Michael Ray Kearney

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.

The net effect of solar absorption on body temperature is difficult to intuit because it depends on nonlinear interactions between the traits of organisms and their immediate environment. We used biophysical modelling to quantify solar absorption effects for Australian jewel beetles across their wide natural range of solar absorptivity (0.67-0.93), mass (more than 2 orders of magnitude) and shape under naturally co-occurring combinations of microclimatic conditions across Australia. Under hot, calm conditions, solar absorptivity could increase steady-state body temperature by 2.3°C on average. Higher wind reduced this effect by more than half, whereas increasing shortwave radiation amplified it. Transient simulations indicated substantial damping of these effects at a time scale of one minute. Across daylight hours during the spring–early summer period when adult jewel beetles are active, the absorptivity effect averaged 0.36°C across Australia. Under locally extreme high-radiation, low-wind conditions, the effect reached 5.69°C in the largest beetles and was more than twice as large at maximum as at minimum body mass. Whether solar absorptivity is of biological significance to heat budgets is therefore highly contextual. Experiments to infer the adaptive significance of insect colour for heat budgets should account for transient responses under realistic environmental combinations.

Climate change is increasing human exposure to novel environments and generating serious practical challenges in human health, while the role of past climates in shaping hominin evolution remains a fascination. Models of human heat exchange vary from simple environmental indices to extremely detailed physiological calculations. Physiologically explicit models vary in their physical explicitness, and significant trade‐offs exist between model realism and computational speed. We presently lack agile models that are not so over‐parameterised that they are slow, that maintain generality across diverse and complex physical environments, and that have sufficient biological realism to capture human (and, more generally, hominin) diversity in physiology, body size and proportions, activity level, clothing, hair, and skin. Here we present a model (HomoTherm) to fill this gap, built upon the general endotherm model from the NicheMapR package for biophysical modelling in R. This steady‐state heat budget model is unique among existing open‐source models in that it solves for the metabolic rate, evaporation rate, skin temperature, and clothing temperature of a multi‐part (head, torso, and limbs) human of variable shape, size, or colour and at variable levels of physical activity. The model can handle complex microclimates, including environments that differ in downwelling and upwelling radiation, and connects directly with the microclimate modelling capabilities of NicheMapR. Because of its general nature, it can easily be adapted to model other hominins by changing proportions, fur properties, and any other known physiological trait. We illustrate the model's capabilities through comparisons with actual human responses in published empirical studies of indoor and outdoor exposures to heat and cold, and compare HomoTherm's performance with that of other models. Vignettes and an open‐source Shiny app facilitate the use of HomoTherm in addressing fundamental and applied problems in human thermal biology.

Hibernation is an important strategy used by many endotherms to conserve energy and water. Global warming is changing species' phenology and hibernation patterns, but whether such changes are beneficial or harmful depends on the species' life history traits, physiology, morphology, and behavior. Mechanistic niche models can be used to make strong inferences on such responses by explicitly quantifying the consequences of changed hibernation patterns for energy and water requirements. However, they have yet to be adapted to heterothermic species. Here, we address this problem by extending the endotherm biophysical model of the NicheMapR package to encompass torpor. This model accurately predicts the energy requirements of hibernating mammals over a broad size range from microbats to bears. We then used this approach to assess the effect of climate change on a Critically Endangered hibernator, the Australian mountain pygmy possum ( Burramys parvus ). Specifically, we contrasted conditions for the year 2010 with two future climate‐change scenarios (2or 4°C of average warming) to identify: (i) the projected changes in energy and water requirements; (ii) the advantage conferred by hibernating for the species' energy and water requirements; and (iii) the areas across southeastern Australia that could continue to support hibernation. We projected an 11%–43% reduction in hibernation hours for the mountain pygmy possum under our two climate‐change scenarios. In consequence, requirements for energy increased by 4%–21%, and for water by 10%–34%. Under current conditions, hibernation reduces annual energy requirements by 44%–52% and annual water requirements by 32%–42%, but in our projections, this energetic and hydric benefit of hibernation will decline due to climate change. The total area where hibernating and not hibernating is energetically equivalent is projected to increase by 60% under 4°C warming, preventing recovery from the species' severely restricted distribution at present. Our results show that climate change will have a profound impact on the duration and patterns of hibernation, a key survival strategy, for Burramys . Our framework for analyzing changing hibernation patterns provides a new and general way to test the vulnerability and plasticity of hibernating endotherms under global change.

Nocturnal endotherms are vulnerable to high ambient temperatures (Ta) during the day when sequestered in retreat sites. Artificial roost design must therefore account for the thermal sensitivity of target species and the potential roost temperatures during heatwave conditions at installation sites. We recorded physiological responses of big brown bats (Eptesicus fuscus) under naturally observed roost temperatures using flow-through respirometry. We used the resulting data to parameterise a biophysical model with which we calculated the evaporative cooling requirements as percent body mass during the hottest day of 2023 and a heatwave during 2021. Our data revealed that the evaporative cooling requirements of bats roosting in certain artificial roosts would have exceeded the lethal dehydration threshold for both females and males during the 2021 heatwave (>22.1% body mass). Regardless of the availability of freestanding water in the environment, bats roosting in artificial roosts prone to overheating are at risk of lethal dehydration during heatwaves, even in high latitude habitats. Therefore, conservation management of small nocturnal endotherms should incorporate both physiological data and roost microclimate data when designing and deploying artificial roosts.

Translocation is a core conservation strategy, yet the outcomes of invertebrate translocations are often poorly documented due to the small size and limited mobility of invertebrates. Levels of genetic diversity and inbreeding are key indicators of translocation success, reflecting breeding success, adaptive capacity, and long‐term viability of translocated populations. This study characterizes the genetic diversity of a recently translocated flightless grasshopper, Vandiemenella viatica , two generations after release. Genome‐wide sequence data revealed significant reductions in observed heterozygosity (19.07% decrease) and nucleotide diversity (12.69% decrease) in the F ₂ generation relative to the source population. Runs of homozygosity were 50.74% more common and 112.98% longer in the F ₂ generation relative to the source population. These rapid reductions in diversity underscore the need for genetic monitoring to be integrated into translocation protocols to inform management actions like genetic supplementation for improved conservation outcomes.

Anthropogenic climate change is leading to more frequent and extreme heat waves. These short-term but large-scale events are radically re-shaping interactions among organisms – impacting biodiversity, community composition and ecosystem services crucial to natural systems and food security. Predicting heat wave impacts on interacting species requires an understanding of the processes driving differential exposure and sensitivity of organisms to extreme heat events in a life-cycle context. To achieve this predictive capacity, we need to integrate models across scales while capturing species-specific responses at the level of individuals. We show how existing models in disparate fields can be linked to achieve a level of understanding necessary for calculated responses to extreme heat from individuals to socioecological systems, now and into the future.