Erethizon dorsatum (North American Porcupine) 

Written by Christa Griffin (Mammalogy Lab--Fall 2003)

Edited by Karah Gallagher and Jennifer Bailey

Map prepared by Greg T. Lewellen

Erithizon dorsatum is widely distributed and can be found in Mexico, much of the United States including Alaska, and Canada.  They are usually found in wooded areas such as pinon-juniper woodland and ponderosa pine forests in the southwestern United States (Reynolds 1957).  They have even been found in desert-shrub type areas of Arizona (Reynolds 1957).  In Texas, Erethizon dorsatum is distributed throughout the western one-half of the state, east to Bosque County (Davis and Schmidly 1994).  Recently, it has expanded its range into southern Texas (Davis and Schmidly 1994).

Photo courtesy Texas Parks & Wildlife © 2003 Photo by R. Matlack

Physical Characteristics:

Erethizon dorsatum is a large rodent with a stout body and short legs and tail (Davis and Schmidly 1994; Woods 1973).  The general pelage of Erethizon dorsatum is fine, long or short coat hairs covering their entire body, except for flexor surface of the feet, the ventral tail area, the auditory meatus, the papillae mammae and adjacent areolar skin, the penis, and the nose (Po-Chedley and Shadle 1955.)   Short, fine coat hairs as well as slightly longer, stiffer variety of coarse hair cover the mesal surfaces of the four legs and the ventral surface of the body (Po-Chedley and Shadle 1955).  Under the tail there are short, stiff bristles (Po-Chedley and Shadle 1955).  Quills are the most obvious characteristic of Erethizon dorsatum.  The crown of the head, cheeks and nape; the entire dorsal and lateral sides of the body; and the dorsal and lateral surfaces of the tail are covered in quills varying in length, flexibility, color, and stiffness (Po-Chedley and Shadle 1955.)  Quills can be white or dichromatic; pigmented on parts of or on the whole quill (Po-Chedley and Shadle 1955).  The quills usually give the animal a yellowish or yellowish brown appearance (Davis and Schmidly 1994).  The coloration of Erithizon dorsatum can vary from black, brown, or chestnut to grizzled gray (Curtis and Kozicky 1944; Po-Chedley and Shadle 1955).  The average measurements are: (males) total length, 808 mm; tail, 235 mm; hind foot, 98 mm; (females) 737-230-81 mm, and the average weight is 5-11 kg (Davis and Schmidly 1994).

Natural History:

Food Habits: Erethizon dorsatum is a herbivorous animal that eats a wide variety of trees and plants (Curtis and Kozicky 1944; Shadle 1950).  They are discreet gluttons, feasting mainly on the bark of trees, food that no other animal wants (Struthers 1928).  During the winter, they depend on the leaves and bark of conifers like hemlock and various pines and the bark and twigs of deciduous trees like aspens, elms, and hard maples (Shadle 1950).  They strip the outer bark to expose the highly palatable inner bark layers of trees like Pin cherry (Prunus pennsylvanicus), a preferred fall and winter food (Thompson 1952).  Acorns and beechnuts are gathered and eaten as well (Curtis and Kozicky 1944).  Mistletoe is another tree-gathered food chosen by Erethizon dorsatum.  During the spring, they browse on herbaceous ground vegetation and the foliage of trees (Curtis and Kozicky 1944; Davis and Schmidly 1994).  Succulent plants growing along the edges of ponds or streams are a favorite food while in season (Batchelder 1948).  They have been observed wading in ponds eating aquatic liverwort (Curtis and Kozicky 1944).  They are especially fond of salt, so it is often used in management (Davis and Schmidly 1994

Photos of bark removed from trees during feeding by porcupines (Photos by R. Matlack)

Reproduction: The rutting season of Erethizon dorsatum is late summer and early fall with the peak of activity in September and early October (Davis and Schmidly 1994).  Rutting is evidenced by a pairing of two individuals during which time they are constantly together (Struthers 1928).  It seems probable that males mate with a single female (Struthers 1928).  The gestation period is 209-217 days and usually only one young is produced (Shadle 1948; Struthers 1928).  At birth, the young have long black hair and barb-less quills about one-quarter inch in length (Whitney 1931).  “A head first presentation at parturition would seem essential to the well being and perpetuation of the porcupine” (Whitney 1931).  The young weigh about 450 g at birth, a mass that is larger than a newborn black bear (Davis and Schmidly 1994).  Incisors and some cheek teeth are well formed and in position and the small dark eyes are wide open at birth (Shadle and Ploss 1943).  Within a day after birth, the young can flee from danger and in a week it no longer needs food from its mother (Struthers 1928).  Females do not reach sexual maturity until their third fall (Struthers 1928).

