Nutria Rat – information

Nutria semi-aquatic rodent native to South America originally was brought to the United States in 1889 for its fu

Nutria Rat

General

The Nutria Rat (Myocastor coypus,) of the order rodentia, is a large, semi-aquatic rodent native to southern South America. It Nutria semi-aquatic rodent native to South America originally was brought to the United States in 1889 for its fuhas been described as “a cross between a beaver and a New York sewer rat.”1 Now found on 4 continents, and recognized as an invasive wildlife species in the United States (present in 22 states,) measures are being taken to control populations and manage the devastation this species is wreaking on coastal ecosystems.

Description

Nutria rats are large, robust rodents that are well equipped for an aquatic life. They are sometimes mistaken for beavers or muskrats due to similar physical traits, but are approximately 1/3 the size of beavers and larger than muskrats. Their small ears, eyes, and nostrils are situated high on their large heads and remain above water during swimming.2 Valves located in their mouths and nostrils prevent water intake when submerged. Nutria rats have a total of 20 teeth, including 4 large yellow/orange incisors that protrude from the front of their mouths. Their white whiskers are 3” to 5” long. Glands located at the corners of the mouth produce oils that are combed through the fur to provide waterproofing.3 Nutria rats have partially webbed back feet (all back toes are connected by webbing except one that is used much like a thumb.) The front feet, which are smaller and not webbed, have 4 toes that are similar and one toe that is smaller and functions similar to a thumb.4 Nutria rats have stout bodies that appear hump-backed when not in the water. They reach a mature weight of 15 lbs. to 22 lbs. (males tending to be larger,) and a mature length of 27” to 41” (including the tail, which tends to make-up over half of the overall length.) Their tails are thick, round and scaly, with sparse bristly hairs. When swimming, the tail glides smoothly through the water behind the body. Because of a lack of insulation on their tails, Nutria rats living in northern climates tend to loose portions of their tails to frostbite during hard winters.5

Their coats are made of a coarse outer layer comprised of yellow to dark brown shaggy hairs and a lush undercoat (called nutria,) that is soft and grey. It is the undercoat that is sought by trappers. Their muzzles and chins are white. Although uncommon, albino Nutria rats have been observed in the wild.

Nutria rats are strong swimmers and spend the majority of their time in the water (since they are more agile in the water than on land.) They see well underwater and can stay submerged for up to five minutes.

Nutria rats are shy and nocturnal so they are not often seen in the wild. However, they are social within their species and live in large colonies.

On average, Nutria rats live for 8 to 10 years.

Habitat

Nutria rats have adapted to a variety of habitats but always maintain a close proximity to fresh or brackish water. They may be found along riverbanks, lakeshores or coastlands, in wetlands, farm ponds, drainage systems, canals, bayous, swamps, marshes, overgrown lots, or even in cities beneath buildings. They build burrows near water in low vegetation or root systems. The inner chambers of their dens are lined with grasses and located above the water line but are accessed by entrances that are up to 24” in diameter and 12” to 24” below the surface of the water. In marshes, Nutria rats build flat platforms of dead vegetation for feeding, birthing, or grooming purposes.6

Within their habitats, Nutria rats are vulnerable to alligators, large snakes, birds of prey, and turtles.7

Location

Nutria are large rodents that look like beavers with long, thin tailsNutria rats are only native to southern South America. However, because of both accidental and intentional introduction, they can now be found in Canada and 22 of the United States (most highly concentrated along the Gulf Coast, but also found in eastern and northwestern coastal regions,) Europe, and Asia. Louisiana has an estimated population of 5 million Nutria rats.8 The fur of this species was once popular in the fur trade and Nutria rats were domesticated around the world on fur farms (the first recorded domestication in the U.S. was in1889.) Wild populations that were started by farm escapees exploded in size when the nutria fur trade collapsed (during the 1940’s in the U.S.,) forcing farmers to release their rats into the wild because they could no longer afford to keep them. Wild populations were intentionally expanded by wildlife agencies and private companies who attempted to use the rats to control invasive or noxious weeds.9

