 Carpenter cited several studies of giant mammalian herbivores, such as elephants and rhinoceros, which showed that larger size in plant-eating animals leads to greater efficiency in digesting food.Since larger animals have longer digestive systems, food is kept in digestion for significantly longer periods of time, allowing large animals to survive on lower-quality food sources.This is especially true of animals with a large number of 'fermentation chambers' along the intestine, which allow microbes to accumulate and ferment plant material, aiding digestion.