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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Review of existing Red Fox, Wild Dog, Feral Cat, Feral Rabbit, Feral Pig, and Feral Goat control in Australia. I. Audit

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

Results (continued)

7.2 Control actions

7.2.1 Years of control

For all pest animal species the majority of control actions collated occurred in recent years (Figure 7.7). The number of control actions per species for the most recent year (e.g., 2003) ranged from 6–26 fold higher than those collated for 1990. In many cases, participants indicated that they were aware of pest animal control having occurred in years prior to their commencement in their current position, however, they could not easily access the information we required. One State organisation (Parks Victoria) provided information only for 1999 to 2003, which strongly influenced the years of control data for feral rabbits, as rabbit control comprised over 53% of all of Parks Victoria’s control actions (see Figure 7.2).

7.2.2 Aims of control

The aims of pest animal control were consistent across the targeted species. Sustained control was the overall aim for most species, but this varied between species (range: 84– 96% for all species except feral cats, 66%; Figure 7.8). Eradication was the aim of 34% of feral cat control actions, with the majority of these actions occurring on islands or within pest animal exclusion fenced areas. Feral pig and goat control actions where the aim was eradication were also mainly located on islands or were localised populations. The ‘other’ aim of control that was stated by survey participants was research (0.7%).

Figure 7.7. Number of collated control actions annually for the period 1990-2003 for each targeted pest species. Data for pre-1990 have been pooled into one class. The total number of actions per species are shown on the figure.

Figure 7.7. Number of collated control actions annually for the period 1990-2003 for each targeted pest species. Data for pre-1990 have been pooled into one class. The total number of actions per species are shown on the figure.

Figure 7.8. Percentage of control actions for each targeted pest species with the aim of eradication, sustained control, or ‘other’. The total number of actions per species are shown on the figure.

7.2.3 Objectives of control

The objectives of control actions varied with the pest animal species being targeted. 'Threatened species' were the main objective for control actions targeting foxes, wild dogs and feral cats (i.e., the carnivore species), with 82%, 57% and 88% of actions, respectively (Figure 7.9). Habitat conservation was also commonly included as an objective for the carnivorous species (range: 19-31% of actions). Production values were an important objective of control actions for foxes (19%) and wild dogs (46%). In most instances the production value of concern was domestic livestock.

In contrast, 'habitat conservation' was the main objective for control actions that targeted feral rabbits (97%), feral pigs (84%) and feral goats (94%); (i.e., the herbivore species). Threatened species was also included as an objective for the herbivore species (range: 32-88% of actions) due to their browsing of native plant species and competition with native animals for resources. Production values were an important objective of control actions for pigs (31%), but less so for rabbits (6%) and goats (12%). Production values were the sole objective of 27% of control actions for wild dogs, but the sole objective for <9% of all other targeted species.

For all species the objectives of control actions remained the same for the duration of the control operations (range across species: 94-100%). Changes in management priorities from production values to biodiversity values was the main reason for changes in objectives.

Figure 7.9. Percentage of control actions for each targeted species with the control objective being; threatened species, habitat conservation, production values, or other (multiple objectives may have been selected per action). The number of actions per species are shown on the figure.

Figure 7.9. Percentage of control actions for each targeted species with the control objective being; threatened species, habitat conservation, production values, or other (multiple objectives may have been selected per action). The number of actions per species are shown on the figure.

7.2.4 Area of control

The total annual area of pest animal control varied temporally within the same species and between species (Figure 7.10). The observed changes in area of control over time for most species is a result of an increase in the number of control operations that have been captured by our survey process (see Section 7.2.1), as in most cases the median area per control action has not altered significantly (see below; Figure 7.11). Therefore, the most recent years provide the best indication of the area of control. In 2002 and 2003, fox control was undertaken on >10.5 million ha per year, wild dog control on >3.2 million ha per year, feral cat control on >0.3 million ha per year, feral rabbit control on >1.2 million ha per year, feral pig control on >6.0 million ha per year, and feral goat control on >5.3 million ha per year. Note that these estimates are not mutually exclusive between targeted species, and are likely to be underestimates as they are based on control operations rather than control actions (see Section 6.4). It is important to note that these areas largely do not include pest animal control undertaken by agricultural focused organisations.

