Erethizon dorsatum (Linnaeus 1758)

Dataset
Erethizontidae: Rank
SPECIES

Classification

kingdom
Animalia: phylum
Chordata: class
Mammalia: order
Rodentia: family
Erethizontidae: genus
Erethizon: species
Erethizon dorsatum

activity

Activity patterns. North American Porcupines are arboreal and nocturnal and remain active year-round, enduring low winter temperatures (e. g. — 39 ° C) while consuming woody plants low in nitrogen and high in fiber and plant secondary metabolites. To survive harsh winter conditions, porcupines rely on fat stores accumulated from late spring to late summer. During winter, fat mass declines from an average of 50 % to 27 %. Fat losses are minimized by lowering rates of energy expenditure, not body temperature. Adult males begin to lose mass during early breeding period in autumn.

biology_ecology

Habitat. Variety of habitats across a large geographical distribution. In the northern part of its distribution, the North American Porcupine can be found in tundra and boreal forest. In the eastern part ofits distribution, it is found in deciduous, mixed, and coniferous forests. In the western and south-western parts of its distribution, it is found in hemlock (7 T 5 uga, Pinaceae) forest, mixed coniferous forest, oak (Quercus, Fagaceae) forest, and scrub desert habitat. Individual habitat selection is sometimes a function of perceived predation risk; in the Great Basin, sleeping adults andjuveniles generally avoided open areas and moved into higherrisk foraging areas more often as body condition deteriorated.

biology_ecology

Movements, Home range and Social organization. Given the very large distribution of the North American Porcupine, space use varies depending on habitat and season and appears to be related to den-site and food availabilities, predation risk, and, in winter, snow depth. In British Columbia, North American Porcupines appear to prioritize den location over food availability, first choosing larger diameter Sitka spruce (Picea sitchensis, Pinaceae) for winter dens and then selecting forage trees (with a preference for western hemlock) based on proximity to a winter den. In the Great Basin Desert of Nevada and mixed deciduous and spruce-fir forests of Quebec, juvenile porcupines, at high risk of predation, select habitats that provide good cover. Body condition can also influence habitat selection; individuals will move into high-risk foraging areas when body condition declines. Snow depth appears to limit movement and thus home rangesize. During years of heavy snow in the Catskill Mountains of New York, winter home range averaged 7 - 4 ha. In contrast, during a year of light snow, winter home range averaged 64 - 9 ha, which did not differ statistically from the average non-winter home range size. In the desert-shrub habitat of southern Idaho, non-winter home range size averaged 23 - 1 ha for females and was 61 - 7 ha for one male; in winter, home range size for two animals followed by telemetry averaged 0 - 07 ha. Winter home ranges in Alaska average 171 ha, are larger than in more temperate zones, and do not differ between sexes or correlate with body mass. Larger winter home ranges in Alaska, despite presence of snow, may be explained by patchily distributed forage trees and low availability of den sites, coupled with potentially low predation risk and larger body size compared with those at lower latitudes. Although North American Porcupines come together to breed, and females are occasionally seen with presumed young, they are, on the whole, solitary animals. Finding food and avoiding predation are the focus of daily activities. Daily movementdistances do not appear to differ by sex or age. In deciduous forests of the Catskill Mountains, female North American Porcupines are strongly territoriality. Female territories do not overlap, although male territories overlap those of females and other males. In an unusual pattern for mammals, males are philopatric and females disperse. Juvenile females disperse from their mother’s territories in first autumn. Young males, in contrast, set up home ranges within or adjacent to territories of their mothers. Porcupines are sometimes observed to den together in either male-female or mother — offspring pairs. Very occasionally, and generally only when they need to escape inclement weather, North American Porcupines can be found denning in larger groups of 3 - 8 or more individuals. Mating system is female-defense polygyny, with males guarding females during the breeding season, butlittle is known about variation in mate choice from year to year, nor is there any information available on genetic structuring within populations. Porcupines are long-lived, some living beyond 20 years old in the wild. Recent development of microsatellite markers for the North American porcupine will allow exploration of questions about mating system, reproductive success, and possibility of kin selection during, for example, periods of group denning. Populations of North American Porcupines are reported to cycle, sometimes in synchrony with lagomorphs. Data collected between 1995 and 2004 from southern Ontario showed population lows of 0 - 02 captures / 100 trap nights and highs of 0 - 08 captures / 100 trap nights; densities are affected by local density of Fishers (Martes pennanti), the one predator that appears to specialize on porcupines.

