Porcupines
Author: Richard Plunkett

Description:
The porcupine is very different from other rodents in North America because it is so large, has a big head and, of course, because of its long quills. Porcupines have around 30,000 quills, mostly on their backs and rumps. The longest quills are near the tail and the shortest are on their cheeks. The quills are stiff and sharp with very tiny barbs on the tips. These barbs make them difficult for other animals to remove after they have been attacked. The quills are surrounded by long guard hairs which can be dark brown to pale yellow or grey. Porcupines have wooly underfur, and do not have quills on their undersides. Porcupines grow to a size of 23 to 51 inches. Their tails can be from 7 to 10 inches in length. Adult porcupines weigh from 8 to 40 pounds. Males generally weigh more than females. Porcupines have four toes on their front paws and five on their rear paws. Each paw has a long curved claw.

Geographic Range:
North American porcupines can be found across all over North America. They live as far north as Alaska and as far east as New England. Theylive all over most of the western United States from the Rocky Mountains to the Pacific Northwest, and as far south as northern Mexico.

Habitat:
North American porcupines live in forests and mountainous areas, but they can be found in nearly every kind of environment. In New Mexico, they are commonly found in coniferous forests within mountainous regions. They can also found in lowlands, cottonwood and willow forests near rivers, semi-desert scrub, and along farmland. Porcupines are often found near roadsides and many are killed by automobiles. They also make dens in rocky walls or slopes and in arroyo-side burrows.

Food Web:
Porcupines' diets change with the seasons. They are herbivores year-round, but their summer diet is quite different from their winter diet. During the summer they eat many different kinds of plants—tender shoots, herbs, twigs, buds, a multitude of fruits, berries and nuts. In the winter they eat the parts of a tree like bark and pine needles. In New Mexico porcupines may feed on ponderosa, lodgepole, white pines, douglas fir, and spruce trees. Porcupines may even climb into trees to get at the bark and branches. Once they find a good comfortable spot to sit and eat, they may end up doing a lot of damage to the tree. Places where porcupines have been feeding during the winter can be spotted very easily by the shiny white branches which have been stripped of their bark and the trunks of trees that have been stripped or girdled by hungry porcupines. Because of their large size and sharp quills, porcupines have few natural enemies, but there are a few animals that hunt porcupines for food. For example, the fisher known for its skill at killing porcupines without getting quilled. Other porcupine predators include coyotes, bobcats, gray wolves and owls. Humans can also be considered a predator because some humans hunt porcupines for food too!

Reproduction and Development:
Breeding season for porcupines is in the fall, usually from September to November. Male porcupines search for females by sniffing around trees and rocks. The males lure the females by making very complicated vocalizations, including loud and shrill screeches. If male porcupines are competing for a female during mating season, they may become very aggressive and fights can break out. Females carry their young for as long as seven months (up to 240 days), which is very unusual for rodents. Young porcupines are born in late April and early May, when there is plenty of grass and plants to eat. Mothers almost always give birth to a single young which weighs around 500 g at birth. Baby porcupines are quite developed compared to other newborn rodents: their eyes are open, they have all their teeth, and their quills harden within a few hours. The young porcupines are born with well-developed defensive skills. If they feel threatened, they will back up towards the intruder and raise their tails. Young porcupines are weaned in a week, but stay near their mothers through their first summer.

Behavior:
Porcupines do not “throw” their quills. They will, however, lash out at attackers with their tails to drive quills into the intruder's face and body. The barbed quills stick to the victim and pull loose from the porcupine's tail, giving the illusion that they have been “thrown.” Young porcupines practice “tail flailing” as a regular part of their play and it is a very common behavior.

Porcupines have very poor eyesight, but have very well-developed senses of hearing and smell. They use vocalizations to communicate. Females may communicate with their young by moaning, grunting, whineing and clicking their teeth.

Porcupines usually move slowly. You can tell that a porcupine has been around by piles of pellets left where they have been sitting in one spot and feeding. They are most active during the night and are often seen on roadsides.

Ecosystem Roles:
The feeding habits of porcupines can have an effect on where they live. In forested areas, porcupines eat the bark of tree trunks and branches. Porcupines tend to park themselves in one spot to eat, and strip all the bark from around a tree (this is called “girdling”). They may climb into trees during the winter and chew all the bark from a branch. Both of these types of behavior can severely damage or kill the trees. Porcupines can wreck seedlings and some agricultural crop plants as well. In addition, they have a habit of gnawing on plywood, power lines, and especially vehicle tires.

Conservation:
Interactions with humans are usually negative for the porcupine. They are often killed by automobiles on roadways and are generally treated as pests by humans. Humans poison, trap and kill them. Once it was common for states to offer bounties for killing porcupines. This no longer happens in most places, because local control of problem porcupines can be enough. In New Mexico, porcupines are given limited protection. They are not hunted as game animals, and the New Mexico population is considered stable. Non-lethal control measures may be taken with porcupines. These may be as simple as removing winter food sources from denning sites, which encourages the porcupines to find another place to live.

Cool Links:

• http://animaldiversity.ummz.umich.edu/accounts/erethizon/e._dorsatum$narrative.html

Taxonomy:

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia (subclass Theria)
Order: Rodentia (suborder Hystricognathi)
Family: Erethizontidae
Genus: Erethizon
Species: Dorsatum (subspecies couesi, NM; epixanthum, NM)

References:
Species information was obtained from the Biota Information System of New Mexico (BISON) and the following sources:

The Smithsonian book of North American Mammals. D.E. Wilson and S. Ruff (eds.). The Smithsonian Institution, 1999.

Mammals of North America. E.R. Hall and K. R. Kelson. The Ronald Press Company, 1959.

Related Terms: erethizon dorsatum, north american porcupine, puerco espin