Flexibility and Specificity in the Roosting Ecology of the Lesser Long-Eared Bat, Nyctophilus geoffroyi: A Common and Widespread Australian Species

Abstract An increasing body of literature suggests that tree-cavity roosting bats are selective in their use of roosts. By comparing aspects of roosting ecology for which there is a high level of specificity with those where roost use appears more flexible, we may gain a better understanding of the key influences on roost selection. Here we review eight studies on the roosting ecology of the lesser long-eared bat, Nyctophilus geoffroyi, a common and widespread vespertilionid in Australia. Nyctophilus geoffroyi is flexible in the distribution of roost sites, with roosts occurring in urban, rural, and a wide range of natural environments. While predominantly roosting in tree cavities, individuals (especially males) also use other natural and artificial roost sites. Tree roosts include a range of forms and orientations, but roosts located under bark and in fissures are common, frequently with a northerly orientation. A strong preference is shown by both sexes for roosts in dead trees, and entrance dimensions of roosts are consistently narrow (2.5–2.8 cm). Males predominantly roost solitarily, while females form larger colonies, especially while breeding. In some studies, females displayed a significant preference for roosts in larger trees, especially for maternity roosts, but this pattern was not consistent in all areas. In all studies, individuals shifted roosts frequently (every 1–2 days), and these roosts occurred within restricted areas. We suggest that key influences on roosting ecology for this species are the thermal requirements of roosts, the risk of predation, social organization within populations, and the pattern of roost availability in the landscape.