North American porcupine

Erethizon dorsatum

SUBFAMILY

Erethizontinae

TAXONOMY

Erethizon dorsatum (Linnaeus, 1758), Quebec, Canada. Seven subspecies.

OTHER COMMON NAMES

English: Canadian porcupine, quillpig, pricklepig, quiller; French: Porc-epic; German: Urson, Baumstachelschwein; Spanish: Puercoespin.

PHYSICAL CHARACTERISTICS

Adults can reach nearly 39 in (1 m), with the tail making up a fifth to nearly a third of that total. Body weight is generally less than 26 lb (12 kg), but a particularly large male can top 33 lb (15 kg). Adults have stiff, black or dark-brown dorsal hair, interspersed with mostly white quills at the head, rear of the body, and on the tail. In all, an adult may have more than 30,000 barbed quills covering its dorsal body. The belly is quill-free and woolly. The young are more camouflaged with a nearly all-black head, back, and tail, and short, though still sharp, quills. Females have two pairs of mammae.

DISTRIBUTION

Most of Canada except the far north-central regions, and most of the western half of the United States as well as the north-central and northeastern states. It also extends into the northern edge of central Mexico.

HABITAT

Mainly arboreal animals that are common to forested areas, but occasionally also exist in open areas and even deserts, provided a water source is nearby.

BEHAVIOR

The most temperate member of the family, this nocturnal species will occupy winter dens, which are commonly hollow trees and logs, or gaps beneath rocks. More than one porcupine may share a den, particularly when available denning locations are low in number. Studies conflict over whether severe weather may also prompt den-sharing. Some individuals do not den, instead spending their winters resting in trees.

Other than the group denning behavior, porcupines are generally solitary animals for much of the year. Although they are not normally territorial, an individual may defend a feeding site if resources are limited.

During the breeding season, females produce olfactory and auditory clues that indicate their readiness to mate and attract males. Two or more males may fight with one another over the opportunity to mate with a female. These battles can lead to quill impalements and other injuries. In an unusual courtship ritual, males will sometimes soak females with streams of urine while standing on their hind limbs facing the female. The purpose of the behavior is unknown. When the female is ready to mate, she indulges in a kind of dance with the chosen male, where they both rise on their hind feet to embrace, all the while whining and grunting loudly. Sometimes they place their paws on each others' shoulders and rub their noses together; then they may cuff each other affectionately on the head and finally push one another to the ground.

FEEDING ECOLOGY AND DIET

Porcupines are vegetarians, dining on foliage for much of the year and turning to the inner bark of oaks and pines in the winter months. They are also known to eat seeds, fruits, nuts, berries, and plant stems. Their chisel-like teeth scrape away the tougher, outer bark, then slice off even bits of inner bark for consumption. Cellulose-eating bacteria in the porcupine's gut assist the digestion of plant material. Mothers and young feed together, but they are otherwise solitary feeders. Feeding generally occurs at night, but occasionally they will feed during the day.

Their primary predators include fishers and mountain lions, although lynx, bobcats, coyotes, red foxes, wolves, wolverines, and even great horned owls will occasionally disregard the quills and attack porcupines.

During winter porcupines do not hibernate. However, they do not usually move far and feed within 300 ft (91 m) of their dens. During snow or rain they remain in the den or, if out feeding, sit hunched in a tree, even during subzero weather, until the weather improves. When the weather is dry in winter, they feed at any time of the day or night, but during the rest of the year they are nocturnal despite the weather. In summer, porcupines range farther from the den, often searching for food up to 1 mi (1.6 km) away. As well as these daily movements within the home range, there may be seasonal movements between winter denning areas and the summer feeding areas. In mountainous country, the porcupines will often descend during the winter along well-defined paths marked by debarked trees. In the spring, they return up the mountainside to summer feeding areas.

REPRODUCTIVE BIOLOGY

Polygynous. Mating typically occurs only once a year in the fall, during a period of eight to 12 hours when the female is receptive. The female has a copulatory plug and if she does not become inseminated, she may mate again a month later. One young per female per pregnancy is the norm, two is rare, and gestation takes about seven months. The young weigh about 1 lb (450-490 g) at birth, and have both spines and fur. They grow quickly, doubling their weight in the first two weeks, but remain with the mother at least until the early fall when lactation ends. Juvenile females then disperse, but juvenile males may move in and out of the mother's range for months and even years. They attain sexual maturity at about 1.5 years and typical longevity is of the order of some 15 years.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

The quills were once highly regarded among Native American populations, and used both in artwork and as a medium of exchange. These populations also hunted porcupines for meat during lean times. Currently, porcupines are generally seen as pests that gnaw through plywood and nearly anything salty, and damage homeowners' trees. ♦

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