An animal that eats vegetation, especially any of the plant-eating mammals, such as ungulates (cows, horses, etc.). Herbivores are characterized by having mouthparts (e.g. teeth) adapted for shearing, chewing, or grinding plants and alimentary canals specialized for digesting cellulose (see caecum). Oligophagous herbivores are specialized feeders that eat just one or a few plant species, whereas polyphagous herbivores eat a wide variety of plants.