Nutria

An invasive species, one female nutria can birth up to 200 babies in just a few years of living!

Facts

• Although the record life span of nutria in captivity is 12 years old, most nutria don’t live past the age of three. Some even die within their first year of life. Nutria are considered to have reached old age at the age of four.
• Nutria have characteristic orange teeth as a result of pigment staining from a mineral in their tooth enamel.
• Nutrias are semiaquatic animals. They prefer the water to land. Agile swimmers, they live in submerged dens located at riverbanks and lake margins. They are called “swamp rats” or “swamp beavers” in many countries because of this.
• Impressively, nutria can stay submerged in water for five minutes without breathing.
• Nutria are often mistaken for beavers. They can easily be told apart by their tails. Beavers have flat, paddle-like tails while nutria tails are cylindrical and long.
• Talk about a foodie! Nutrias can eat up to 25% of their own body weight every day, amounting to two and a half pounds of food.
• The nutria is considered an invasive species. The U.S. state of Louisiana offer monetary incentives to people who hunt and kill them, around 5 bucks per tail as of 2012.

Summary

Nutria are large, semiaquatic rodents with a stronger affinity for water than for the land. Hunted for their fur and meat, these animals were taken from their native regions in South America and introduced into the world. Now an invasive species, booming nutria populations are forcing countries to consider creative ways to tackle them.

Scientific Name

The name “nutria” means “otter” in Spanish. Nutrias belong to the order Rodentia with other rodents and to the genus Myocastor. Myocastor is derived from two Ancient Greek words mys meaning “rat” or “mouse” and kastor meaning “beaver.” The description “rat beaver” is an allusion to the physical similarities between the two animals.

The scientific name of the nutria is Myocastor coypus. Nutrias were formerly classified as the only living member of the family Myocastoridae but has now been moved into the spiny-rat family, Echimyidae.

Nutria are also called coypu, coipu, swamp beavers, and nutria rat. It is known around the world either as nutria, coypu, or, in different languages, variations of other common names like “swamp beaver” or “swamp rat.”

The nutria has four recognized subspecies:

• Myocastor coypus bonariensis
• Myocastor coypus coypus
• Myocastor coypus melanops
• Myocastor coypus santacruzae

Evolution and History

Nutria belong to the genus Myocastor which is now a part of the spiny-rat family, Echimyidae. The ancestors of the nutria lived during the Early Miocene Epoch 23.8 to 16.4 million years ago. The fossils of nine extinct genera from which descended the nutria were found in the southern region of South America.

Nutria have developed several adaptations to aid their semiaquatic life. Their webbed feet aid their agile swimming. Female nutrias have mammary glands located high on their flank so that they can nurse their offspring while in the water. Nutrias also live in partially submerged burrows at the margins of lakes, riverbanks, or along the coast of the water body they inhabit. They have dens in these burrows where they hide out during the daytime. They usually come out at night to forage for food when most of their predators tend to be inactive. Fascinatingly, nutrias can hold their breath for up to five minutes while submerged.

Appearance

Nutria have three sets of fur. First is their outer fur which can be yellow or brown. This fur looks very disheveled and unpleasant and measures about three inches in length. Underneath this outer coat is the mid-layer fur which is coarse and dark brown. Finally, underneath this is a lush gray undercoat also called “nutria” and is sought-after in the fashion industry for making clothes. Nutrias also have a distinctive white patch on their muzzles.

Adult nutrias typically weigh around 9 to 20 pounds and reach 16 to 24 inches in body length. Their tails are 12 to 18 inches long. The heaviest nutrias may weigh 35 to 37 pounds and with little surprise seeing as they can consume up to a quarter of their body weight in food daily. Male and female nutria have no distinguishable features. The two sexes look the same, weigh the same, and are generally the same size.

Nutrias are a species of semiaquatic rodents and they have developed many adaptations to suit their partial life in the water. They have webbed feet for more agile swimming. Female nutria also have teats that are located high on their flanks in order to allow their offspring to nurse while they are in the water.

Nutria have about 20 teeth in total and four prominent incisors that never stop growing. Their teeth are characteristically orange due to pigment staining from the mineral iron in their enamel. They also have long whiskers on each side of their cheeks measuring four inches.

Nutria vs. Beavers and Capybara

Nutria look a lot like beavers and capybaras, and are often mistaken for the two. However, the difference is in their tails. Beavers have large, flat tails while the nutria’s tail is long, skinny, and hairless. Also, capybaras don’t have tails. They are significantly larger than nutria and have different behavioral traits.

Behavior

Nutria are super swimmers and spend a lot of time in the water. They reside near bodies of water such as river banks, ponds, lakes, or wetlands. Their bodies have also adapted to a semiaquatic lifestyle. Nutria can stay submerged in water for up to five minutes without breathing. They can snip off aquatic plants underwater without swallowing water by closing off their mouths behind their incisors.

