Summary1. Cavity quality is important for the productivity and survival of many species of treedwelling wildlife. Intensive land management practices, such as logging and agriculture, frequently reduce cavity availability and potentially affect the long-term viability of populations. 2. The New Zealand long-tailed bat Chalinolobus tuberculatus selects roosts in small knot-hole cavities with specific structural properties relative to available cavities. They also change roosts daily among a large pool of different roosts. Such behaviour is likely to make C. tuberculatus vulnerable to human-induced deterioration in roosting habitat. 3. This study represents a case study of the degree of sophistication sometimes required to assess availability and quality of roost sites, by testing whether roosts selected by C. tuberculatus also have specific microclimates. 4. Selection for microclimate was demonstrated by comparing temperature and humidity inside unoccupied maternity roosts with available, apparently unused, knot-hole cavities, large trunk-hollows and ambient conditions. 5. Compared with ambient conditions, roost and available knot-hole cavities had stable microclimates displaying only small ranges in temperature and humidity. Temperature inside cavities was lower than ambient temperature in the day and was warmer (and peaked) at night. Humidity in cavities was constantly high. Mean temperatures within trunk-hollows (not known to be used by C. tuberculatus ) were cooler than mean ambient and roost temperatures, and temperature ranges in hollows were large and fluctuated similarly to ambient temperatures. 6. Compared with available cavities and hollows, roost cavities had higher minimum temperatures, and maximum temperatures occurred significantly later in the day and continued for significantly longer. Humidity ranges were less and high humidity was maintained for longer. 7. The results suggest that C. tuberculatus selects maternity roost sites with microclimatic conditions that are likely to accrue substantial energetic benefits. Predicted energy savings for adult bats using roost cavities compared with available knot-holes were 1·1-3·3%, and compared with hollows 3·4-7·3%. Greater energy savings would occur at night and benefit non-volant young. 8. In order to evaluate adequately and mitigate the full impacts of land-use practices, there is a need for wider tests to provide direct evidence of interactions between habitat management, cavity provision and survival of cavity-dependent wildlife.

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SUMMARY The New Zealand short-tailed bat Mystacina tuberculata evolved in the absence of terrestrial mammals and initially with few potential predators. Unusual among bats, it is well adapted for the capture of prey on the ground. Bats from Fiordland, New Zealand had relatively low wing loadings and aspect ratios adapted for flight in cluttered habitats. We predicted that M. tuberculata would locate prey in air (uncluttered space) by echolocation. Echolocation call sequences associated with prey capture (terminal buzzes)were heard in the field, and bats detected and localized prey suspended on fishing line by echolocation in a flight cage. The bats emitted brief,multiharmonic echolocation calls at low duty cycle during search phase, and 64% of calls contained most energy in the fundamental harmonic. Approach- and terminal-phase calls were also broadband and multiharmonic. We predicted that bats would not use echolocation to locate prey hidden on the ground in leaf litter (cluttered space). Bats seemed unable to locate hidden prey precisely from the air and instead hunted for such prey while crawling. Echolocation calls were emitted at a low repetition rate on the ground, suggesting that here echolocation was used for orientation and not for prey detection. We experimentally removed cues available to the bats and showed that bats located mealworms in leaf litter by listening for prey-generated noises and possibly by olfaction.

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