According to the University of Michigan, Department of Zoology, porcupines are generalist herbivores; their predators include lynx, bobcats, mountain lions, wolves, wolverines and great horned owls. These predators employ different strategies for coping with the porcupines’ quills; some attack from the front to avoid the sharp spikes, while others simply deal with the wounds caused from the quills.
Porcupines consume many different plant species, and they often vary their diet throughout the year as different foods become available. The University of Michigan, Department of Zoology explains that in the Rocky Mountains, porcupines feed extensively on the phloem of ponderosa pines. By contrast, porcupines living in eastern deciduous forests consume a variety of tree species. The buds of sugar maples are a particular favorite of eastern porcupines, particularly early in the year. The cambium of basswood and aspen saplings is another preferred food source.
During the fall, porcupines rely heavily on acorns, hickory nuts and beechnuts that fall to the forest floor. However, squirrels, rodents and deer outcompete the porcupines over time, and eventually the porcupines revert to eating bark and cambium. According to the University of Michigan, Department of Zoology, hemlocks and sugar maples are consumed by porcupines during the winter.