Koalas use their extremely sharp claws for climbing eucalyptus trees. They subsist almost exclusively on eucalyptus leaves and bark. They are picky eaters, eating only about 20 of the approximately 350 species of eucalyptus in Australia. Since eucalyptus leaves contain the precursors to hydrocyanic acid, or cyanide, koalas also occasionally eat soil, which helps detoxify their food. Koalas in the wild rarely, if ever, drink water.
Koalas are tiny, approximately one half of a gram, when they are born.
Twin births are very unusual, but a mother koala will adopt an abandoned baby if she finds one. The young koala stays in its mother's pouch for approximately seven months. Unlike most marsupials, the koala's pouch opens towards the rear, not towards the head. At the end of the seven month period, the mother begins to wean the baby off of a purely milk diet by introducing it to predigested eucalyptus leaves. After leaving the pouch, the young koala is carried on its mother's back until it is a year old.