By Paul Rincon
Science reporter, BBC News
Relaxing controls on dingo numbers in some parts of Australia could help arrest the decline of native marsupial mammals, a study says.
The dingo is regarded as Australia's last "top predator"
In the last 150 years, marsupial populations have collapsed and many species have disappeared.
Most of this has been blamed on the introduction from Europe of foxes and cats, which prey on native animals.
The dingo - a wild dog - keeps fox and feral cat numbers in check, say researchers.
But sheep and cattle farmers have traditionally been hostile to the dogs, because they also prey on livestock. Poison is the most common method of controlling dingo populations.
"For much of south-east and south-west Australia - where there are sheep - farmers attempt to completely eliminate them," Professor Chris Johnson of James Cook University in Queensland told BBC News.
"The experience is that you really can't succeed as a sheep farmer if there are dingoes around."
Attitudes towards the dog have also been influenced by occasional attacks on people.
Since Europeans began settling in Australia en masse in the 19th Century, 18 species of marsupial have become extinct. This represents half of all mammal extinctions worldwide in the last 200 years. Many more native mammals have severely declined in number.
The Europeans brought with them foxes and cats, which began to prey on ground-dwelling marsupials such as wallabies, causing populations to dive.
The Dingo (Canis lupus dingo) was brought to Australia 3,500-4,000 years ago by seafarers from South-East Asia. It is regarded as an intermediate stage between wolves and domestic dogs.
They are considered to be Australia's last "top predator", taking up a place in the food web that was once filled by the extinct thylacine and marsupial lion.
The analysis carried out by Professor Johnson and colleagues shows that Australia's last native "top predators" perform an essential role in maintaining biodiversity.
DINGO WILD DOG
Descended from a domestic dog brought in from Indonesia
The social dingo is a pack hunter but will also scavenge
Females only breed once a year, having four or five pups
It found that marsupial populations have a much better chance in areas that also have stable populations of dingoes. The dingoes are thought to kill off foxes and feral cats, preventing overkill of the marsupials.
"The scientific community wants a big experiment," said Chris Johnson, "In places where dingoes are currently controlled, if we relaxed that control, we'd see dingoes increase. Would we then see foxes decline as a direct consequence?
"That's been done in a few places, and if you put them together they paint a fairly consistent picture."
Professor Johnson said he would also like to see large areas of Australia designated as "wild country", where dingoes were accepted as a natural part of the ecosystem.
This, he said, would require "some acceptance and tolerance of other land users, especially cattle producers and sheep producers".
He added: "It probably won't happen across sheep land, but it can happen with cattle.
"In cattle country, by and large, dingoes will hunt kangaroos or rabbits. If there's an alternative prey available, they'll leave the cattle alone. Sheep are so easy to kill; they will be the preferred prey," he said.
"Possibly, we'd need to rethink the reasons for controlling dingoes in cattle country. The reason it is done is because dingoes do sometimes kill calves. But we really have to trade off all the costs and all the benefits of having a predator."
Dingoes control populations of animals that compete for pasture with cattle such as kangaroos - and possibly feral goats and feral pigs.
A spokesman for the Australian National Farmers' Federation declined to comment on the report for the time being.
It is published in the journal Proceedings of the Royal Society B.