nutria farms in the 1930s.

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Nutria (CDFW)

Escapees from these nutria farms form the basis for nutria infestations in several states and now also in California again. CDFW hopes and acts to suppress the still relatively small nutria population in the Valley because of their potential to do severe damage to the environment.

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The competition

Because of their destructive behavior and the terrible damage nutria can do to the environment, several states pay a bounty for each tail of a captured nutria. So, boar hunters, if you find it too cumbersome and difficult to locate your elusive, smart prey, go hunt some nutria instead. But you have to wait for a bounty program to get paid in California.

At present, CDFW hopes that early intervention could eradicate the invasive species before their populations become too big to be successfully eradicated.

The South American native is a large, semi-aquatic rodent. They can grow to 2.5 feet in length and weigh up to 20 pounds. Their tail reaches up to 12 inches in length. Females start reproducing at an age of six months. Female nutria can have three litters per year. One female alone can disperse up to 200 offspring in one year over a distance of about 50 miles.

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Beaver, nutria, groundhog, muskrat (left to right),

They have a strong resemblance to muskrats and beavers. Yet, while the whiskers of nutria are white, muskrats have dark whiskers, an almost triangular tail and weigh only about five pounds. Beavers, on the other hand, have flat, wider tails and dark whiskers, Nutria can reach up to 60 pounds as you can see in the Nutria Identification Guide published by CDFW.

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These destructive rodents have established themselves in wetlands, rivers, canals, and freshwater habitat in Merced, Fresno, and Stanislaus counties. Left to their own devices, they will cause the loss of wetlands, severe soil erosion, damage to agricultural crops, levees and banks, dikes, and roads.

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Typical nutria damage to marshland (

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Typical sus scrofa damage

The semi-aquatic rodents have done severe damage in Louisiana, Chesapeake Bay and in the Pacific Northwest. They also degrade the water quality and contaminate drinking water supplies with parasites and diseases that can be transmitted to humans, livestock, and pets.

Sounds familiar?

Do you know an ungulate that is also an invasive species, muddies up water supplies, and damages agriculture and infrastructure?  I do.invasive species

Invasive species polluting water

It is commonly known as a feral pig or wild boar. And, just like nutria, it did not come to the United States on his own volition. Man introduced it to the environment for his own purposes. Now that they outlived their welcome, they are suddenly considered invasive species. Oh, well . . .

Just live with it and get ready for some hunting fun in the afternoon.

Nutria damage water management structures by building burrows with entrances that typically are below the water line. They also create runs and paths between several aquatic sites.

Their tracks show four visible front toes and webbing between four of five toes. As a bonus, the tracks occasionally also show tail drags.

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To make matters worse, nutria waste much food instead of consuming it. A nutria can destroy up to 10 times the food consumed. This destructive wastefulness is also a sure sign of the presence of nutria in an area. Suspect nutria when you see emergent vegetation, such as from cattail and bulrushes floating in the water. Typically, nutria only eat the base and leave the rest to rot.

Between March 2017 and today, over 20 nutrias have been documented on private wetlands near Gustine, duck clubs, near Cressey, and the San Joaquin River near Grayson. The San Luis National Wildlife Refuge, the Salt slough on the San Joaquin River and south of Dos Palos are other infested areas. Nevertheless, wildlife authorities and experts do not yet know the full extent of the infestation.

In response to this new threat from invasive species, CDFW, the California Departments of Food and Agriculture, Parks and Recreation, and Water Resources, the U.S. Department of Agriculture, the U.S. Fish and Wildlife Service and local county agricultural commissioner offices have established a Nutria Response Team to investigate the extent of the infestation and to develop on eradication plans to get rid of the invasive pests.

Determining the size and severity of the nutria infestation is step one in this plan. Therefore, the Nutria Response team is encouraging local landowners and the public in the Central Valley and the Sacramento-San Joaquin Delta to watch for signs of nutria and to report locations.

Please report suspected observations and signs of nutria immediately to the CDFW’s Invasive Species program (with photographs if possible)  online, by e-mail to, or by phone to (866) 440-9530.

You should report an observation of nutria on state and federal land immediately to local management of the properties.

CDFW publishes a nutria webpage and a pdf file with pictures and detailed descriptions of the rodents, their preferred habitat and the threat the invaders present to the environment.

Observations on state or federal lands should be immediately reported to local agency staff at that land. CDFW has a nutria webpage and a downloadable PDF with photos and detailed descriptions of these rodents, their preferred habitat and the environmental threats they present.

Nutria are not new to California. They were kept on large nutria farms for their fury coats that were much in demand by the fashion industry. With the collapse of plush fur as a fashion accessory, many farms let their animals go wild. The release of nutria was followed by eradication programs as soon as it became apparent that they pose a significant danger to the environment. By 1978 most, if not all, nutria had been eradicated from California.

CDFW hopes to control and ultimately to eradicate the new infestation with aggressive eradication actions.

I am more skeptical. Nutria reproduce even faster than sus scrofa. They are smaller and leave less obvious ‘footprints’ in the environment. Though they are edible, their reputation as an edible game is somewhat hampered because they look suspiciously like big rats.

But ‘eradication’ nutria can make for a fun afternoon of plinking without the need to navigate steep and treacherous terrain. And, of course, the recoil of a high-powered rifle.

Good luck and have fun putting some nutria on the table.


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