Fire Cues Research Articles

Analyzing Risk Perception, Evacuation Decision and Delay Time: A Case Study of the 2021 Marshall Fire in Colorado

Climate change is increasing the threat of wildfires to populated areas, especially those within the wildland-urban interface (WUI). The 2021 Marshall fire forced the evacuation of over 30,000 people in Boulder, Jefferson and Adams Counties in Colorado, US. To improve our understanding of wildfire evacuation response, we surveyed individuals affected by the Marshall fire to analyze their evacuation decisions and resulting behavior. We used linear and logistic regression models to determine the factors influencing individuals’ risk perceptions, their decisions to evacuate or stay, and the associated evacuation delay times. We found higher levels of risk perception at the time of the evacuation decision were associated with higher levels of pre-fire perceived risk, having mid-level household income, the receipt of fire cues and having a medical condition. Increased pre-event risk perception increased the likelihood of evacuating, along with gender (female-identified), being aged between 55 and 64 years, and having a higher household income. On the other hand, having a prior awareness of wildfires had a negative effect on evacuation likelihood. Additionally, having previous experience with fire damage, owning their home, having a larger household size and being alerted later in the fire event reduced the delay time; whereas engaging in preparation activities and having children in the home led to longer delay times. These research findings can be used by emergency managers to better prepare WUI communities for future wildfire events.

Assessment of pre-warning, pre-travel and travel behavior interactions with smoke and toxic gases during fire incidents

Evaluation of potential fire scenarios and escape outcomes involves data and calculations for many different parameters and their interactions, with uncertainties regarding application to real systems. Assessment of fire development, occupant behaviors and effects of toxic smoke exposure during actual incidents can provide a reality check on engineering methods, data quality, assumptions and limitations. Because incidents encompass the performance of entire occupied built systems, they enable witness accounts, survival, medical and pathology outcomes and evidence of fire development and toxic smoke spread to be combined with fire, evacuation and toxicity modelling calculations. Since outcomes are known, they constrain the predictions derived, revealing previously unidentified parameters and enabling validation of current methodology. Examples from incidents highlight the following findings.• Pre-warning delays – neglected parameter, high consequence.• Effects of fire cues and warnings on occupant behavior and pre-travel times, and stair descent speeds in relation to visibility – generally validate current methods.• Probability of evacuation through irritant smoke– high consequence, needs more consideration.• Times to incapacitation from asphyxiant gases as a function of fuel composition and smoke density – useful assessment method.• Using smoke and carbon monoxide exposure toxicology to estimate fire development and exposure history - Useful method for fire scenario validation, confirms FED method validity.

Do Fire Cues Enhance Germination of Soil Seed Stores across an Ecotone of Wet Eucalypt Forest to Cool Temperate Rainforest in the Central Highlands of South-Eastern Australia?

Soil seed banks play an important role in plant species persistence in fire-prone systems. Response to fire related germination cues often reflect historical fire regimes and can be important in maintaining ecotones between different forest types. We assessed the effects of heat and/or smoke on the soil stored seed banks across an ecotone of eucalypt to rainforest overstorey comprising wet forest, cool temperate mixed forest, and cool temperate rainforest in south-eastern Australia. Soils from five replicates of each forest type were subjected to very low (45 °C), low (65 °C) and high (90 °C) heat with or without two different smoke treatments: –smoke-infused vermiculite, and karrikinolide—a phytoreactive compound derived from smoke. Soils were placed in a glasshouse and germinants were identified and counted at weekly intervals. Response to fire cues was consistent among forest types despite underlying differences in the diversity of soil seed banks. There was no overall response of species richness, abundance, or composition to fire cues. Phanerophytes and ant-dispersed species with hard seed coats demonstrated positive response, and endozoochores negative response, to high heat independent of smoke. Endozoochores were concentrated (albeit at low densities) in cool temperate rainforest with no overall effect of seral affiliation on response to fire cues. Given the lack of response to karrikinolide, response to soil disturbance would most likely be associated with mechanical seed abrasion and/or exposure to increased light availability than to non-fire related production of smoke products. Forest type was a stronger determinant of floristics in the germinated soil seed bank than simulated fire related germination cues. Both smoke treatments had little influence on floristics in the germinated seed bank suggesting other, non-fire disturbances such as treefalls and soil turnover by fauna may be more important for germination for many of the species in these forest types.

