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North American Porcupine (Erethizon dorsatum)

We do not offer trapping and removal services for porcupines but fortunately, they usually keep their distance from our homes and cottages. However, if porcupines set up house too close to yours, such as in a crawl space to have their young, the following information may be helpful in determining how to deal with their presence. 

By Christopher Weber
Last updated: October 14, 2004
Courtesy: Weber, C. 2004. "Erethizon dorsatum" (On-line), Animal Diversity Web. 

North Amer­i­can por­cu­pines, Erethi­zon dor­sa­tum, have the north­ern most range of all por­cu­pines. They in­habit much of North Amer­ica be­tween the Arc­tic Ocean and north­ern Mex­ico. Por­cu­pines are found through­out most 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. (Griese­mer, et al., 1998; Ilse and Hell­gren, 2001; Roze, 1989; Sweitzer, et al., 1997)


Erethi­zon dor­sa­tum uses a broad va­ri­ety of habi­tats. With an ex­ten­sive range, por­cu­pines can be found in var­ied cli­mates, and at var­ied el­e­va­tions. Por­cu­pines live in open tun­dra, de­cid­u­ous forests, and desert chap­ar­ral. Por­cu­pine habi­tat varies ge­o­graph­i­cally. In the Pa­cific North­west, these an­i­mals are pri­mar­ily ground dwelling. In New York, por­cu­pines are mainly tree dwellers. In Mass­a­chu­setts, they spend 13% of their time on the ground. The time por­cu­pines spend on the ground is re­lated to the amount of ground cover that ex­ists for for­ag­ing and pro­tec­tion from preda­tors. In places of deer over­pop­u­la­tion, ground cover can be scarce, thus keep­ing por­cu­pines in the trees. Den­sity of preda­tors also de­ter­mines time spent on the ground, be­cause most por­cu­pine preda­tors are non-ar­bo­real species. Por­cu­pines will spend win­ter in dens, usu­ally rock dens where avail­able. When ground dens are not avail­able, por­cu­pines choose trees to rest in. Dif­fer­ent trees are cho­sen for rest­ing than for feed­ing. In east­ern habi­tats, hem­locks are usu­ally cho­sen over other conifers for both rest­ing and feed­ing. These trees have su­pe­rior ther­mal pro­tec­tion, sight pro­tec­tion (hem­locks have thick fo­liage), are stronger, and have higher nu­tri­tional value.

South­ern pop­u­la­tions of por­cu­pines ex­hibit no sea­sonal use of trees. In south­west­ern Texas, por­cu­pine pop­u­la­tions both rest and feed in pa­per­shell pinyon pines (Pinus re­mota), as well as in oaks and other hard­wood species. Por­cu­pines in the Rocky Moun­tains feed pri­mar­ily on pon­derosa pines, and rest in dens on the ground. Sim­i­larly, por­cu­pines in the Great Basin have been ob­served to use dens in rock out­crop­pings and ju­niper trees for cover dur­ing the win­ter. They travel be­tween dens and small ri­par­ian areas to for­age on tree bark, mak­ing them sus­cep­ti­ble to preda­tors. (Griese­mer, et al., 1998; Ilse and Hell­gren, 2001; Roze, 1989; Sweitzer and Berger, 1992)

Phys­i­cal De­scrip­tion

Erethi­zon dor­sa­tum is the sec­ond largest ro­dent in North Amer­ica, out­sized only by beavers. In­di­vid­u­als range in length from 600 to 900 mm, and weigh be­tween 5 and 14 kg.

It is dis­tin­guished by its stout, slow, lum­ber­ing form and by its spiny coat. On the whole, por­cu­pines ap­pear dark brown to black, with dor­sal guard hairs and spines that con­tain bands of yel­low. Spines called quills ex­tend from head to tail on the dor­sal sur­face. The mid­dle of the tail and lower back are marked by a black line. Quills on the black area are fringed with white. Be­cause por­cu­pines are noc­tur­nal, the white on black mark­ings stand out, alert­ing their mostly color blind noc­tur­nal preda­tors of the dan­ger they pre­sent. This pat­tern is vis­i­ble after por­cu­pines are three months old.

