Koalas are nocturnal marsupials famous for spending most of their lives asleep in trees. During the day, they doze while tucked in trees, sleeping for up to 18 hours. Koalas do not drink much water and they get most of their moisture from leaves. In Aborigine language, the word ‘koala’ means ‘no water’. However, Koalas can become dehydrated in very high temperatures.