The area of control operations varied in size for all species. The range in size of control operations during 1998-2003 was as follows; fox 0.01 to 1300 km2, wild dog 0.02 to 4000 km2, feral cat 0.01 to 1050 km2, feral rabbits 0.005 to 8000 km2, pigs 0.01 to 20000 km2, and goats 0.01 to 11357 km2 (Figure 7.11).

The area of control operations varied between the species targeted, but remained relatively constant over time (Figure 7.11). The median size of control operations was smallest for feral rabbits (44 km2) and feral cats (35 km2). Variation between species largely reflects the spatial nature of the different pest animal species distributions and the different control types employed. For example, feral goats and feral pigs are often controlled by aerial shooting and mustering (Choquenot et al. 1996; Parkes et al. 1996), which are normally carried out over large areas (see Section 7.2.6). In contrast, feral rabbit control is often undertaken on small areas using warren ripping and fumigation (Williams et al. 1995; see Section 7.2.6), and large-scale cat control is infrequently undertaken.

The majority of pest animal control was distributed in the south-west and south-east of Australia, despite many of the pest animal species being distributed throughout Australia (Figures 7.12-7.17). Note that for many control actions the AMG's supplied were not accurate and were subsequently not used.

Figure 7.10. Total annual area of control for each of the targeted species for the period 1998-2003 (area of control is based on control operations). The number of operations per species in each year are shown on the figure.

Figure 7.10. Total annual area of control for each of the targeted species for the period 1998–2003 (area of control is based on control operations). The number of operations per species in each year are shown on the figure.

Figure 7.11. Box plots of control operations annual area of control for each targeted species for the period 1998–2003. The number of operations per species are shown on the figure.

Figure 7.11. Box plots of control operations annual area of control for each targeted species for the period 1998–2003. The number of operations per species are shown on the figure.

Figure 7.12. Distribution of foxes (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=38), and red circles represent those actions with either a conservation or threatened species objective (n=376). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.12. Distribution of foxes (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=38), and red circles represent those actions with either a conservation or threatened species objective (n=376). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.13. Distribution of wild dogs (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=69), and red circles represent those actions with either a conservation or threatened species objective (n=106). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.13. Distribution of wild dogs (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=69), and red circles represent those actions with either a conservation or threatened species objective (n=106). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.14. Distribution of feral cats (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=2), and red circles represent those actions with either a conservation or threatened species objective (n=27). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.14. Distribution of feral cats (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=2), and red circles represent those actions with either a conservation or threatened species objective (n=27). Size of circles represents area (km2). Some control actions directly overlay other actions.

Figure 7.15. Distribution of rabbits (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=1), and red circles represent those actions with either a conservation or threatened species objective (n=115). Size of circles represents area (km2). Some actions directly overlay other actions.

Figure 7.15. Distribution of rabbits (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=1), and red circles represent those actions with either a conservation or threatened species objective (n=115). Size of circles represents area (km2). Some actions directly overlay other actions.

Figure 7.16. Distribution of feral pigs (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=11), and red circles represent those actions with either a conservation or threatened species objective (n=99). Size of circles represents area (km2). Some actions directly overlay other actions.

Figure 7.16. Distribution of feral pigs (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=11), and red circles represent those actions with either a conservation or threatened species objective (n=99). Size of circles represents area (km2). Some actions directly overlay other actions.

Figure 7.17. Distribution of feral goats (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=2), and red circles represent those actions with either a conservation or threatened species objective (n=82). Size of circles represents area (km2). Some actions directly overlay other actions.

