Preservation Of Our Macropods

by Dr. Ian M. Gunn, BVSc (Hons), FACVS. Dr Gunn is the Project Leader for the Animal Gene Storage Resource Centre of Australia, Institute of Reproduction and Development, Monash Medical Centre .

It is a sad reflection on our communities and our social system that civilisation, as we know it, has not been able to save or maintain our natural resources. Civilisation appears hell bent on a course of self-destruction; destruction of our environment, resources, wildlife and humanity itself.

History continues to repeat itself without our ability to accept the lessons of the past - the overwhelming disregard for tomorrow, today's greed, our desire to slaughter anything that moves, including our own species, and the human race's desire to reproduce regardless. These contributing factors have led to the loss of natural habitats, pollution and human over-population, with the resultant extinction of species and races.

The challenge is to save and preserve our remaining wildlife. With the current policies and pressures from Governments and commercial interests, there seems little chance to reverse the continual decline in habitat, native wildlife numbers and genetic diversity. There are definitely exceptions and successful recovery programs but these are few and limited. Concentrating solely on the marsupial macropod's history records, at the time of European settlement 207 years ago, there were 49 macropod species. Since then, six have become extinct, 7 are endangered and 10 are classified as vulnerable due to their small population in restricted ranges. Have we halted this decline? No - it continues. Only 9 of the remaining 25 species are considered widespread and abundant; however numbers of the remaining species are killed annually.

The concern is that continued culling has the potential to precipitate the possible extinction of a number of remaining species. Why? There are three major factors that can clearly be identified as contributing causes. These are:

1. The indiscriminate culling of kangaroos. I refer to the practice of eliminating the largest, healthiest kangaroos from the selected popul ation.
2. The unreliable and largely estimated kangaroo population density figures presented to justify and secure culling p e r m i t s .
3. The transfer or re-location of species habitat. Since 1940-50, competition for grazing, clearing and culling has significantly altered the species habitat range and the population density in these areas. With reference to NSW, there has been a continuing shift of the population concentration further and further west, into areas which are extremely sensitive to climatic variations and to increased grazing pressures.

The evidence is indisputable and, if left to continue, has the potential to result in reduced genetic variability, lower reproductive efficiency and a radical reduction in the population density below sustainable levels in certain regions of the country when associated with habitat reduction or during seasonal conditions such as droughts.

I refer to H.J. Lavery (1985) 'The Kangaroo Keepers': A computer simulation model has been developed that shows the harvest sex ratio (that is, the percentage of females in the harvest) taken by a professional shooter actively selecting for the largest available animals is a reliable index of the state of under- or over-harvest. Measured in conjunction with properly defined environmental conditions, harvest sex ratios obtained over a series of years can in fact indicate

• the extent of net population losses (which may result from reduced reproduction, natural deaths and harvests), and
• when the population has reached a signal point.

This latter is when the harvest is 50 per cent female, and the population is reduced to about one-half its original size. Other indicators of a population approaching the signal point are

• when the harvest by a shooter selecting for the largest animals comprises only 1 per cent - 2 per cent males age 10 or more years,
• when the harvests consist of approximately equal proportions of males aged 1-3 years and 4-9 years; and
• when professional shooters are operating at the maximum practical level of effort.

From this signal point, the population enters a critical phase when rate of population decline accelerates significantly to extermination. The decline can be reversed if appropriate action is then taken to reduce harvesting. If corrective action is not taken, the period to extinction can be predicted from the model. I wonder as to the status of this model and its adoption as a regular guide to current culling programs.

Australia has the expertise, technology, resources, facilities\ and hopefully, the commitment to save our animal genetic resources, our native wildlife, and especially the remaining macropod species. We do not have the population pressures, wars, or the economic distress evident in other countries fighting similar battles to preserve their native resources.

We have no excuses.

The critical point is that the survival of any of our wildlife species depends on a multitude of interrelated complex factors. If we continue to exert further pressure through inappropriate culling, this could very well precipitate the rapid extinction of the species.