The introduction of the domestic cat and the red fox has devastated Australian native fauna. We synthesised Australian diet analyses to identify traits of prey species in cat, fox, and dingo diets, which prey was more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal, bird, and reptile species occurred in the diets of one or more predators. Cat and dingo diets overlapped the least (0.64±0.27, n=24 location/time points) and the cat diet changed little over 55 years of study. Cats were more likely to have eaten birds, reptiles, and small mammals than foxes or dingoes. The dingo's diet remained constant over 53 years and constituted the largest mammal, bird, and reptile prey, including more macropods/potoroids, wombats, monotremes, and bandicoots/bilbies than cats or foxes. Fox diet had greater overlap with both cats (0.79±0.20, n=37) and dingoes (0.73±0.21, n=42), fewer distinctive items (plant material, possums/gliders), and significant spatial heterogeneity over 69 years, suggesting prey switching (especially of mammal prey) to mitigate competition. Our study reinforced concerns about mesopredator impacts on scarce/threatened species and the need to control foxes and cats for fauna conservation. However, extensive dietary overlap and low incidence of mesopredators in dingo diets precluded the resolution of the debate about possible dingo suppression of foxes and cats.

We systematically searched the literature for empirical data on the frequency of occurrence (FOO; the proportion of all samples that contain the diet item) of foods consumed by each of the three predator species and traced all citations for further potential sources, including journal articles, book chapters, theses, unpublished reports, and contacted authors directly where possible for clarification and additional data. For the 157 studies using classical morphological methods (macro and microhistology) to identify diet items, we calculated FOO data for 421 location–time point combinations for 264 sites across Australia for:

(i) 7 main food categories: all mammals (summed), birds, squamate reptiles (‘squamates’), amphibians (frogs), fish, invertebrates and plant material, and

(ii) 15 broad mammal taxonomic groups: 

- Nine native mammal taxonomic groups – dasyurids (Family Dasyuridae); possums and gliders (Suborder Phalangerida); macropods and potoroids (Suborder Macropodiformes); bandicoots and bilbies (Order Peramelemorphia); koalas Phascolarctos cinereus (Goldfuss); wombats (Lasiorhinus spp., bare-nosed wombat Vombatus ursinus (Shaw)); bats (Order Chiroptera); monotremes (short-beaked echidna Tachyglossus aculeatus (Shaw) and platypus Ornithorhynchus anatinus (Shaw)); and marsupial moles (Notoryctes spp.). Data were insufficient for the numbat (Myrmecobius fasciatus Waterhouse), which has a limited geographical range.

- Two introduced mammal categories – lagomorphs (European rabbit and European brown hare, Lepus europaeus Pallas), and livestock. These included farmed (mostly sheep, cattle, and goat Capra hircus Linnaeus) and feral livestock, some likely to have been scavenged (from most to least commonly recorded: sheep, cattle, feral pig Sus scrofa Linnaeus, camel, goat, sambar deer Cervus unicolor Kerr, chital deer Axis axis (Erxleben), horse, water buffalo Bubalus bubalis Linnaeus, fallow deer Dama dama (Linnaeus), hog deer Axis porcinus (Zimmermann), red deer Cervus elaphus Linnaeus and donkey Equus asinus Linnaeus).

Rodents – FOOs were mostly calculated separately for introduced and native species but were analysed together because species were not always distinguished. Their separate FOO values contributed to the calculations of the FOO of native vs. introduced species.

The three predator species themselves.