Diet

Nutria rats are omnivorous surface eaters who often over-harvest their dietary staple, aquatic vegetation (including the roots, stems, leaves, and bark.) They do not eat vegetation in the water, but rather swim with it or carry it back to their platforms to feed. Their diets also include small animals, such as snails and mussels. Nutria rats are capable of consuming 25% of their own body weight every day.10 Their eating habits have proven detrimental to coastal ecosystems, destroying vegetation that is important in the prevention of soil erosion. They are also troublesome to farmers, devouring crops such as rice, corn, alfalfa, wheat, oats, barley, sugarcane, peanuts, and vegetables.11

Reproduction

Nutria rats are prolific reproducers. Typically, a male will live in the same burrow as several females and breed throughout the year. Each female has, on average, 2 to 3 litters a year, each consisting of 1 to 11 young (but usually 4 to 6.) It has been observed that litter sizes are cyclical, with a large litter of 4 to 6 young followed by a small littler of 2 to 4, and so on.12 Gestation lasts slightly longer than 4 months and the young reach sexual maturity in 4 to 8 months, leaving their mother after only 1 to 2 months. Females’ teats are situated high on their backs so the young may feed while she is swimming. Females are ready to breed within days of birthing a litter.13

Notes of Interest

Common names of the Nutria rat include coypu, coypu rat, swamp beaver, and nutria.14

The aquatic diet of the Nutria rat is partially to blame for an increased rate of coastal erosion. In Louisiana, with a population estimated to be around 5 million, the nutria rat is responsible for a rate of erosion of 40 square miles per year. This species damages and destroys vegetation that is necessary for anchoring soil, turning marshes and wetland environments into open water. Additionally, Nutria rats have been known to undermine levees, dams, buildings and roadbeds. Nutria rats have also negatively affected agricultural resources and are responsible for disease transmission. They may carry tuberculosis, septicemia, blood flukes, tapeworms, liver flukes, and a type of nematode that causes “nutria itch,” a rash that is spread through water contaminated by feces and urine.

Federal, state, and local governments are working closely with wildlife agencies to manage Nutria rat populations and protect native vegetation and resources.15

1. http://www.usatoday.com/story/news/nation/2013/05/09/nutria-rats-louisiana-erosion/2147077/
2. http://animals.nationalgeographic.com/animals/mammals/nutria/
3. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
4. http://www.nationaltrappers.com/nutria.html
5. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
6. http://www.nationaltrappers.com/nutria.html
7. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
8. http://www.usatoday.com/story/news/nation/2013/05/09/nutria-rats-louisiana-erosion/2147077/
9. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
10. http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Myocastor_coypus2.html
11. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
12. http://www.nationaltrappers.com/nutria.html
13. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
14. http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Myocastor_coypus2.html
15. http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf

http://animals.nationalgeographic.com/animals/mammals/nutria/
http://www.usatoday.com/story/news/nation/2013/05/09/nutria-rats-louisiana-erosion/2147077/
http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/fs_nutria10.pdf
http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Myocastor_coypus2.html
http://www.nationaltrappers.com/nutria.html

 

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North American Porcupine – Information

The North American porcupine is second only to the beaver as the largest rodent native to this continent.

North American Porcupine

General

The North American Porcupine (Erethizon dorsatum,) is the largest species of porcupine and the only one that can be found inThe North American porcupine is second only to the beaver as the largest rodent native to this continent. the United States and Canada. Within their range, they are the second largest species of rodent, aside from the beaver. Although not an aggressive animal, porcupines are equipped with a coat of sharp defensive quills that makes them easily identifiable. This species faces no risk and enjoys an extensive geographic range.

Description

The North American Porcupine is easily identifiable by their stout lumbering bodies and spiny coats. NAP’s reach a mature length of 33” to 46” (the tail comprises approximately 1/3 of that length.) Adults weigh between 12 to 35 lbs. (males tend to be the larger sex.)1 NAP’s have small ears, small heads, and large front teeth that aid in consuming wood. There is a prominent diastema between the front teeth that allows them to draw in their lips while gnawing. Their skulls exhibit a lack of canines. Like other hystricomorphs, they have unique chewing muscles.

