Cat predation of Kangaroo Island dunnarts in aftermath of bushfire

Kangaroo Island (~4400 km2, KI hereafter) is the third largest island in Australia. It underwent substantial land clearing, and consequent fragmentation of the natural bushland habitat, after World War II1.2. Relatively intact western KI was eventually identified as a key biodiversity hotspot3home to several endangered and endemic native species including the KI dunnart.

Dunnarts (Sminthopsis spp.) are small insectivorous dasyurid marsupials. The KI dunnart is distinguished from the other 17 dunnart species found in Australia by morphological features, including manus, pes, and penis shape4. This endangered species is the only dasyurid found on the island, exclusively resident in ~342 km2 before 20205and found nowhere else in the world2. The species is rarely recorded, with only 28 individuals found during > 33,000 trap-nights pre-20195. With a low number of individuals restricted to a small geographic area, the KI dunnart is exceptionally vulnerable to stochastic events. Predation by feral cats (Felis catus) is likely to be another source of pressure on the KI dunnart. Cats were introduced to KI during European settlement and quickly became apex predators, reaching higher relative abundance than adjacent mainland6 with an estimated density of 0.37 ± 0.15 cat/km25. Cat predation has been the cause for extinction or near-extinction of several native species around the globe7, with the extinction risk becoming increasingly acute in insular islands like KI. Cat predation on islands has contributed to > 13% of globally recorded extinction events, accounting for > 8% of instances within these taxa of species being pushed to critically endangered status8. A recent meta-analysis found evidence of cat predation for three critically endangered species and four endangered species in Australia on the IUCN Red List of Threatened Species7.

Australian bushfires in 2019–2020 burned ~97,000 km2 of vegetation9.10, with damage overlapping with habitats of > 100 threatened species. Dry lightning storms in the remote and vegetated northwest of the Island started the bushfire in the KI. The bushfire eventually spread easterly, burning approximately 98% of the known and predicted habitat of the KI dunnart10.

In this study, we have analyzed the diet of feral cats humanely euthanized in designated areas of local conservation interest immediately after the 2019 KI bushfire.

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