North American porcupine

North American porcupine Temporal range: Pleistocene - Recent
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Erethizontidae
Subfamily:	Erethizontinae
Genus:	Erethizon F. Cuvier, 1823
Species:	E. dorsatum
Binomial name
Erethizon dorsatum (Linnaeus, 1758)
Subspecies
E. d. dorsatum E. d. bruneri E. d. couesi E. d. epixanthum E. d. myops E. d. nigrescens E. d. picinum
Synonyms
Erethizon dorsata Erethizon dorsatus

The North American porcupine (Erethizon dorsatum), also known as the Canadian porcupine or common porcupine, is a large rodent in the New World porcupine family. The beaver is the only rodent in North America that is larger than the North American Porcupine. The porcupine is a caviomorph rodent whose ancestors rafted across the Atlantic from Africa to Brazil over 30 million years ago, and then migrated to North America during the Great American Interchange after the Isthmus of Panama rose 3 million years ago.

They range from Canada, Alaska, and into northern Mexico. They are commonly found in coniferous and mixed forested areas, but have adapted to harsh environments such as shrublands, tundra, and deserts. They make their dens in hollow trees or in rocky areas.

Origin

The word "porcupine" comes from the middle or old French word porcespin, which means quill pig. Its roots derive from the Latin words porcus or pig and spina meaning thorns. Other colloquial names for the animal include quill pig. It is also referred to as the Canadian porcupine or common porcupine. The porcupine's scientific name, Erethizon dorsatum, can be loosely translated as "the animal with the irritating back". Several native American names exist, such as the Lakota name pahin meaning quill and the Chipewyan name ts'l.

Evolution

The North American porcupine is descended from South America, where all New World porcupines or hystricomorphs evolved. Erethizon appeared in North America shortly after the two continents joined together in the later Tertiary period. Other hystricomorphs also migrated, but Erethizon was the only one to survive north of Mexico. No known fossils are attributed to hystricomorphs prior to the late Tertiary period. Some fossils, such as species from the family Paramyidae, show resemblance to the porcupine, but they are so primitive and generalized that they could be ancestors to all later rodents.

South American hystricomorphs first appeared in the Lower Oligocene period. They are thought to have migrated from Africa, ancestors of the Old World porcupines or Hystricidae or they originated based on a migration of the North American Paramyidae.

The earliest appearance of E. dorsatum is from the Pleistocene era found along the Arroyo del Cedazo near Aguascalientes, Mexico.

Subspecies

Seven subspecies of E. dorsatum are recognized. They are subdivided by different ranges across North America. By far the most common is E. d. dorsatum, which ranges from Nova Scotia to Alberta and from Virginia to the Yukon. E. d. picinum occupies a small range in northeastern Quebec and Labrador. E. d. couesi is the most southern ranging from northern Mexico to Colorado. E. d. bruneri can be found in the midwest from Arkansas to Montana. The last three are western species. From south to north they are E.d. epixanthum, E. d. nigrescens, and E. d. myops.

Characteristics

Juvenile male – young males spend their first winters with their mothers

E. d. dorsatum, resting in a tree, Ottawa, Ontario

Porcupines are usually dark brown or black in color, with white highlights. They have a stocky body, a small face, short legs, and a short, thick tail. This species is the largest of the New World porcupines and is one of the largest North American rodents, second only to the American beaver in size. The head-and-body length is 60 to 90 cm (2.0 to 3.0 ft), not counting a tail of 14.5 to 30 cm (5.7 to 11.8 in). The hind foot length is 7.5 to 9.1 cm (3.0 to 3.6 in). Weight can range from 3.5 to 18 kg (7.7 to 39.7 lb), although they average about 9 kg (20 lb).

The porcupine is the only native North American mammal with antibiotics in its skin. Those antibiotics prevent infection when a porcupine falls out of a tree and is stuck with its own quills upon hitting the ground. Porcupines fall out of trees fairly often because they are highly tempted by the tender buds and twigs at the ends of the branches. The porcupine, wolverine, and the skunk are the only North American mammals that have black and white colours because they are the only mammals that benefit from letting other animals know where and what they are in the dark of the night.

Quills

The most distinguishing feature of the porcupine is its coat of quills. An adult porcupine has about 30,000 quills that cover all of its body except its underbelly, face, and feet. Quills are modified hairs formed into sharp, barbed, hollow spines. They are used primarily for defense, but also serve to insulate their bodies during winter. Porcupines do not throw their quills, but when threatened, they contract the muscles near the skin which causes the quills to stand up and out from their bodies. When the quills are in this position, they become easier to detach from the body, especially when the porcupines swing their tails towards attackers. The barbs at the tip become lodged in the flesh of an attacker and are difficult and painful to remove. The quills are normally flattened against the body and in this position are less easily dislodged.

Stink

The North American porcupine has a strong odor to warn away predators, which it can increase when agitated. The smell has been described as similar to strong human body odor, goats, or some cheeses. The odor is generated by a patch of skin called the rosette, on the lower back where modified quills serve as osmetrichia to broadcast the smell. The characteristic odor comes from the R-enantiomer of delta-decalactone. Not present is the S-enantiomer which smells like coconut and is used in flavorings and perfumes.

Ecology

Diet

During the summer, they eat twigs, roots, stems, berries, and other vegetation. In the winter, they mainly eat conifer needles and tree bark. Porcupines are selective in their eating; out of 1000 trees in the Catskill forest, one or two are acceptable lindens, and one is a bigtooth aspen.

