Invasive Species Alert! Coypu River Rat (Nutria) confirmed in Los Banos, California

As some of you may have heard- the Bay-Delta (San Francisco Bay and the Sacramento-San Joaquin River Delta in California) is one of the most invaded estuaries in the world (Cohen and Carlton, 1998).

Yesterday, at the IEP Aquatic Vegetation Project Work Team Meeting, I found out that one more exotic species will likely cause harm to this important ecosystem (unless we can stop it of course!).

Details-David Kratville, a Senior Environmental Scientist at the California Dept. of Food & Agriculture, called in yesterday to inform all of us at the meeting that a Coypu River Rat / Nutria was caught by a trapper doing beaver control work near Los Banos California (just south of the legal Delta Boundary)

Photos of nutria from left to right by Joyce Gross at UC Berkeley and Tony Northrup.

Damage- This river rat,  Myocastor coypus, is an aquatic rodent native to South America and can cause massive damage to ecosystems and native species. Nutria consumes up to 25% of its body weight daily, and destroying additional plants and marsh area while burrowing for food. Nutria feeds primarily on marsh plants, including the base of the plants, and often dig through the soil for additional roots and rhizomes to eat. Additionally, nutria is known to carry many pathogens and parasites that threaten humans, livestock and pets such as: bacteria that cause tuberculosis and septicemia, tapeworms, a nematode (Strongyloides myopotami, resulting in a rash known as “nutria itch”), and blood and liver flukes. All of these pathogens can contaminate swimming areas and drinking water supplies.

kjp-52-531-g002.jpg
Strongyloides myopotami recovered from a feral nutria in Korea-Figure from (Choe et al. 2014)

History of Introduction- Although nutria was originally purposefully introduced for fur trade and control of aquatic weeds to Elizabeth Lake in Ca in 1899, and later in the 1930s in many other southern states- the damage from this species was soon recognized and eventually an eradication program in California was successful, with eradication announced in 1978. Unfortunately… it looks like this menace of a species is back.

What to do? –All is not lost at this early stage of detection. The best method at this point is to eradicate or relocate the current population before it grows (and hope that we don’t have too many gravid females in the area). Early control is key since nutria has a high population growth rate potential as they reproduce fast and all year round. If you spot this River Rat in California (see photos above), Immediately contact the CDFW Invasive Species Program to report your sighting ONLINE, by email to Invasives@wildlife.ca.gov, or by calling (866) 440-9530.  If this species is found in California, do not release it. More information on the current status of nutria near the Bay-Delta will be posted to this blog as I obtain further updates.

Additional information on nutria


Carter, J. & B. Leonard. 2002. A review of the literature on the worldwide distribution, spread of, and efforts to eradicate the coypu (Myocastor coypus). Wildlife Society Bulletin 30: 162-175.

Carter, J., Foote, A.L. & Johnson-Randall, A. 1999. Modeling the effects of nutria (Myocastor coypus) on wetland loss. Wetlands 19: 209. doi:10.1007/BF03161750

Cohen, A.N., Carlton, J.T., 1998. Accelerating invasion rate in a highly invaded estuary. Science 279, 555-558.

Choe, S., Lee, D., Park, H., Oh, M., Jeon, H.-K., & Eom, K. S. 2014. Strongyloides myopotami (Secernentea: Strongyloididae) from the Intestine of Feral Nutrias (Myocastor coypus) in Korea.  The Korean Journal of Parasitology,  52(5), 531-535. DOI:10.3347/kjp.2014.52.5.531


Advertisements