Koala Facts | Australia South Wildlife Guide
Koalas are nocturnal, and they sleep for up to 20 hours per day. Rather than being inherently lazy, their low-energy lifestyle is a direct result of their diet. Eucalyptus leaves are not terribly nutritious, and they are toxic to most animals. Sleeping so many hours per day allows the koala to conserve energy and also gives their bodies time to neutralize the toxins from their food.
Koalas are also another living example of evolution in Australia. Prehistoric koalas burrowed rather than living in trees, so their pouches open to the rear instead of opening upwards like kangaroos. This was a perfect adaptation to prevent dirt from falling into the pouch while digging but is not ideal when the pouch sometimes opens up to a 150-foot drop from a tree. To keep the joey safely inside, the mother koala has muscles that can keep the pouch closed.
Although they are an iconic symbol of Australia, koalas are at risk. 80% of their traditional range has been destroyed by human development. This puts significant pressure on the remaining habitat which is restricted to the eastern and southeastern regions of Australia. Climate variability can also stress their reproduction, and the San Diego Zoo is currently researching links between rainfall and koala births.