Porcupine
Order Rodentia : Family Erethizontidae : Erethizon dorsatum (Linnaeus)

Description. A large rodent with distinct, barbed quills on back, sides, and tail; long guard hairs usually yellowish, impart a yellowish or yellowish-brown appearance to the animal. External measurements average: (males) total length, 808 mm; tail, 235 mm; hind foot, 98 mm; (females) 737-230-81 mm. Weight, 5-11 kg.

Distribution in Texas. Known from western one-half of state, east to Bosque County.

Habits. The porcupine is adapted to a variety of habitats. It is largely an inhabitant of forested areas in the West and prefers rocky areas, ridges, and slopes. It is less common in flats, valleys, and gulches. Porcupines wander about a great deal and may be found irregularly in areas that appear wholly unsuited to them. In recent years, it has expanded its range into southern Texas.

They are expert at climbing trees, although their movements are slow, methodical, and seemingly awkward. They apparently are aware of their limitations and they take few chances. Porcupines seem to be as much at home in the rocks as on the ground or in trees. The more massive and broken the rocks the better they serve the animals for the numerous crevices and caves can be used as den sites and the large boulders as resting places. Where rocky dens are accessible, they are visited at intervals by many porcupines from the surrounding region and are used from year to year. Where such dens are unavailable a hollow log, a windfall, or an upturned or loosened tree root system may serve the purpose.

In winter when snow covers the ground, porcupines seldom travel far from their dens, especially in freezing weather. As warm weather approaches, the amount of travel increases.

Herbaceous ground vegetation makes up 85% of the food of both old and young in summer. In fall only 27% of their food is herbaceous; 73% is tree-gathered and includes mistletoe, the inner bark of a variety of trees, and pine needles. In winter the food is wholly from trees, and pine needles and inner bark are consumed at their peak during this season. In spring they again return to herbaceous ground vegetation which then makes up nearly 40% of their diet. Throughout the year the porcupine is more of a browser than a grazer and subsists in large measure on the inner bark of trees and shrubs; grass is of no importance at any time of the year. Porcupines are especially fond of salt and are easily attracted to it, a fact which is useful in their control.

Breeding takes place in late summer and early fall, with the peak of activity in September and early October. The young, usually one, rarely two, are born about 7 months later in April and May. The gestation period is 209-217 days. At birth the young porcupine weighs about 450 g and is larger than a newborn black bear. It is covered with a good coat of blackish hair, the quills are well-developed, the eyes and ears are functional, and the incisors and some of the cheek teeth have erupted. It is usually suckled for only a short period, begins to feed on vegetation shortly after birth, and soon becomes entirely dependent upon its own resources. The young porcupines grow slowly as compared with most rodents, and females do not mature sexually until their second fall when they weigh about 4 kg. Porcupines have a relatively long lifespan. One marked female is known to have lived more than 10 years under natural conditions.

Photo courtesy of U.S. Fish and Wildlife Service.