Abstract: Animal models are viewed to understand the major types of fiber digestion. Faunivores, omnivores and granivores differ in their amounts of fiber digestion. These differences are partially due to the morphology of the gut and opportunities in abundance and Sacristy of food stuffs. The funivore model is the anteater, who utilizes autoenszymes to deal with the chitin in the diet. The frugivor model is the bat, who has to deal with cellulose and seeds. The herbivore model is the rabbit, who must consume large amounts of dietary fiber as dose the grazer. Adaptions vary in gut and selection