Assessment of habitat usage by bats in the rangelands of Western Australia: comparison of echolocation call count and stable isotope analysis methods

Abstract

The activity levels of seven species of insectivorous microbats in five habitats widespread across the Charles Darwin Reserve in the Murchison region of Western Australia were measured using echolocation detectors and compared with results of habitat usage revealed by stable isotope analysis. The activity levels were further compared with projective foliage density as a surrogate of productivity within each habitat. Habitat use, estimated from echolocation activity of the microbat species and from stable isotope analysis of their fur, agree and each provides complementary information on the habitats preferred by species. Both methods show that five of the species, Chalinolobus gouldii, C. morio, Mormopterus species 3, Nyctophilus geoffroyi and Tadarida australis, are active and forage over each of the five habitats. Scotorepens balstoni is shown by both methods to prefer habitats with C3 woodland over C4 shrubs and grasses. Vespadelus baverstocki is shown by both methods to fly and forage over habitats with developed arid-zone shrubland understorey vegetation. The echolocation method shows that bat activity levels align with the foliage mass of the vegetation as measured by the projected foliage density. The species’ stable isotope signatures show that the insects captured are feeding primarily on the ground cover of the habitats. The two species that have high δC signatures, S. balstoni and V. baverstocki, are shown to be most active in habitats with a C4 ground cover.