breeding

Breeding. Female North American Porcupines become receptive to mating in autumn and experience an 8 - 12 hour estrus during which mating takes place. Vaginal and perineal secretions carry olfactory signals that help male porcupines determine when a female is reaching peak receptivity. Mating system is female-defense polygyny, in which males compete for access to females. Male home ranges become larger in autumn when they seek mating opportunities; males will fight with one another to gain access to a receptive female. These fights can be vicious; porcupines are just as susceptible as nonporcupine aggressors to injury from quills. Reproductive success in male porcupinesis variable and appears to be correlated with body size. A male will guard a female for a few days surrounding estrus. He may climb into a tree and sit in branches below the female, occasionally showering her with urine; chemicals in the male’s urine may advance estrus. When a female porcupine has accepted a male as a mate, she raises her hindquarters to him and arches hertail above her rosette; doing so presents a relatively quillfree and hence safe approach for the male. Copulation takes place repeatedly over several hours. Vaginal plug forms an hour or two after copulations end. Purpose of the plug has not been studied, but it likely helps to block copulation by other males, prevents semen loss, and may also reduce chemical signaling by the female toward other males. Reproductive success is much less variable for females than males; typically, 95 - 99 % of females in a population breed every year. Gestation of the North American Porcupine is long at c. 210 days (compare with an average of 280 days for humans). Lengthy gestation may be required due to a porcupine’s inability to maintain a positive energy balance in winter; females lose weight (as a result of burning fat stores) during the same period in which they are developing a fetus. North American Porcupines give birth to a single offspring called a “ porcupette. ” Porcupettes are precocial, born with fur and quills. Soft quills harden within a few hours of birth. Although porcupettes begin consuming herbaceous vegetation within a few weeks of birth, they typically nurse for ¢. 127 days. Thus, an adult female North American Porcupine typically spends 337 days / year pregnant or nursing. Because female porcupines need to feed in trees, they will leave their young in brush piles and return to them periodically through the night to nurse. Female porcupines typically have four nipples: one pair near armpits and the other pair on abdomen. Young apparently takes turn nursing from different nipples. When young are c ¢. 3 months old, they spend nights away from its mother.

conservation

Status and Conservation. Classified as Least Concern on The IUCN Red List. Humans are the greatest threat to North American Porcupines because they are viewed as pests throughout their distribution and are often killed in response to foraging on valued trees and buildings, or in orchards. Cars frequently hit North American Porcupines because they are attracted to road salt and likely tend to stand their ground and erect their quills in response to threats.

description

Descriptive notes. Head — body 600 - 1300 mm, tail 160 - 250 mm, hindfoot 75 - 110 mm; weight 5 - 12 kg. The North American Porcupine is the largest member of the family Erethizontidae. Robust with round bodies and relatively short legs, North American Porcupines generally appear blackish, reddish, brownish, or yellowish at a distance; thick underfur and long guard hairs conceal many of defensive quills. Tail is short, with tail length ¢. 31 % of head-body length. Head and body are well protected by ¢. 30,000 defensive quills that are distributed everywhere except on venter, inner limbs, face, and ears and are ¢. 20 - 100 mm long. Quills are bicolored, creamy white or yellowish at bases with black tips, resulting in aposematic coloration when quills rest against the body. Quills are composed of keratin proteins fabricated during quill growth into a cylindrical outer shell with an interior foam core, and tips are barbed, as is the case for most defensive quills in erethizontids. Head of the Northern American Porcupine is small and round with a squarish muzzle. Mouth has two chambers. Yellow incisors are located in the outer chamber and cheek teeth in the inner chamber; lips meet across diastema, behind incisors, allowing an individual to gnaw on bark without holding its mouth open, which may reduce heat loss in cold weather. Thick and relatively shorttail is solidly muscular; dorsal surface is covered with defensive quills. Underside oftail is covered with stiff bristles that, when combined with muscular action of the tail, aid in climbing. Unlike other species of erethizontids, tail of the North American Porcupine lacks prehensile surface. Dorsal region at base oftail, called the rosette, is distinguished by absence of fur or guard hairs; naked skin in this area appears greasy due to secretions from sebaceous glands, and quills are somewhat shorter and more barbed, functioning as osmotrichia to aid in propagating the porcupine’s distinctive warning odor. When a porcupine erects its quills to enter a defensive posture, lack of hair in the rosette amplifies the “ pin cushion ” appearance. North American Porcupines are plantigrade; soles of feet are naked and textured. Feet have long claws (four on forefeet and five on hindfeet) that can close tightly around the footpad and enable grasping. These adaptations make North American Porcupines excellent climbers but somewhat awkward and slow walkers.

discussion

Seven subspecies are recognized.

distribution

Subspecies and Distribution. E. d. dorsatumLinnaeus, 1758 — CanadaEofYukonTerritoryandBritishColumbiaProvince (exceptLabradorandNewfoundlandProvince) andNC & NEUSA. E. d. bruneriSwenk, 1916 — CUSA (GreatPlainsEoftheRockyMts). E. d. couesiMearns, 1897 — SWUSA (CArizona, NewMexico, andWTexasstates) andNMexico (Sonora, Chihuahua, Coahuila, NuevoLeon, Tamaulipas, NSinaloa, andNDurangostates). E. d. epixanthumBrandt, 1835 — WUSA (SWashingtonStateEtoIdaho, Montana. Wyoming, Nevada, Utah, WColorado, andStoCaliforniastates). E. d. myopsMerriam, 1900 — AlaskaandtheYukonTerritoryinNWCanada. E. d. nagriscensJ. A. Allen, 1903 — WCanada (BritishColumbiaProvince) andNWUSA (NWashingtonState). E. d. picinum Bangs, 1900 — NE Canada (Newfoundland and Labrador Province).

food_feeding

Food and Feeding. Diets of North American Porcupines change with season and location. During spring, they feed on emerging leaf buds and will descend to the ground to eat fresh stems of grasses, wildflowers, and sedges. It will also eat leaves, forbs, and herbs on the ground and in trees during spring and summer. During autumn, diets may include agricultural crops, such as corn and apples, and acorns. Winter diet of the North American Porcupine consists of inner bark and cambium of a variety of species of deciduous tree and foliage of select conifers. In Alaska, porcupines alternate between eating needles of white spruce (Picea glauca, Pinaceae) and inner cambium of paper birch (Betula papyrifera, Betulaceae). In eastern North America, important deciduous food trees include sugar maple (Acer saccharum, Sapindaceae), red maple (A. rubrum), American beech (Fagus grandifolia, Fagaceae), and yellow birch (Betula alleghaniensis) and important coniferous food trees include the highly preferred eastern hemlock (75 uga canadensis), white pine (Pinus strobus), and balsam fir (Abies balsamea). In western parts of its distribution, preferred food trees include western hemlock (7. heterophylla), Douglas fir (Pseudotsuga menziesii), and ponderosa pine (PF. ponderosa); other pines, spruces, and firs are also eaten. Winter feeding on bark of trees can result in tree death and is one reason that North American porcupines are considered as pests throughout much of their distribution, although there is little evidence that their feeding results in significant economic damage. Selective feeding on dominant species in the forest may in fact relieve competition on subdominant tree species, increasing tree diversity. Diets of North American Porcupines are typically low in nitrogen and high in fiber and contain a variety of plant secondary chemical compounds including tannins and terpenes. Mechanisms for detoxifying plant secondary chemicals are not yet known. Nevertheless, the North American Porcupineis a hindgut fermenter with long intestine and enlarged, fermenting cecum. Distal colon is four times longer than that of the similarly sized North American Beaver (Castor canadensis), and food is retained for a relatively long time in the digestive system, about 1 - 5 times longer than whatis typical of an 11 kg hindgut fermenter. In Alaska, North American Porcupines alternate between feeding on more nutritious but secondary chemical-laden white spruce and less nutritious but low in secondary chemical paper birch; they may switch to paper birch when detoxification pathways used to process spruce needles are saturated.

materials_examined

“ Habitat in Canada. ”

Name

Synonyms: Hystrix dorsata Linnaeus 1758
Homonyms: Erethizon dorsatum (Linnaeus 1758)
Common names: Nordamerikanischer Baumstachler in 德语; North American Porcupine in 英语; Porc-épic dAmérique in 法语; Puercoespin de Norteameérica in language.; Quill Pig in 英语; Quiller in 英语