Por­cu­pine quills have mi­cro­scopic barbs on the tip. They are usu­ally around 75 mm long and 2 mm wide. Each an­i­mal has ap­prox­i­mately 30,000 quills. If a quill be­comes lodged in the tis­sues of a would-be at­tacker, the barbs act to pull the quill fur­ther into the tis­sues with the nor­mal mus­cle move­ments of the at­tacker, mov­ing up to sev­eral mil­lime­ters in a day. Preda­tors have been known to die as a re­sult of quill pen­e­tra­tion and in­fec­tion. (Kurta, 1995; Roze, 1989; Sweitzer and Berger, 1997; Vaughn, et al., 2000)

Skull char­ac­ter­is­tics in­clude a lack of ca­nine teeth and a den­tal pat­tern of 1/1, 0/0, 1/1, 3/3. The promi­nent di­astema al­lows the lips to be drawn in while gnaw­ing. Like other hys­tri­co­morphs, por­cu­pines have unique chew­ing mus­cles. Ef­fi­cient chew­ing move­ments are made pos­si­ble by an arm of the mas­seter mus­cle, which passes through the in­fra­or­bital fora­men. (Vaughn, et al., 2000)

Like the por­cu­pines found in Cen­tral and South Amer­ica, North Amer­i­can por­cu­pines have ar­bo­real adap­ta­tions in­clud­ing long claws (four in front with a ves­ti­gial thumb, and five in back). These claws, along with rather unique palms, allow for un­prob­lem­atic nav­i­ga­tion in trees. Por­cu­pines can eas­ily climb large trunks and sur­pris­ingly minute branches. The palms and soles of por­cu­pines are naked with a peb­bly sur­face. This tex­ture in­creases the sur­face area and thus the fric­tion while in con­tact with a branch. As­so­ci­ated with this adap­ta­tion, por­cu­pines have a keenly de­vel­oped sense of touch. This fur­ther aids them in their noc­tur­nal nav­i­ga­tion. It also al­lows por­cu­pines to se­cure them­selves in trees with their hind feet while ma­nip­u­lat­ing food with their front ap­pendages. Fi­nally, the quills of por­cu­pines pre­vent down­ward slid­ing while an­i­mals are grasp­ing trees with their hind feet. The quills on the tail are used to stab the tree, fur­ther in­creas­ing fic­tion and sta­bi­liz­ing the an­i­mal in the tree. (Roze, 1989)

A char­ac­ter­is­tic unique to E. dor­sa­tum, com­pared to its Cen­tral and South Amer­i­can rel­a­tives, is adap­ta­tion to cold. No other hys­tri­co­morphs can with­stand such high vari­ance in tem­per­a­ture as North Amer­i­can por­cu­pines can tol­er­ate. (Roze, 1989; Vaughn, et al., 2000)

North Amer­i­can por­cu­pines are sex­u­ally di­mor­phic, with males being larger than fe­males. The size di­mor­phism is ex­plained prox­i­mately by the faster growth rates and longer pe­ri­ods of growth which males ex­pe­ri­ence rel­a­tive to fe­males. Be­cause males with larger size have higher re­pro­duc­tive suc­cess than do smaller males, sex­ual se­lec­tion pro­motes in­creased male size in this species. (Sweitzer and Berger, 1997)


The mat­ing sys­tem of E. dor­sa­tum is con­sid­ered 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 "best" male fa­thers a fe­male's off­spring.

Fe­males main­tain a ter­ri­tory, and de­fend it against other fe­males; how­ever male ter­ri­to­ries typ­i­cally over­lap those of sev­eral fe­males. The ter­ri­to­ries of dom­i­nant males rarely over­lap. Fe­males all main­tain sim­i­lar sized ter­ri­to­ries, but male ter­ri­tory size varies with age and dom­i­nance sta­tus. Ju­ve­nile males set­tle as per­ma­nent res­i­dents in their natal area. They have smaller ter­ri­to­ries than do adults, but ex­pand their ter­ri­tory size as they ma­ture. Fe­males dis­perse from their natal area be­fore reach­ing ma­tu­rity.

