Christopher Turbill

At the foundation of a species' vulnerability to climate change are the linkages between its physiological capacity, microclimate exposure and behavioural decision‐making. In mild Australian winters, the large‐footed myotis ( Myotis macropus ) hibernates in thermally variable roosts and regularly arouses from torpor to forage on insects. This bat provides a tractable system to examine how changes in temperature interact with physiological capacity and behavioural flexibility to shape energy and water balance in warm‐temperate hibernators. We integrated data from temperature telemetry, laboratory respirometry and biophysical modelling to link the expression of physiological states in the wild (i.e. behavioural decisions to enter and arouse from torpor and forage) with their energetic and water costs across thermal environments (warm‐temperate, subtropical and tropical). Daily energy expenditure (DEE) predicted from respirometry data differed by less than 7% from estimates generated by the biophysical model, permitting the estimation of hibernation energetics from free‐ranging skin‐temperature data. DEE was sixfold greater on days that included an arousal from torpor, and 40%–70% greater for males because they exhibited a ~2 h longer euthermic duration than females. In our warm‐temperate study site, DEE increased with sunset temperature, and projecting this relationship to tropical conditions predicted DEE values 2.6–3.6 times lower than those expected in tropical climates. Across temperate, subtropical and tropical sites, +2°C and +4°C warming scenarios shifted mean energy expenditure beyond the 75th and 90th percentiles of their current DEE distribution, respectively, highlighting increasing energetic demands for hibernators in warmer regions under projected climate change scenarios and the importance of reliable foraging opportunities to maintain energy balance. Read the free Plain Language Summary for this article on the Journal blog.

Extreme heat weather events can lead to energy deficits by increasing thermoregulatory energy costs while reducing energy intake because of limits to dissipating the metabolic heat generated by foraging activity. Understanding the consequences of exposure to extreme heat is increasingly important under ongoing climate warming. We measured acceleration forces using collar‐mounted loggers to gain indices of activity and energy expenditure in grey‐headed flying‐foxes ( Pteropus poliocephalus ) during mild and hot summer conditions. Overall dynamic body acceleration (ODBA) is positively correlated with energy expenditure in a wide range of animals. During the daytime rest phase, air temperatures above 30°C decreased low‐level activity indicative of rest, whereas during the nocturnal active phase, temperatures above 21°C reduced high‐level activity indicative of flight. On hot days (maximum T _a : 40.6°C ± 3.1°C), ODBA increased threefold during the daytime and decreased by one‐third during the first 2 h of the night, compared to milder summer conditions. These patterns indicate that extreme heat simultaneously elevates energy expenditure and constrains foraging activity. Our data support the hypothesis that heat‐induced energetic deficits are an important component of the negative effects of extreme heat exposure. Such energy deficits could reduce survival and population growth, especially as heat events become more frequent and severe under climate change.

Many small endotherms employ torpor as a survival strategy to reduce energy expenditure during periods with low food availability and cold temperatures. The expression and physiology of torpor can vary substantially within species because of phenotypic plasticity and local adaptation. Understanding how plasticity and genetics influence intraspecific variation is fundamental to identifying the drivers of phenotypic variance in nature. Using a widely distributed bat species, the eastern bent‐wing bat ( Miniopterus orianae oceanensis ), we exposed individuals from two thermally distinct sites to cold temperature regimes (ranging from 15 to 5°C). We measured oxygen consumption, and carbon dioxide production (proxies for torpor metabolic rate, TMR), and water loss during torpor (TEWL) using open‐flow respirometry, and quantified skin surface temperature ( T _sk ) using temperature‐sensitive telemetry. Analysis of the data using phylogenetically controlled, multilevel models indicated that bats from both sites exhibited a similar TMR at low T _sk , whereas bats from the colder site had a higher TMR at higher T _sk . We found no evidence of genetic differentiation of bats between the sites and estimates of heritability for TMR and TEWL showed broad credible intervals, yielding high uncertainty in interpreting genetic effects. Differences in torpor physiology responses between warm and cold sites were likely driven by phenotypic plasticity, with among‐individual variation in responses partially explained by genetic effects. Such flexibility in the expression of thermoregulatory strategies is important for a highly mobile and widely distributed endotherm to be successful across a large range of thermal climates. Read the free Plain Language Summary for this article on the Journal blog.

