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.

A new cue for torpor induction: charcoal, ash and smoke

“…Torpor appears to be an important survival strategy for many small mammals in response to catastrophic events (Lovegrove et al, 2014;Nowack et al, 2015Nowack et al, , 2016aStawski et al, 2016), but how animals employ torpor immediately or in the short to long term after a fire varies among species (Doty et al, 2016). Importantly, our study identifies a charcoal and ash substrate as a new cue that signals antechinus to enhance torpor use to save energy.…”

“…The physiological and behavioural responses of individual mammals to fire have attracted some recent scientific attention (Scesny, 2006;Dickinson et al, 2010;Doherty et al, 2015;Perry and McDaniel, 2015;Doty et al, 2016;Matthews et al, 2016;Nowack et al, 2016a;Stawski et al, 2016). For example, volant bats employed less torpor, characterised by reduced metabolic rate and body temperature (T b ), shortly after a wildfire in comparison to 2 years later (Doty et al, 2016).…”

“…For example, volant bats employed less torpor, characterised by reduced metabolic rate and body temperature (T b ), shortly after a wildfire in comparison to 2 years later (Doty et al, 2016). This response is probably because of the ease of foraging in the canopy and an increase in aerial insects after a wildfire.…”

More functions of torpor and their roles in a changing world

“…Torpor use and activity periods were monitored in lesser long-eared bats ( Nyctophilus geoffroyi ) 4 months after a severe wildfire and again 2 years later (Doty et al 2016). These authors found that shortly after the wildfire, bats expressed shorter torpor bouts and longer normothermic periods in comparison with 2 years after the wildfire (Doty et al 2016).…”

“…Torpor use and activity periods were monitored in lesser long-eared bats ( Nyctophilus geoffroyi ) 4 months after a severe wildfire and again 2 years later (Doty et al 2016). These authors found that shortly after the wildfire, bats expressed shorter torpor bouts and longer normothermic periods in comparison with 2 years after the wildfire (Doty et al 2016). As aerial insect abundance was significantly greater shortly after the fire and ambient conditions were warmer, it is likely that bats took advantage of the increase in insect numbers and also in the decrease in vegetation, which would have made foraging easier (Doty et al 2016).…”