Koalas protect themselves from predators such as dingoes by spending their time high up in trees. They only descend to move from tree to tree or to drink water.
The sharp claws, strong grip, and rough pads on the hands and feet make koalas ideally adapted for life in trees. They have two opposable thumbs for clinging to branches and strong muscles that enable them to climb high and leap from branch to branch. Because eucalyptus leaves, their preferred food, contain a lot of water, koalas seldom descend to drink. Their diet does not have much nutrition, so they are sedentary animals and sleep in trees up to 20 hours a day. Impregnation and gestation take place high above the ground. Koalas are marsupials, so when the baby, or joey, is born at the embryonic stage, it crawls into its mother's pouch and stays there safely for at least six months. When it finally emerges, it spends more months clinging to its mother's back. Gradually it learns to grasp branches and become self-sufficient.
More threatening to koalas than predators are bacteria and parasites. In addition, when they are about six years old, their chewing teeth begin to wear away. Eventually, the teeth are completely gone, and the koala starves to death. Brush fires are also dangerous to koalas, as they have a tendency to climb higher into trees rather than flee. Also threatening to koalas are periodic droughts, which dry up the eucalyptus leaves.