After a pregnancy of 35 days, the newly born koala is about a quarter of an inch long, and is born with no ears, eyes, or hair. It crawls into its mothers pouch on its own. After 12 months the young koala is old enough that it does not go into its mother's pouch or need milk anymore. The female koala can have another baby then. Young koalas usually leave their mothers when they are 18 months old, but if their mother does not have another baby they sometimes stay for up to three years. Koalas become mature when they are about two years old, but they often have their first baby after another two years.