Scientists believe water may be the key in the battle between two introduced species - the cane toad and the dung beetle.

Cane toads have left a trail of ecological destruction in their wake as they march ever further south and west.

The poisonous South American toad is perhaps the most notorious example of Australia's dubious track record of introducing species to control pests.

But it is now being held responsible for the demise of one of the few success stories of introduced species - the humble, but very valuable, dung beetle.

Dung beetles were introduced to Australia in the 1960s and according to Dr Mike Letnic from the University of New South Wales, they have made a valuable contribution to Australia's cattle farming industry.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 26 seconds 3 m 26 s Water could be the key in the battle between cane toads and dung beetles Download 6.3 MB

"Dung beetles were introduced... to solve a problem where we just had too much dung clogging up Australian farms and cattle stations," he said.

"There was dung lying all over the ground, it wasn't being broken down, and it prevented cattle from grazing in large areas.

"And so these dung beetles were brought over from Africa to break down the dung and they've actually done an amazing job."

Dung beetles also control parasites such as buffalo flies and worms, which breed in cow dung and pose a major health risk to cattle.

But Dr Letnic said the same dung these beetles feed on is effectively acting as bait for millions of hungry cane toads.

"Cane toads are major predators of dung beetles," he said.

"What they do at night is just sit themselves on a freshly-deposited dung pat and they'll eat all the dung beetles that come and settle on the dung pats.

"We've found cane toads with up to 150 dung beetles in their stomach, so basically that's 150 dung beetles in a sitting they're consuming."

Studies suggest availability of water the key

Dr Letnic has led a study, in conjunction with the Hawkesbury Institute for the Environment, investigating the relationship between cane toads, dung beetles and water.

PhD student Ben Feit surveyed the areas surrounding two different water sources on three Northern Territory cattle stations, and compared water in open dams with water stored in closed tanks.

He discovered that there was a direct correlation between access to water and the number of cane toads in that area.

"The numbers of cane toads at dams where cane toads can access open water were... about 6.4 times higher than the cane toad abundance found at tanks," he said.

"Dung beetles in turn were about 9.6 times lower in abundance at dams than at tanks.

"The availability of free water increases the abundance of cane toads and that has negative impacts on dung beetle abundance."

Mr Feit said the findings suggest cane toads have an enormous economic impact on the cattle industry.

"With cane toads now pretty much counteracting these introduction programs, we would expect an increase in cattle parasites," he said.

"That ultimately would lead to a loss in cattle production and would translate into money loss for landholders and cattle farmers."

Cane toads need constant access to water in order to survive.

And researchers believe that blocking the toad's access to water on farms will not only protect the dung beetle, it could also help control the spread of cane toads.

"If we can restrict cane toads' access to water, we can basically lock the cane toads out of the country," Dr Letnic said.

Dr Letnic said he believes it would be feasible, and even cost effective, for farmers to convert their dam systems to tanks.

"It's something that could be done strategically in places to prevent the spread of cane toads," he said.

"But there are also other savings - the sorts of water storage systems we're proposing are actually more efficient, so they use less fuel because there's less losses of water due to evaporation and seepage.

"So in the long term, the benefits of actually restricting cane toads' access to water will also have other economic benefits."

The study has been published in the journal Ecosystems.