The effect of wild dog control on cattle production and biodiversity in the South Australian arid zone

EXECUTIVE SUMMARY: Throughout Australia, wild dogs (i.e. dingoes, feral domestic dogs and their hybrids) are widely recognised as a significant threat to livestock production systems. In the rangelands, where cattle predominate, most producers consider poison baiting of wild dogs to be a critical component of economically viable cattle production. Yet, recent research has demonstrated that baiting may not always be effective in reducing predation impacts on cattle. Moreover, other studies have shown that economically significant damage to cattle production does not occur routinely, and that wild dog control may not always be necessary. At times when they are not causing economic harm to cattle, wild dogs may actually have a net benefit to livestock production, through limiting the abundance of herbivores such as kangaroos which compete with livestock for food, and also regulating populations of feral animals such as pigs, goats, cats and foxes which are all known to be seriously detrimental to the environment. Balancing the negative and positive impacts of wild dogs may be critical to achieving best practice management of rangeland beef cattle. However, this is not possible without a good understanding of the relationships between wild dogs and their prey in the area to be managed. In northern South Australia’s pastoral zone, wild dog management is the responsibility of the South Australian Arid Lands (SAAL) NRM Board. The Board identified a need for more information to help predict when wild dogs are likely to cause economic harm in this region, so that an optimal strategy for wild dog management could be developed that minimises the economic impacts of wild dogs, yet harnesses the benefits associated with the continued presence of wild dogs in the landscape (albeit at manageable levels). A 6-year study began in mid-2008 to investigate the effect of 1080 poison baiting for wild dogs on beef cattle production and biodiversity in the far north of South Australia. The study was conducted on five individual cattle stations with the objective of identifying potential indicators of predation risk (or “triggers”) that would enable pastoral land managers to apply lethal wild dog control optimally according to risk and the likelihood of significant calf loss. Using paired treatment areas on each property (one nil-treatment area and the other subjected to broadscale poison baiting for wild dogs), the impact of poison baiting on calf production was measured by comparing lactation failure rates in cows between treatments. Sand plot activity indices were used to examine the impact of poison baiting on the relative abundance of predators and prey species. Wild dog diet was assessed by analysing the content of scats collected throughout the study. Water point usage by wild dogs was examined by tracking the movements of 11 individuals fitted satellite GPS transmitters. On average, wild dog activity was 60% lower in baited areas during the study, suggesting that poison baiting caused at least temporary reductions in wild dog activity. Despite this, no consistent effect of poison baiting on calf production was identified. Numerous predation events on cattle were witnessed by researchers and pastoralists during the project, so there was definitely predation happening, but the study found no consistent evidence that it was lessened by baiting. Within properties, substantial differences in lactation failure rates occurred over time and also between treatments, but this variation was inconsistent and likely to be due to a range of property-specific variables. Cow age was the only factor found to have consistently affected lactation failure, with rates in first lactation heifers almost double that of adult cows. Importantly, wild dog activity was never reduced completely to zero in the baited treatment areas, indicating that the baiting treatment (which was modelled on conventional baiting techniques in northern South Australia) never completely eradicated wild dogs. As well as the observed differences in wild dog activity between treatments, we also found considerable temporal variation. The study period was characterised by a 2-year period (2010-2011) of unusually high rainfall at all sites. Either side of this period, rainfall was generally average to below average. A general increase in wild dog activity was evident in late 2011/early 2012 which is likely to have resulted (at least in part) from higher birth rates and increased survival of pups in the flush climatic period that began about 18 months previously. Temporal variation was also evident in the activity of wild dog prey species (e.g. small mammals, kangaroos and rabbits) and other predators (e.g. foxes). In some species, this fluctuation was related to variation in seasonal conditions but in others, other factors appear to have been responsible. But in all cases, temporal fluctuation tended to occur equally across both treatments and was not associated with poison baiting. Wild dog diet did not differ between baited and unbaited treatments. However, it did vary considerably between properties and there appeared to be different dietary staples on each property (e.g. rabbits on Quinyambie, rodents and rabbits on Cordillo Downs and kangaroos on Todmorden). Moreover, when small mammal populations increased in response to above average rainfall in 2010/11, they became the principal component of wild dog diet across all properties. Once conditions deteriorated and small mammal populations declined, wild dogs switched back to their staple prey. Cattle remains were commonly detected in wild dog scats, but their occurrence was not affected by poison baiting. It was, however, influenced by the availability of alternative prey, with consumption of cattle declining to almost negligible levels when small mammal populations increased after the 2010/11 rains. Implications for Wild Dog Management Unfortunately the study did not yield the anticipated clearly defined trigger points for wild dog control in northern South Australia. However, it did contribute significantly to the knowledge and general understanding of wild dog predation in northern South Australia. Following are the key management outcomes arising from the project. 1. The disappearance of cattle from wild dog diet when alternative prey availability was high indicates that the risk of calf predation by wild dogs during flush climatic periods is quite low. 2. The finding that poison baiting (using conventional techniques) never completely removed wild dogs. 3. Satellite tracking found that wild dogs tended to visit water points more frequently in summer. This suggests that a greater number of wild dogs will be exposed to baits if they are laid around water points in the hotter months, particularly as this period also coincides with the emergence of juvenile wild dogs from their dens. 4. The observed variation in wild dog diet between properties suggests that the drivers for calf predation differ from property to property. Thus, a “one-size-fits-all” approach to wild dog management is not likely to be successful. The study has shown that there are so many property-level variables that affect calf production that strategies for wild dog management need to be tailored to individual properties. 5. There are still many unknowns around the predation dynamics of wild dogs in northern South Australia. This calls for a “learn by doing” approach to wild dog management, where careful monitoring and evaluation of management practices is used in conjunction with other new information as it comes to hand to continually improve the effectiveness of wild dog management. The current SAALNRM Wild Dog Management Plan fits well with this approach. It provides for landholders to have access to baits if and when they need them, while promoting the responsible use of baits and acknowledging the benefits of maintaining a certain number of wild dogs in the system. It endeavours to work with pastoralists and other stakeholders equitably and provides them with a level of ownership of wild dog management on their own property. Maintaining communication between stakeholders, and between landholders and government agencies will be key in ensuring wild dog impacts continue to be managed optimally across all land tenures.