Porcupines are large rodents with coats of sharp spines, or quills, that protect them against predation.

[1][2] Both families belong to the infraorder Hystricognathi within the profoundly diverse order Rodentia and display superficially similar coats of rigid or semi-rigid quills, which are modified hairs composed of keratin.

Weighing 5–16 kg (12–35 lb), they are rounded, large, and slow, and use an aposematic strategy of defence.

Porcupines' spiny protection resembles that of the only distantly related erinaceomorph hedgehogs and Australian monotreme echidnas as well as tenrecid tenrecs.

[7] Fossils belonging to the genus Hystrix date back to the late Miocene of the continent of Africa.

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.

[citation needed] Porcupines have a relatively high longevity and hold the record for being the longest-living rodent, with one individual named Cooper living over 32 years.

[9] The North American porcupine is a herbivore and often climbs trees for food; it eats leaves, herbs, twigs, and green plants such as clover.

[2] It is mostly nocturnal[10] but will sometimes forage for food during the day, eating bark, roots, fruits, berries, and farm crops.

There are four main displays seen in a porcupine: (in order from least to most aggressive) quill erection, teeth clattering, odour emission, and attack.

[15] Porcupines' quills, or spines, take on various forms, depending on the species, but all are modified hairs coated with thick plates of keratin,[16] and embedded in the skin musculature.

Long reported the taste of the North American porcupine as "vile" and "malodorous" and delightful only to a lover of strong cheese.

[23] The presence of barbs, acting like anchors, causes increased pain when removing a quill that has pierced the skin.

Porcupines occupy a small range of habitats in tropical and temperate parts of Asia, Southern Europe, Africa, and North and South America.