The North American Porcupine (Erethizon dorsatum) is a native and established species in Washington State. It is one of the largest rodents in North America, surpassed only by the American Beaver. Porcupines are primarily herbivores, spending much of their life searching for plant material to consume. They possess a unique defense mechanism.
Physical Characteristics
An adult porcupine can range from two to three feet in length and typically weighs between 15 and 27 pounds, though some individuals may reach up to 40 pounds. Their most distinctive feature is the covering of approximately 30,000 quills, which are modified, barbed hairs used solely for defense. Porcupines are currently classified as “Unclassified Wildlife” in Washington, indicating they are not a protected species.
Geographic Distribution within Washington
The distribution of porcupines in Washington is widespread, though their population density varies significantly across the state’s geographic regions. They can be found in forested areas and brushy wetlands, from sea level up to the treeline. However, their presence is notably absent only from the coastal San Juan and Island counties.
The highest concentration of porcupines is generally located east of the Cascade Mountains. This includes the dry, forested, and shrub-steppe habitats in areas like the Okanogan region and the Blue Mountains. Recent research suggests a shift in their preferred habitat, with greater numbers now found in shrub-steppe and grassland vegetation communities compared to historically forested areas. While they are present in the eastern slopes of the Cascades, they are comparatively rarer in the dense, wet forests of Western Washington.
Ecology and Encounter Safety
Porcupines are mostly nocturnal, meaning they are active during the night as they travel slowly between their dens and feeding sites. Their diet shifts seasonally; in the spring and summer, they consume fruits, leaves, and buds, but in winter, they rely heavily on the inner bark, or cambium, of trees and conifer needles. This winter foraging behavior can sometimes lead to damage or even death of individual trees, which is a concern for property owners.
A significant source of conflict is the porcupine’s strong attraction to salt. Because their natural diet is low in sodium, they seek out salt sources, leading them to chew on wooden tools, tires, or structures that have absorbed road salt or human perspiration. To avoid property damage, it is helpful to secure items that may contain residual salts, such as tool handles or garden hoses.
The porcupine’s primary defense is its coat of quills, which are not thrown but are loosely attached and easily detach upon contact. If threatened, the porcupine will erect its quills, turn its back, and lash its barbed tail at the perceived attacker. Pet owners should be cautious, as quills can embed deep into flesh, and their barbs make them difficult and painful to remove. Hikers and pet owners should keep dogs leashed and avoid approaching or cornering a porcupine.