this sleepy koala opened his eyes for just a few seconds: so I could get the pic before he was closing them again, very slowly.......... . The koalas are one of nature?s most fussy eaters. It will only eat the leaves and young shoots of the eucalyptus tree. It also eats the tree?s stems, flowers, and bark, but it likes the leaves best. And not just the leaves of any eucalyptus tree. Of the more than seven hundred varieties of eucalyptus, the koala will only eat from about three dozen of them. If you are thinking that eucalyptus is highly nutritious because they are almost the only food that koalas eat, you are wrong. The leaves of eucalyptus have little protein, lots of material that is hard to digest, and are actually poisonous to most animals. Bacteria in koala?s stomach break down the poisonous oils in the leaves so they do not harm the koala. The koala must eat between 1 and 1.5 pound (454 and 680 grams) of eucalyptus leaves a day to provide it with enough nutrition to survive. That is a lot to eat for a small animal. The koalas spend s about two to four hours a night chewing the tough leaves into a thin paste that it can swallow. When its stomach is full, it will store more leaves in its fat cheeks. Much of the other eighteen or more hours of a koalas? day are spent sleeping. All that eating is hard work, and the koala?s poor diet provides it with a limited amount of energy. . taken through glass, at Beauval Zoo, France.