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Thermoregulatory decisions impact nearly every aspect of the physiology, performance, and ecology of ectotherms. Thus, understanding the factors which influence ectotherm thermoregulatory behaviors across ecological contexts and environmental conditions is essential in predicting responses to novel or changing environments. Specifically, quantifying such behaviors across the entire diel cycle – day and night – is key to understanding the impact on physiological processes that happen during periods of inactivity, such as digestion. Utilizing high-resolution time-series data, we quantified the diel cycle of thermoregulatory behaviors in fed and unfed common wall lizards (Podarcis muralis) over five consecutives days. We first tested the hypothesis that feeding status affects diurnal and nocturnal thermoregulation. Second, we quantified the impact of feeding status on patterns of consistency and correlation within and among individuals in diurnal and nocturnal thermoregulatory behaviors. Lizards modulated their behavior in response to feeding status, conserving energy by choosing lower temperatures when unfed and by seeking higher temperatures when fed. We observed consistent among-individual differences (repeatability) in thermoregulatory behaviors across diurnal and nocturnal periods. Furthermore, diurnal and nocturnal thermoregulatory behaviors were positively correlated within individuals. We demonstrate that this diurnal ectotherm actively thermoregulates during the night, a finding particularly pertinent in urban environments, where artificial light and heat can prolong the active period of lizards. Overall, this research provides valuable insight into the flexible thermoregulation strategies of a species highly successful in expanding its range, demonstrating the importance of considering both diurnal and nocturnal activity. 

Abstract Thermoregulatory decisions impact nearly every aspect of the physiology, performance, and ecology of ectotherms. Thus, understanding the factors which influence ectotherm thermoregulatory behaviors across ecological contexts and environmental conditions is essential in predicting responses to novel or changing environments. Specifically, quantifying such behaviors across the entire diel cycle—day and night—is key to understanding the impact on physiological processes that happen during periods of inactivity, such as digestion. Utilizing high-resolution time-series data, we quantified the diel cycle of thermoregulatory behaviors in fed and unfed common wall lizards (Podarcis muralis) over five consecutives days. We first tested the hypothesis that feeding status affects diurnal and nocturnal thermoregulation. Second, we quantified the impact of feeding status on patterns of consistency and correlation within and among individuals in diurnal and nocturnal thermoregulatory behaviors. Lizards modulated their behavior in response to feeding status, conserving energy by choosing lower temperatures when unfed and by seeking higher temperatures when fed. We observed consistent among-individual differences (repeatability) in thermoregulatory behaviors across diurnal and nocturnal periods. Furthermore, diurnal and nocturnal thermoregulatory behaviors were positively correlated within individuals. We demonstrate that this diurnal ectotherm actively thermoregulates during the night, a finding particularly pertinent in urban environments, where artificial light and heat can prolong the active period of lizards. Overall, this research provides valuable insight into the flexible thermoregulation strategies of a species highly successful in expanding its range, demonstrating the importance of considering both diurnal and nocturnal activity. 

ABSTRACT An animal's morphology influences its ability to perform essential tasks, such as locomoting to obtain prey or escape predators. While morphology–performance relationships are well-studied in lizards, most conclusions have been based only on male study subjects, leaving unanswered questions about females. Sex-specific differences are important to understand because females carry the bulk of the physiological demands of reproduction. Consequently, their health and survival can determine the fate of the population as a whole. To address this knowledge gap, we sampled introduced populations of common wall lizards (Podarcis muralis) in Ohio, USA. We measured a complete suite of limb and body dimensions of both males and females, and we measured sprint speeds while following straight and curved paths on different substrates. Using a multivariate statistical approach, we identified that body dimensions relative to snout-to-vent length in males were much larger compared with females and that body dimensions of P. muralis have changed over time in both sexes. We found that sprint speed along curved paths increased with relative limb size in both males and females. When following straight paths, male speed similarly increased as body dimensions increased; conversely, female speed decreased as body dimensions increased. Female sprint speed was also found to have less variation than that of males and was less affected by changes in body size and hindfoot length compared with males. This study thus provides insights into how selective pressures might shape males and females differently and the functional implications of sexual dimorphism. 

This is a short note describing an observation of a trifurcated tail and an analysis of tail regeneration rates of lizards among populations in Ohio. 

Many species exhibit color polymorphisms which have distinct physiological and behavioral characteristics. However, the consistency of morph trait covariation patterns across species, time, and ecological contexts remains unclear. This trait covariation is especially relevant in the context of invasion biology and urban adaptation. Specifically, physiological traits pertaining to energy maintenance are crucial to fitness, given their immediate ties to individual reproduction, growth, and population establishment. We investigated the physiological traits ofPodarcis muralis, a versatile color polymorphic species that thrives in urban environments (including invasive populations in Ohio, USA). We measured five physiological traits (plasma corticosterone and triglycerides, hematocrit, body condition, and field body temperature), which compose an integrated multivariate phenotype. We then tested variation among co‐occurring color morphs in the context of establishment in an urban environment. We found that the traits describing physiological status and strategy shifted across the active season in a morph‐dependent manner—the white and yellow morphs exhibited clearly different multivariate physiological phenotypes, characterized primarily by differences in plasma corticosterone. This suggests that morphs have different strategies in physiological regulation, the flexibility of which is crucial to urban adaptation. The white‐yellow morph exhibited an intermediate phenotype, suggesting an intermediary energy maintenance strategy. Orange morphs also exhibited distinct phenotypes, but the low prevalence of this morph in our study populations precludes clear interpretation. Our work provides insight into how differences among stable polymorphisms exist across axes of the phenotype and how this variation may aid in establishment within novel environments. 

Lizards selecting higher body temperatures in the field exhibited reduced hydric status. In a lab experiment, mild wind conditions prompted lizards to select higher body temperatures. We validated the use of infrared thermography to measure body temperature in lizards. 

The following are the data and code that supplied the figures, results, and tables from "Lizards in the wind: The impact of wind on the thermoregulation of the common wall lizard" by Spears et. al., 2024. Published in the Journal of Thermal Biology. 

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.