The Black Summer bushfires of 2019-20 brought a host of threatened species one step closer to extinction, including the critically endangered Kangaroo Island dunnart. And as our research published today shows, feral cats posed a second deadly threat to the species in the weeks following the disaster.
The Kangaroo Island dunnart is a mouse-sized marsupial found only on the western end of the island. The January 2020 bushfires burned over 98% of its habitat. The Dunnart population was thought to be around 500 before the fire; its current numbers are under investigation, but are thought to have fallen further since.
Cat predation has caused the extinction or near extinction of several native species around the world. Our results confirm for the first time that wild cats feed on dunnart and did so directly after bushfires.
The findings underscore the importance of immediate action to protect endangered species from predators following catastrophic natural events.
Analyzing wild cat diets
Prior to the Black Summer fires, Kangaroo Island dunnart habitat was fragmented due to land clearing and other pressures. The island’s feral cats were also suspected of contributing to the decline of the species, but this had not been proven.
A federally funded feral cat eradication program has been in place since 2015 and aims to rid Kangaroo Island of feral cats by 2030.
A 2020 study estimated that there were between 1,000 and 2,300 feral cats on Kangaroo Island. We set out to determine if the cats were a threat to the dunnart.
We analyzed the diet of humanely euthanized feral cats immediately after the 2019 bushfire. We accessed the stomach contents and digestive tract of 86 cats captured between February and August 2020.
The cats were not killed for our study, but as part of the National Feral Cat Control Program and were euthanized in accordance with South Australian animal welfare laws. They were captured in unburned areas where dunnarts and other species that survived the fire would likely have sought refuge.
We identified 263 distinct prey items in the stomachs and digestive tracts of cats. They included:
- 195 mammals
- 46 birds
- 10 reptiles
- 12 arthropods (invertebrates such as beetles).
Among them, the introduced house mouse represented the largest proportion, forming part of the diet of 47 cats.
We found the remains of eight Kangaroo Island dunnarts in seven different cats. Three dunnarts were easily identifiable as they were nearly whole carcasses. Five others were identified based on hair characteristics.
We observed dunnart tissue in one cat’s stomach and large intestine, suggesting it had recently hunted at least two individuals.
Our results confirm for the first time that feral cats prey on Kangaroo Island dunnarts and are effective hunters of this species directly after fires.
Our results only provide a small snapshot of what the wildcat had eaten. Indeed, once the prey is completely digested (between 27 and 36 hours after being captured), we cannot analyze it. So the cats may well have recently consumed more prey than we could identify.
Safe to say, cats present a significant threat to the dunnart. We also found the remains of the endangered southern brown bandicoot in the stomach of a male cat. This endangered species is likely the last of eight native bandicoot species still living in the wild in South Australia.
Save the most vulnerable
The Kangaroo Islands dunnart is emblematic of the challenges faced by endangered species across the globe, particularly those confined to increasingly fragmented habitats, facing the catastrophic consequences of climate change and preyed upon by introduced species.
Already compromised species can easily slide towards extinction after disasters such as the Black Summer fires – events of which are predicted to become more frequent as the world warms and dries up.
After such events, we must act immediately to protect vulnerable species from invasive predators. These measures can make the difference between survival and extinction.
But prevention is better than cure, and we must not wait until after a catastrophic event to protect our most endangered wildlife.
/ Courtesy of The Conversation. This material from the original organization/authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the authors.