Most researchers have thought this consisted of soft pellets or droppings of partly digested gum leaves which have passed through the mother's caecum and digestive tract, but recent observations suggest that the young is actually feeding on a soft green fluid called 'pap' assumed to be derived from the contents of the caecum and produced with the normal droppings by the mother. No other animal is known to be weaned in this way. This is thought to prime the caecum of the young koala with the bacteria essential for its function, but it may also provide a rich supply of bacterial protein for accelerated growth. At 12 months the young koala is fully weaned and independent of its mother. By 18 months it has usually moved away from the area where it was born.
Females become sexually mature at the age of two years, males at three to four years.
There is little information on longevity in the wild, but captive animals have lived for more than 15 years, and some authorities suggest the maximum lifespan is about 20 years. Competition and Survival Australia's first settlers, the Aborigines, frequently used the koala for food, but apart from that risk it probably had few natural predators. However, periods of drought may often result in the death of many koalas. The coming of white settlement, with the subsequent clearing of land and the increase in the frequency of bushfires, plus shooting for its highly prized fur, brought the koala to the verge of extinction earlier this century. It is now fully protected, large tracts of eucalypt forests are being preserved, and a vigorous research program is under way to reduce further threats to its survival.