Porcupine, Porcupines, Erethizon dorsatum, fauna, herbivore, herbivorous, herbivores, Mammal, Mammals, Rodent, Rodents, North American wildlife, wildlife, Forest, Forests, Woodland, Woodlands, Boreal Forest, North America, Rocky Mountains, Kitchin, Hurst, quill, quills, White, Winter, Snow, Track, Tracks, Animal Tracks, Trail, Vertical