Research highlights solution to mammal crisis

Protecting and recovering complex habitat by improving fire regimes and reducing feral cattle, horse and buffalo impacts is a more likely solution to northern Australia’s native mammal crisis than targeted feral cat control, according to a new study. 

The research was conducted by the Northern Territory Government’s Department of Environment and Natural Resources (DENR) with assistance from Charles Darwin University and funding from the Australian Government’s National Environmental Science Program. 

Researchers deployed more than 1500 camera traps and almost 7500 live traps across 300 sites in the Top End, surveying national parks, private conservation reserves and Indigenous-managed land, to make the discovery. 

CDU researcher Dr Alyson Stobo-Wilson said the research was urgently needed as many small- and medium-sized native mammal species were in rapid decline, with many once-common species now restricted to offshore islands. 

“We undertook one of the most comprehensive assessments of the patterns of native mammal declines in northern Australia to date,” Dr Stobo-Wilson said.

“We found the role of large feral herbivores in mammal declines, including feral cattle, horses and buffalo, has been greatly underestimated.

“Frequent, large fires and over-grazing by these introduced herbivores remove critical shelter and food for native mammals and attract cats and dingoes.”

DENR’s Director of Terrestrial Ecosystems Dr Graeme Gillespie said the findings would assist conservation managers to recover dwindling native mammal populations in northern Australia. 

The team also examined the factors influencing where feral cats occurred and if dingoes played a role, which is a popular conjecture.

“Despite a very large data set, we did not find any evidence that dingoes were limiting where feral cats occurred, in fact, they often occurred in the same areas,” Dr Gillespie said.

“Rather, habitat was the most important factor influencing cat occurrence. As habitat complexity increased with more shrubs and trees, the likelihood of detecting a cat at the site reduced.”

Dr Gillespie said feral cats were less likely to occur in places such as the Tiwi Islands, Groote Eylandt and the Cobourg Peninsula as the relatively high rainfall supported more complex vegetation. 

“These areas have an abundance of small mammals and other animals, so it is not the absence of prey that reduces feral cat numbers there,” he said.

“Cats play a role in mammal declines, but the impact of cats is greatly magnified in areas where vegetation has been degraded by frequent fire and over-grazing. 

“This research adds to a growing body of work from northern Australia indicating that across most of these landscapes, managing herbivores and fire rather than culling cats, is likely a more effective way of protecting small mammals.”

The research has been published in "Diversity and Distributions" and "Biological Conservation".