Exotic megaherbivores as ecosystem engineers in Australian savannas: Do they facilitate predator movement?

An understanding of how terrestrial mammalian predators use their environment is critical for the development of effective management and monitoring. Mammalian predators often use anthropogenic linear features—such as roads, fencelines, and infrastructure corridors—to increase movement efficiency and prey encounter rates. However, there has been little investigation into how predators use more subtle linear features such as game trails (i.e., well‐trodden paths created by megaherbivores). This is despite native and exotic megaherbivores being abundant across many of Earth's most intact landscapes and conservation areas. We investigated how the two largest terrestrial mammalian predators in northern Australian savannas—the dingo (Canis familiaris, introduced ca. 4000 years ago) and cat (Felis catus, introduced ca. 200 years ago)—use game trails created by exotic megaherbivores (Asian water buffalo Bubalus bubalis and horse Equus caballus). We deployed two camera traps at 52 sites, with one camera positioned on a game trail and another in undisturbed vegetation < 60 m away. We compared the activity of predators on game trails to adjacent undisturbed vegetation and explored how trail use varied with vegetation structure and prey activity. Dingoes and cats were 34 times and 6 times more likely to be detected on game trails than in adjacent vegetation, respectively, suggesting these predators preferentially use game trails. We speculate that the extensive network of game trails created by exotic megaherbivores across northern Australia's vast savannas has potentially facilitated terrestrial mammalian predator movement at very large scales. Controlling exotic megaherbivores may, therefore, provide a means of disrupting the activity of dingoes and cats, thereby benefiting predation‐susceptible native species. However, further research is needed to understand the ecological implications of game trails in Australian savannas and other habitat types.

Methods
At each site there were two cameras. One camera was placed on a game trail termed 'on' and the other camera was placed approximately 60m away in undisturbed vegetation termed 'off'.

Data csv includes the the number of independent detections of a species on the 'on-trail' camera and 'off-trail' camera. Detections were considered independent when >30 minutes had elapsed since the previous detections of that species on that same camera. 

'feral_herbivore' category includes detections of two species: Bubalus bubalis and Equus caballus

'sm_mam' category includes detections of Sminthopsis spp., Pseudomys spp. and Rattus spp.

'all_prey_spp' category is the sum of independent detections of all native mammal species less than 2.5kg i.e. all native mammal species excluding agile wallaby