North American Porcupine

About the North American porcupine

The North American porcupine, also called the Canadian porcupine, is a large, quill-covered rodent in the New World porcupine family. It ranks as the second-largest rodent native to North America, behind only the American beaver. Its ancestors are believed to have crossed from Africa to Brazil roughly 30 million years ago before migrating north across the Isthmus of Panama once it rose about 3 million years ago; seven subspecies are now recognized across a range that stretches from Alaska and Canada south to northern Mexico.

The porcupine has a stocky body, small face, short legs, and a short, thick tail, colored dark brown or black with white highlights. Head-and-body length runs 2.0 to 3.0 ft (60–90 cm), with a tail of 5.7 to 11.8 in (14.5–30 cm) and a hind foot of 3.0 to 3.6 in (7.5–9.1 cm). Weight ranges widely, from 7.7 to 39.7 lb (3.5–18 kg); adult females average around 15 lb (7 kg), while a sample of wild-caught males averaged closer to 23.5 lb (10.67 kg). Like the wolverine and the skunk, the porcupine's strong black-and-white contrast is thought to signal its identity to other animals in the dark.

Its most distinctive feature is a coat of roughly 30,000 quills, covering the entire body except the underbelly, face, and feet. The quills are modified hairs — sharp, barbed, hollow spines that normally lie flat against the body for insulation. When threatened, the porcupine contracts muscles that raise the quills, making them easier to detach and drive into an attacker, especially when the tail is swung. Barbs at the quill tips lodge painfully in flesh and are hard to remove; a fatty-acid coating on the quills also has antibiotic properties, which helps prevent infection when a porcupine — as it fairly often does, tempted by tender buds at branch tips — falls out of a tree onto its own spines.

Behavior and diet

Porcupines are herbivores whose diet shifts with the seasons: twigs, roots, stems, fruits, and leaves in summer, and mainly conifer needles and bark in winter, though how selective they are varies by season. They are nearsighted, slow-moving, and nocturnal, resting in trees on summer days and staying near their dens in winter without truly hibernating. Unlike many herbivores that rely on the safety of a herd, the porcupine's quill defense lets it live a solitary life, and it has a notable capacity to learn and remember complex mazes for as long as 100 days.

When threatened, a porcupine relies on a layered defense. It first gives off a strong odor — compared to body odor, goats, or certain cheeses — generated by a gland patch on the lower back. If that fails, it bristles its quills to expose a warning white stripe and clacks its teeth. As a last resort it turns its rear to a predator and swings its tail, driving in barbed quills on contact; despite popular belief, it does not throw them. Fishers are its most persistent predator, sometimes flipping a weakened porcupine to attack its unprotected underbelly, while cougars, wolverines, coyotes, wolves, and black bears will also take porcupines, sometimes at real cost to themselves from embedded quills.

Breeding begins in fall, when females secrete a scent that draws in males; a dominant male establishes mating rights after fights with rivals, then sprays urine on the female to bring her into estrus before they mate on the ground. Gestation averages 202 days, unusually long for a rodent — well beyond the 128 days of the similarly sized beaver. A single young, called a porcupette, is born weighing about 16 oz (450 g) and nearly doubles that within two weeks, though it does not reach its adult weight of 9.9 lb (4.5 kg) until the end of its second summer. Young nurse for up to four months, into the fall mating season, when they separate from their mothers.

Range and habitat

In eastern North America, porcupines range from Canada south through the Appalachians into West Virginia and Maryland, though east of the mountains they extend no farther south than northern New Jersey. In the west, their range stretches from Alaska down to the northern mountains of Mexico. They favor coniferous and mixed forest but have adapted to harsher habitats such as shrubland and tundra, denning in hollow trees or rocky crevices.

The species is common throughout most of this range and is listed globally as Least Concern, though it is scarcer in parts of the southeastern United States — Maryland, for instance, lists it as a species in need of conservation. In north-central Mexico, only about fifteen remnant populations remained as of 1999, living in riparian forest, mesquite scrubland, grassland, and thorn forest; hunting and habitat loss led Mexico to list the species as endangered there in 1994.

Conservation status

Globally, the North American porcupine is classified as Least Concern (LC), and it remains common across most of its range. The clearest exception is the southeastern edge of that range, including parts of the U.S. Southeast and north-central Mexico, where hunting and habitat loss have reduced numbers enough to prompt state-level conservation concern in places like Maryland and an endangered listing in Mexico. Beyond hunting pressure, common causes of death across the species' range include predation, starvation, falls from trees, and vehicle strikes, though none of these has threatened the overall population.