Selection of roost sites by the lesser long‐eared bat (Nyctophilus geoffroyi) and Gould's wattled bat (Chalinolobus gouldii) in south‐eastern Australia

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Abstract
Physical characteristics of roost sites used by the lesser long‐eared batNyctophilus geoffroyiand Gould's wattled batChalinolobus gouldiiwere investigated in a farmland–remnant vegetation mosaic and adjacent forested floodplain in south‐eastern Australia. A total of 45 individuals ofN. geoffroyiand 27C. gouldiiwere fitted with radio‐transmitters, resulting in the location of 139 and 89 roosts, respectively. MaleN. geoffroyiroosted in trees, fallen and decayed timber and artificial structures. These roosts were low to the ground, mainly under bark and in cracks in timber. Roosts of femaleN. geoffroyiwere located higher above ground, and all within trees. Maternity roosts were predominantly located in large dead trees, approximately twice the diameter of roost trees used by females outside the breeding season. No maternity roosts were found under bark, despite half the roosts used by non‐breeding females being located in these situations. Both sexes roosted primarily in dead timber and used cavities where the narrowest dimension of the entrance was 2.5 cm. Most roosts ofC. gouldiiwere in dead spouts on large, live river red gumEucalyptus camaldulensistrees. Intraspecific differences in roost characteristics were less pronounced for this species. Despite access to the same roosting opportunities, there were marked differences in roost selection betweenN. geoffroyiandC. gouldii. Both species favoured large diameter trees, but differed significantly for all other measured variables: type of roost structure, condition of roost tree (live or dead), height of roost tree, height of roost, and entrance dimensions. Although these species are among the most widespread bats in Australia and are often considered to be habitat ‘generalists’, both displayed a high level of discrimination in the roosts used. Clearly, roosting requirements are a complex and important issue in the conservation of even the most common species of bats.