Centuries of efforts to wipe out dingoes in order to benefit sheep and cattle have backfired, new research suggests. Echoing the famous transformation of Yellowstone National Park after the reintroduction of wolves, researchers have found Australia's wild dogs help keep grasslands open. Their slaughter has been to the long-term detriment of the animals – and profits – it was supposed to protect, with implications for the killing of top predators far beyond Australia.
In the 1880s the world's longest fence was established, stretching 5,614 kilometers (3,488 miles) across South Australia and Queensland to exclude dingoes from sheep country. Dingoes were systematically exterminated on the eastern side, but largely allowed to roam in peace to the west.
The fence provided an ideal controlled experiment for Dr Mike Letnic of the University of New South Wales. He examined aerial photos of two regions on the eastern side. At one of these sites grazing stopped in the 1970s, while it continues today at the other. These were compared with two sites to the west. All four sites are climatically similar and were photographed in four surveys between 1948 and 1999.
Both dingo-free sites have been taken over by weeds called woody shrubs, which Letnic described in a statement as “Pos[ing] a major problem for farmers...their abundance in semi-arid areas has risen dramatically in recent decades.” Where dingoes flourish, however, shrubs had only increased to an extent Letnic called “negligible”, which he suggests means dingoes help reduce the shrub spreading.
A short stretch of the dingo fence, which appears to be doing more harm than good. Ben Moore
Letnic and his team investigated whether these observations were a coincidence. In the Journal of Animal Ecology, they report the dingoes' absence led to a 26-48 percent increase in shrub coverage. The connection lies in the apparently insignificant form of the dusky hopping mouse, a vulnerable native rodent that eats woody shrub seeds, hindering their spread.
“Taken together, our results suggest a cascading effect. A loss of dingoes allows foxes and feral cats to thrive and prey on the small mammals that eat the shrub seeds,” said co-author Dr Christopher Gordon of the University of Western Sydney.
The concept that apex predators can determine the health of entire ecosystems was popularized in a video about the re-introduction of wolves to Yellowstone. Naturally, ecologists have been familiar with the idea for much longer, but Gordon said the effect has never before been associated with dingoes and shrubs. He thinks similar effects may be at play in many other parts of the world where other native predators stand in place of dingoes.
“The first thing pastoralists do is kill all the predators,” Letnic told IFLScience. “But removing predators unleashes a chain of events. People have always assumed it must be livestock driving a pattern. But when you remove the bigger predators, smaller predators are favored.” These smaller predators take a heavy toll on small herbivores. Letnic added that the rabbit, while a huge pest in Australia, is endangered in much of its native range from just this process, and its absence can transform the ecology.
The true savior of the grasslands is this little critter, the dusky hopping mouse. Dingos are just their protectors. Ben Moore