North American Porcupine Erethizon dorsatum

Head and body lengths of E. dorsatum range from 645-680 mm and tail lengths are 145-300 mm. Weights are 3.5-7.0 kg, but large males can weigh as much as 18 kg. The pelage is usually dark brown or black, woolly and dense with the upperparts of the body covered with more than 30,000 quills which are yellowish at the base and have a dark tip. These quills are about 2 mm in diameter and 75 mm long with a barbed end. The underparts of the North American porcupine lack the quills, but are covered with stiff, dark hairs.

E. dorsatum is primarily terrestrial, but the arboreal and the naked feet have strong curved claws which enable it to move easily throughout the trees to get food. There are four toes on the forefoot and five on the hindfoot. The skull is very large in proportion to the body and the eyes are set far apart. Females have two sets of mammae, one pectoral pair and one abdominal pair.

The preferred habitat of E. dorsatum is mixed hardwood and softwood forest, though it is highly adaptable and may be found in open tundra, rangeland and desert. Vegetated riparian areas are preferred, however, when the animal is away from forested areas. E. dorsatum is also a capable swimmer, the quills providing a great amount of buoyancy. Several dens are used in a variety of settings: hollow logs and trees, caves, crevices, burrows, snowbanks, or nests in trees. The North American porcupine has poor vision, but highly developed senses of smell and hearing. It is primarily nocturnal, but will forage during the day as well. E. dorsatum does not hibernate. It will remain in its burrow for long periods of time when the weather is bad, though. Foraging distances from the den site vary from and average of 8 meters in the winter and 150 meters in the summer, using distinctive runways from the den to the food source.

During the winter, the diet consists primarily of pine needles, and the cambium and inner bark layers of trees. In spring and summer, E. dorsatum is treated to buds, tender twigs, roots, stems, leaves, flowers, seeds, berries, nuts and other vegetation.

North American porcupines are generally solitary, though two individuals may share a feeding tree and several individuals may share a den on a rotating basis. Only during the winter may several individuals be found together in one den. In the fall, a number of animals may gather at a nocturnal feeding site and vocalize. Vocalizations are varied, including grunts, moans, coughs, whines and tooth chatters.

The North American porcupine is not an aggressive animal and when threatened will flee or climb a tree to escape harm. If cornered, the North American porcupine erects its quills, which are not shot from the animals body, but will work their way into the skin of an unfortunate victim at the rate of 1 mm per hour. If the quill reaches a vital organ, it can cause death. Among animals that prey on E. dorsatum, a few are very adept at avoiding the quills: bobcats, wolverines and fishers flip the porcupine on its back exposing its vulnerable underside. Great horned owls and other carnivorous mammals also prey on E. dorsatum.

Mating season occurs in fall and early winter with the male and female both engaging in a dance, after which the male sprays the female with urine. Once mating is done, the female repels the male. She is polyestrous and if fertilization has not occurred, she will be receptive again in 25-30 days. Gestation is 207-215 days resulting in one, or sometimes two, offspring. The newborns have open eyes, are covered with long, black hair and short soft quills. They weigh 340-360 grams and can walk somewhat unsteadily, but can climb trees within days and instinctively turns its rump toward danger. Weaning is thought to occur fairly early in the wild as the babies can survive solely on vegetation at about 2 weeks of age. Weight is gained rapidly - about 450 grams per day - and males reach sexual maturity at about 2.5 years. There are records of some individuals living as long as 18 years in the wild.

E. dorsatum is found from C Alaska (USA) to S Hudson Bay and Labrador (Canada), south to E Tennessee, C Iowa, and C Texas (USA), N Coahuila, Chihuahua, and Sonora (Mexico), and S California (USA).