In addition to being fantastic swimmers, nutria are also wonderful burrowers. They live underground in burrows at riverbanks and by the coasts of lakes. These burrows are usually about 3.3 feet long and open at either end with one end leading to a body of water.

Nutria are mostly nocturnal and crepuscular animals, although their activity level depends on their location as well as the time of year. They forage during the daytime if resources are running low, or during winter. These rodents are also very social and a group of them is called a colony.

Nutria are known to be highly aggressive towards domestic animals such as dogs, and humans as well. They are territorial animals and will attack if they feel threatened.

Diet

Nutria are mostly herbivorous animals, but they do eat animals from time to time which makes them omnivores. Their staple diet consists of aquatic plants such as grains, rhizomes, roots, stems, cattails, water lilies, duckweed, leaves, black willow tree bark, tubers, and white clover. Nutria also eat food crops such as corn, rice, alfalfa, and sugarcane. They are known to occasionally consume mollusks and snails as well. However, they are usually strictly herbivorous.

Nutria can eat up to 25% of their body weight in food every single day, which amounts to almost two and a half pounds of food.

They also build floating masses out of vegetation which they use as feeding platforms.

Habitat and Population

The nutria is native to the temperate and subtropical regions of South America, including Argentina, Bolivia, Paraguay, Uruguay, Brazil, and Chile. They inhabit wetlands, marshes, riverbanks, ponds, and lakes and build burrows along the water stretch.

The high demand for nutria fur in the early 19^th century led to the widespread hunting and killing of nutria in South America to meet these needs. This resulted in severe waning of the animal’s population to the point of extinction in their native range. Thus, fur farms were created in other countries where the nutria was introduced such as the United States, Canada, United Kingdom, Denmark, Greece, Japan, Kenya, France, Italy, Germany and Sweden, to name a few.

Many nutria escaped from these fur farms into the wild and became invasive species in their new countries. Some of them were also released when the decline in nutria demand occurred. Their burrowing and excessive eating has been shown to be damaging to the ecosystem. They also started competing with local wildlife (such as muskrats in the United States) for resources and space and are winning. Invasive nutria populations are recognized in at least 15 U.S. states, particularly in Louisiana and Washington. It got so bad that bounties were placed on the animals for killing them, up to five dollars per tail as of 2012.

Nutrias are listed as Least Concern on the IUCN Red List of Threatened Species.

Reproduction and Lifespan

Nutrias are not sexually dimorphic, meaning that the males and females are not easily distinguishable from one another. Male nutrias reach sexual maturity at four months of age while female nutria typically become sexually mature at three months. Sometimes, both male and female nutrias might not reach sexual maturity until nine months old.

Male nutrias share burrows with up to four females and their offspring. After mating, female nutrias gestate for about 127 to 135 days. They usually birth an average of four young per litter and can mate again one to two days after giving birth. The size of the litter tends to alternate between years, with some years producing a smaller litter, and other years a larger one. Female nutrias typically birth two litters in a year and, on average, six litters throughout her lifetime.

Baby nutrias are precocial. They are born fully developed, open-eyed and with fur. Within hours after their birth, they can swim and eat aquatic vegetation. They typically nurse for seven to eight weeks before graduating the nest and leaving their mothers.

Nutria are very prolific animals. One female can produce up to 200 offspring in her lifetime.

Nutria live anywhere from three years to six and a half years in the wild. They are considered to have reached old age at age four. Nutria in captivity can live to be 10 years old, but this is uncommon. Most nutria die within their first year of life. The oldest nutria on record was 12 years old.

Predators and Threats

Nutrias have a sizeable amount of predators that prey on them. These predators include hawks, snakes, dogs, turtles, alligator, bald eagles, and gars. Humans also hunt nutria and rear them for their fur and meat. Nutria are mostly nocturnal and this helps them avoid being predated by animals who are usually awake during the day and asleep at night. They spend the daytime in their burrows and come out at night to forage.

Because they are an invasive species, nutria have been bounty-hunted in several locations within the United States as well as other countries. These animals were imported from their native region in South America to various countries for the purpose of fur farming in the 19^th and 20^th centuries. When the demand for nutria fur went on the decline, fur farmers released the animals into the wild or they escaped. Because of their prolific nature in reproduction, they quickly became a menace to the environment. In Louisiana, the government offered bounties in exchange for killing invasive nutria in order to control their population. In countries like the United Kingdom, programs were set up to eradicate nutria from the ecosystem.

Related Animals

• Capybara
• Beaver
• Muskrat

1. Nutria Fact Sheet, Available here: https://www.laseagrant.org/wp-content/uploads/NIS-Nutria-Fact-Sheet.pdf
2. Wikipedia, Available here: https://en.wikipedia.org/wiki/Nutria
3. National Geographic, Available here: https://www.nationalgeographic.com/animals/mammals/facts/nutria
4. Nutria, Available here: https://nutria.com/biology/
5. Animal Diversity, Available here: https://animaldiversity.org/accounts/Myocastor_coypus/