However, recent observations of koala populations suggest that the males often have two or three females fairly close by, forming a kind of harem. This may occur, of course, only during the mating season. The male's behaviour and loud bellowing seem to be involved in the spatial separation of mature males and in their competition for mates. At night, in areas where they are numerous, the grunting, pig-like sounds of koalas can be heard. When alarmed or distressed they make a continuous loud wailing sound.
Koalas are, however, generally inoffensive.
Not surprisingly, they have a characteristic eucalyptus-like odour. Mating takes place in spring and summer. At these times the males fight fiercely, their loud angry growls echoing through the night. The gestation period for the koala embryo is thought to be about 35 days. Of particular interest is the fact that the female koala's pouch opens backwards, that is, towards the rear.