Koalas spend something like 20 hours a day asleep. This is because the food
they eat (gum leaves) are so hard to digest, and so lacking in nutrients,
that they simply don't have the energy to live a more active life. However,
when the time is right, they can often be seen running and during the mating
season the males can become very determined in chasing down a prospective
mate.
Koalas are often, incorrectly, known as koala bears.