|
Nutria - Frequently Asked Questions
 What are nutria?
Nutria are large rodents that look like beavers with long, thin tails. Nutria may weight up to 20 lbs and reach about 24 inches from tip of nose to tip of tail. Nutria have thick brown fur and orange front teeth. They are designed for aquatic life, with webbed feet and eyes, nostrils and ears located high on their heads to enable them to expose as little of their bodies as possible when breathing at the surface of the water.
What Threat Does Nutria Pose to the Health of the Chesapeake Bay?
In the past 40 years, Blackwater National Wildlife Refuge in Dorchester County has lost over 7000 acres of salt marsh from a combination of nutria feeding activity, sea level rise, and erosion of soil that supports marsh plants. Marsh is also being lost on state and private conservation lands.
This represents a significant loss of habitat for nesting waterfowl, including black ducks, which are declining in population, wetland birds, including the state-listed black rail, and a variety of song birds. Fish and crabs depend on salt marsh for shelter and protection from predators and as a source of food, since the plants and sediment support many insects and other invertebrates. The loss of these species, in turn, reduces the value of these areas for commercial fisheries and for local ecotourism, which brings $15 million each year from visitors to Blackwater National Wildlife Refuge alone.
Nutria poses a significant threat not only to the health of the Chesapeake Bay, but also to the very conservation purposes for which state, federal and private conservation refuges were purchased and are maintained, with both public and private funds.
How Do Nutria Cause This Damage?
Nutria eat wetland plants and prefer the roots, rhizomes, and tubers of the following types of plants:
Cordgrass, bulrush, spikerush, chafflower, pickerelweed,
cattails, arrowheads, and flatsedges.
Nutria will eat entire plants and will exploit wetlands in fresh, brackish and salt water. In Maryland, nutria currently pose the greatest threat to salt marshes in the lower eastern portion of Maryland’s Chesapeake Bay, including Dorchester, Wicomico, Somerset, and Worcester Counties and are specifically impacting three-square bulrush. When nutria remove entire sections of bulrush from the marsh, the sediment supporting the plants erodes away and the level of sediment falls, preventing establishment of new native plant colonies. Nutria also fragment the marsh by creating deep swimming channels, preventing less mobile, marsh-dependant species from using all available habitat.
How Many Animals are in the U.S. and Maryland Nutria Populations?
In Louisiana, the population of nutria has risen from a few pairs of animals
to an estimated 20 to 30 million animals. The population of nutria at Blackwater
National Wildlife Refuge was about 7,000 animals before. The Dorchester County
population has been estimated to be as high as 75,000 animals. The larger the
population of nutria, the greater their impact on marsh habitat.
What is the Capacity for Nutria Populations to Grow?
Like most rodents, nutria are very prolific. They are ready to breed at 4-7 months of age and may breed throughout the year. Nutria can produce up to three litters of four offspring each year, but litter sizes can reach 13 young. After mating, females give birth in a little over 4 months and are ready to breed again within 1-2 days of giving birth. Young nutria are capable of surviving without the mother after about 4 days of nursing, but most young continue to nurse for 7-8 weeks and remain with their mother for about 10 weeks.
Mortality, or the percentage of animals that die in a population each year, is estimated to be 80% during the first year of life and few animals live more than 2 or 3 years. Predators of nutria in the Chesapeake Bay include humans, bald eagles, and carnivorous mammals.
Where Are Nutria Considered Native?
Nutria are native to South America.
How Did Nutria Become Established in Maryland?
Introduced at Blackwater National Wildlife Refuge in 1943, where they were farmed for fur. Nutria were introduced to the southern United States early in the 20th Century for this purpose and were subsequently introduced to 22 states by mid-20th Century.
Where are Nutria Found in the United States?
Animals escaped or released from captive populations became established in 18 states across the U.S., including Louisiana, Florida, Texas, Georgia, Alabama, Mississippi, North Carolina, South Carolina, Delaware, and Virginia.
Where are Nutria Found in Maryland?
Nutria are found throughout the Eastern Shore, concentrated in Dorchester County, and in the Potomac and Patuxent Rivers on the Western Shore.
For More Information Contact:
Jonathan McKnight
Associate Director, Habitat Conservation
Wildlife & Heritage Service
Maryland Dept. of Natural Resources
580 Taylor Ave., E-1
Annapolis, MD 21401
(410) 260-8539
Toll-free in Maryland: 1-877-620-8DNR, Ext. 8539
E-Mail: jmcknight@dnr.state.md.us
|
