Elephants eat enormous amounts of vegetation daily , but the digestive system only uses about 40 percent of the intake. It is estimated that nearly 60 percent of elephant feces is undigested or partially digested vegetation. This poor absorption of nutrients is one of the reasons why elephants are considered a keystone species. The undigested or partially digested vegetation generates new plant growth as it is deposited on the elephant's travels. Keystone species play a key role in an ecosystem. Their presence or absence affects many other species.
Elephants are a keystone species in the savannah ecosystem because many plant species require seeds to go through a digestive system before germination. It is estimated that at least one-third of tree species in West Africa rely on the elephants' digestive system for germination. Many savannah species, including elephants, benefit from the new vegetation growth for food and shelter.
Elephants are non-ruminants, meaning the food is fermented after it has been digested by the stomach (hindgut fermentation), and is pushed through the gut at a rapid rate. Because the contact time the fermented food has with the absorptive surfaces of the intestines is limited, non-ruminants are not able to extract as many nutrients from the food. These animals compensate the nutrient loss by eating greater quantities and are capable of eating lower quality vegetation.
Elephants are capable of consuming vegetation that is too fibrous and protein-deficient for ruminants to consume. Ruminants are foregut fermenters, that consume lower quantities of higher quality vegetation. Elephants are capable of thriving in a wide range of habitats due to the digestion of lower quality vegetation.
Elephants impact the environment in numerous ways. During migration elephants use the same paths, creating trails that other animals and humans use to travel. The tusks are used to dig wells, generating multiple water sources throughout the habitat. As elephants traverse through the environment, the large size helps bring down vegetation, which then become accessible to smaller species.