Incorporating disturbance into trophic ecology: fire history shapes mesopredator suppression by an apex predator.
Apex predators can suppress smaller bodied "mesopredators." In doing so, they can provide refuge to species preyed upon by mesopredators, which is particularly important in regions where mesopredators are invasive. While most studies of mesopredator suppression focus on the response of mesopredators to human control of apex predators, other factors - including natural and anthropogenic disturbance - also drive the occurrence of apex predators and, in doing so, might shape spatial patterns of mesopredator suppression. We examined the role of fire in shaping the occurrence of an apex predator and, by extension, mesopredators and small mammals in a fire-prone region of semiarid Australia. We measured the activity of an apex predator (the dingo Canis dingo); an invasive mesopredator it is known to suppress (the red fox Vulpes vulpes); and two species of native small mammal (Mitchell's hopping mouse Notomys mitchelli; silky mouse Pseudomys apodemoides) that are potential prey, across 21 fire mosaics (each 12.56 km2). We used piecewise structural equation modelling and scenario analysis to explore the interactions between fire, predators and prey. We found that dingoes were affected by fire history at the landscape scale, showing a preference for recently burned areas. While foxes were not directly affected by fire history, a negative association between dingoes and foxes meant that fire had an indirect impact on foxes, mediated through dingoes. Despite the suppression of foxes by dingoes, we did not observe a trophic cascade as small mammals were not negatively associated with foxes or positively associated with dingoes. Synthesis and applications. Disturbance regimes have the capacity to shape patterns of mesopredator suppression when they alter the distributions of apex predators. Environmental change that promotes native predators can therefore help suppress mesopredators - a common conservation objective in regions with invasive mesopredators. The indirect consequences of disturbance regimes should be considered when managing disturbance (e.g. fire) for biodiversity conservation.