The North American Porcupine, Erethizon dorsatum, is a large rodent and a specialized herbivore whose diet shifts significantly with the seasons. Although they consume a variety of plants, trees become the most consistent and substantial food source, particularly during colder months. Porcupines are active year-round, and their need for a dependable food supply when snow covers the ground drives their reliance on woody plants. Their ability to climb and forage high in the canopy allows them to access this resource when other options are scarce.
Preferred Coniferous and Deciduous Species
The porcupine’s diet depends highly on locally available species, but they consistently prefer certain types. Coniferous trees form the bulk of their winter food, including Eastern Hemlock, White Pine, Spruce, and Fir across their range. These evergreens provide both bark and needles, offering a sustained food supply when deciduous trees are bare.
Porcupines in the western United States frequently feed on pines, Douglas-fir, and spruces, sometimes focusing exclusively on the bark of one dominant species, such as Ponderosa Pine. Selection is often based on the tree’s nutritional density and ease of access, favoring stands with a more open canopy structure. In eastern habitats, porcupines often choose Hemlocks for both resting and feeding, as they offer superior thermal protection and a reliable food source.
Deciduous trees are less dominant in the winter diet but are still targeted, particularly for their sweet inner bark. Favorite hardwood species include Sugar Maple, Aspen, young Beech, and Birch. Porcupines also consume the bark of Cottonwoods and Willows, depending on the region. The preference for maple bark in the spring aligns with the period when sap is running, providing a sugar-rich meal.
Seasonal Consumption and Targeted Tree Components
The porcupine’s feeding behavior changes dramatically between the growing season and winter months. In spring and summer, their diet expands to include a wide array of leaves, buds, fruits, nuts, and herbaceous ground plants. This diversity is possible when ground access is easy and nutrient-rich foliage is abundant.
When winter arrives and snow limits ground foraging, porcupines become primarily arboreal, shifting focus to the inner bark of trees. They chew through the rough outer bark to reach the cambium and the phloem, the living layers responsible for transporting nutrients. The cambium is a concentrated source of carbohydrates, which aids survival when food quality is low.
Porcupines also consume the needles of coniferous trees, which provide some sustenance despite low nutritional value. The consumption of woody material, even with low energetic return, helps mitigate body mass loss through the winter. Additionally, porcupines gnaw on outer bark, tools, or even plywood to obtain trace minerals like sodium and calcium. This behavior is particularly noticeable in the spring when they are sodium-depleted.
Identifying Porcupine Feeding Damage
Porcupine feeding damage is identified by observing distinct signs left on the tree and at the base of the trunk. The most characteristic evidence is the removal of bark in large, irregular patches, often high in the canopy or on main branches. Porcupines typically feed by stripping the bark to expose the pale sapwood.
The specific markings left by their incisors are a reliable clue, as the exposed wood will be deeply gnawed and grooved. These parallel tooth marks are noticeably wide (3.6 to 4.8 millimeters across), distinguishing them from the smaller marks left by squirrels or other rodents. When the feeding encircles the trunk or a branch, a condition known as girdling, it can kill the tree above the wound.
Another clear indicator is the presence of coarse, peanut-shaped scat pellets and wood chips accumulated directly at the base of the damaged tree. The porcupine’s habit of remaining in one tree for an extended period creates a concentrated pile of debris below its feeding location. In contrast, damage closer to the ground is often attributed to rabbits or voles.