U.S. Department of the Interior

U.S. Geological Survey

USGS FS-020-00 (Updated 4/20/01)

June 2000

For more information, contact:

U.S. Geological Survey/National Wetlands Research Center,

700 Cajundome Blvd., Lafayette, LA 70506; 337-266-8500;

Fax: 337-266-8541; http://www.nwrc.usgs.gov

Nutria, Eating Louisianas Coast

Eating-out might be a term you

associate with a pleasant experience,

especially in south Louisiana where the

food is good and the atmosphere is casual.

Another kind of eat-out in Louisiana that

is not so pleasant, though, is where nutria,

large semiaquatic rodents introduced from

South America, have literally eaten up the

coastline.

Nutria live in fresh, intermediate, and

brackish marshes and wetlands and feed on

vegetation (herbivory) that is vital to

sustaining the Louisiana coastline. Their

eat-outs create openings in the marsh

vegetation, and they are currently affecting

an estimated 100,000 acres of coastal

wetlands.

With Louisianas coastal wetlands

converting to open water at a rate of 25-35

square miles (65-91 square kilometers)

each year, nutria are an additional burden

to an already stressed ecosystem.

The nutria, or coypu (Myocastor

coypus), was introduced into the United

States in 1899 in California for the furfarming industry. Since then, they have

been introduced to many states and

currently have viable populations in 15.

Like many introductions of nonnative

plants and animals, the introduction of

nutria into the United States was intentional and originally viewed as a way to

provide economic benefit.

Subsequent introductions as well as

escapes from captivity resulted in feral

populations. The population along the Gulf

of Mexico coast, for example, reportedly

originated in Louisiana around 1937, when

nutria imported for fur farming escaped

from captivity.

Nutria were also released into the

Louisiana wild by state and federal

agencies to provide a new fur resource and

to control problem plants such as the water

hyacinth (Eichhornia crassipes) and

alligator weed (Alternanthera

philoxeroides). Intentional and accidental

introductions of nutria had an impact in

Louisiana beyond what was originally

realized; by the late 1950s there were an

estimated 20 million nutria in coastal

Louisiana.

Because of increasing damage to sugar

cane and rice fields in the 1950s, the

Louisiana legislature promoted fur harvest

by offering a $0.25 bounty in 16 parishes

(counties) for every nutria killed. To date,

the best method of nutria control has been

trapping and harvest, and approximately

95% of the nutria harvest in United States

occurs in Louisiana. Nutria, a nonnative species from South America,

have been able to thrive in the marshes and

wetlands of Louisiana. They were introduced to

many other states and currently have viable

populations in 15.

Nutria eat-outs, like the one here, create openings in the marsh vegetation that sustains the Louisiana

coastline and are an additional burden for an already stressed ecosystem.
Since 1989, however, low pelt prices

have decreased the harvest, thus increasing

population levels. As with any harvest,

management involves maintaining a

delicate balance between supply and

demand, and there are factors that are

difficult to control or dictate, such as

changing attitudes about wearing fur. Low

demand, high reproductive rates, and low

natural predation have enabled the nutria

population to increase.

Other than annual fur harvesters,

alligators are the only significant predator

of nutria. Nutria are a prime food source

for adult alligators; however, even in areas

with an abundance of alligators, nutria can

thrive if habitat conditions are suitable.

Nutria are extremely prolific, reaching

sexual maturity at six months of age. With

a gestation period of only 130 days, in one

year, an adult nutria can produce two litters

and be pregnant for a third. Litter size

averages from four to five young, which

are born fully furred with their eyes open.

With this high productivity, nutria populations can withstand high predation rates

and still cause significant wetland damage.

Because of the nutrias feeding habits,

high population densities can be especially

damaging to wetland vegetation and

further wetland loss. Nutria predominately

feed on the base of plant stems and dig for

roots and rhizomes in the winter. Their

grazing can strip large patches of marsh,

and their digging overturns the marshs

upper peat layer. Plant growth can be

reduced when grazing is intensive with

little recovery time for the plants or when

grazing is coupled with other sources of

stress.

Moreover, nutria have contributed to the

failure of several planting efforts of

baldcypress, uprooting and eating as many

as 500 newly planted seedlings literally

overnight.

Nutria have been introduced to every

continent except Antarctica and Australia.

Not all countries view nutria as a pest. The

perception of nutria as a pest largely

depends upon the damage they impose as

well as the fluctuating

price of their pelt. In

some countries, they

are considered a

prime resource and

regarded highly for

their pelt. In

Azerbaijan, for

example, breeders

raise a pedigree group

of nutria called

Azerbaijan white

coypus.

 Testing the effectiveness of tree shelters

in reducing nutria damage to planted

seedlings.

 Studying plant responses to grazing

herbivores.

 Studying changes in brackish marsh in

areas of intense animal activity,

including the effects of herbivory on

soil elevation.

 Marking nutria to determine population

estimates.

Recent efforts to

control nutria populations in Louisiana have

been aimed at creating

a market for human consumption of the

meat as well as for fur. Nutria meat is

healthy; it is higher in protein and carbohydrates, and lower in fat and cholesterol

than most game and domestic animals.

Specific research of nutria at NWRC

include:

 Studying the impacts of grazing nutria on

vegetation in coastal wetlands, including plant responses.

 Using models to determine the effects of

nutria on marsh loss.

Nutria pelts drying on racks at Sabine National Wildlife Refuge.

Nutria on grass mats.