North American porcupines are found at the northern most range of all porcupines. They inhabit most of North America between the Arctic Ocean and northern Mexico. Porcupines are found throughout much of Alaska and Canada, in the northern part of the Great Lakes region, all throughout the west and northeast regions of the United States. Populations have been studied extensively in the eastern deciduous forests of New York and Massachusetts, the Great Basin Desert, and the woodlands of Texas.
N.A. porcupines utilize a broad variety of habitats. With an extensive range, porcupines can be found in varied climates, and at varied elevations. Because their habitat varies geographically it can include open tundra, deciduous forests, and desert chaparral.
Porcupines are generalist herbivores. Diets vary throughout the year in response to minute changes in plant chemistry. Feeding rates also change seasonally. Throughout the spring and summer months, when high protein foods are readily available, feeding rates are reduced. However, in the autumn, feeding rates increase, probably in preparation for the winter scarcity of high quality forage.
Although typically a generalist, research has shown some selectivity between plants with higher nutrient content.
Plants eaten by porcupines include sugar maple trees, basswood, aspen, sapling beech trees, aspen catkins, raspberry stems, grasses, flowering herbs, oak acorns, beechnuts, and a large amount of apples. Herbivory has an effect on the sodium metabolism of porcupines, which results in a desire for salt. Porcupines will chew on the wooden handles of human tools, other human-made wood structures, and areas of collected roadside salt runoff.
Porcupines feed primarily at night. This is related to changes in plant and leaf chemistry at night. Porcupines take advantage of the added nutrients available during the nighttime metabolic processes of plants.
N.A. porcupines usually weigh between 25 to 40 lbs. Male porcupines are generally larger than females.
North American porcupines posses about 30,000 quills covering their body from their snout to the tip of their tail but are absent from their underside. N.A. Porcupines are the only species of mammal in North America to use quills to deter predators. When a porcupine makes contact with an attacker it needs to quickly separate from the quills, and thus separate from the enemy, so they have evolved a unique quill-release system. Quills have a design that promotes their movement deeper into a predator once they have been embedded. The quills are not hollow, but are filled with a spongy matrix, which makes them very rigid but light.
Even with this elaborate defense system, certain predators still occasionally prey on porcupines. There are several predators that have been known to kill a porcupine. The list includes lynx (lynx Canadensis), bobcats (Lynx rufus), coyotes (Canis latrans), wolves (Canis Lupus), wolverines (Gulo gulo), martins (Martes pennanti), and great horned owls (Bubo virginianus). The most aggressive porcupine predators include fishers and mountain lions. Fishers will attack from the front repeatedly, avoiding the tail quills, until they are able to flip a porcupine on its back and attack the unprotected belly area. Mountain lions supposedly make no attempt to avoid the quills of porcupines; instead they attack at will and deal with the consequences.
N.A. porcupines are primarily solitary, spending most of their time alone foraging for food. There is some sharing of dens in the winter (up to eight in a den have been reported). Also, some porcupines forage in groups of up to twenty during the winter months. Both males and females defend their territories, but males tend to defend their territories more vigorously. An individual knows its territory quite well and usually does not venture too far from it.
Young porcupines display an unusual characteristic with respect to dispersal. In many species of animals it is the male that disperses when he can survive on his own. However, with porcupines it is the young females that disperse. This is probably because dominant males establish breeding territories for up to 3 breeding seasons. Daughters, who are usually capable of mating by the age of 22 months, run the risk of mating with their fathers. Selection would favor female dispersal in order to ensure viable offspring. Because males have no contact with their offspring, the offspring and the father have no way of recognizing one another. For male offspring, the chance of becoming dominant enough to effectively guard a receptive female (his mother) is quite slim, since it will take years to reach a high enough social rank needed to establish breeding rights.
The mating system of North American porcupine is known as female defense polygyny. Males defend a pre-estrous female from 1 to 4 days prior to copulation. Porcupines breed only once a year. Female porcupines advertise their 8 to 12 hour estrous period well ahead of time through vaginal secretions, urine marking, and high pitched vocalizations. In doing this, females attract many males who compete with each other to determine dominance. A dominant male breeds with a number of different females, but only when the females are willing. This ensures that the most “fit” male fathers a female’s offspring.
A porcupine pair will mate for several hours until a sperm plug is formed, which then stops the copulation, and prevents further copulation with other males. This plug is formed by enzymatic action in the semen.
Male porcupines display an unusual courtship ritual, which involves dousing of the female with his urine. The urine showers are continued until the female is receptive to both the shower and the male.
Breeding occurs in October and November with a gestation period of 210 days, after which a female gives birth to a single offspring. Newborns weigh between 400 and 530 g. Young are nursed for about 4 months. They become independent of their mothers at approximately 5 months of age, but are not sexual mature until the age of 25 months for females, and 29 months for males.
Exclusively the mother gives parental care, mostly by providing her baby with food. The father has no contact with their offspring. For the first six weeks of a porcupine’s life, its mother is always close by but they actually meet only at night. During the day the baby is hidden on the ground, while the mother sleeps in the trees. After six weeks, the baby porcupine follows the mother to feeding trees and waits for her at the bottom. Over the next couple months, resting positions and foraging distances show increasing separation between the young porcupine and its mother. By mid-October the baby completely loses contact with the mother and is left to survive its first winter alone.
Porcupines are relatively long-lived animals that can live up to 18 years in the wild. Porcupine longevity is probably limited by the life of their grinding teeth. Porcupines over 12 years show diminished feeding and are usually smaller in size.
This species is not a special conservation concern
Weber, C. and P. Myers. 2004. “Erethizon dorsatum” (On-line), Animal Diversity Web. Accessed December 07, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Erethizon_dorsatum.html.