The Kangaroo Island dunnart (Sminthopsis aitkeni) is a small insectivorous marsupial found only on the western end of Australia’s third-largest island, Kangaroo Island (KI) off the coast of South Australia.
After extensive wildfires in late 2019 and early 2020 burned 98% of the species’ remaining habitat, it was classified as critically endangered – it is estimated that there are no more only about 500 dunnarts in this restricted geographical area.
Now scientists have discovered that dunnarts are threatened with extinction by feral cats.
Evidence of eight dunnarts in the digestive tracts of seven feral cats has been discovered, confirming for the first time that feral cats predate KI dunnart and that they were effective hunters of the species directly after the fires.
The new study was published in Scientific reports.
Because there are so few dunnarts confined to a small, fragmented geographic area, they are exceptionally vulnerable to stochastic events (unpredictable events that can affect population and community dynamics, such as bushfires and predation from introduced species ) that could lead to their extinction.
“Efforts to provide immediate relief to an invading predator, including the provision of refuge, are critical and can mean the difference between survival and extinction,” the authors state.
Controlling feral cats after the 2019 bushfires
Feral cats accompanied European colonizers to the continent in the late 1700s and have since contributed to the mass extinctions of many species of smaller native fauna.
Their effect is particularly acute on islands – cat predation has contributed to over 13% of recorded extinction events worldwide.
Because it had not yet been confirmed whether feral cats also posed a threat to dunnarts on Kangaroo Island, researchers from the University of Adelaide and Nanyang Technological University in Singapore set out to discover it.
Immediately following the 2019 bushfire, feral cats on KI were captured under the National Feral Cat Control Program and humanely euthanized in accordance with South Australia’s animal welfare laws.
“Controlling feral cats was seen as a priority to reduce the pressure they could put on wildlife in these places,” says lead author Dr Louis Lignereux, from the School of Animal and Veterinary Sciences at University of Adelaide.
“Not only the pressure on the dunnarts, but also the pygmy opossum, the southern brown bandicoot and many other species including birds and reptiles,” he adds. “They’ve all just suffered the loss of a lot of their habitat.”
The cats were captured from two areas: a 12 ha unburned patch at the Western River Refuge and a 420 ha completely unburned vegetation patch at the North-West Conservation Alliance in the De Mole River watershed.
First author Pat Hodgens of Terrain Ecology and the organization played an important role in feral cat control and data collection for this research, and led the construction of a wild predator-free safe haven in the Western River Refuge to protect the KI Dunnart .
Feral cat populations need to be controlled
“Thanks to this control cat, we had the possibility of accessing the contents of the gastrointestinal tract of 86 cats, which we analyzed”, explains Lignereux. “The contents of the gastrointestinal tract represent what the cat has eaten over the previous 26-35 hours.”
8.1% of cats sampled had signs of KI dunnarts in their stomachs, suggesting that they are effective hunters of the small number of dunnarts that remain after bushfires.
This finding raises concerns about the survival of the species in places where feral cats are unchecked and has implications for future conservation measures for KI dunnart – such as the need to study KI dunnart both in places that weren’t burned, but also where the KI dunnart was thought to live before the fires.
“The first implication is of course to protect the remaining KI dunnarts in these unburnt patches by increasing efforts to control feral cats and constructing cat proof fencing to prevent reinfestation once the cat has been controlled. “, explains Lignereux.
“Outside of Kangaroo Island, feral cats are a threat to several wildlife species. With our study, we would like to highlight the need to control these cat populations,” he adds.
“More broadly, through our study, we wish to show the dramatic effects of the succession of anthropogenic stochastic events and invite readers to reflect on the preservation of biodiversity.”
Interested in having the science explained? Listen to our new podcast.