The name porcupine is derived from the Latin for “quill pig.” Their coats are comprised of three types of hair: a soft, dense woolly undercoat, long, course, brownish-yellow to black guard hairs, and quills. There are 24 species of porcupines that have coats made of more than 30,000 quills that act as sharp defense mechanisms. These tubular quills are filled with a spongy matrix (making them rigid but light,)2 and cover a porcupine’s head, back, sides and tail. The longest quills are found on the rear and may be up to 12” long, while the shortest quills are on the cheeks.3 The quills located within a central black line on their lower backs and tails are accented with white. This contrast appears on porcupines by three months old and acts as a preliminary warning to approaching predators (many being color blind.)4 Porcupines are non-aggressive mammals that only attack if they are unable to escape a threat. Typically, their quills lay flat but in defense, these quills become erect to fend-off predators. If an attack occurs, the porcupine lashes out at the predator, and the quills detach from the porcupine’s body (despite popular belief, porcupines cannot throw their quills.) The quills have sharp tips and barbs that embed into the predator’s body. The predator’s body heat causes the barbs to expand and muscle movements push the quills further into the predator’s skin. Embedded quills may cause infection or death.5 Growing new quills is possible but difficult for porcupines. To avoid losing quills, porcupines exhibit several warning behaviors to fend off predators before an attack ensues. These include visual cues (contrasting warning colors and erected quills,) acoustic clues (teeth chattering,) and chemical clues (porcupine’s emit a strong chemical odor when threatened.)

The porcupine is a quill-bearing rodentPorcupines are well suited for climbing and spend much of their time in trees. Different trees are chosen for feeding and resting. Their feet feature specific adaptations that allow them to grip surfaces and brace themselves high off the ground. They have four long claws on their front feet in addition to a vestigial thumb, and five long claws on the back feet. The palms and soles of their feet are hairless and have pebbly surfaces that create friction with surfaces. Porcupines often secure themselves when climbing with their hind feet and grasp food with their front feet. The quills are also useful climbing implements. Quills located on the tail are thrust into the tree to help stabilize the porcupine and prevent downward sliding. Porcupines are known to spend the majority of time in trees; however, this behavior is directly related to the amount of ground cover available and the types of predators within a habitat. If appropriate ground cover exists, a porcupine will tend to forage and take cover on the ground more often. NAP’s are also good swimmers, aided by their lightweight quills that help keep them afloat.

They are solitary animals but are known to den and forage with other porcupines during the winter, most likely for protection from predators. These groups do not tend to reflect mating preferences. They build their dens in hollow trees, rock piles or caves. These dens are not used for hibernation, rather sporadically throughout the winter during severe weather.

Both males and females establish and defend territories. Males establish territories that overlap those of several females, but never that of another dominant male. Females’ territories tend to be consistent in size but the size of a male’s territory reflects his age and dominance. Juvenile males settle and establish their initial territories within their birth territories. As males mature, their territories increase in size. Juvenile females part from their birth territories and establish new territories before they reach maturity.6

Porcupines use several methods of communication with other members of their species and with predators. They are vocal animals, creating sounds that include moans, grunts, coughs, wails, whines, shrieks and tooth chattering (used to warn predators.)7 NAP’s also emit chemical signals and display the white/black markings on their quills when confronted by a threat. Their padded palms and soles provide them with a keen sense of touch.

Porcupines in the wild may live up to 18 years. It has been observed that a porcupine’s life expectancy is proportionate to the health and longevity of their grinding teeth. By 12 years of age, these teeth begin to show wear, resulting in a diminished diet and, therefore, a diminished body mass.

Habitat

NAP’s have adapted to many types of climates due to their extensive range that includes a variety of elevations and geographic locations. They may be found living in coniferous or deciduous forests, savannahs, grasslands, mountains, or open tundra. Their behaviors are impacted by their habitat. In the Pacific Northwest, porcupines tend to be more ground dwelling, while populations in New York are primarily arboreal.

