Australian farmers found to unwittingly help boost kangaroo populations

Providing watering points for livestock and controlling wild dogs like dingoes has come at their own detriment.

One of Australia's largest-scale animal studies has revealed how using land for agriculture and livestock have benefitted kangaroos.

The study examined 22 years of aerial surveys of kangaroos across the southern rangelands of Western Australia to understand how populations have changed, and the reasons behind those changes.

The study, led by Murdoch University, with the WA government, analysed the surveys to learn how kangaroos has responded to environmental and management factors, the presence of a state barrier fence, and the control of dingoes for the protection of livestock.

"Providing water and dingo control to support livestock industries and food production has given rise to these abundant kangaroo populations, to the unfortunate detriment of pastoral industries," Dr Stuart Dawson, lead author of the research at the university's Harry Butler Institute, said.

"We have no easy way to control kangaroo populations," he said.

"Harvesting does not keep their numbers in check people don't eat enough of it to make a dent in the population sizes.

"There are very few tools available to land managers and regulators."

The research found rangelands worldwide have been subject to major change, from widespread predator control, to the introduction of permanent livestock water sources and altered vegetation to improve grazing.

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"In Australia, these changes have essentially removed important limitations to the growth of kangaroo populations, that are really now only food limited, and that's seen kangaroo numbers grow dramatically.

"While kangaroos are obviously a natural part of most systems throughout Western Australia, when native grazers are combined with livestock, sheep and cattle, and feral herbivores, the total grazing pressure is unsustainable. In many places, there are too many mouths to feed for the fragile landscape."

The study found red kangaroos were abundant in flat, open vegetation, on pastoral land where area permitted for dingo control was high, with a jump in populations 12 months after rains.

Western grey kangaroos were most abundant on flat, agricultural land, but less abundant in pastoral areas with high permitted dingo control.

Euros were most abundant in rugged pastoral land with open vegetation, where permitted dingo control was high.

"While environmental factors are key drivers of food availability and kangaroo populations, anthropogenic factors such as land use and dingo control are strongly associated with kangaroo populations," the study found.

"This should provide land managers and regulators with pause for thought, because the long-term degradation of rangelands due to overgrazing presents a significant threat to biodiversity, and the viability of pastoral enterprises."

Dr Dawson said kangaroo management was a wicked problem.

"They are a natural part of the landscape, but not in such numbers, especially when combined with livestock."