Male/fe­male pairs some­times share win­ter dens, al­though this den shar­ing is not ex­clu­sive to mated pairs. Den shar­ing is not nec­es­sar­ily con­sid­ered part of the mat­ing sys­tem of por­cu­pines. (Griese­mer and De­Graaf, 1996; Roze, 1989; Sweitzer and Berger, 1997)

Fe­males ad­ver­tise their readi­ness to mate by vagi­nal se­cre­tions, urine mark­ing, and high pitched vo­cal­iza­tions, well be­fore the time of ovu­la­tion. This means that sev­eral males con­verg­ing on an ad­ver­tis­ing fe­male will have to com­pete for, and then de­fend, the fe­male. Mat­ing will only hap­pen after a fe­male has cho­sen a male and is re­cep­tive to him.

Males com­pete with each other using loud vo­cal­iza­tions, vi­o­lent bit­ing, and each uses his quills as weapons. Al­though the com­pe­ti­tion hap­pens in trees, mat­ing ex­clu­sively hap­pens on the ground. The pair will mate for sev­eral hours until a vagi­nal 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 a strange 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. Ac­cord­ing to Roze (1989), "Every­thing sug­gests the urine is fired by ejac­u­la­tion, not re­leased by nor­mal blad­der pres­sure. Por­cu­pines with every­day full blad­ders don't squirt their urine, don't have erec­tions, and don't aim at fe­males."

Breed­ing oc­curs in Oc­to­ber and No­vem­ber. Ges­ta­tion in this species is 210 days, after which a fe­male gives birth to a sin­gle off­spring. New­borns weigh be­tween 400 and 530 g. Young are nursed for about 127 days. 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. (Roze, 1989; Sweitzer and Berger, 1998; Woods, 1999)

Parental care is pro­vided by the mother. Mainy, a mother pro­vides her baby with food. For the first six weeks of a por­cu­pine's life, its mother is al­ways close by. They 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. The mother con­tin­ues to travel to the po­si­tion of the baby every night, fol­low­ing land­marks and not scent trails back to the in­fant. By mid-Oc­to­ber the baby com­pletely loses con­tact with the mother and is left to sur­vive its first win­ter alone. The fa­ther spends no en­ergy in the rear­ing of or car­ing for the off­spring. Males have lit­tle to no con­tact with their off­spring. (Roze, 1989; Sweitzer and Berger, 1998)


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. (Kurta, 1995; Roze, 1989)


Por­cu­pines are not very so­cial crea­tures, al­though their so­cial struc­ture is well de­fined. They spend most of their time alone. There is some shar­ing of dens in the win­ter (up to eight in a den). Also, some por­cu­pines for­age in groups of up to twenty dur­ing the win­ter months. Her­bi­vores which live in groups usu­ally do so as a re­sponse to preda­tors, but with the acute de­fenses of por­cu­pines, a soli­tary ex­is­tence is en­tirely tol­er­a­ble.

Both males and fe­males de­fend their ter­ri­to­ries, the for­mer more so than the lat­ter. An in­di­vid­ual knows its ter­ri­tory quite well and usu­ally does not ven­ture too far from it; the main ex­cep­tions being salt or apple ex­cur­sions.

Young por­cu­pines dis­play an un­usual char­ac­ter­is­tic with re­spect to dis­per­sal. Nor­mally in polyg­y­nous mam­mals, fe­males are philopatric, be­cause of the amount of re­sources used in off­spring pro­duc­tion and care. In por­cu­pines, dis­per­sal is fe­male bi­ased. Dom­i­nant males main­tain es­tab­lished breed­ing ter­ri­to­ries for up to 3 breed­ing sea­sons. Philopatric daugh­ters, who are usu­ally ca­pa­ble of maing 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 an ad­ver­tis­ing fe­male (his mother) is quite re­mote, since it will take years to reach that so­cial rank. (Roze, 1989; Sweitzer and Berger, 1998)

Home Range

In the Great Basin Desert, home range size in dom­i­nant males was found to re­late to in­creased mat­ing pos­si­bil­i­ties and not meta­bolic in­creases due to the larger size. Dom­i­nant males ranged over a larger area (20.7 ha) than sub­or­di­nate males (12.9 ha) and fe­males (8.2 ha). Male home ranges dur­ing breed­ing pe­ri­ods were found to over­lap parts of 3 to 10 fe­male ranges. (Sweitzer, 2003)