Wind turbine collisions are a leading cause of bat mortality globally, yet the vulnerability of Australian bat taxa remains poorly understood. Trait-based assessments offer a valuable method for evaluating mortality risk in the absence of data on species- and region-specific turbine interactions. Behavioural and morphological traits are strongly associated with bat fatalities at wind farms globally. Here, we use a trait-based approach to identify the relative vulnerability of bat genera to the increasing threat of wind turbine fatalities in Australia. Through a global literature review, we identified three traits associated with increased mortality rates: foraging guild, movement distance, and wing morphology. For each trait we estimated the level of sensitivity at the genus level based on available published data. Sensitivity scores were summed to produce an overall vulnerability score. Our assessment identified Saccolaimus and Taphozous (Emballonuridae); Austronomus, Chaereophon, Micronomus, Ozimops, and Setirostris (Mollosidae); Falsistrellus (Vespertilionidae); and Miniopterus (Miniopteridae); as the most vulnerable genera. Pteropus (Pteropodidae) was assessed as high vulnerability for wing morphology and movement distance but low for foraging guild (as a non-aerial forager). However, because of their exceptional mobility, we assessed Pteropus as high overall vulnerability. We also attributed a confidence score to trait estimates, which reflected data availability. Confidence was rated as relatively high for foraging guild (61% genera rate as high) and wing morphology (50% high), and lowest for movement distance (14% high). Our framework provides a timely foundation for predicting mortality risk from the rapid expansion of wind energy infrastructure in Australia, which requires urgent conservation assessment and implementation of management actions to minimise the impacts. Our trait-based assessment also provides direction for targeted research to better understand and quantify the threat of wind turbine mortalities to populations of Australian bats.

Context: Extreme heat events are a serious concern for the conservation management of wildlife. In flying-foxes (Pteropus spp.), exposure to air temperatures (Ta) > 42°C can result in mass mortality, sometimes at catastrophic scales. To mitigate the worst of the impacts on flying-foxes, sprinklers are increasingly being deployed in roosts to cool flying-fox roosting habitat and/or the flying-foxes directly. However, while anecdotal reports suggest positive outcomes from these interventions, the effects of sprinklers on microclimatic conditions and flying-fox thermoregulatory responses have not been studied empirically. Aims: We aimed to test experimentally the impacts of sprinklers on microclimatic conditions of a flying-fox roost and so provide a much-needed evidence base for flying-fox heat stress mitigation. Methods: We used an automated split-system sprinkler setup in the understory of a permanently occupied grey-headed flying-fox (P. poliocephalus) roost site in Campbelltown, New South Wales. High-resolution weather data were systematically collected at sprinkler and control areas throughout the roost across a range of daily meteorological conditions between the austral summers of 2020–2021 and 2023–2024, including during an extreme heat event that resulted in mortality of flying-foxes across the region. Key results: Our results showed that on days ≥ 35°C, sprinklers cooled Ta by 1.5°C and increased dewpoint (Tdew) by 1.2°C, on average; and during an extreme heat event, the sprinklers kept the local microclimatic conditions within known thermoregulatory tolerances of flying-foxes, in contrast to the lethal conditions that were observed elsewhere in the roost. The effects of the sprinklers were highly localised to the treatment area both horizontally and vertically; and the timing and duration of effect differed for Ta and Tdew. Conclusions: This study made important progress in identifying the impacts of understory-based sprinklers on roost microclimatic conditions, and the results are promising for the utility of sprinklers for flying-fox heat stress mitigation. Implications: To understand where, when, and how sprinklers can be used to achieve net-positive outcomes for heat stressed flying-foxes, it remains necessary to determine directly how this management intervention influences flying-fox thermoregulatory responses.

Research Highlight : Allison, A., Conway, C., Goldberg, A., Morris, A., and Hakanson, E. (2025) Seasonal body mass dynamics mediate life‐history trade‐offs in a hibernating mammal. Journal of Animal Ecology . https://doi.org/10.1111/1365‐2656.70160 . Body mass is an important proxy of individual state, especially for animals in seasonal environments. Storage of energy, primarily as fat, decouples daily energy expenditure from current food availability, providing flexibility in how animals respond to temporal variability in conditions and resources. Hibernating mammals take this to the extreme among endotherms: By fattening extensively and entering prolonged bouts of energy‐saving torpor, they can remain inactive for part of the year, which maximises their chances of survival until the productive season. Allison et al. (2025) used a large data set of annual body mass change to investigate among‐individual variation in the extent and timing of pre‐hibernation fattening, its ecological co‐variates and survival consequences in the endangered northern Idaho ground squirrel ( Urocitellus brunneus ). Delayed fattening was a cost of reproduction for females. Relatively fat squirrels had increased survival over the hibernation season, which is likely explained by fatter individuals choosing to enter hibernation earlier to avoid predation risk, rather than an energetic constraint imposed by a short growing season. Allison et al. found support for hypotheses relating fattening dynamics to thermal conditions, conspecific density and possibly time limitation, but not to limited food availability or interspecific competition. These results provide insight into state‐dependent behavioural decisions about activity in seasonal environments and their consequences for life‐histories in an unusual model among endotherms. They are important also for informing management actions to help conserve this endangered species.

