Porcupines are generally solitary animals, and are strongly attached to a territory. Territory sizes vary and can be up to several hundred acres throughout the summer months. During winter, this territory shrinks considerably, usually down to six acres or so. The female generally has one offspring per year in May or June. Porcupine diets vary with the seasons and differing habitats.
Porcupines feed on herbaceous vegetation in the spring.
By late August, when ground vegetation has dried up, porcupines begin their winter diet of the inner bark of native conifers, especially Ponderosa pine. A porcupine's long claws and stout, muscular tail makes it well adapted to tree climbing. Porcupines have long been a pest in Idaho forests, causing wide-scale damage. Porcupines do not usually kill trees. They also reduce a larger tree's ability to produce seed and can kill or deform seedlings and saplings.