Old World porcupines are stout, heavily-built animals, with blunt rounded heads, fleshy mobile snouts, and coats of thick cylindrical or flattened spines, which form the whole covering of their body, and are not intermingled with ordinary hairs. The habits of most species are strictly terrestrial. They vary in size from the relatively small Brush-tailed Porcupines with body lengths of , and a weight of , to the much larger Crested Porcupines, which are long, discounting the tail, and weigh from .
The various species are typically herbivorous, eating fruit, roots, and bulbs. Some species also gnaw on dry bones, perhaps as a source of calcium. Like other rodents, they have powerful gnawing incisors, and no canine teeth. Their dental formula is:
One or two (or, rarely, three) young are born after a gestation period of between 90 and 112 days, depending on the species. Females typically give birth only once a year, in a grass-lined underground chamber within a burrow system. The young are born more or less fully developed, and the spines, which are initially soft, harden within a few hours of birth. Although they begin to take solid food within two weeks, they are not fully weaned until 13 to 19 weeks after birth. The young remain with the colony until they reach sexual maturity at around two years of age, and share the burrow system with their parents and siblings from other litters. Males, in particular, help defend the colony from intruders, although both sexes are aggressive towards unrelated porcupines.
These rodents are also characterized by the imperfectly rooted cheek-teeth, imperfect clavicles or collar-bones, cleft upper lip, rudimentary first front-toes, smooth soles, six teats arranged on the side of the body, and many cranial characters.
The Crested Porcupine (Hystrix cristata) is a typical representative of the Old World porcupines, and occurs throughout the south of Europe and North and West Africa. It is replaced in South Africa by the Cape Porcupine, H. africaeaustralis, and in India by the Malayan Porcupine (H. leucura).
Besides these large crested species, there are several smaller species without crests in north-east India, and the Malay region from Nepal to Borneo.
The genus Atherurus includes the brush-tailed porcupines which are much smaller animals, with long tails tipped with bundles of flattened spines. Two species are found in the Malay region and one in Central and West Africa. The latter species, the African Brush-tailed Porcupine (Atherurus africanus), is often hunted for its meat.
Trichys, the last genus, contains one species, the Long-tailed Porcupine (Trichys fasciculata) of Borneo. This species is externally very similar to Atherurus, but differing from the members of that genus in many cranial characteristics.