3D printed models are an accurate, cost-effective, and reproducible tool for quantifying terrestrial thermal environments.

Predicting ecological responses to rapid environmental change has become one of the greatest challenges of modern biology. One of the major hurdles in forecasting these responses is accurately quantifying the thermal environments that organisms experience. The distribution of temperatures available within an organism's habitat is typically measured using data loggers called operative temperature models (OTMs) that are designed to mimic certain properties of heat exchange in the focal organism. The gold standard for OTM construction in studies of terrestrial ectotherms has been the use of copper electroforming which creates anatomically accurate models that equilibrate quickly to ambient thermal conditions. However, electroformed models require the use of caustic chemicals, are often brittle, and their production is expensive and time intensive. This has resulted in many researchers resorting to the use of simplified OTMs that can yield substantial measurement errors. 3D printing offers the prospect of robust, easily replicated, morphologically accurate, and cost-effective OTMs that capture the benefits but alleviate the problems associated with electroforming. Here, we validate the use of OTMs that were 3D printed using several materials across eight lizard species of different body sizes and living in habitats ranging from deserts to tropical forests. We show that 3D printed OTMs have low thermal inertia and predict the live animal's equilibration temperature with high accuracy across a wide range of body sizes and microhabitats. Finally, we developed a free online repository and database of 3D scans (https://www.3dotm.org/) to increase the accessibility of this tool to researchers around the world and facilitate ease of production of 3D printed models. 3D printing of OTMs is generalizable to taxa beyond lizards. If widely adopted, this approach promises greater accuracy and reproducibility in studies of terrestrial thermal ecology and should lead to improved forecasts of the biological impacts of climate change.

Mismatches between phenotype and environment shape fitness at hyperlocal scales.

In the era of human-driven climate change, understanding whether behavioural buffering of temperature change is linked with organismal fitness is essential. According to the 'cost-benefit' model of thermoregulation, animals that live in environments with high frequencies of favourable thermal microclimates should incur lower thermoregulatory costs, thermoregulate more efficiently and shunt the associated savings in time and energy towards other vital tasks such as feeding, territory defence and mate acquisition, increasing fitness. Here, we explore how thermal landscapes at the scale of individual territories, physiological performance and behaviour interact and shape fitness in the southern rock agama lizard (Agama atra). We integrated laboratory assays of whole organism performance with behavioural observations in the field, fine-scale estimates of environmental temperature, and paternity assignment of offspring to test whether fitness is predicted by territory thermal quality (i.e. the number of hours that operative temperatures in a territory fall within an individual's performance breadth). Male lizards that occupied territories of low thermal quality spent more time behaviourally compensating for sub-optimal temperatures and displayed less. Further, display rate was positively associated with lizard fitness, suggesting that there is an opportunity cost to engaging in thermoregulatory behaviour that will change as climate change progresses.

Opportunities for behavioral rescue under rapid environmental change.

Laboratory measurements of physiological and demographic tolerances are important in understanding the impact of climate change on species diversity; however, it has been recognized that forecasts based solely on these laboratory estimates overestimate risk by omitting the capacity for species to utilize microclimatic variation via behavioral adjustments in activity patterns or habitat choice. The complex, and often context-dependent nature, of microclimate utilization has been an impediment to the advancement of general predictive models. Here, we overcome this impediment and estimate the potential impact of warming on the fitness of ectotherms using a benefit/cost trade-off derived from the simple and broadly documented thermal performance curve and a generalized cost function. Our framework reveals that, for certain environments, the cost of behavioral thermoregulation can be reduced as warming occurs, enabling behavioral buffering (e.g., the capacity for behavior to ameliorate detrimental impacts) and "behavioral rescue" from extinction in extreme cases. By applying our framework to operative temperature and physiological data collected at an extremely fine spatial scale in an African lizard, we show that new behavioral opportunities may emerge. Finally, we explore large-scale geographic differences in the impact of behavior on climate-impact projections using a global dataset of 38 insect species. These multiple lines of inference indicate that understanding the existing relationship between thermal characteristics (e.g., spatial configuration, spatial heterogeneity, and modal temperature) is essential for improving estimates of extinction risk.