Actually modified hairs, the black-tipped, yellowish quills are stiff, barbed spines about 3 inches long that can be easily barbs once embedded in another animals' flesh. The Porcupine's feet have 4 toes on the forefeet and 5 on the hindfeet, all with long, curved claws and small textured knobby pads on the bottom. The long claws make depressions far ahead of the oval tracks, which are about 3 inches long and 5 to 6 inches apart. Although the Porcupine is usually regarded as arboreal and found in woodlands, individuals wander widely and have been observed among Creosote in all of the North American deserts. The Porcupine is primarily nocturnal and may rest by day in hollow trees and logs, crevices in rocky bluffs or underground burrows.
Porcupines are strict vegetarians.
In the Spring they feed on leaves, twigs and green plants. In Winter, they chew through the outer bark of fir, hemlock, aspen and pines trees to eat the tender layer of tissue below. Sometimes, they will completely girdle, and thus kill, trees. They may also gnaw used ax handles, canoe paddles and other items for the salt and oil they contain. The two large, front gnawing teeth continue to grow as long as the Porcupine lives.