The primary diet of a koala consists mainly of eucalyptus leaves. These leaves are low in nutrients, which means koalas have to consume a large quantity to meet their dietary needs. Eucalyptus leaves also contain toxins, but koalas have a specialized digestive system, including a large cecum, which helps detoxify these compounds. As a result, koalas are highly selective feeders and primarily eat the leaves from specific eucalyptus species. They are also known for their slow metabolism, which allows them to conserve energy while digesting their fibrous diet.