Prey capture behaviour by pygmy bluetongue lizards with simulated grazing

Endemic biota of native grasslands commonly co-exist with introduced grazing mammals, and often this is seen as a conservation threat. The endangered pygmy bluetongue lizard (Tiliqua adelaidensis) is restricted to remnants of native grassland in the mid-north of South Australia, with a long history of sheep grazing. Pygmy bluetongue lizards use ambush predation from their burrow entrances, and prey capture may be more efficient in a habitat with low vegetation density. We experimentally investigated changes in predatory behaviour in this lizard, with different grass density. We maintained and filmed captive lizards, in sequence, in grassed and bare habitat, and in habitat with low and high grass density, and provided them with crickets (Teleogryllus commodus) as prey. In habitats with lower grass density lizards emerged from their burrows more, made more prey capture attempts, and these attempts were more often made with the body further emerged from the burrow. We suggest that some grazing by domestic stock might benefit predatory efficiency for this lizard, perhaps by allowing a clearer view of approaching prey when grass density is lower. Our results conform with a previous study of the behaviour of pygmy bluetongue lizards in their natural burrows in the field under different simulated grazing regimes. From a broader perspective, together the results suggest a balance between detrimental impacts and benefits from grazing pressures on grassland lizard species in other geographical regions, and the potential to maintain conservation good will among farming communities.