Behavior

Porcupines are nearsighted and slow-moving. Porcupines are mainly active at night (nocturnal); on summer days, they often rest in trees. They do not hibernate, but sleep in and stay close to their dens in winter. The strength of the porcupine's defense has given it the ability to live a solitary life, unlike many herbivores, which must move in flocks or herds. Consequently, the porcupine has "an extraordinary ability to learn complex mazes and to remember them as much as a hundred days afterward".

Defense

The North American porcupine has specific behaviors to warn or defend against predators. It has a strong warning odor which it can increase when agitated. When threatened, an adult porcupine can bristle its quills, displaying a white stripe down its back, and use its teeth to make a warning, clacking sound. If the olfactory, visual, and auditory warnings fail, then it can rely on its quills. An adult porcupine when attacked turns its rear to the predator. When approached, the porcupine can swing its tail at an attacker's face. Despite popular myth, the porcupine does not throw its quills. Instead, when it comes in contact with the attacker, it can easily penetrate and become embedded in its skin. Each quill contains microscopic barbs which allow it to stick into the flesh of an attacker. This strategy is successful against most attacks. With a face full of quills which can be very painful, an attacking creature often retreats. Its last line of defense is to climb a tree which provides protection from most predators.

Predators

Natural predators of this species include fishers (a cat-sized marten), wolverines, coyotes, wolves, bears, and cougars, as well as humans. The only known avian predators of this species are golden eagles and great horned owls.

The North American porcupine is most at risk (other than humans) to the fisher (Martes pennanti). Fishers are related to the weasel and weigh up to 5.5 kg. Fishers have two advantages that make them capable hunters of the porcupine. First, they are agile tree climbers. If a fisher locates a porcupine, it cannot hide by fleeing into a tree because the fisher can pursue it and force it down to the ground. A porcupine can sometimes defend itself by facing the trunk on a branch and presenting its tail to the fisher. If the fisher manages to force a porcupine down to the ground, the porcupine will try to present its hind quarters and tail to the attacker, but the fisher is quick and agile. As it circles the porcupine, every chance it gets, it bites the face. After repeated attacks, the porcupine eventually weakens, allowing the fisher to bite the porcupine's underbelly, thus killing it. The fisher will then consume the porcupine through the chest and abdomen, avoiding the quills. One study suggested that since male fishers are larger than females, only males are likely to hunt porcupines.

Another effective predator is the mountain lion. It does not bother with quill avoidance, but tolerates them. Some individuals have been found with dozens of quills embedded in their gums to no ill effect. It can climb trees, so its favorite method is to position itself below the porcupine and knock it to the ground, where it is quickly dispatched. Other predators can attack, such as wolves, lynx, and great horned owls, but do not pose much of a threat.

Reproduction

Porcupines prior to mating. The female is higher in the tree.

Female porcupines are solitary for most of the year except during the fall, when breeding season begins. At this time, they secrete a thick mucus which mixes with their urine. The resulting odor attracts males in the vicinity. Males that approach a female do not automatically begin mating. The first male that comes along typically sits in the same tree below a female. If another male approaches, he may fight for the right to mate. Once a dominant male is successful, he approaches the female and uses a spray of his urine on the female. Only a few drops touch the female, but the chemical reaction allows the female to fully enter estrus. Once this is accomplished high in the tree, the mating process takes place on the ground. When porcupines are mating, they tighten their skin and hold their quills flat, so as not to injure each other. Mating may occur repeatedly until the female loses interest and climbs back in to the tree.

The North American porcupine has a long gestation period relative to other rodents. The female's pregnancy lasts for 202 days. By contrast, the North American beaver, which is comparable in size, has a gestation period of 128 days. The eastern grey squirrel (Sciurus carolinensis) has a gestation period of just 44 days. Porcupines give birth to a single young. At birth, they weigh about 450 g, which increases to nearly 1 kg after the first two weeks. They do not gain full adult weight until the end of the second summer about 4.5 kg. Their quills harden soon after birth.

Female porcupines provide all the maternal care. For the first two weeks, the young rely on their mother for sustenance. After this, they learn to climb trees and start to forage. They continue to nurse for up to four months, which coincides with the fall mating season. They stay close to their mothers. Mother porcupines do not defend their young, but have been known to care for them even after death. In one case, when a baby had fallen to its death from a tree, the mother came down and stayed by her baby's side for hours waiting vainly for the baby to revive.

Life expectancy

North American porcupines have a relatively long life expectancy. Some individuals have been found to live up to 30 years of age. Common causes of mortality include predation and starvation. Porcupines can also die from falling out of a tree and are they are also killed by motor vehicles.

Porcupines and humans

They are considered by some to be a pest because of the damage that they often inflict on trees and wooden and leather objects. Plywood is especially vulnerable because of the salts added during manufacture. The quills are used by Native Americans to decorate articles such as baskets and clothing. Porcupines are edible and were an important source of food, especially in winter, to the native peoples of Canada's boreal forests. They move slowly (having few threats in its natural environment which would give it the need to flee quickly) and are often hit by vehicles while crossing roads.

Conservation status

Globally, the North American porcupine is listed as a species of least concern. It is common throughout its range except in some U.S. states in the southeast part of its range. For example, it is listed as a species in need of conservation in Maryland. As of 1999, 15 remnant populations remain scattered throughout north-central Mexico. They live in riparian forests, mesquite scrubland, grasslands, and thorn forests. They are threatened by hunting and habitat loss. As of 1994, it was listed as an endangered species in Mexico.

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  Bark of sugar maple eaten by a porcupine

• Porcupine tracks in sand.jpg

  Tracks in sand (human handprint shown for scale)

External links

• Porcupine videos, photos, and facts Arkive.org