Within their habitats, porcupines have many predators, despite their weaponry. These include bobcats, coyotes, wolves, lynx, mountain lions, fishers, wolverines, and birds of prey. These predators have adapted to the porcupine’s weaponry, attacking from the front and flipping the porcupine over exposing its vulnerable stomach.

Location

The NAP has the most northern geographic range of all porcupine species. Their range includes most of North America, spanning from the Arctic Ocean to northern parts of Mexico.

Diet

Porcupines have herbivorous diets that vary seasonally. During the spring and summer, their feeding rates decrease due to the increased availability of and their preference for high protein foods. Their diets include leaves, clover, twigs, bark, grasses, flowering herbs, and fruit (especially apples.) The herbivorous nature of their diets affects their sodium metabolism, causing porcupines to crave salt. As a result, they are driven to chew on wooden implements, structures, vehicles, and other items with residual salt. They are generally nocturnal foragers.

Reproduction

They breed once a year, between late summer and early fall. Females secrete chemicals, make high-pitched vocalizations, and mark with urine to alert males of their 8 to 12 hour estrous period that occurs prior to ovulation. Sexually mature males fight to establish sexual dominance, using loud vocalizations, biting, and erect quills. The dominant, and often largest, male establishes a breeding territory (which he may use for up to three seasons,) and wins breeding rights (and must defend the pre-estrous female for 1 to 4 days until copulation.) The dominant male performs a peculiar mating dance, which includes spraying the female’s head with urine. This display will continue until the female becomes receptive to the dance and mating. A male may mate with several consenting females.

Copulation takes place on the ground and may last for several hours. Mating ends when a vaginal plug is formed by an enzymatic action that occurs in the semen. The plug prevents other males from mating with the female.

After a gestational period of 210 days, the female gives birth to a single baby. The newborn has soft quills (which harden an hour after birth,) and weighs between .9 to 1.2 lbs.

The mother nurses her young for approximately 130 days, although young porcupines can eat solid food within a few days of birth. For the first 6 weeks, the baby remains close to its mother. The female sleeps and feeds in trees during the day (leaving her baby hidden on the ground nearby,) and returns to her baby at night.

By six weeks old, the baby begins following its mother to feeding trees, remaining at the base while she feeds. Over the next few months, the distance between the mother and her offspring increases during foraging trips and by 5 months old, the juvenile is independent (left by its mother to survive alone during the upcoming winter.)

Female reach sexual maturity by 25 months old. Males do not reach sexual maturity until 29 months old.

Notes of Interest

While quills are obviously dangerous for predators, they pose some risk to porcupines as well. Porcupines can fall out of trees, resulting in self-impalement. Additionally, the force it takes to impale a predator with quills might exceed the weight of the porcupine, resulting in a difficult or impossible separation of quills from the porcupine.

Native Americans once revered the porcupine for its meat and quills (which were used as decoration and to establish status.)

NAP’s are considered a pest by the timber industry. Their tendency to feed on bark and twigs leaves trees stunted or deformed and unsuitable to be turned into lumber.8

1. http://animals.nationalgeographic.com/animals/mammals/porcupine/
2. http://animaldiversity.ummz.umich.edu/accounts/Erethizon_dorsatum/
3. http://www.nhptv.org/natureworks/porcupine.htm
4. http://animaldiversity.ummz.umich.edu/accounts/Erethizon_dorsatum/
5. http://www.nhptv.org/natureworks/porcupine.htm
6. http://animaldiversity.ummz.umich.edu/accounts/Erethizon_dorsatum/
7. http://animals.nationalgeographic.com/animals/mammals/porcupine/
8. http://animaldiversity.ummz.umich.edu/accounts/Erethizon_dorsatum/

http://animals.nationalgeographic.com/animals/mammals/porcupine/
http://www.nhptv.org/natureworks/porcupine.htm
http://animaldiversity.ummz.umich.edu/accounts/Erethizon_dorsatum/

 

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