The common porcupine is a large, short-legged rodent with up to 30,000 bare-tipped quills (modified hairs) covering the upper parts of the body and the dorsal and lateral surfaces of the tail. The quills are scattered among much longer, course guard hairs; the underfur is woolly. The quills are arranged in rows across the body, the longest quills are on the rump, the shortest on the face. Quills used in defense are replaced commencing about 10-42 days after loss. The overall color of the porcupine is dark brown or blackish. The front feet have four toes, the rear feet five; all have strong, curved claws. The soles are naked.
In Oregon, the porcupine is found throughout most of the state east of the Cascade Range. West of the Cascades, it is found in only a few scattered localities. Porcupine attains its greatest abundance in mixed coniferous and hardwood forests.
Porcupines do not hibernate and are active throughout the year. Activity is mostly nocturnal or crepuscular, but those feeding in trees may be observed at any time as they usually do not retire to dens during the daylight hours. Some use is made of dens in winter.
Porcupines make a variety of vocalizations and sounds with the teeth, some which can be heard at considerable distance. They seemingly are intelligent and are able to learn quickly; they have good memories and especially remember being mistreated.