Diets of insectivorous marsupials in arid Australia: selection for prey type, size or hardness?

The diets of six species of arid zone dasyurid marsupials were investigated at study areas in Queensland and Western Australia. At least 11 orders of insects were taken, as well as spiders, scorpions and centipedes. Beetles and spiders were taken more frequently than expected along foraging trails, whereas ants were avoided; there was no selectivity for other taxa. All species ate small prey (< 2•5 mm long) less frequently than expected. Four of the five species of smaller dasyurids ( 13 g) showed some preference for prey 5•0-7•4 mm long, whereas the largest species, Dasycercus cristicauda (65 g), preferred prey >7•5 mm in length. Dasycercus cristicauda was also the only dasyurid regularly to include large, hard beetles in its diet. Beetles with hard cuticles were not eaten by the small dasyurids, although the three smallest species foraged in areas where hard prey were seldom encountered. Dasyurid marsupials are conspicuously successful inhabitants of the arid zone of Australia; most species are wholly insectivorous. Dietary generalism should be advantageous in arid zone dasyurids by permitting continuous exploitation of a temporally and spatially unpredictable food resource.