March 1997 Vol.18 No.1

Biorational

Integrated pest management involves the use of many techniques, including biological control, to provide effective control of pests with minimum harmful side effects. Those techniques which are compatible with the use of biological control or have little impact on natural enemies have been described as "biorational".

Koala Contraception

The cuddly koala is giving wildlife scientists in Victoria, Australia, a headache. Numbers in the state are increasing, but a cull is considered totally unacceptable, while relocation is no longer an option because agriculture has reduced the amount of suitable habitat. Koalas eat the leaves of only one type of eucalyptus, E. viminalis, so they will destroy their own food supply if numbers are allowed to increase further.

The Victorian government has started on a three year trial using contraceptive techniques. Dominant males will be given vasectomies and females hormone implants to prevent them from ovulating. The plan has been criticised by koala experts, who say that missing a few animals, especially a single dominant male, will negate the whole exercise. The Australian Koala Foundation, a private conser-vation group, has suggested that better results would be obtained by encouraging the spread of Chlamydia, a sexually transmitted bacterial disease that sterilises females, because in areas where it exists the koala population is stable. Combined with planting more Eucalyptus viminalis, this would provide a long term solution to the problem.