A global synthesis of fire effects on soil seed banks

Fire is a major disturbance affecting plant communities in terrestrial ecosystems. Understanding fire effects on soil seed banks is critical in the context of altered global fire regimes. Through a systematic and quantitative review of the literature, we provide the first global assessment of how soil seed banks respond to fire based on 539 paired comparisons. The overall effects of fire on soil seed bank richness ( i.e. , the species richness in soil seed bank) and abundance were negative and neutral, respectively. Wildfires and high-intensity fires led to greater decreases in the richness and abundance of the seed bank than prescribed burns and low-severity fires, respectively. As an important fire cue, the presence of simulated smoke increased seed bank richness and abundance, but simulated heat shock had no effect on both two metrics, in contrast to the findings of previous empirical studies. Strong, positive fire effects on soil seed bank abundance were found in Mediterranean ecosystems, but fire effects were negative for forest ecosystems, especially tropical forests. Both the richness and abundance of tree species in the seed bank decreased after fire. Burning only had a negative effect on the soil seed bank in habitats with no previous fire history or a short fire history. As time elapsed post-fire, the soil seed bank abundance also increased. Overall, fire tended to decrease soil seed bank richness globally, and this was especially the case for high-severity fires in non-fire-prone ecosystems. Our findings enhance our understanding of the spatiotemporal variability in fire effects on soil seed banks, and highlight the importance of monitoring post-fire seed bank composition across ecosystems, with crucial implications for vegetation regeneration and ecosystem recovery.

Exploring ‘wait and see’ responses in French and Australian WUI wildfire emergencies

For Wildland-Urban Interface (WUI) residents, wildfire is a constant, growing risk. A timely response to wildfire is vital for human survival. Yet, upon receiving fire cues, previous studies show that instead of taking protective action, people often first wait and see how the situation unfolds. The circumstances under which ‘wait and see’ responses manifest have received research attention in Australia and North America. However, it is unclear whether the findings extend to European regions, given the scarcity of such research there. So, this study surveyed and systematically compared the responses of residents in French and Australian at-risk regions (N = 450). Those with recent wildfire experience described their actual responses; those lacking experience provided responses to a hypothetical fire. The results showed regional differences, with participants in France tending to choose to ‘wait and see’ more often than participants in Australia. There was less waiting when participants received environmental as compared to social cues, although the type of environmental/social cue appeared to moderate this behaviour. The cessation of waiting requires further study but early signs are that it may not always be followed by optimal action. Lacking preparedness and wildfire experience affected responses. Peri-event perceived risk also proved meaningful, unlike pre-event perceived risk.. These findings have implications for wildfire evacuation modelling (when developing simulation scenarios and evacuation triggers) as well as for wildfire management (when using evacuation models for planning or response, when designing interventions such as the education of residents).

From germination to seedling development: the effects of smoke on a native and an invasive grass species of the Cerrado

AbstractThe Brazilian Cerrado, a Neotropical savanna, is a fire-prone ecosystem where the ground layer biomass consists mainly of graminoids. However, as for other savannas, the effects of fire cues (such as smoke) on Cerrado grasses do not present a clear pattern, either for germination or seedling development. Smoke can stimulate different stages of the plant life cycle, which can alter the community and invasion processes. So far, most research on the subject focuses on germination, not addressing post-germinative phases, a sensitive stage of plant development. Here, we investigated the effect of smoke on a native (Echinolaena inflexa) and an invasive (Urochloa decumbens) grass species common in the Cerrado. We analysed germinative parameters and seedling mass and length after exposing the seeds to dry smoke for 5, 10, 15 or 20 min. Seedling development was assessed by measuring shoot and root systems after cultivating germinated seeds for 3, 7 or 15 d. Smoke did not affect germination percentages. However, fumigation reduced the mean germination time of both species and the germination onset of E. inflexa. U. decumbens had higher length values in all periods of cultivation, whereas mass values only surpassed that of E. inflexa at 15 d. Smoke exposure reduced the aboveground length of 7-d seedlings of U. decumbens, and mass of 15-d plants of both species. Also, smoke enhanced the root investment of the native and invasive species in different cultivation periods. Therefore, studying post-germinative parameters on seedling development may bring further insights into the smoke effects.

Fire-Related Cues Significantly Promote Seed Germination of Some Salt-Tolerant Species from Non-Fire-Prone Saline-Alkaline Grasslands in Northeast China.