Behavior: Erethizon dorsatum does not hibernate (Struthers 1928).  They live in dens in large colonies depending on the space and physical advantages of the den (Struthers 1928).  They travel in runways connecting the dens with feeding grounds and watering places (Struthers 1928).  They show a strong disinclination to jump and tend to travel beneath windfalls, dense cover, and leaning trees rather than over them (Curtis and Kozicky 1944).  In the winter, the more snow there is, the closer they stay to their dens (Curtis and Kozicky 1944).  But, pregnant females have been observed braving severe weather to visit feeding grounds while males will not venture out of their dens except in clear weather (Struthers 1928).  Erethizon dorsatum utters a variety of human-like sounds that have been referred to as “talking” (Batchelder 1948).  Erethizon dorsatum is very attracted to salt and will gnaw any wooden article where human hands have touched, such as ax handles, oar or paddle handles, etc. (Wyman 1923).  Observations of Erethizon dorsatum strongly indicate that they rely greatly on their ability to hear and smell (Curtis and Kozicky 1944).  They are found to use their noses continuously either by keeping their heads still and flexing their nostrils or by raising their nose and sniffing the air (Curtis and Kozicky 1944).

Habitat: Erethizon dorsatum is largely an inhabitant of forested areas in the West and prefers rocky areas, ridges, and slopes (Davis and Schmidly 1994).  They make their dens in rocky areas in crevice or caves, where available, and otherwise in logs, windfalls or upturned or loosened tree root systems (Davis and Schmidly 1994).  They have become adapted for survival in the desert-shrub type of the Southwest (Reynolds 1957).

Erethizon dorsatum is sometimes considered to be a pest because they do considerable damage to coniferous trees by eating the bark in the tops and so girdling the trees (Batchelder 1948).  They have also been charged with destructive attacks on vegetable gardens and corn fields (Batchelder 1948).

Conservation Status:

Erethizon dorsatum is not rare, threatened or endangered.  In the past, the state of New York and certain parts of Canada protected the species by law during the same time that Vermont and New Hampshire offered a bounty for each animal killed (Struthers 1928).

References:

Batchelder, C. F. 1948. Notes on the Canada Porcupine. Journal of Mammalogy 29:260-268.

Curtis, J. D., and E. L. Kozicky. 1944. Observations on the eastern porcupine. Journal of Mammalogy 25:137-146.

Davis, William B., and David J. Schmidly. 1994. The Mammals of Texas. University of Texas Press, Austin.

Linnaeus, C. 1758. Systema naturae. 10^th edition, 1:57.

Po-Chedley, D. S. and A. R. Shadle. 1955. Pelage of the porcupine, Erithizon dorsatum dorsatum. Journal of Mammalogy 36:84-95.

Reynolds, H. G. 1957. Porcupine behavior in the desert-shrub type of Arizona. Journal of Mammalogy 38:418-419.

Shadle, A. R. 1948. Gestation Period in the porcupine Erethizon dorsatum. Journal of Mammalogy 29:162-164.

Shadle, A. R. 1950. Feeding, care, and handling of captive porcupines (Erethizon). Journal of Mammalogy 31:411-416.

Shadle, A. R., and W. R. Ploss. 1943. An unusual porcupine parturition and development of the young. Journal of Mammalogy 24:492-496.

Struthers, P. H. 1928. Breeding Habits of the Canadian Porcupine (Erethizon dorsatum). Journal of Mammalogy 9:300-308.

Thompson, D. Q. 1952. Travel, range and food habits of Timber wolves in Wisconsin. Journal of Mammalogy 33: 429-442.

Whitney, L. F. 1931. Barbless quills of porcupine. Journal of Mammalogy 12:433.

Woods, C. A. 1973. Erethizon dorsatum. Mammalian Species 29:1-6.

Wyman, L. C. 1923. A hungry porcupine. Journal of Mammalogy 4:190.