Com­mu­ni­ca­tion and Per­cep­tion

Por­cu­pines use a com­bi­na­tion of acoustic, chem­i­cal, vi­sual, and tac­tile com­mu­ni­ca­tion. Fe­males com­mu­ni­cate their readi­ness to mate by vagi­nal se­cre­tions, urine mark­ing, and high pitched vo­cal­iza­tions. When threat­ened, a por­cu­pine will chat­ter its teeth and pro­duce a chem­i­cal odor, in­tended to warn off any preda­tor. Males com­pete using fierce vo­cal­iza­tions. Vi­su­ally, the por­cu­pine com­mu­ni­cates the pre­sents of its weaponry by dis­play­ing the white on black mark­ings on its back and tail. Tac­tile com­mu­ni­ca­tion oc­curs when phys­i­cal ag­gres­sion erupts, as well as be­tween mates, and be­tween moth­ers and their young. (Roze, 1989; Roze, 2002)

Food Habits

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. How­ever the amount of se­lec­tiv­ity does not ap­proach that shown by other spe­cial­ized her­bi­vores.

Se­lec­tiv­ity varies be­tween pop­u­la­tions, with por­cu­pines in some habi­tats show­ing more se­lec­tiv­ity. Por­cu­pines in the Rocky Moun­tains feed ex­clu­sively on pon­derosa pine phloem, prob­a­bly be­cause this species dom­i­nates the ecosys­tem. Por­cu­pines in east­ern de­cid­u­ous forests, how­ever, feed on a num­ber of dif­fer­ent species of trees. In Mass­a­chus­settes, por­cu­pines were found rarely to feed on bark, whereas in Texas they for­age largely on bark. (Roze, 1989; Sny­der and Lin­hart, 1997)

The cru­cial nu­tri­tional re­source for por­cu­pines is ni­tro­gen. Win­ter sources of ni­tro­gen in­clude bark, twigs, and ever­green nee­dles. These are rel­a­tively poor sources of ni­tro­gen, so por­cu­pines move con­tin­u­ously to­wards star­va­tion, con­stantly loos­ing weight through­out the win­ter.

Por­cu­pines are able to for­age on low ni­tro­gen, high fiber foods be­cause of their unique abil­ity to re­tain ni­tro­gen from their food. This is done by re­duc­ing fecal ni­tro­gen losses. The abil­ity of por­cu­pines to di­gest very high fiber foods bet­ter than some hindgut fer­menters and ru­mi­nants may be due to the ex­tended time food mat­ter stays in the di­ges­tive sys­tem. (Fe­licetti, et al., 2000; Fournier and Thomas, 1997; Roze, 1989)

Di­etary pat­terns of por­cu­pines have been ex­ten­sively stud­ied in east­ern de­cid­u­ous forests. In the spring, they focus their feed­ing en­ergy on the buds of sugar maple trees, a rich source of pro­tein. As soon as the leaves flush out, the sugar maple is aban­doned be­cause leaves con­tain high amounts of tan­nins (chem­i­cals toxic to por­cu­pines). Por­cu­pines move on to the cam­bium of bass­wood, aspen, and sapling beech trees. Un­der­story beech trees con­tain much less tan­nin than adult trees, a trait a por­cu­pine can eas­ily as­cer­tain. Aspen catkins are uti­lized for their high level of pro­tein. Also ashes are fed upon heav­ily, be­cause they are rel­a­tively easy to climb (com­pared to the smooth bark of beeches), and be­cause they have rel­a­tively low tan­nin lev­els. Fall feed­ing abruptly changes when oak acorns and beech nuts be­come avail­able. Por­cu­pines feed on these nu­tri­ent packed meals be­fore they have fallen to the ground. How­ever, after the nuts have fallen, por­cu­pines are out-com­peted by deer and squir­rels. Mast years in nut pro­duc­ing trees have a di­rect ef­fect on these her­bi­vores. Win­ter for­ag­ing is fo­cused on the phloem of hem­lock, sugar maple, pri­mar­ily within the canopy of these stands.

