Few faces rival the cuteness of the koala, and the way they hug those branches just adds to their snugliness. They're also a rather sleepy animal, since their low-nutrition diet of eucalyptus leaves makes them sluggish. In fact, they typically sleep for at least 18 hours a day. Like most of the world's marsupials, koalas hail from Australia. Although they aren't officially considered endangered, wild koala populations are under constant threat due to habitat loss from deforestation and development, and their numbers have dropped by as much as 90 percent in the last decade.