Figure 7.17. Distribution of feral goats (2001) and location of control actions in 2003 (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001). Yellow circles represent those actions with production values being the only objective (n=2), and red circles represent those actions with either a conservation or threatened species objective (n=82). Size of circles represents area (km2). Some actions directly overlay other actions.

7.2.5 Duration of control

The number of days per year of targeted control (i.e., duration of control) varied between species, but was consistent across time (Figure 7.18). However, the median duration of control actions was higher for the carnivore species (foxes, wild dogs and feral cats) than the herbivore species (feral rabbits, feral pigs and feral goats). From 1998-2003 the median duration for foxes ranged from 70-90 days per year, wild dogs ranged from 53-60 days per year, and feral cats ranged from 21-42 days per year. In contrast, the median duration for the same period for feral rabbits ranged from 10-20 days per year, feral pigs ranged from 13-21 days per year, and feral goats ranged from 5-8 days per year. The observed difference between the carnivore and herbivore species largely reflects differences in the types of control techniques undertaken (see section 7.2.6), and also the frequency of control in a given area. The predator species were often more intensively targeted (i.e., multiple control events per year) by control than the herbivore species.

7.2.6 Control techniques

A wide range of control techniques were utilised for the control of pest animals, with the techniques varying between the targeted species (Figure 7.19). Only one control technique was used in 92-99% (range across all species) of control actions. For the carnivorous species (foxes, wild dogs and feral cats), the most frequent techniques were ground baiting (76%, 72% and 12% of all control techniques undertaken, respectively), and trapping (7%, 19% and 58% of all control techniques undertaken, respectively). Ground baits were mainly Foxoff® or dried meat baits, and exclusively contained 1080 poison. Ground shooting was also a common control technique (18% of techniques undertaken) when feral cats were targeted.

The main control techniques for rabbits were warren fumigation and ripping (73%), followed by ground baiting with carrots and grain (18%). Trapping was the most frequent technique for feral pigs (50%), followed by aerial shooting (25%). Aerial shooting was also a frequent technique for feral goats (29%), as was ground shooting (43%). The techniques summarised as 'other' included the release of rabbit fleas and the mxyoma virus for feral rabbits, and the injection of feral rabbits with rabbit haemorrhagic disease virus.

Figure 7.18. Number of days per year that control actions targeted each pest species. The number of actions per species for each year are shown on the figure.

Figure 7.18. Number of days per year that control actions targeted each pest species. The number of actions per species for each year are shown on the figure.

Figure 7.19. Percentage of control techniques utilised for the control of each of the six targeted pest species (data based on control actions). The total number of control techniques utilised across all control actions per species are shown on the figure. GB=ground baiting; AB=aerial baiting; A=aerial; G=ground. * carrot and grain baiting; ** Foxoff and meat baits; *** warren ripping and fumigation.

Figure 7.19. Percentage of control techniques utilised for the control of each of the six targeted pest species (data based on control actions). The total number of control techniques utilised across all control actions per species are shown on the figure. GB=ground baiting; AB=aerial baiting; A=aerial; G=ground. * carrot and grain baiting; ** Foxoff® and meat baits; *** warren ripping and fumigation.

7.2.7 Intensity of control

The intensity of control varied between control techniques (Figure 7.20). For actions targeting the carnivores (foxes, wild dogs and feral cats), the median density of aerial meat baiting (range across species: 2.01-4.05 baits per km2) was consistently higher than that of ground meat baiting (range across species: 0.66-1.37 baits per km2). The density of trapping was similar for foxes and wild dogs (median of 0.50 traps per km2 for both) but higher for feral cats (median of 1.72 traps per km2). Higher trapping densities for feral cats is likely a result of their smaller home ranges (Molsher 1999) and the high proportion of actions where cats were targeted for eradication. For the herbivore species (feral rabbits, feral pigs and feral goats), comparisons of control densities between all species is difficult as the main control techniques varied (see Section 7.2.6). However, for both feral pigs and feral goats the control densities of aerial and ground shooting, and trapping were similar (Figure 7.20).

