Koalas are very fussy eaters! Their diet consists of leaves from eucalyptus trees. Eucalyptus leaves are very fibrous and low in nutrition. Koalas are the only mammal that can survive on eucalyptus trees. To most animals eucalyptus leaves are very poisonous! Sometimes koalas will eat from other trees such as wattle, tea tree or paperbark. They also eat gum leaves. Gum leaves contain a lot of water, so koalas don't have to drink. They eat about 200 to 500 grams of food per day. They sometimes store extra food in their pouch! A koala will pull down a branch of eucalyptus or gum leaves and sniff the juicy buds before it decides to eat it or not. Koalas also sleep up to 16 hours per day in order to conserve energy.

Baby koalas drink their mother's milk for the first 6 to 7 months. After that they start eating gum leaves.

Koalas have 3 kinds of teeth. Cutting teeth are called incisors, tearing teeth are called canines, and grinding teeth are called molars. The sharp front incisors bite the leaves from the trees. The molars, or back teeth are shaped to allow the koala to cut the leaves rather than crush them. A gap between the inscisors and the molars, called a 'diastema', allows the tongue to move the mass of the leaves around in the mouth.

Koalas have a special fiber-digesting organ called the caecum. The caecum contains millions of bacteria. The bacteria break down the fiber into digestible substances. Even so, the koala still absorbs 25 percent of the fiber eaten.