Seed germination in response to fire-related cues has been widely studied in species from fire-prone ecosystems. However, the germination characteristics of species from non-fire-prone ecosystems, such as the saline-alkaline grassland, where fire occasionally occurs accidentally or is used as a management tool, have been less studied. Here, we investigate the effects of different types of fire cues (i.e., heat and smoke water) and their combined effect on the seed germination of 12 species from the saline-alkaline grassland. The results demonstrated that heat shock significantly increased the germination percentage of Suaeda glauca and Kochia scoparia var. sieversiana seeds. Smoke water significantly increased the germination percentage of Setaria viridis and K. scoparia seeds. However, compared with single fire cue treatments, the combined treatment neither promoted nor inhibited seed germination significantly in most species. These results suggest that fire cues can be used as germination enhancement tools for vegetation restoration and biodiversity protection of the saline-alkaline grassland.

Smoke and heat can increase germination of common wildflowers and grasses—implications for conservation and restoration of critically endangered grassy ecosystems

SummaryCritically endangered grasslands and grassy woodlands were once widespread across south‐eastern Australia. However, more than 200 years of European land use means less than 1% of their pre‐European extent remains today. Conservation and restoration of these ecosystems involves reintroducing fire to periodically reduce competition and allow smaller species to establish. Furthermore, seeds of native species are sown – but often fail to establish as many forbs and grasses are hard‐to‐germinate. Therefore, data on how these species respond to fire‐related germination cues, such as smoke and heat, can benefit our understanding of both how species respond to fire and identify treatments which can be used to increase germination. We conducted a germination trial to determine if smoke and heat cues increase percent germination and germination speed of 55 common grassy ecosystem species. Fire cues increased germination speed and/or percent germination of 44 of the 55 study species. These results have three implications for grassy ecosystem conservation and restoration: (i) fire may aid conservation by maximizing germination of native species; (ii) pre‐treating seed with smoke and/or heat prior to sowing may increase germination when restoring these ecosystems via direct seeding; and (iii) smoke and heat can be used to increase germination when growing seedlings for plantings.

Smoke and heat accelerate and increase germination in fire‐prone temperate grassy ecosystems

AbstractFire increases seedling recruitment by reducing competition for space and resources. As such, many species in fire‐prone ecosystems germinate in response to fire cues such as smoke and heat. A notable exception is fire‐prone temperate grassy ecosystems, where >20 yr of research has found that fire‐cued germination is rare. We tested the hypothesis that fire cues promote germination in temperate grassy ecosystems of south‐eastern Australia. We treated seeds of 55 common species with smoke, heat, and a combination of smoke and heat and tracked germination over time. We analyzed the effect of all combinations of treatments on germination speed and percent germination. Interestingly, we found that smoke and heat combined—which is more ecologically relevant to an actual fire than smoke and heat alone—was needed to increase germination speed, a mostly unstudied component of the germination ecology of grassy ecosystems. Smoke alone increased percent germination. Both plant family and seed traits influenced the germination response to smoke and heat. Poaceae species were the most responsive (in both speed and percent germination) to smoke alone. Water permeability of the seed coat was a key determinant of whether species responded to heat alone, smoke alone, or combined smoke and heat. Species with water‐impermeable seed coats responded to heat alone for both speed and percent germination. Species with water‐permeable seed coats germinated faster in response to combined smoke and heat and percent germination was increased by smoke alone. In contrast with more than two decades of research—our study of this large and representative group of species demonstrates that fire (via smoke and heat) is an important germination cue in fire‐prone temperate grassy ecosystems of south‐eastern Australia.

Modeling evacuation decisions in the 2019 Kincade fire in California

Communities around the world are increasingly exposed to larger and more intense wildfires. A common method that officials use to protect community members from harm is evacuation. Data on how people behave during wildfires is critical when planning for evacuation and deciding when and how to evacuate entire communities during an event. Using a similar method to the 2016 Chimney Tops 2 Fire study, an online survey was conducted with households impacted by the 2019 Kincade fire in Sonoma County, California. The survey measured pre-event and event-based factors to 1) predict household perceptions and evacuation decisions and 2) compare results across fire events. Regression analysis identified the factors that influenced risk perception at the time of evacuation decision, i.e., pre-fire perceptions of safety, household makeup (of adults, pets, and livestock), income, education and threat assessment. Logistic regression analyses found that risk perception, length of residence, household makeup, income, education, evacuation order, fire cues, pre-fire perceptions of the safety, and homeownership influenced evacuation decisions. These results differ widely from the 2016 fire due to differences in fire conditions and experiences across populations. Results from this work bring the field closer to a generalized theory of human behavior during wildfire evacuation and improve community-wide evacuation planning and real-time decision-making.

