The following report is from a September 1996 article in the Encarta Yearbook.

Australia Plans Birth Control Trial for Koalas

Hundreds of koalas will receive vasectomies and hormone implants under a plan announced September 19, 1996, in the state of Victoria, in Australia. The birth control plan is designed to prevent a population explosion and eventual starvation in areas where the presence of too many koalas is already stripping eucalyptus trees bare of leaves, the koalas' favorite food.

Hunted to near extinction during the last century, koalas are thriving in some of Australia's protected eastern forests. They are doing so well, in fact, that they are eating their way through their food source. Overpopulation could ultimately destroy the stands of manna gum trees, a type of eucalyptus, and cause mass starvation.

The image of booming colonies of koalas is in stark contrast to the overall picture in Australia. Humans have moved into traditional koala habitats and the numbers of koalas are dwindling as their forests shrink.

That is not the case, however, on some protected islands and mainland forests. In some areas in Victoria, populations of the voracious vegetarians reportedly were up to ten times the normal size. The state minister for conservation and land management, Marie Tehan, said: “If we don't face up to this issue, several areas will suffer long-term ecological damage and koalas will starve.” Beginning in December, wildlife officials planned to conduct the birth control trials in three koala colonies over three years.

Wildlife officials in Victoria consider contraception the most viable option for controlling koala overpopulation. The South Australia government proposed shooting the animals earlier this year and was forced to drop the plan due to public outcry. Moving the animals to other areas is not possible because of a lack of suitable sites.

But the chief biologist of the Australian Koala Foundation, a private research group, was critical of the fertility plan. Steve Phillips said artificial contraception would cause social disharmony in the complex social hierarchy of the koala communities. He predicted that the promiscuous animals would seek other partners if there were suddenly no baby koalas.

Wildlife officials were considering introducing venereal disease to control the koala population. Chlamydia, a sexually transmitted disease, is devastating to koala communities, causing infertility and blindness. However, the disease slows down the koalas' breeding cycle to a sustainable level and could be used as a form of birth control, according to some wildlife experts.

Source: Encarta Yearbook, September 1996.

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