Post-wildfire physiological ecology of an Australian microbat

Abstract

Historical patterns of wildfires are being altered as a result of changing climate and therefore are becoming an increasingly pressing global issue. How small mammals deal physiologically with changes in landscape and food availability due to fire remains largely unknown, although recent studies on small heterothermic terrestrial mammals have shown an increase in post-fire torpor use to reduce energy and foraging requirements. However, data on the behavioural and physiological responses of bats after fires are scarce, although potentially these volant species may differ from terrestrial mammals. Therefore, we investigated the post-fire thermal biology and activity of lesser long-eared bats ('Nyctophilus geoffroyi') using temperature-telemetry in Warrumbungle National Park, NSW, which experienced a devastating wildfire in 2013. The study comprised two field seasons, one in 2013 within 4 months after the fire, and one in 2015 two years after the fire to identify potential changes in behaviour and physiology. Interestingly, soon after the fire, bats showed significantly shorter torpor bout duration (11.8 ± 12.5 h) and longer normothermia duration (8.7 ± 4.6 h) in comparison to those in 2015 (torpor bout duration: 24.1 ± 23.5 h; normothermia duration: 2.5 ± 1.5 h). Insect availability was significantly (20-fold) higher in 2013 than in 2015, which was likely an important factor resulting in the short average torpor bout duration by 'N. geoffroyi' after the fire. Our data indicate that volant bats appear to show the opposite post-fire behavioural and physiological responses to small terrestrial mammals, showing longer normothermic and active periods and shorter torpor bouts to capitalise on an increase in available post-fire resources.