Fire-mediated germination syndromes in Leucadendron (Proteaceae) and their functional correlates

A mechanistic understanding of fire-driven seedling recruitment is essential for effective conservation management of fire-prone vegetation, such as South African fynbos, especially with rare and threatened taxa. The genus Leucadendron (Proteaceae) is an ideal candidate for comparative germination studies, comprising 85 species with a mixture of contrasting life-history traits (killed by fire vs able to resprout; serotinous vs geosporous) and seed morphologies (nutlets vs winged achenes). Individual and combined effects of heat and smoke on seed germination of 40 species were quantified in the laboratory, and Bayesian inference applied to distinguish biologically meaningful treatment effects from non-zero, but biologically trivial, effects. Three germination syndromes were identified based on whether germination was dependent on, enhanced by, or independent of direct fire cues (heat and smoke). Seed storage location was the most reliable predictor of germination syndromes, with soil-stored seeds c. 80% more likely to respond to direct fire cues (primarily smoke) than canopy-stored seeds. Notable exceptions were L. linifolium, with an absolute requirement for smoke to germinate (the third serotinous species so reported), and two other serotinous species with smoke-enhanced germination. Nutlet-bearing species, whether serotinous or geosporous, were c. 70% more likely to respond to fire cues than winged seeds, but there was no evidence for an effect of phylogeny or persistence strategy on germination. This comprehensive account of seed germination characteristics and identification of germination syndromes and their predictors, supports propagation, conservation and restoration initiatives in this iconic fynbos genus and other fire-prone shrubs with canopy or soil-stored seeds.

Investigation of 18 physiologically dormant Australian native species: germination response, environmental correlations and the implications for conservation

AbstractFor physiologically dormant (PD) species in fire-prone environments, dormancy can be both complex due to the interaction between fire and seasonal cues, and extremely deep due to long intervals between recruitment events. Due to this complexity, there are knowledge gaps particularly surrounding the dormancy depth and cues of long-lived perennial PD species. This can be problematic for both in situ and ex situ species management. We used germination experiments that tested seasonal temperature, smoke, dark and heat for 18 PD shrub species distributed across temperate fire-prone Australia and assessed how germination was correlated with environmental factors associated with their home environments. We found extremely high levels of dormancy, with only eight species germinating above 10% and three species producing no germination at all. Seven of these eight species had quite specific seasonal temperature requirements and/or very strong responses to smoke cues. The maximum germination for each species was positively correlated with the mean temperature of the source population but negatively correlated with rainfall seasonality and driest months. The strong dependence on a smoke cue for some of the study species, along with examples from other studies, provides evidence that an obligate smoke response could be a fire-adapted germination cue. Germination response correlated with rainfall season of the source populations is a pattern which has often been assumed but little comparative data across sites with different rainfall seasonality exists. Further investigation of a broader range of species from different rainfall season environments would help to elucidate this knowledge gap.

Calibrating the Wildfire Decision Model using hybrid choice modelling

Wildfire occurrences is creating serious challenges for fire and emergency response services and a diverse range of communities around the world due to the increment of the occurrence of these disasters. As such, understanding the physical and social dynamics characterizing wildfires events is paramount to reduce the risk of these natural disasters. As such, one of the main challenges is to understand how households perceive wildfires and respond to them as part of the evacuation process.In this work, the Wildfire Decision Model originally proposed in Lovreglio et al. [1] is calibrated using a hybrid choice model formulation. The Wildfire Decision Model is a newly developed behavioural choice model for large-scale wildfire evacuations based on the estimation of the risk perceived by households and the impact that this has on the decision-making process. This model is calibrated using a hybrid choice modelling solution and survey data collected after the 2016 Chimney Tops 2 wildfire in Tennessee, USA. The proposed model shows good agreement with the preliminary findings available in the wildfire evacuation literature; namely, the perceived risk is affected by both external factors (i.e., warnings and fire cues) and internal factors (i.e., education, previous wildfire evacuation experience and time of residency in a property).

