The North American porcupine (Erethizon dorsatum), also known as the Canadian porcupine, is a large quill-covered rodent in the New World porcupine family. It is the second largest rodent in North America after the North American beaver (Castor canadensis). The porcupine is a caviomorph rodent whose ancestors were believed to have crossed the Atlantic from Africa to Brazil 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.
Etymology The word "porcupine" comes from the middle or old French word porcespin, which means 'thorn 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". Indigenous terms for it include the Lakota name pahin meaning quill, the Ho-Chunk name waxąhį, and the Chipewyan name tsʼl.
Taxonomy and evolution The North American porcupine migrated 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. 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 purported appearance of E. dorsatum in the fossil record is from the Pleistocene (Irvingtonian) era, found along the Arroyo del Cedazo near Aguascalientes, Mexico. However, the validity of this fossil's taxonomy is a cause for debate, with some paleontologists arguing that it represents a member of the genus Coendou (the prehensile-tailed porcupines) instead. The earliest uncontroversial fossils of E. dorsatum, found in the Conard Fissure of Arkansas, date back to the Middle Pleistocene (~130,000 YBP).
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 found in the west. From south to north they are E.d. epixanthum, E. d. nigrescens, and E. d. myops.
Description
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 the second largest rodent endemic to North America, after the American beaver (the Lesser capybara, which is larger, does range into North American Panama, but mostly occurs in South America). 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). Weight in adult females can average some 7 kg (15 lb) while 5 wild-caught males averaged 10.67 kg (23.5 lb). The porcupine, the wolverine, and the skunk are North American mammals that have strongly contrasting black-and-white coloration, which benefits them by letting other animals know where and what they are in the dark of night. The coloration of E. dorsatum generally does not vary. However in the Pacific Northwest, members of the E. d. epixanthum subspecies have been found with a recognizable yellow coloration to their quills. The porcupines found with this distinct coloration did not have albinism and the eyes and nose had their typical pigmentation, they are believed to be isabelline in terms of coloration.
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. The quills are normally flattened against the body and in this position are less easily dislodged. Porcupines do not throw their quills, but when threatened contract superficial muscles which cause the quills to stand up and out from their bodies. In this position they become easier to detach from the body, especially when the tail is swung toward an attacker. The barbs at the end of the spines lodge in the flesh of a victim and are difficult and painful to remove. The quills have a fatty acid coating which gives them antibiotic properties that help protect the porcupines from injuries. This helps 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 succulent buds and tender twigs at the ends of the branches.
Distribution and habitat In eastern North America, porcupines range from Canada to the Appalachian Mountains in West Virginia and Maryland, though east of the Appalachians their range extends no farther south than northern New Jersey. In the west they range from Alaska to northern mountains in Mexico. They are commonly found in coniferous and mixed forested areas, but have adapted to harsh environments, such as shrublands and tundra. They make their dens in hollow trees or in rocky areas.
Ecology
Diet
Porcupines are herbivores. During the summer, North American porcupines eat twigs, roots, stems, fruits, leaves, and other vegetation. In the winter, they eat mainly conifer needles and tree bark. Porcupines are selective in their consumption, but the degree of selectivity depends on the season.
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