These guidelines describe strategies for managing rabbits in four classes of land use:
- high production cropping and grazing land;
- low production rangeland;
- forestry plantations; and
- conservation areas.
The management option recommended for all classes of land use is sustained, strategic management. Ideally, rabbit management aims to reduce rabbit damage to the level where the benefits of management are greatest relative to the costs.
This approach requires knowledge of the relationship between rabbit density and the costs and benefits of management.
This is difficult and costly to determine, and it is unlikely that the rabbit, with its high reproductive potential, could be managed with this degree of precision.
For most circumstances, it is assumed that rabbit damage is related to rabbit density, although it is recognised that there is not always a direct correlation between rabbit numbers and levels of damage.
For example, there is evidence that in the rangelands of New South Wales, competition between sheep and rabbits only occurs when pasture biomass is less than 250 kilograms per hectare. The relationship between rabbit density and level of damage will vary with both the type of damage being considered and other factors, such as the total grazing impact from all species and variation in the vegetation cover.
This has implications for the selection of appropriate management strategies for rabbits in relation to different land uses and changes in market prices for wool, other commodities and for conservation values which are affected by rabbits.
In the authors’ opinion, based mainly on the experience of state rabbit control authorities, data from small-scale field trials, and on rabbit population ecology, reducing and maintaining rabbit populations at minimum densities is more likely to be successful and profitable for damage management than some lesser level of control to densities from which rabbit populations can rapidly rebound.
Even where resource damage only occurs when rabbit numbers are high, it may still be most cost-effective to maintain rabbits at very low densities at all times. Such a strategy could bring the greatest benefits at the onset of drought, when the impact of rabbits on both production and conservation values is likely to be high, and when land managers may have inadequate time, labour or funds to mount a rabbit control program.
The relative cost-effectiveness of aiming for sustained minimum levels as a long-term strategy will depend on the cost of this level of rabbit control relative to the benefits resulting from the control, in comparison to the cost–benefit ratios of some lesser level of control or no control.
The initial extra cost of achieving very low rabbit numbers could be offset by the reduced costs of continuing control to maintain these low numbers and reduced impacts. Strategic, sustained management (SSM) to reduce and maintain rabbits at minimum densities is most likely to be profitable in places where uncontrolled rabbit densities would usually be moderate or high (greater than three rabbits per hectare).
Rabbit control to achieve and maintain minimum densities is also likely to be profitable in conservation reserves where a high value is placed on the resources being protected from rabbit damage. In the rangelands, the high cost of reducing rabbits to very low densities might prevent this from being a feasible goal.
Although there may be high benefits from rabbit control in such areas, in terms of increased wool clip and land values, the large areas involved mean that initial control costs may be high and land managers may lack sufficient funds, especially at times of low wool values.
Rabbit control to increase production may not be profitable in areas which naturally have low rabbit densities (less than one rabbit per hectare). More information on the relationships between rabbit density and damage, and between control costs and benefits, is needed for assessments of the most effective strategies for rabbit management for different areas and land uses, and on the best approaches for integrating rabbit management with other property operations.
A goal of reducing rabbit numbers to as close to zero as possible and then maintaining them at that level has the advantage of providing land managers with a clear, readily monitored, long-term goal. This may counter any tendency of land managers to develop tolerance to rabbits which could undermine efficient long-term management.
Land managers need to be committed to a longterm strategy for a successful outcome. Wherever practicable, SSM includes assessing the effectiveness of the management program in reducing rabbit damage, especially when aiming to protect conservation values.
Local eradication is achievable only in special situations such as on small islands and on properties protected by natural barriers or rabbit-proof fences and monitored continuously for reinvasion by rabbits.
Economic frameworks need to be developed to assist in the assessment of the relative value of alternative control strategies whenever this is feasible. Such frameworks require: definition of the economic problem; data on the relative costs and benefits; an understanding of why the actions of individual landholders may not lead to optimal rabbit management; assessment of the means by which governments can overcome identified market failures; and an assessment of the likely returns from alternative rabbit management strategies.
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