There was a large range of control densities reported for all control techniques. For example, ground meat baiting ranged from 0.003-80 baits per km2 for foxes, 0.01-200 baits per km2 for wild dogs, and warren ripping and fumigation for feral rabbits ranged from 0.001-266 days per km2 per year. The observed high control densities largely result from control actions undertaken with relatively small control areas.

7.2.8 Labour time and labour cost

The average number of labour days per year required to carry out each control action varied between pest animal species (Figure 7.21). During 1998-2003, the highest average number of labour days occurred for dogs (range: 43-67 days per year) and cats (range: 30-111 days per year). Over 19% of dog control actions utilised trapping as a control technique, which is time intensive due to the requirement to check traps frequently, when compared with common techniques used for other species. The high average number of labour days per year for feral cats during 1998-2001 was a result of a successful cat eradication attempt from Macquarie Island where staff days per year ranged from 1001 to 1870 over that period. The number of labour days per year for the remaining species was relatively consistent.

The estimated total labour cost to undertake pest animal control per year varied between species (based on labour days per action x $320 per day, and extrapolated to include those actions where labour time was not supplied by survey participants; Figure 7.22). The total cost for foxes, ranging from $1.8 to $5.3 million per year for 1998-2003, was highest in 2003, corresponding with the highest number of control actions. Wild dogs also showed a trend of increasing labour costs over the period 1998-2003, with the highest cost occurring in 2003 ($3.2 million). The remaining species had relatively constant labour costs over the period 1998-2003 (i.e. feral cats range: $0.4-1.1 million/year; feral rabbits $0.8-1.4 million/year; feral pigs $0.5-0.9 million/year; and feral goats $0.7-0.9 million/year).

Due to the wide variation in the types of control costs reported, results are not presented on the operational costs (excluding the cost of labour) of control actions.

Figure 7.20. Density of control techniques, for each of the six targeted pest species. GB and AB carrot, kilograms/km2; GB and AB meat, baits/ km2; A and G mustering, A and G shooting and Warren, days/ km2; trapping, traps/ km2. GB=ground baiting; AB=aerial baiting; A=aerial; G=ground. The number of actions per control technique for each of the targeted pest species are shown on the figure. * includes grain baiting; ** Foxoff® and meat baits; *** warren ripping and fumigation. Note that y-axis is a log-scale.

Figure 7.20. Density of control techniques, for each of the six targeted pest species. GB and AB carrot, kilograms/km2; GB and AB meat, baits/ km2; A and G mustering, A and G shooting and Warren, days/ km2; trapping, traps/ km2. GB=ground baiting; AB=aerial baiting; A=aerial; G=ground. The number of actions per control technique for each of the targeted pest species are shown on the figure. * includes grain baiting; ** Foxoff® and meat baits; *** warren ripping and fumigation. Note that y-axis is a log-scale.

Figure 7.21. Average number of staff days to undertake control for each of the six targeted pest species per year, per control action, from 1998–2003. The total number of actions per year are shown on the figure.

Figure 7.21. Average number of staff days to undertake control for each of the six targeted pest species per year, per control action, from 1998–2003. The total number of actions per year are shown on the figure.

Figure 7.22. Estimated total labour cost to undertake all control actions for each of the targeted pest species per year from 1998–2003 (assumes a daily labour cost of $320). Costs have been extrapolated to include those actions where labour time was not supplied. The total number of actions (including those extrapolated) per year are shown on the figure.

Figure 7.22. Estimated total labour cost to undertake all control actions for each of the targeted pest species per year from 1998–2003 (assumes a daily labour cost of $320). Costs have been extrapolated to include those actions where labour time was not supplied. The total number of actions (including those extrapolated) per year are shown on the figure.