Field burn versus fire-related cues: germination from the soil seed bank of a South American temperate grassland

AbstractFire and grazing are large-scale disturbances that shape the structure and function of open habitats. In temperate grasslands of southern South America, fire is used as a management tool to control tussock grasses and improve forage quality. In this study, we examined if fire and two of its components (heat and smoke) affect germination from the soil seed bank of a temperate grassland in Uruguay. Soil samples were extracted from a recently burned site and from an adjacent area that had not been burned for at least 4 years. The latter was subjected to four treatments: (1) heat shock, (2) smoke, (3) heat shock and smoke and (4) control. The samples were placed in a germination chamber and germination was recorded for 140 days. Field burn was the treatment that differed most from the control. This treatment produced a significant increase in density and richness of germinants and the germination peak preceded those of the remaining treatments. The three treatments involving fire-related cues did not affect the seedling richness and density, but the germination of some individual species was enhanced by some of them, mainly those in which the seeds were smoked. Our results show that fire and its components stimulate the germination of some species of the Río de la Plata grasslands, contrary to what had been observed previously in the region. We also suggest that, unlike Mediterranean-type systems, other fire cues, alone or in combination with heat and smoke, may promote germination after a fire event.

Impacts of fire cues on germination of Brassica napus L. seeds with high and low secondary dormancy.

Agricultural burning is used in farm management operations; however, information about the impact of fire cues on the release and/or induction of secondary dormancy in crop seeds is scarce. Seeds from two oilseed rape cultivars were induced for high (HD) or low (LD) secondary dormancy using polyethyleneglycol (PEG) pre-treatment, and their germination after exposure to various fire cues was compared to control PEG pre-treated and non-dormant seeds. Non-dormant seed germination was unaffected by various fire cues. Low doses of aerosol smoke released secondary dormancy in HD seeds, while higher doses increased dormancy of LD seeds. Dilute smoke water also released HD seed secondary dormancy, but concentrated smke water enhanced dormancy in both LD and HD seeds. The concentrated aqueous extracts from charred oilseed rape straw only promoted germination of HD seeds, while dilution inhibited LD seed germination. Heat shock (80°C, 5min) released secondary dormancy in HD seeds; however, higher temperatures and/or increased exposure time was associated with seed death. GC-MS analyses of smoke water revealed two butenolides and an array of monoaromatic hydroxybenzene compounds with potential germination inhibitor or promoter activity. The extent of secondary dormancy induction in seeds affects their subsequent responses to fire cues. Both aerosol smoke and smoke water have both germination promoter and inhibitor activity. Lacking any butenolides, aqueous extracts of charred straw contain a potential germination stimulating steroid, i.e. ergosterol. The significance of fire-derived cues on behaviour of oilseed rape seeds in the soil seed bank is discussed.

Fire cues and germination of invasive and native grasses in the Cerrado

Fire-related cues may enhance seed recruitment in flammable ecosystems and differences in fire-germination responses of invasive vs. native species can drive the invasion process. We evaluated the effects of heat shock and smoke water solution treatment on seed germination of invasive (Melinis minutiflora, Urochloa decumbens, U. brizantha) and native grasses (Axonopus pressus, Aristida setifolia, Gymnopogon foliosus) of the Cerrado. The effect of fire temperature was tested by exposing seeds to heat shock treatments of 60, 100, and 200 °C for one minute, comparing them to untreated seeds. The effect of smoke was tested by soaking seeds for 24-h in an aqueous smoke comparing them to seeds soaked in distilled water. Differences among treatments were evaluated by ANOVA and randomization tests. None of the tested species had germination stimulated by the temperature or smoke. Both species of Urochloa experienced decreased viability with increasing temperature, while seeds of native species and M. minutiflora tolerated heat shock up to 200 °C. The invasive grasses usually germinated faster than the native grasses. Germination time is therefore a crucial trait driving the invasion process, irrespective of fire-related cues. Other seed traits (e.g. dormancy) and higher resprouting capacity may help invasive species to persist in frequently burned savannas.

Modelling evacuation decision-making in the 2016 Chimney Tops 2 fire in Gatlinburg, TN

As wildfires occurring at the wildland–urban interface (WUI) continue to become more severe, there is an increasing need to understand human behaviour in these situations, and evacuation decision-making in particular. To contribute to this understanding, an online survey (using both mail and online sampling methods) was disseminated to households impacted by the 2016 Chimney Tops 2 fire in Tennessee. The survey instrument measured pre-event variables such as awareness of fire risks and previous experience with evacuations as well as the types of warnings and fire cues received during the event, with a focus on factors known to impact evacuation decisions and risk perception. Using linear and logistic regression analyses, it was found that fire cues and receiving warnings from a trusted source influenced risk perceptions leading up to an evacuation decision. In line with the Protective Action Decision Model, risk perception also highly influenced evacuation decisions, along with other variables, i.e. gender and prior preparation actions. Results from this work provide support for findings from previous wildfire evacuation research as well as produce some novel findings, along with several methodological recommendations, which will be further explored.

