Mammals

North American Porcupine

Erethizon dorsatum · also called Canadian porcupine, quill pig

Least Concern → herbivore Temperate forest Temperate grassland

The North American porcupine is a slow, near-sighted, waddling rodent that has almost no need to hurry, because it is wearing 30,000 reasons for other animals to leave it alone. It also has a weakness that turns it into a camp-country nuisance: it is desperate for salt.

Overview

Erethizon dorsatum lives across northern North America, mostly in coniferous and mixed forest but also in deserts and brushland. It is the second-largest rodent on the continent, after the beaver, at up to about 14 kg. In summer it eats leaves and buds; in winter it lives on tree bark, sometimes stripping and killing a tree.

The quills

The roughly 30,000 quills are stiff, hollow hairs tipped with backward-pointing barbs that flare with body heat, so a quill that strikes an animal works its way deeper and is very hard to pull out. It cannot throw them — they simply detach on contact. The quills also carry a natural antibiotic coating, thought to protect the porcupine when it falls onto its own.

Salt and the fisher

Its woody diet is so low in sodium that it will gnaw sweat-soaked tool handles, paddles, and salted tyres. Its main predator is the fisher, a weasel that flips the porcupine over to reach the quill-free belly.

Status

Least Concern and stable, common across the north, locally controlled where it damages timber.

North American Porcupine: common questions

Can a porcupine shoot its quills at you?

No. This is one of the most persistent animal myths, and it is not true for any porcupine species. The quills are not launched; they are simply held loosely in the skin so that they pull out of the porcupine and stay in whatever touches them. A threatened porcupine turns its rump toward the danger, raises the quills so they stand out from the body, chatters its teeth, releases a strong smell, and lashes its quill-covered tail, and if a predator makes contact it comes away with a face full of quills while the porcupine keeps them all at the ready. But a porcupine cannot hit a target it has not touched.

Why are the quills so hard to remove?

Because of the tips. The last centimetre or so of a quill is covered in layers of tiny, backward-angled barbs, like the barbs on a fish hook but far smaller and more numerous. When a quill enters flesh the barbs lie flat and let it slide in easily, and body heat then causes them to swell and splay outward, gripping the surrounding tissue. Muscle movement works the barbed quill steadily deeper, up to about a millimetre an hour, and pulling it straight out drags all those barbs against the tissue and is painful and difficult. Quills that migrate can reach internal organs, which is why a dog or a person with quills, especially near the face, throat, or joints, needs prompt veterinary or medical removal.

Why does a porcupine chew on tools and buildings?

For salt. The porcupine's diet of bark, wood, leaves, and conifer needles is very low in sodium, an essential mineral, so the animal is chronically short of it and seeks out concentrated sources. Human sweat is salty, so anything a person has gripped and perspired on, an axe handle, a canoe paddle, a work glove, a wooden tool handle, becomes a target, and porcupines will also gnaw plywood and outhouse seats treated with glue or preservative, and chew on vehicle tyres, hoses, and wiring for the residue of road salt. In camp and cabin country this makes the porcupine a well-known nuisance, and gear is hung out of reach at night for this reason.

Is a porcupine related to a hedgehog?

No, and the resemblance is convergence. The North American porcupine is a rodent, a large one, related to guinea pigs, capybaras, and, distantly, to squirrels and mice. The hedgehog is a small placental insectivore related to shrews and moles, on a completely different branch of the mammal tree. Both independently evolved spines, modified hairs stiffened into defensive points, because a covering of sharp spines is an effective, low-cost defence for a slow-moving animal, and the same solution has also arisen in the echidna, the tenrecs, and some other unrelated mammals. Old World porcupines are yet another separate rodent lineage that evolved quills.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published October 3, 2026. Last updated October 3, 2026.

Quick facts

Scientific name: Erethizon dorsatum
Diet: In summer, leaves, buds, twigs, flowers, and fruit; in winter, the inner bark and needles of trees, especially conifers, which it eats for weeks at a time from a single tree, sometimes girdling and killing it
About 30,000 quills: The quills are stiff, hollow, modified hairs; each is tipped with a patch of microscopic backward-pointing barbs that flare when warmed by body heat, so an embedded quill works itself deeper rather than falling out, and is very hard to pull free
It cannot throw its quills: The old belief that a porcupine shoots its quills is a myth; the quills are loosely rooted and detach on contact, so a porcupine that has been struck by a swatting paw or a nose leaves quills behind, but it cannot launch them across a gap
Antibiotic quills: The quills carry a coating of fatty acids that slows bacterial growth, which is thought to protect the porcupine itself from infection when it slips and falls out of a tree onto its own quills, a common accident
A craving for salt: Its woody, low-sodium diet leaves it desperate for salt, and it will gnaw sweat-soaked axe handles, canoe paddles, plywood, outhouse seats, and road-salted tyres and brake lines to get it
The fisher problem: Its main specialist predator is the fisher, a large weasel that circles the porcupine biting its face until it weakens, then flips it over to attack the quill-free belly; reintroducing fishers has been used to reduce porcupine damage in commercial forests
Careful courtship: Before mating the male sprays the female with urine, and she relaxes her quills and flattens her tail against her back to make contact possible; a single well-developed baby is born with soft quills that harden within an hour
Range: North America from Alaska and across Canada south through the western United States to northern Mexico and, in the east, to the northern states, in coniferous and mixed forest, but also in deserts, brushland, and tundra edges.
Conservation status: Least Concern → ≈ Common and widespread across northern North America, with a stable overall population; heavily reduced in parts of the northeastern United States by historic bounties and then recovered, and locally controlled where bark stripping damages timber in the wild