A female koala with her joey. (Photo: Chris Round)
At 11 months of age the young koala no longer shows signs of distress when separated from its mother but goes to sleep. If another adult sits close by, the youngster climbs aboard. It is not uncommon to see young koalas of this age by themselves or making longer journeys between trees. After nearly a year of close contact with the mother, the young koala is taking the final steps towards permanent separation. Weaning is a gradual process, but is sometimes accelerated by the arrival of the next joey when the young is approximately 12 months of age and weighs about 2.5 kilograms.32 At this time the mother will rebuke the older koala if it tries to suckle. Usually, however, the joey's long period of dependence on its mother means that female koalas tend to breed every second year. If she has unlimited access to good-quality foliage, however, a female koala may be able to breed in consecutive years.
After weaning, the young koala can continue to associate with its mother for another year and will often occupy a home range within its mother's. From two to four years of age, most young koalas, male and female, move away from their mothers to seek their own territories, sometimes prompted by aggressive behaviour on the part of the older female.
Although the joey koala spends most of its first year in very close contact with its mother, there is no evidence of later recognition between a mother and her offspring. So why do koalas have such a long weaning period? Perhaps it may be to protect the joey from predators such as owls and goannas, by keeping it with its mother until it is of a sufficient size to discourage those looking for an easy prey, but it may also be that the manipulative skills necessary to navigate slender branches, balance and eat are only fully developed at the time of weaning.
Many of the studies which formed the background of this chapter took place under the auspices of koala sanctuaries and zoos, both in Australia and much, much further afield. While it is an undeniable boon to researchers to have such uninterrupted access to their subjects, what is it that makes the koala such a desirable inmate for zoos and wildlife parks many thousands of kilometres from its native home? In fact, as we will see in the next chapter, the most sedentary and solitary of Australia's marsupials is arguably one of its most-travelled ambassadors.
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