Other foods uti­lized by por­cu­pines in­clude rasp­berry stems, grasses, flow­er­ing herbs, and a large amount of ap­ples. Her­bivory has an ef­fect on the sodium me­tab­o­lism of por­cu­pines, which re­sults in a lust for salt. Por­cu­pines will chew on the wooden han­dles of human tools, other hu­man-made wood struc­tures, and areas of col­lected road­side salt runoff. (Roze, 1989)

Por­cu­pine feed­ing hap­pens 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 night-time meta­bolic processes of plants. (Roze, 1989)


Por­cu­pines pos­sess a very unique de­fense sys­tem. A por­cu­pine’s first line of de­fense is es­cap­ing from dan­ger by climb­ing up a tree. How­ever, if such an es­cape is not pos­si­ble, the por­cu­pine has many op­tions. Por­cu­pines are the only mam­mal in North Amer­ica to use quills to deter preda­tors. Around 30,000 quills are pre­sent on the dor­sal side of a por­cu­pine. Be­cause loos­ing quills is very ex­pen­sive to a por­cu­pine, these an­i­mals have de­vel­oped sev­eral warn­ing signs to pre­cede their use of their ul­ti­mate weapon.

First are the apose­matic col­orations on the an­i­mal. The white-tipped quills on a black band on the tail and back stand out, and warn pos­si­ble as­sailants of dan­ger. Sec­ond, por­cu­pines emit an au­di­tory warn­ing: a quiet clat­ter­ing of the teeth. If both vi­sual and ac­coustic warn­ings fail, a por­cu­pine will erect its quills, and si­mul­ta­ne­ously re­lease a nasty scent. Quills are only used if the threat has not been de­terred by these other means. (Roze, 1989; Roze, 2002; Sweitzer and Berger, 1992)

Por­cu­pines use their quills in two ways, de­fen­sively (as a shield made of barbs) and of­fen­sively (when they are dri­ven into the preda­tor). Upon con­tact, the por­cu­pine needs to quickly sep­a­rate from the quills, and thus sep­a­rate from the enemy, so they have evolved unique quill-re­lease sys­tems. Erect quills re­lease eas­ier from the por­cu­pine after the quill has been pushed into the would-be as­sailant's body. The force is sup­plied by the con­tact with the would-be preda­tor. Re­laxed quills show no dif­fer­ence in re­lease en­ergy re­quired.

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 and light. (Roze, 1989; Roze, 2002)

Quills pre­sent some dan­gers to por­cu­pines. Falling out of trees is quite com­mon for por­cu­pines, and self-im­pale­ment is def­i­nitely a haz­ard. Also, the force needed to re­move the quills from the por­cu­pine, after they are em­bed­ded in the as­sailant, may be larger than the weight of the por­cu­pine, so sep­a­rat­ing may be prob­lem­atic. (Roze, 2002)

Even with this elab­o­rate de­fense mech­a­nism, por­cu­pines are preyed upon by a cou­ple of co-adapted preda­tors. Sev­eral preda­tors exist that at least have been known to kill a por­cu­pine. The list in­cludes lynx, bob­cats, coy­otes, wolves, wolver­ines, and great horned owls. Im­por­tant preda­tors in­clude moun­tain lions and fish­ers 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 ven­tral sur­face. Moun­tain lions sup­pos­edly make no at­tempt to avoid the quills of por­cu­pines; in­stead they at­tack at will and deal with the con­se­quences. Preda­tors tend to hunt and kill por­cu­pines mostly in open habi­tats. (Sweitzer and Berger, 1992; Sweitzer, et al., 1997)

Known Predators
fishers (Martes pennanti)
mountain lions (Puma concolor)
lynx (Lynx canadensis)
bobcats (Lynx rufus)
coyotes (Canis latrans)
gray wolves (Canis lupus)
wolverines (Gulo gulo)
great horned owls (Bubo virginianus)

Ecosys­tem Roles

Por­cu­pines of the Rocky Moun­tains pre­fer habi­tats on rocky, south fac­ing slopes. This brings them into con­tact with wood ticks that share the same habi­tat. Wood ticks, Der­ma­cen­tor an­der­soni, are the host of Col­orado Tick Fever virus; how­ever por­cu­pines do lit­tle to spread this virus. This is be­cause only adult ticks at­tach to por­cu­pines, and adult ticks do not spread the virus. In one study, 18 por­cu­pines yielded a total of 448 ticks. (McLean, et al., 1993)

