Effects of wildland fire smoke on a tree-roosting bat: integrating a plume model, field measurements, and mammalian dose–response relationships

Abstract

Faunal injury and mortality in wildland fires is a concern for wildlife and fire management although little work has been done on the mechanisms by which exposures cause their effects. In this paper, we use an integral plume model, field measurements, and models of carbon monoxide and heat effects to explore risk to tree-roosting bats during prescribed fires in mixed-oak forests of southeastern Ohio and eastern Kentucky. Tree-roosting bats are of interest primarily because of the need to mitigate risks for the endangered Indiana bat ( Myotis sodalis ), our focal species. Blood carboxyhemoglobin concentrations predicted from carbon monoxide data supplemented by model output only approached critical levels just above flames in the most intense fires. By contrast, an ear-heating model driven by plume model output suggested that injury to the bat’s thermally thin ears would occur up to heights similar to those of foliage necrosis, an effect for which predictive relationships exist. Risks of heat injury increase with fireline intensity and decrease with both roost height and ambient wind. Although more information is needed on bat arousal from torpor and behavior during fires, strategies for reducing the risk of heat injury emerge from consideration of the underlying causal processes.

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

“…Interestingly, in these two species, smoke was sensed even by torpid individuals and induced rapid arousal, whereas none of the antechinus were still torpid when smoke was introduced in the present study. Arousal from torpor in response to smoke has also been recorded in bats (Scesny, 2006) and it is possible that fire cues other than smoke may influence activity and arousal from torpor, such as an increase in T a or changes in humidity (Dickinson et al, 2010;Perry and McDaniel, 2015). Regardless, it is likely that smoke is perceived as a warning signal and will elicit an escape response in both torpid and normothermic small mammals, therefore strengthening the chances of surviving an approaching fire front provided a secure shelter can be found in time.…”

“…Further, the third activity bout in the afternoon (in addition to two activity bouts at night) started in response to smoke at a time when the animals would not have known whether they would be fed or not; therefore, this emergency response was not food related. The intrusion of smoke into a nest site would indicate the vulnerability of this particular site to fire and heat (Dickinson et al, 2010;Perry and McDaniel, 2015), probably causing animals to retreat into a more secure shelter. In our experimental setup, such secure sites like underground burrows or rocky crevices (Howard et al, 1959) were not provided, perhaps explaining the protracted length of the activity bout following smoke exposure.…”

“…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).…”

The response of bats (Mammalia: Chiroptera) to an incidental fire on a gallery forest at a Neotropical savanna

“…Most studies reporting the effects of fire on bats have been carried out on North American forests with special attention to insectivorous species (Boyles & Aubrey 2006;Dickinson et al 2008;Loeb & Waldrop 2008;Lacki et al 2009;Layne 2009;Fisher & Wilkinson 2005;Johnson et al 2010;Dickinson et al 2010;Perry 2011;Silvis 2011;Armitage & Ober 2012). According to Fisher & Wilkinson (2005), bat activity after fire may vary according to the density of the remaining trees.…”

Activity of an endangered bat increases immediately following prescribed fire

“…Fire may positively affect bats by opening up flight space under the canopy and by creating new snags and cavities in live trees for roosting (Boyles and Aubrey 2006, Hayes et al 2009, Knapp et al 2009, Armitage and Ober 2012. In contrast, temporary adverse effects may come from the smoke, heat, or carbon monoxide in roosts during ignition, whereas longer-term negative effects may occur with the destruction of roost trees (Morrison and Raphael 1993, Rodrigue et al 2001, Dickinson et al 2010. Insect communities (prey for insectivorous bats) may similarly experience benefits or harm from fire.…”