Rabbits are herbivores that feed by grazing on grass, forbs, and leafy weeds. In consequence, their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem via a form of hindgut fermentation. They pass two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are immediately eaten (a behavior known as coprophagy).
Rabbits re-ingest their own droppings (rather than chewing the cud as do cows and numerous other herbivores) to digest their food further and extract sufficient nutrients. Rabbits graze heavily and rapidly for roughly the first half-hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding.