Once a female koala sexually matures, she mates as often as once a year. These marsupials typically breed during the late spring and early summer, a period during which females experience estrus multiple times until they find mates. Though their gestation periods are short, they may go on taking care of their young for more than a year after they're born.
Finding a Mate
Koalas live in the southern hemisphere, where late spring and early summer fall around October and November. During this period, females experience estrus, the biological compulsion to find a mate. As they go through estrus, males advertise themselves to females by marking trees with their scents and bellowing. In some cases, males may physically fight each other in competition for a female.
Mating and Gestation
After mating with a female, the male koala does not assist in caring for the young. Females experience a short gestation period, giving birth after only about 35 days. The birthing process is relatively simple for her, as she typically gives birth to only one baby, called a joey. The joey is less than 1 inch long when he's born and incapable of caring for himself. Deaf, blind and hairless, he uses his relatively strong upper body to crawl unassisted into his mother's pouch, where he attaches to a nipple.
Raising the Joey
Once attached to his mother's nipple, the joey stays in place for about six months, living exclusively on a diet of milk. After six months or so, he is developed enough to leave the pouch, and his mother weans him off of her milk and onto a diet of semi-digested leaves called pap -- a non-fecal waste matter excreted by the mother. He leaves the pouch for increasingly long periods of time until he's about 11 months old, at which point he lives outside permanently.
The Life Cycle Continues
Though the young koala may stay near his mother for several more months, he is capable of complete independence when he is about 1 year old. Males and females are both sexually mature when they are 2 years old, at which point the females begin experiencing their seasonal estrus cycles. While the males are capable of reproducing, they may not mate for several more years, as younger males may not be large enough to compete against older koalas in the fight for female affections.
- Tom Brakefield/Stockbyte/Getty Images