Productivity impacts on the beef industry from wild dogs go well beyond the most obvious effect, being newborn and young calf losses caused by predation.
Researcher Dr Peter Fleming (see companion story, ‘National approach needed for wild dog challenge’) said two questions researchers still needed to answer was whether wild dog impacts were net costly, and from that, whether wild dog control was net beneficial.
He said an early study from 1968 in Queensland suggested up to 30pc of calf losses could be attributed to dog predation. A second study in the Tanami region showed that after two big seasons (when there was plenty of food about), one beef herd producing only 47pc calving, with 6pc of surviving weaners showing evidence of dog-bite.
In contrast, another study in northern SA found that after an effective dog control program, calvings improved by 30pc. But over time, there was no increase in total calves produced because carrying capacity declined as the kangaroo population rose, in the absence of dogs.
“Studies of impact on calf loss through baiting programs produced varying results, in different areas, so it’s a very difficult thing to get a handle on. We really need to know more,” Dr Fleming said.
“We need to support information being generated, such as that being put together through AgForce Queensland, with on-the-ground measurements, putting all that information together.”
Apart from direct calf loss, the overall impact on industry came from a number of other areas:
- Hydatids carried by wild dogs. Two studies suggested this was significant. One study showed in Queensland abattoirs, about $7 million worth of offal was condemned and lost each year because of hydatid infection
- Similarly, neospora had potential to be a problem in some areas, such as the NSW north east coast, where dog numbers were increasing. More effort needed to be done in measuring prevalence.
- Damage to hides could in some cases be substantial. Hides are downgraded in value based on dog damage, together with tick damage, brands and general scratches from barbed wire and other sources. A small amount of work had been done in this area through an AgForce study which examined saleyards prices for dog-damaged animals. Currently there was no knowledge of any statistical relationship between dog-bite evidence, and calf losses, for example. One regional NSW study had suggested, however, that for every calf carrying evidence of dog-bite, another three had probably died from predation.
An obvious factor in increasing dog numbers and impacts on cattle was the decline in sheep numbers in many districts. As sheep numbers dwindled, control effort by producers tended to subside, and predation on cattle tended to increase.
In the Murweh Shire area in southwestern Queensland, for example, 2200 dogs had been taken out through baiting and shooting in two years inside the fence, according to Greg Mifsud, a member of the Invasive Animals CRC based in Toowoomba.
Also, the most common hybrid dogs in many areas were crosses with kelpies, cattle dogs and collies – potentially producing hybrids with some stock-sense, Mr Mifsud said.
The distribution of wild dogs in the north coast area of NSW had also shown an increasing trend in activity, distribution and predation, Peter Fleming said.
The provision of artificial waters in remote parts of Australia had also undoubtedly contributed to increasing dog numbers.
“There’s much more water now provided through poly pipe than existed back in the 1960s, particularly across northern Australia,” he said. “More opportunities for permanent water means more dogs, and more fauna like wallabies on which they can prey.”
Balancing roo populations
Dr Fleming said it needed to be remembered that wild dogs could also have positive effects.
“They may prey on competitors for pasture against livestock like in kangaroos and wallabies, and by doing that, increase stock carrying capacity. Some people are content to leave dogs in an area for that reason.”
He said it was hoped to add on to existing industry projects such as Cash Cow, through Biosecurity Queensland, building components looking at the contribution of dogs to reproductive failure in cattle.
One of the questions asked of Dr Fleming after his Brisbane presentation was whether potential bio-control agents for wild dog management had been examined. Distemper and parvo-virus were raised as possible targets.
He said there had been no prevalence studies for either virus in wild dog populations.
“We do know that outbreaks have occurred, however. While vaccination of local domestic dogs might permit their use as a biological control agent, given that there is such a broad proportion of the community that wants wild dogs in the ecosystem, there would be little chance of getting approval for a biological control for wild dogs. Effective contact rates between dogs would also vary, depending on the habitat,” he said.
Another question raised the prospect of using NLIS devices in areas where waters are ‘controlled’, to use available technology to limit access to a fenced-off watering point.
“It’s a good idea, in those areas where open waters can be removed from the equation, and cattle can drink only from troughs. But we would need an eartag that is 100pc reliable, to avoid perishing cattle.”
Central Queensland cattleman Peter Hughes said dogs over the past ten years had moved from targeting only young calves to including bigger weaners. While that had started along the east coast, it had quickly spread across to the Kimberley.
Dr Fleming said there was no way to tell whether that was occurring as a result of genetics (crossbreeding with bigger domestic dogs) or a learned behaviour.
“In some areas, foxes, for example, do not touch lambs, but are murder on lambs in other areas. That’s a learned behaviour. Once one learns to do something, they quickly train their young, and wild dogs are no different.”
Another factor could be the year-round calving cycles typically seen in northern Australia, providing a plentiful, regular supply of prey.