We surveyed dingoes and feral cats on eighteen properties spread across North and Central Australia, spanning tropical to arid climates, in habitats varying from open forest and woodlands to native grasslands (Fig. 1). The properties were arranged in pairs, each consisting of one property on which dingoes were controlled and a matched property with no dingo control. Properties varied in size from 7850 to 705 496 ha and ranged from being adjacent to up to 153 km apart. Paired properties were selected to minimize differences in habitat, climate and management. Most properties were working cattle stations, with three exceptions: the Townsville Field Training Area (TFTA), owned by the Department of Defence, and Mt Zero-Taravale, owned by the Australian Wildlife Conservancy (AWC) and managed for conservation, both in the Einasleigh Uplands, and Piccaninny Plains on the Cape York Peninsula (CYP), jointly owned by the AWC and WildlifeLink. The TFTA was paired with Mt Zero-Taravale. Neither property controls dingoes, but we selectively surveyed sections of the TFTA along the property boundary with cattle stations that do control dingoes to measure the effect of that baiting and obtain a contrast with Mt Zero-Taravale. Piccaninny Plains, which has a herd contained behind wire and is grazed at low levels by feral cattle and horses outside these paddocks, was paired with a cattle station with patchy grazing pressure and broad areas of ungrazed woodland.
We surveyed dingoes and feral cats (and other wildlife) using infrared remote movement-triggered cameras. We used either I-60 Game Spy (Moultrie; EBSCO Industries, Birmingham, AL, USA) or DLC Covert II (DLC Trading Co., Lewisburg, KY, USA) cameras. Cameras were distributed in pairs along transects, with a spacing of 2–5 km to avoid correlation between pairs (Sargeant, Johnson & Berg 1998). We used minor, unsealed vehicle tracks as transects, and each camera pair consisted of one camera placed 1–5 m from the track and the other 50–200 m away, to allow for fine-scale differences in predator activity due to the presence of the track. Cameras were baited with different combinations of attractants such as chicken, the synthetic fermented egg spray FeralMone™ (Animal Control Technologies, Somerton, VIC, Australia), Felid Attracting Phonics (Westcare Industries, Bassendean, WA, Australia), bird seed or wild cat urine (Outfoxed Pest Control, Ivanhoe, VIC, Australia). In some paired areas, we surveyed for prey prior to predator surveys, using small mammal bait (rolled oats, vanilla and peanut butter) and positioning cameras 100 m off the road midway between camera pairs. We used 20–40 cameras on each property depending on property size and available tracks and operated the cameras for 5–8 days. Surveys were generally run consecutively or concurrently on the properties within each pair, except on two occasions where surveys were up to 2 months apart but still within the same season. Camera type, number and spacing, survey duration and lure combinations were consistent within paired study areas. In the three most northern areas (areas 7, 8 and 9; Fig. 1), surveys were repeated in the early and late dry season, with a maximum of three surveys on CYP over 3 years. For this analysis, repeat surveys in the same area were pooled. Other pairs of properties were surveyed once, between March and November. Cameras were programmed to record 5-s videos at night and 20- or 5-s videos during the day. Time and date were recorded with each video.