Koala (Phascolarctos cinereus)
The koala is truly one of a kind. This marsupial has no close relatives and lives only in eucalyptus woodlands, where it dines mostly on the toxic leaves. Bacteria in its stomach neutralize the harmful chemicals. To hold onto small branches or ascend slippery trunks, koalas rely on long, needle-sharp claws, opposable fingers and toes, and ridged pads on their hands and feet.