Herbivores have traditionally been categorized as either dietary generalists or specialists based on what they eat or what they are capable of eating. Shipley and others (2009) argued that specialization should also be based on the limitations imposed on an animal by genetics, physiology, and behavior. They categorized herbivores along a specialist-generalist continuum, with specialists defined as facultative or obligatory, based on seasonal or regional niche breadth. The North American Porcupine (Erethizon dorsatum) has traditionally been considered a generalist herbivore. However, Porcupines often function as dietary specialists consuming a difficult and narrow diet seasonally, regionally, or individually. Porcupines possess physiological and morphological adaptations to consume a difficult diet and do so at a rate higher than other herbivores. Porcupines should therefore be reclassified as facultative specialists. Additional research is required, however, to better understand the degree of specialization exhibited by Porcupines throughout their range. Comparative studies of diet selection across habitats will provide insight into regional and seasonal dietary specialization, and captive studies are required to understand the physiological mechanisms used by Porcupines to consume difficult foods. Documenting inter-population and individual differences in the ability to metabolize plant secondary metabolites will provide insight into the ecology of Porcupines, and will assist in managing potential impacts of Porcupines on native flora as they expand into new habitats.