Koalas are very solitary animals and, although the territories of males and females overlap, males will not tolerate intruders of the same sex. Resident koalas usually attack intruders savagely. Males mark out their territories with strong-smelling scent, and make loud calls to warn off other males.
During the breeding season, males try to guard as many female territories as they can. The single young or joey stays in its mother's pouch for seven months, then rides on its mother's back until the next season's joey matures. Koalas used to be very common in south-eastern Australia, but a mixture of hunting for fur in the early 20th century, habitat loss and severe forest fires have reduced their numbers.