Bad news for bobtails: Understanding predatory behaviour of a resource-subsidised corvid towards an island endemic reptile

Abstract

Context: Resource subsidisation as a result of urbanisation and other human activity can have positive impacts for some opportunistic predators. Many species of corvid have benefitted from the expansion of human-dominated habitats; however, their impacts on co-occurring prey fauna are generally poorly understood. Aims: We aimed to test the hypothesis that urbanisation associated with tourism impacts the predator-prey relationship between Australian ravens, or wardongs (Corvus coronoides), a ubiquitous corvid of southern Australia, and Rottnest Island bobtails (Tiliqua rugosa konowi), a subspecies of bobtail lizard isolated to a small (19 km2) island off the coast of Western Australia. Methods: Using clay model lizards and camera traps, we assessed the wardongs' attack rates by distance from the settlement and by whether the model was in closed or open habitat. Key Results: We found that while wardongs preyed upon Rottnest Island bobtails, predation was not affected by proximity to human settlement despite the highest number of wardongs being found there. Models in closed vegetation were attacked by wardong significantly more than were those in open vegetation. Implications: Increased predation rates in closed vegetation suggests that current revegetation efforts on the island may be increasing the availability of preferred hunting habitat for the wardong. This finding may influence decisions by management on whether to control the large population of wardongs on the island.