The primary food source for koalas is eucalyptus leaves. These marsupials are native to Australia and have a highly specialized diet, relying almost exclusively on the leaves of various eucalyptus species. Eucalyptus leaves are low in nutrients and high in fiber, making them a challenging food source. However, koalas have evolved a unique digestive system, including a large cecum, which allows them to break down toxins and extract energy from these leaves. Because of their dependence on specific types of eucalyptus, their habitat is crucial for their survival.