Seasonality is a fundamental challenge for life on Earth and energy storage prior to colder and drier periods by fattening is a common strategy for survival. Fattening should reflect a trade‐off between an expected seasonal energy deficit and the costs of increased body mass, which are particularly important to flying endotherms. We examined body mass change (ΔM_b), a proxy of fat storage, among bat populations over low productivity periods with global variation in yearly average and seasonality of local climates. We found that ΔM_b increased with decreasing mean annual surface temperature (MAST) but ΔM_b also increased at higher MAST with higher seasonality of rainfall. Seasonal use of body energy reserves by bats is predicted to be widespread in warm, seasonal climates at low latitudes but is poorly studied compared to cold temperate regions. In colder climates only, females lost less mass than males over winter, supporting the ‘thrifty females’ hypothesis, and ΔM_b has increased with year of study in warm climates, possibly linked to effects of global climate change on their energetics. Our quantitative synthesis highlights how intrinsic and environmental factors shape seasonal fattening in bats, and its global importance for survival in this diverse and widespread mammal group.

Animal decisions trade-off the mortality risks of starvation and predation, and anti-predator behaviors generally incur a cost of reduced energy intake. Torpor and shallow rest-phase heterothermy are widespread physiological responses to starvation risk among small mammals and birds. Here, we present a field-based experimental test of the hypothesis that energy savings from torpor use can also reduce predation risk by moderating the energy cost of anti-predator behavioral responses in a small bird during winter. We manipulated perceived predation risk in wild populations of the superb fairy-wren (Malurus cyaneus) by playback of conspecific alarm calls during the daytime active-phase and tested for effects on body temperature measured continuously by telemetry during the nocturnal rest-phase. We found that alarm call playback was associated with subsequent rest-phase torpor bouts that were significantly deeper (minimum skin temperature: 28.7 ± 1.7 °C vs. 30.0 ± 1.5 °C) and longer (duration in torpor: 6.0 ± 2.7 h vs. 3.8 ± 2.3 h) compared to control periods. By demonstrating the connection between resting energy expenditure and energy costs of behavioral decisions during activity, our study has implications for understanding both the ecological functions of torpor and survival consequences of behavioral responses by small birds to environmental challenges.

White‐nose syndrome (WNS), a disease affecting hibernating bats, is caused by the fungal pathogen Pseudogymnoascus destructans (Pd). Since the initial introduction of Pd from Eurasia to the United States in 2006, WNS has killed millions of bats throughout the temperate parts of North America. There is concern that if Pd is accidentally introduced to the Southern Hemisphere, WNS could pose similar threats to the bat fauna of the Southern Hemisphere's more temperate regions. Efforts are required to better understand the vulnerability of bats globally to WNS. We examined phylogenetic distances among cave roosting bat species globally to estimate the probability of infection by Pd. We predicted cave thermal suitability for Pd for 441 cave‐roosting bat species across the globe via spatial analysis. We used host specificity models based on 65 species tested for Pd to determine phylogenetic specificity of Pd. Phylogenetic distance was not an important predictor of Pd infection, confirming that Pd has low host specificity. We found extensive areas (i.e., South America, Africa, and Australia) in the Southern Hemisphere with caves that were suitable for cave‐roosting bat species and for Pd growth. Hence, if Pd spreads to the Southern Hemisphere, the risk of exposure is widespread for cave‐roosting bats, and infection is possible regardless of relatedness to infected species in the Northern Hemisphere. Predicting the consequences of infection remains difficult due to lack of species‐specific information about bat winter biology. Nevertheless, WNS is an important threat to naive Southern Hemisphere bat populations. Hence, biosecurity measures and planning of management responses that can help prevent or minimize a potential WNS outbreak in the Southern Hemisphere are urgently needed.