The mating season for koalas is from December to March, which is summertime in Australia and the rest of the Southern Hemisphere.
During this time, male koalas compete with one another to attract mates. They bark, grunt, and even fight to get the attention of female koalas.
Males are usually quite docile but can fight during the mating season. Two males will often fight each other savagely to win the right to mate with a female.
Evidence of past conflicts can be seen in the scars that most adult males have on their faces, ears, and arms. The winner of the struggle gets the female.
The sounds tell other males to keep away, and also attract females. Each male judges the size and power of his rivals by the amount of noise they make. Often a young or small male hears the loud growls of a large male nearby, and keeps quiet.
A male koala makes a lot of noise so that females will notice him. He bellows loudly from the treetops so that nearby females will come closer to find out what all the racket is about. The call is so loud that it can be heard up to a half mile (0.8 km) away. A female koala makes a high pitched sound to call to her mate.
Females koalas usually mates every other year. She does not mate if she has a Joey that is less than a year old with her in her home range.
A male koala’s home range often overlaps with the home ranges of a few female koalas. If there are no females nearby, a male must travel on the ground to find one. The trip can be very risky.
They are more active at this time of year, and the males are noisier than usual. The koala’s breeding rate is fairly low. Females usually produce only one young each year, and twins are rare. Some females give birth only every two or three years, depending on their age and the quality of their habitat.
When a female koala reaches the age of 2 years, she is ready to mate. Males can mate when they are about 4 years old. As the breeding seasons arrives, and nearby males make their deep, roaring grunts, she replies with her own call to attract them. The male approaches, but he must wait until the female allows him to mate. If he tries too soon, she drives him away with bites and scratches. Most mating take place at night.
After mating, male and female koalas return to their own home ranges. The male does not help raise the baby. The mother feeds and protects it. With each new Joey, another life cycle begins.
A female koala may live 12 years and produce around six Joeys. She does not give birth every year, especially if there is a drought or a serious forest fire. There is no point in breeding if her young would have little chance of survival. Also, caring for a Joey makes her life slightly more dangerous. She must drink more than other koalas, because extra moisture is needed to produce milk. This brings the mother down from the trees, in search of pools and streams. On the ground, she is at greater risk from predators.
*On average, Koala females live longer than Koala males.
During the mating season, a male koala rubs his chest against the tree in which he lives. A gland on his chest produces smelly oil that tells other male koalas to stay away.
The Koalas have a life expectancy of about 15 years, can measure up to about 60 cm and the largest specimens weigh 12 kg.