Impacts of the Australian black summer fires on bat occupancy and activity: the role of traits and conservation status

Megafires are predicted to become more frequent with global warming and it is crucial that we improve understanding of their impacts on biodiversity. We assessed the response of insectivorous bats 1 year after the 2019–2020 megafires in south-eastern Australia. An intense 2-year drought preceded the fires, but after the fires above average rainfall fell prior to our study. We used paired ultrasonic detectors along gullies and on adjacent upper-slope tracks to compare bat occupancy (low occurrence species; n = 6) and activity (widespread species; n = 11) among sites across two large regions and stratified by whether the surrounding landscape was dominated by unburnt forest, high or low severity fire. Total bat activity declined with the extent of high severity fire. Fire influenced the activity or occupancy of six species, either via species associations with the extent of high severity fire (negative) or unburnt forest (positive). Ten species were not associated with any fire covariate. Although not explicitly modelled, wing traits were partly related to fire-sensitivity of bats, with two closed-space species, Rhinolophus megaphyllus and Nyctophilus gouldi, displaying the strongest negative response to fire extent. A greater number of state-listed threatened species were found to be fire-sensitive than Least Concern species. Neither species activity nor occupancy was strongly related to the extent of low severity fire (weak positive responses were recorded for two species), although N. gouldi was most often captured where low severity fire dominated. Overall, bat responses were complex and not predicted by traits or conservation status alone. Monitoring is needed for both assessing recovery and tracking the effects of increased frequency and severity of fires predicted with climate change.