|North American porcupine|
Porcupines are rodents with a coat of sharp spines, or quills, that defend them from predators. They are indigenous to the Americas, Southern Asia, Europe, and Africa. Porcupines are the third largest of the rodents, behind the capybara and the beaver. Most porcupines are about 25–36 in (64–91 cm) long, with an 8–10 in (20–25 cm) long tail. Weighing 12–35 lb (5.4–15.9 kg), they are rounded, large and slow. Porcupines come in various shades of brown, gray, and the unusual white. Porcupines' spiny protection resembles that of the unrelated erinaceomorph hedgehogs and monotreme echidnas.
The common porcupine is an herbivore. It eats leaves, herbs, twigs and green plants like clover and in the winter it may eat bark. The North American porcupine often climbs trees to find food. The African porcupine is not a climber and forages on the ground. It is mostly nocturnal, but will sometimes forage for food in the day. Porcupines have become a pest in Kenya and are eaten as a delicacy. A male porcupine urinates on a female porcupine prior to mating, spraying the urine at high velocity. 
A porcupine is any of 29 species of rodent belonging to the families Erethizontidae (genera: Coendou, Sphiggurus, Erethizon, Echinoprocta, and Chaetomys) or Hystricidae (genera: Atherurus, Hystrix, and Trichys). Porcupines vary in size considerably: Rothschild's Porcupine of South America weighs less than a kilogram (2.2 lb); the Crested porcupine found in Italy, Sicily, North Africa and sub-Saharan Africa can grow to well over 27 kg (60 lb). The two families of porcupines are quite different, and although both belong to the Hystricognathi branch of the vast order Rodentia, they are not closely related.
The eleven Old World porcupines tend to be fairly big, and have spikes that are grouped in clusters.
The two subfamilies of New World porcupines are mostly smaller (although the North American Porcupine reaches about 85 cm or 33 in in length and 18 kg or 40 lb), have their quills attached singly rather than grouped in clusters, and are excellent climbers, spending much of their time in trees. The New World porcupines evolved their spines independently (through convergent evolution) and are more closely related to several other families of rodent than they are to the Old World porcupines. Porcupines have a relatively high longevity and had held the record for being the longest-living rodent, until it was recently broken by the naked mole-rat.
Porcupines' quills, or spines, take on various forms, depending on the species, but all are modified hairs coated with thick plates of keratin, and they are embedded in the skin musculature. Old World porcupines (Hystricidae) have quills embedded in clusters, whereas in New World porcupines (Erethizontidae), single quills are interspersed with bristles, underfur and hair.
Quills are released by contact with them, or they may drop out when the porcupine shakes its body. New quills grow to replace lost ones. From ancient times, it was believed that porcupines could throw their quills at an enemy, but this has long been refuted.
Porcupines are only occasionally eaten in western culture, but are very popular in Southeast Asia, particularly Vietnam, where the prominent use of them as a food source has contributed to significant declines in their populations.
More commonly, their quills and guardhairs are used for traditional decorative clothing. For example, their guardhairs are used in the creation of the Native American "porky roach" headdress. The main quills may be dyed, and then applied in combination with thread to embellish leather accessories such as knife sheaths and leather bags. Lakota women would harvest the quills for quillwork by throwing a blanket over a porcupine and retrieving the quills it left stuck in the blanket.
Porcupine quills have recently inspired a new type of hypodermic needle. Thanks to backward-facing barbs on the quills, when used as needles, they are particularly good at two things – penetrating the skin and remaining in place.
Porcupines occupy a short range of habitats in tropical and temperate parts of Asia, Southern Europe, Africa, and North and South America. Porcupines live in forests, deserts, rocky outcrops and hillsides. Some New World porcupines live in trees, but Old World porcupines stay on the rocks. Porcupines can be found on rocky areas up to 3,700 m (12,100 ft) high. Porcupines are generally nocturnal but are occasionally active during daylight.
- Infraorder Hystricognathi
- Family Hystricidae: Old World porcupines
- African brush-tailed porcupine, Atherurus africanus
- Asiatic brush-tailed porcupine, Atherurus macrourus
- Crested porcupine, Hystrix cristata
- Cape porcupine, Hystrix africaeaustralis
- Indian porcupine, Hystrix indicus
- Malayan porcupine, Hystrix brachyura
- Himalayan porcupine, Hystrix (brachyura) hodgsoni
- Sunda porcupine, Hystrix javanica
- Sumatran porcupine, Hystrix (Thecurus) sumatrae
- Bornean porcupine, Hystrix (Thecurus) crassispinis
- Philippine porcupine, Hystrix (Thecurus) pumilis
- Long-tailed porcupine, Trichys fasciculata
- Parvorder Phiomorpha sensu stricto
- Parvorder Caviomorpha
- Superfamily Erethizontoidea
- Family Erethizontidae: New World porcupines
- Brazilian porcupine, Coendou prehensilis
- Bicolored-spined porcupine, Coendou bicolor
- Andean porcupine, Coendou quichua
- Black dwarf (Koopman's) porcupine, Coendou nycthemera (koopmani)
- Rothschild's porcupine, Coendou rothschildi
- Santa Marta porcupine, Coendou sanctemartae
- Mexican hairy dwarf porcupine, Sphiggurus mexicanus
- Paraguaian hairy dwarf porcupine, Sphiggurus spinosus
- Bahia porcupine, Sphiggurus insidiosus
- Brown hairy dwarf porcupine, Sphiggurus vestitus
- Orange-spined hairy dwarf porcupine, Sphiggurus villosus
- Streaked dwarf porcupine, Sphiggurus ichillus
- Black-tailed hairy dwarf porcupine, Sphiggurus melanurus
- Roosmalen's dwarf porcupine, Sphiggurus roosmalenorum
- Frosted hairy dwarf porcupine, Sphiggurus pruinosus
- North American porcupine, Erethizon dorsatum
- Stump-tailed porcupine, Echinoprocta rufescens
- Bristle-spined porcupine, Chaetomys subspinosus (sometimes considered an echimyid)
- Family Erethizontidae: New World porcupines
- Superfamily Cavioidea
- Superfamily Octodontoidea
- Superfamily Chinchilloidea
- Superfamily Erethizontoidea
- Family Hystricidae: Old World porcupines
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- Porcupines: Wildlife summary from the African Wildlife Foundation
- "Resource Cards: What About Porcupines?" Pacific Northwest National Laboratory
- Porcupine control in the western states hosted by the UNT Government Documents Department
- Porcupine Tracks at the Wayback Machine (archived October 15, 2009): How to identify porcupine tracks in the wild