Koala around and its head has doubled in size. The eyes begin to open and fine fur grows on the forehead, nape, shoulders, and arms. At 26 weeks, the fully furred animal resembles an adult, and begins to poke its head out of the pouch. As the young koala approaches six months, the mother begins to prepare it for its eucalyptus diet by predigesting the leaves, producing a faecal pap that the joey eats from her cloacum. The pap is quite different in composition from regular faeces, resembling instead the contents of the caecum, which has a high concentration of bacteria.
Koala brown fur and a wider skull. The boundaries of these variations are based on state borders, and their status as subspecies is disputed. A 1999 genetic study suggests that the variations represent differentiated populations with limited gene flow between them, and that the three subspecies comprise a single evolutionarily significant unit. Other studies have found that koala populations have high levels of inbreeding and low genetic variation. Such low genetic diversity may have been a characteristic of koala populations since the late Pleistocene. Rivers and roads have been shown to limit gene flow and contribute to the genetic differentiation of