Australasian Science: Australia's authority on science since 1938

Cause of Native Mammal Declines in Northern Australia Revealed

New research has found that the decline of small mammals across northern Australia is most likely driven by feral cats, with the impacts of cats worsened by high-intensity bushfires and heavy cattle grazing.

“Fires and cattle remove groundcover – such as grass, small shrubs and logs – making it easier for feral cats to hunt,” said

Dr Brett Murphy of Charles Darwin University. “Unique Australian species such as the northern quoll, golden bandicoot and brush-tailed rabbit-rat could become extinct within our lifetimes if we don’t act on these new discoveries.”

The vast uncleared landscapes of northern Australia have experienced a wave of mammal extinctions, with populations of small mammals collapsing by as much as 95% since the 1970s. “Northern Australia is facing a biodiversity crisis, with a wide range of mammal species heading for extinction,” Murphy said. “We have good evidence that feral cats are the biggest problem, and that their impacts are amplified by high-intensity bushfires and heavy grazing.”

Research led by the Australian Wildlife Conservancy shows that feral cats can rapidly exterminate populations of small mammals, especially when habitat has been degraded by repeated high-intensity bushfires and cattle grazing. However, research in the Kimberley region has shown that the impact of feral cats is reduced in areas that are burnt less frequently and by lower-intensity bushfires that leave more of the vegetation and groundcover unburnt. Similarly, removing cattle helps mammal populations recover.

While Federal Environment Minister Greg Hunt has called for the eradication of “all of the significant populations of feral cats around Australia” within a decade, scientists remain sceptical about how this could be achieved. “The resources directed to managing conservation areas are woefully inadequate to eradicate all major cat populations,” Murphy said.

“Because cats take advantage of the conditions created by high-intensity fire and cattle in northern Australia, there is a fantastic opportunity to reduce the impact of cats by limiting livestock grazing and better managing late dry season fires.”