The scientific name of the koala is Phascolarctos Cinereus, from the Greek for "pouched bear" and "ash gray." The koala lives in trees, specifically some 35 of the more than 600 species of the genus eucalyptus that grow in Australia. The diet of the adult koala is almost exclusively eucalyptus leaves, and since the oils of eucalyptus leaves are toxic to most other mammals, one wonders what adaptations enable the koala to thrive on them.
A fully grown koala weighs about 9 kilograms and its body is at most about 62 centimeters long. Its fur is thick and woolly, its limbs are long, and its toes are strongly clawed. On each front foot the two innermost digits can be opposed to the others like two thumbs as can the innermost digits on each rear foot. It is this articulation, or moveable joint, that makes the koala a good climber. On the ground to which it normally descents only to move from one tree to another, the koala goes on all four limbs. Most of the time it is in a tree, intermittently sleeping and foraging among the leaves by day and at night.