When do koalas mate?

Female Koalas are mature at 2 to 3 years old and the male at 3 to 5 years old. A female can have one baby a year for as many as 12 years, but generally, older females may breed only once every two years. Twins are not common, but they have been recorded. Breeding season is in the Australian spring through to summer/early Autumn (September through to March). Female koalas are pregnant for about 35 days on average. The young joey then stays in the pouch for five to seven months, after which it continues to cling to its mother's back antil about one year old.