Management of donkeys in the Kimberley
The Kimberley Rangelands Biosecurity Association has been managing feral donkeys in the Kimberley since 1978. The program has seen two phases of management since that time. It started initially with Phase 1, a population reduction program (or Management Culls) when the densities of donkeys were very high of one animal/km2 or more.
The program covered several stations per year and number of animals removed was up 150 per helicopter hour. The total number of donkeys removed during this Phase was nearly 505,000 and did not include animals removed by individual landholders and other organisations.
When the number of donkeys was reduced to a level of under 20 animals removed per helicopter hour Phase 2 (the Judas Program) began as a means to remove the remaining animals. Phase 2 involved the use of radio collars fitted to ‘Judas animals’. It was introduced in 1994 (West Kimberley), 1995 (Halls Creek), and in 1997 (East Kimberley). A Judas ‘network’ was created by collaring donkeys on average every 7 – 12 km (depending on terrain) to cover the area associated with their home ranges. Initial estimates of home ranges of Judas animals were at that time between 5 – 45 km2. Once a property was declared as eradicated, Judas animals were monitored over three additional runs during a dry season and once the following year.
Benefit cost analyses
Two benefit cost analyses were recently undertaken to provide an estimation of the cost-effectiveness of various options for the KRBA’s donkey control program. The first analysis looked forward 30 years with four different options considered -
Current control: This option represents the current level of donkey control resulting in an estimated 3% increase in donkey numbers through time. This option gave a Benefit Cost Ratio of 2.1 (the ratio of the benefits to costs - meaning for a $1.00 spent, the ‘bang for the buck’ is $2.10) with a net present value gain to the pastoral industry of $2,623,000 over the 30 years.
Maintain numbers: This represents a small increase in effort compared to current control to maintain current donkey numbers in the region. This option gave a Benefit Cost Ratio of 2.6 with a net present value gain to the pastoral industry of $3,831,000 over the 30 years.
Eradication: This option reflects halving donkey numbers each year until extremely low, potentially only increasing through migration. This option gave a Benefit Cost Ratio of 2.0 with a net present value gain to the pastoral industry of $3,934,000 over the 30 years.
Stop control for 10 years then start again: This option represents a break from control for 10 years, then starting again in year 11 with the control effort resulting in a similar number of donkeys in the region after 30 years as is expected from option 2. This option gave a Benefit Cost Ratio of 2.1 with a net present value to the pastoral industry of $2,468,000 over the 30 years.
The second analysis provided an estimation of the cost-effectiveness of the program over the 40 years life of the program. The results suggest that the program has provided excellent value for money for the pastoral industry. The Association has spent to date approximately $8.4million. Adjusting this value for inflation and compounding it to account for the opportunity cost of investing this money elsewhere, this has an estimated present value of $78million. The benefit derived is estimated to be $268million (in present values and accounting for inflation). The Net Present Value (the difference between the benefits and costs) is estimated to be $220million and the Benefit Cost Ratio is estimated to be 3.8. Only the economic benefits and costs of control were considered in the analyses.
Other benefits include the opportunistic removal of other large herbivores and pigs, reduced environmental impact, reduced biosecurity risk, more timely identification of significant weed infestations, and reduced nuisance value for the cattle industry. Actual examples include the prickly acacia and mimosa pigra infestations found in the East Kimberly as a result of DPIRD Biosecurity Officers overflying the sites whilst carrying out donkey control. Noting the unfamiliar plants they landed and had the plants identified. Eradication programs now currently exist for those infestations and both have made significant progress.
Wild dog control in the Kimberley
Currently the Kimberley Rangelands Biosecurity Association runs two aerial baiting programs each year, the first in May followed up by the second in Late September. These programs are designed to supplement ground baiting carried out by individual stations by giving land managers access to more remote regions of the station and a rapid deployment of baits in those areas.
Cattle enterprises across the Western Australian rangelands have reported significant and increasing levels of damage and losses from wild dogs. Calves are particularly susceptible to attack, while attacks on adult cattle may not be lethal but significantly impacts their productivity. The costs flow through to the processing sector with bite marks and scarring downgrading carcass values. The extent of the economic losses due to wild dog predation is difficult to quantify, particularly under the extensive rangeland grazing conditions in Western Australia. The Pastoral Lands Board annual returns from 2007 to 2014 show an increase in stock losses from $2.4 m to over $6.0 m across the WA Pastoral Region.
Current wild dog management activities in the Kimberley region is estimated to have very good returns to investment (Benefit Cost Ratio = 5.1) according to the Western Australian Wild Dog Action Plan. Management is partially focused on aerial baiting at relatively low cost compared with the cost of management activities in other regions. Benefits are also relatively low, but far exceed the costs.
WA has a unique and internationally recognised biodiversity. There is recognition of the cultural and conservation value of the dingo within the conservation estate. There is also acknowledgement of the need to consider a range of values in the landscape including ecological, wildlife movement, cultural and heritage values. Conservation of dingoes is considered an important conservation goal. For livestock producers the key is to manage the clear risk of continuing encroachment of wild dogs into the agricultural regions that disrupts livestock production. Wild dog management is complex and demands a balance between the economic drivers to reduce wild dog impact on livestock enterprises in the pastoral and some agricultural areas, with the conservation values of the dingo and community expectations of humane treatment of all animals.
