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Ben Reddiex, David M. Forsyth, Eve McDonald-Madden, Luke D. Einoder, Peter A. Griffioen, Ryan R. Chick, and Alan J. Robley.
Department of the Environment and Heritage, 2004
Project and client
Red foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats separately and in various combinations are believed to be responsible for the extinction or decline of a wide range of native species and for adverse changes in ecological communities in Australia. Predation by foxes and feral cats are key threatening under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act), whilst competition with native species and land degradation by feral rabbits, feral pigs and feral goats are also listed as key threatening processes under that Act. The belief that pest animals have caused declines in native species (and damaged production values) is reflected in legislation and has led to many attempts to control these pests. Many agencies and organisations including Federal, State and Local governments commit significant resources managing these species. However, there is limited hard evidence that this management has led to a reduction in threats and to a reversal in the decline.
The Department of the Environment and Heritage (DEH) commissioned the Arthur Rylah Institute for Environmental Research to undertake a project aimed at increasing the understanding on whether control of foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats lead to a reduction in threats to native species and ecological communities. The project is being completed in three stages. This report is the first stage, and details an audit of existing pest animal control activities in Australia. Future stages include identification of gaps in information on control activities and recommendations for filling these gaps (see Reddiex and Forsyth 2004), development of pest species monitoring protocols, and designing a process to determine priority ranking for control of pest animals in order to minimise threats to native species and ecological communities.
The objectives of this study were:
- To conduct a comprehensive audit and evaluation, of all available information on existing control activities/programs, for foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats, across Australia.
- To review all available information on control activities/programs that include measures of the outcomes of differing levels/types of control activities, in terms of reductions in pest species and recovery of native species/ecological communities, especially those listed under the EPBC Act, and those known or perceived to be threatened by foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats.
- Federal, State/Territory and local government agencies potentially involved in pest animal control for environmental management purposes were surveyed.
- The key information collected for each control operation included: (1) background information such as land tenure, agencies funding and conducting the control, other pest animal species present in the control area, and the status of the control operation; (2) detailed information on the control activities, including objectives of control, years of control, control techniques, area of control, and staff time to undertake the control; (3) the presence of EPBC Act listed species in the control area; and (4) the monitoring undertaken, including the species/resources being monitored, monitoring design, presence of non-treatment areas, and the number of years monitoring had been undertaken.
- Information on 1306 pest animal control operations were collected from 27 organisations. A further 486 local governments, 39 universities and 55 agricultural boards were contacted, but information on control operations were not suitable for inclusion in the review. The majority of control operations were undertaken in Victoria (45%), New South Wales (28%) and Western Australia (13%).
- Foxes and feral rabbits were the most frequently targeted species. Few operations targeted feral cats despite their wide distribution.
- The majority of control information collected relates to the last five years.
- The primary objective of control operations for the carnivorous pest species (foxes, wild dogs, feral cats) was the protection of threatened species. Habitat conservation was the primary objective for the herbivorous species (feral rabbits, feral pigs, feral goats).
- The total area of land on which pest animal control was undertaken in 2002 and 2003 ranged from >0.3 million ha per year for feral cats to c.10.5 million ha per year for foxes.
- A wide range of control techniques were utilised with the techniques and intensities of control varying between the targeted species.
- The estimated labour cost of pest animal control in 2003, ranged from $0.4 million for feral cats to $5.3 million for foxes.
- Only 42% of the operations surveyed had knowledge of whether EPBC Act listed species were present or absent in the control area, and only 88 of 165 EPBC Act listed species threatened by the pest animals had at least one control operation where the threatening pest species was being controlled.
- Monitoring was undertaken in 50.56% of all control actions where carnivorous pests were targeted, but only occurred in 22.26% of actions where herbivorous pests were targeted. The main focus of monitoring was on pest species (>77% of control actions that had undertaken monitoring, included monitoring of pest species). However, of all control actions surveyed where monitoring was undertaken, <20% had undertaken monitoring that provided some inference on whether the objectives of the control operation could be addressed (i.e., both pest species and resources monitored). In addition, monitoring designs rarely included non-treatment areas or were randomly allocated, and few had assessed the pest species/resources of interest prior to control.
- The field of wildlife management has been strongly criticised for its heavy reliance on information generated from descriptive studies and its slow adoption of experimental designs to examine the effects of management actions. This review indicates that these criticisms apply equally well to our understanding of the consequences of pest animal control in Australia.
- Based on the survey results there is almost no reliable knowledge concerning the consequences of pest animal control, including benefits or otherwise to native species. Reliable knowledge on the effects of manipulating a system (i.e., pest control) is derived from experiments, which should include the basic tenets of experimentation with an appropriate monitoring design.
- Experimental demonstration of the benefits of fox control has been undertaken for several native species, largely in Western Australia. The benefits of feral cat, feral rabbit, feral pig and feral goat control are largely derived from observational studies, and no information is available on the benefits of wild dog control. This situation will only be remedied if agencies fund control programs that are designed to deliver reliable knowledge.
- Based on the available funding for pest animal control and research, and logistic constraints it is not possible to incorporate the key elements of experimental and monitoring design to all pest animal control programs. We recommend focusing resources on a limited number of properly designed experiments (i.e., "evaluation" sites).
- Meta-analysis of replicated studies will be a useful tool in assessing benefits of pest animal control, as long as control programs are adequately designed and the data is available in a form suitable for meta-analysis.
- Given this lack of reliable knowledge, we were unable to review measures of the outcomes of differing levels or types of control activities in terms of reductions in pest species and recovery of native species/ecological communities.
- Standard protocols for monitoring the efficacy of pest animal control operations and the resulting benefits to conservation resources are required.
- Results of the review were primarily derived from control actions undertaken over the last six years. The most likely explanation for this is that control information for ≥7 years ago has been was lost from 'institutional memory'.
Until the following are enacted our knowledge of the costs and benefits of pest animal control for native species will remain unreliable:
- The benefits and costs to native species and ecological communities of pest animal control need to be determined using study designs that include replicated and where possible randomly allocated treatment and non-treatment areas, and adequate monitoring of changes in the abundance of both pests and resources. We recommend focusing on a limited number of properly designed experiments (i.e., "evaluation" sites).
- Contracts for the delivery of pest animal control must stipulate strict conditions about the design of the control program and its associated monitoring programs and reporting. At the least, actions should include pre- and post-control monitoring of the abundance of the pest animal and conservation resources being protected, and if at all possible include one or more non-treatment areas.
- Federal and State/Territory agencies should design and implement pest animal control operations with the intention of undertaking meta-analysis on the key outcomes of the operations.
- Standard protocols are required for estimating: (i) the kill rate of pest animals and native species during control operations, and (ii) the absolute or relative abundance of pest animals and conservation resources.
- Organisations/funding bodies need to collate and store data from pest animal control operations and any associated monitoring in a way that is both accessible to managers and amenable to future meta-analysis.
- Impediments to the incorporation of experimental design principles in pest animal control programs should be investigated to ensure future control programs are driven by reliable knowledge.