Fire-adapted traits of threatened shrub species in riparian refugia: implications for fire regime management

Fire management at the landscape scale may be detrimental to threatened species restricted to fire refugia, such as riparian zones, if their fire response is assumed based on the broader vegetation community type. Conserving threatened plant species in fire-prone habitats requires understanding how life-history traits allow persistence under prevailing fire regimes. Using three threatened Pomaderris species associated with riparian zones in south-east Australia, we tested for evidence of fire-adapted traits to identify if key life-history traits are coupled to specific fire cues and determine how their current distribution relates to prevailing fire regimes. We did this by (i) exposing seeds to heat-shock treatments with fire-related temperatures (60–100 °C) in germination trials; (ii) testing for the presence of a soil-stored seed bank and its response to fire by using ex-situ experimental burns on soil samples and (iii) conducting field surveys of post-fire demographic responses for P. adnata. All species showed maximum germination following heat-shock treatment at 100 °C, strongly suggesting adaptation to high severity fire. Seedling emergence from soil samples was positively affected by fire for P. bodalla and P. walshii, while there was an in situ post-fire germination pulse in P. adnata seedling recruitment and moderate increases in resprouting and survivorship of mature plants. The study demonstrates that these riparian-occurring species have life-history traits that may enable persistence under high severity fire and highlights how the possession of bet-hedging strategies may allow species to use riparian zones as fire refugia in a landscape dominated by an anthropogenically altered fire regime.

Fire cues trigger germination and stimulate seedling growth of grass species from Brazilian savannas.

Although fire cues (high temperatures and smoke) influence seed germination in numerous species from fire-prone environments, their effects on seed germination of species from neotropical savannas are poorly understood. We exposed seeds of eight grass species from the Cerrado, the Brazilian savanna to heat-shock (80°C or 110°C for 5 min) and/or smoke water, and then set them to germinate in light or dark, at either summer (28°C/18°C) or winter (27°C/14°C) temperature regimes in an incubator. In addition, we evaluated the effects of smoke water on seedling root and shoot growth for four of the species. Smoke interacted with the dark treatment to increase germination from 28% to 93% in Aristida recurvata and 77% to 95% in Aristida riparia. Smoke had no effect on germination of either of these species in the light. Heat-shock alone also promoted seed germination in A. recurvata. For Digitaria lehmanniana, smoke interacted with heat-shock to improve germination from 5% to 16%. In contrast, the fire treatments did not have any effect on the seed germination of the remaining five species. Smoke water stimulated root growth for A. riparia, A. recurvata, and Ctenium cirrosum but had no effect on their shoot growth. The strong promotive effect of smoke on Aristida germination suggests that these species are fire-adapted. Aristida species have an active awn system, which facilitates seed burial, and the smoke and dark interaction would ensure buried seeds germinated post-fire. The species that showed no response to fire cues may either have adapted via alternative strategies or require different concentrations of smoke or levels of heat. This study is one of very few examples showing a positive germination and seedling growth response to smoke for species from neotropical savannas.

Physiological and behavioral responses of an arboreal mammal to smoke and charcoal-ash substrate

The recent observation that torpor plays a key role in post-fire survival has been mainly attributed to the reduced food resources after fires. However, some of these adjustments can be facilitated or amplified by environmental changes associated with fires, such as the presence of a charcoal-ash substrate. In a previous experiment on a small terrestrial mammal the presence of charcoal and ash linked to food restriction intensified torpor use. However, whether fire cues also act as a trigger of torpor use when food is available and whether they affect other species including arboreal mammals remains elusive. To evaluate whether smoke, charcoal and ash can act as proximate triggers for an impending period of food shortage requiring torpor for mammals, we conducted an experiment on captive sugar gliders (Petaurus breviceps), a small, arboreal marsupial, housed in outside aviaries under different food regimes and natural ambient conditions. When food was available, fire simulation via exposure to smoke and charcoal-ash substrate caused a significant earlier start of activity and a significant decrease in resting body temperature. In contrast, only when food was withheld, did smoke and charcoal-ash exposure significantly enhance torpor depth and duration. Thus, our study not only provides evidence that fire simulation does affect arboreal and terrestrial species similarly, but also suggests that smoke and ash were presumably selected as cues for torpor induction because they indicate an impending lack of food.