Por­cu­pines can gen­er­ate stress on their en­vi­ron­ment, al­though their over­all detri­men­tal ef­fect is usu­ally largely over-em­pha­sized (usu­ally fo­cused on their in­tre­pid salt ex­cur­sions). One ex­am­ple of por­cu­pines adding a stress to their en­vi­ron­ment is in Texas, where they feed largely upon the bark of pinyon pines. It has been sug­gested that be­cause of por­cu­pine for­ag­ing, these trees have been made more vul­ner­a­ble to the in­fes­ta­tion of bark bee­tles. (Ilse and Hell­gren, 2001; Roze, 1989)

Sev­eral fac­tors have led to stresses on por­cu­pine pop­u­la­tions. In the Great Basin, near ex­tinc­tion of a pop­u­la­tion of por­cu­pines was dis­cov­ered to be a di­rect re­sult of in­creased moun­tain lion pre­da­tion. In­creased pre­da­tion may have been a re­sult of low mule deer pop­u­la­tions in the area. In­creased pre­da­tion on por­cu­pines can also be a con­se­quence of preda­tor shift­ing when snow­shoe hare num­bers de­cline. In­creased stress from nat­ural preda­tors sig­ni­fies the frag­ile dy­nam­ics be­tween por­cu­pines and their en­vi­ron­ment. His­tor­i­cal stud­ies have in­di­cated a very cycli­cal fluc­tu­a­tion in pop­u­la­tions of por­cu­pines. (Keith and Cary, 1991; Sweitzer, et al., 1997)

In north­ern Michi­gan, Fish­ers Martes pen­nanti were rein­tro­duced to limit the por­cu­pine pop­u­la­tion growth and nearly elim­i­nated the species from the area. Lim­ited den sites (stand­ing hol­low snags), brought about by log­ging prac­tices, in­creased por­cu­pine ex­po­sure to fish­ers. In the north­east, where hem­lock plays a major role in por­cu­pine win­ter for­ag­ing, pests such as the hem­lock wooly adel­gid, Adelges tsugae, along with in­creased hem­lock log­ging may pose prob­lems for fu­ture por­cu­pine habi­tat. (Griese­mer, et al., 1998)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Por­cu­pines were once revered by Na­tive Amer­i­can cul­tures through­out the con­ti­nent as a food source, a source of quills for dec­o­ra­tion, and leg­endary sta­tus. Today, how­ever, they are mostly con­sid­ered a pest. Boun­ties, large poi­son­ing ef­forts and un­reg­u­lated killing have only re­cently been dis­con­tin­ued. Some would argue that por­cu­pines’ in­her­ent value is the ease and ac­ces­si­bil­ity of the species to re­search and study. (Roze, 1989)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Por­cu­pines have two areas of con­flict with hu­mans. Their salt crav­ings often lead them to chew on hous­ing struc­tures, au­to­mo­biles, and any­thing made of ply­wood or with salt residue (usu­ally from road de-ic­ing salt). They also have a neg­a­tive im­pact on the tim­ber in­dus­try. Trees that have been fed on by por­cu­pines tend to have stunted growth and twisted evil look­ing crowns, usu­ally mak­ing the tree un­suit­able for use as lum­ber. (Ilse and Hell­gren, 2001; Roze, 1989)

Con­ser­va­tion Sta­tus

This species is not a spe­cial con­ser­va­tion con­cern.

IUCN Red List
Least Concern 


Nancy Shef­ferly (ed­i­tor), An­i­mal Di­ver­sity Web.

Christo­pher Weber (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor, in­struc­tor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.


living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

uses sound to communicate

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

uses smells or other chemicals to communicate

desert or dunes
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

dominance hierarchies
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care
parental care is carried out by females

union of egg and spermatozoan

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

an animal that mainly eats seeds

An animal that eats mainly plants or parts of plants.

induced ovulation
ovulation is stimulated by the act of copulation (does not occur spontaneously)

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

having the capacity to move from one place to another.

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range
the area in which the animal is naturally found, the region in which it is endemic.

active during the night

chemicals released into air or water that are detected by and responded to by other animals of the same species

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

having more than one female as a mate at one time

scent marks
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest
scrub forests develop in areas that experience dry seasons.

seasonal breeding
breeding is confined to a particular season

remains in the same area

reproduction that includes combining the genetic contribution of two individuals, a male and a female

associates with others of its species; forms social groups.

lives alone

uses touch to communicate

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

Living on the ground.

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

uses sight to communicate

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial
young are relatively well-developed when born


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