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1. Feeding status impacts thermoregulation and its repeatability across day and night in a diurnal lizard

   https://doi.org/10.1093/beheco/araf045  

   Perry, Constant; Aubret, Fabien; Chaine, Alexis S; Gifford, Matthew E; Livingston, Ethan H; Moore, Maya; Hankison, Shala; Gangloff, Eric J (May 2025, Behavioral Ecology)

   Ringler, Eva (Ed.)

   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. 

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2. Nocturnal Activity of Antiguan Lizards Under Artificial Light

   Maurer, Andrew S.; Thawley, Christopher J.; Fireman, Alexandra L.; Giery, Sean T.; Stroud, James T. (April 2019, Herpetological conservation and biology)

   Widespread human development has led to the proliferation of artificial light at night, an increasingly recognized but poorly understood component of anthropogenic global change. Animals specialized to diurnal activity are presented opportunities to use this night-light niche, but the ecological consequences are largely unknown. While published records make note of nocturnal activity in a diversity of diurnal taxa, few case studies have gone beyond isolated observations to quantify patterns of nocturnal activity, document animal behavior, and describe new species interactions. From 13 June to 15 July 2017, we conducted hourly nocturnal surveys to assess how two species of diurnal Anolis lizards (Leach’s Anole, Anolis leachii, and Watt’s Anole, A. wattsi) use artificial light on Long Island, Antigua. Our data show that both anole species foraged in artificially illuminated habitats and were more active prior to sunrise compared to the early night. Mark-resight data for a focal species, A. leachii, suggest that patterns of nocturnal activity were not significantly different between individuals. Finally, our behavioral observations for the two anoles and a third lizard species, the nocturnal Thick-tailed Gecko (Thecadactylus rapicauda), reveal a lack of agonistic interactions. Our study reveals an altered temporal niche for two diurnal Antiguan lizards and adds to a growing body of evidence documenting the broad influences of anthropogenic change on biodiversity. 

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3. A global analysis of field body temperatures of active squamates in relation to climate and behaviour

   https://doi.org/10.1111/geb.13808  

   Dubiner, Shahar; Aguilar, Rocío; Anderson, Rodolfo O; Arenas Moreno, Diego M; Avila, Luciano J; Boada‐Viteri, Estefania; Castillo, Martin; Chapple, David G; Chukwuka, Christian O; Cree, Alison; et al (April 2024, Global Ecology and Biogeography)

   Lenoir, Jonathan (Ed.)

   Abstract AimSquamate fitness is affected by body temperature, which in turn is influenced by environmental temperatures and, in many species, by exposure to solar radiation. The biophysical drivers of body temperature have been widely studied, but we lack an integrative synthesis of actual body temperatures experienced in the field, and their relationships to environmental temperatures, across phylogeny, behaviour and climate. LocationGlobal (25 countries on six continents). TaxaSquamates (210 species, representing 25 families). MethodsWe measured the body temperatures of 20,231 individuals of squamates in the field while they were active. We examined how body temperatures vary with substrate and air temperatures across taxa, climates and behaviours (basking and diel activity). ResultsHeliothermic lizards had the highest body temperatures. Their body temperatures were the most weakly correlated with substrate and air temperatures. Body temperatures of non‐heliothermic diurnal lizards were similar to heliotherms in relation to air temperature, but similar to nocturnal species in relation to substrate temperatures. The correlation of body temperature with air and substrate temperatures was stronger in diurnal snakes and non‐heliothermic lizards than in heliotherms. Body‐substrate and body‐air temperature correlations varied with mean annual temperatures in all diurnal squamates, especially in heliotherms. Thermal relations vary with behaviour (heliothermy, nocturnality) in cold climates but converge towards the same relation in warm climates. Non‐heliotherms and nocturnal species body temperatures are better explained by substrate temperature than by air temperature. Body temperature distributions become left‐skewed in warmer‐bodied species, especially in colder climates. Main ConclusionsSquamate body temperatures, their frequency distributions and their relation to environmental temperature, are globally influenced by behavioural and climatic factors. For all temperatures and climates, heliothermic species' body temperatures are consistently higher and more stable than in other species, but in regions with warmer climate these differences become less pronounced. A comparable variation was found in non‐heliotherms, but in not nocturnal species whose body temperatures were similar to air and substrate irrespective of the macroclimatic context. 

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4. Activity modulation and selection for forests help giant anteaters to cope with temperature changes

   https://doi.org/10.1016/j.anbehav.2023.04.008  

   Giroux, Aline; Ortega, Zaida; Attias, Nina; Desbiez, Arnaud Léonard; Valle, Denis; Börger, Luca; Rodrigues Oliveira-Santos, Luiz Gustavo (March 2023, Animal Behaviour)

   Mammals use thermoregulatory behavioural strategies to reduce the cost of physiological thermoreg- ulation. Environmental temperatures should, therefore, impact their decisions. We investigated the effect of environmental temperature on the movement decisions of a large mammal with low capacity for physiological thermoregulation: the giant anteater, Myrmecophaga tridactyla. We GPS-tracked 14 giant anteaters in the Brazilian Pantanal wetland over 5 years. We used hidden Markov models to identify two behavioural states (encamping, as a proxy of resting, and moving, as a proxy of being active) across individuals' trajectories. Then, we estimated the effect of environmental temperature on the probability of moving across the hours of the day in open and forested habitats. We also used integrated step se- lection analysis to understand how environmental temperature drives giant anteater's habitat selection across the day. Giant anteaters showed three important behavioural thermoregulatory strategies in response to environmental temperature changes: they modulated activity duration, completely shifted activity period on a scale of days and selected forests as thermal shelters. With increasing environmental temperature, giant anteaters increased activity duration, nocturnality and diurnal selection for forests, increasing energy intake while avoiding heat gain by solar radiation. With decreasing environmental temperature, they decreased activity duration, increased diurnality and increased nocturnal selection for forests, thus gaining heat from solar radiation when active and taking shelter in milder microclimates when resting. Besides their high short-term behavioural plasticity regarding activity, giant anteaters also used forests to thermoregulate. These results provide insights into how other mammals could respond to climate change. In particular, we highlight the importance of forests as thermal shelters, offering milder temperatures than adjacent open areas during both hot and cold weather spells. Thermal shelters will become more and more indispensable to animal thermoregulation as the frequency and intensity of extreme weather events increase. 

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5. Intense nocturnal warming alters growth strategies, colouration and parasite load in a diurnal lizard

   https://doi.org/10.1111/1365-2656.13502  

   Rutschmann, Alexis; Dupoué, Andréaz; Miles, Donald B.; Megía‐Palma, Rodrigo; Lauden, Clémence; Richard, Murielle; Badiane, Arnaud; Rozen‐Rechels, David; Brevet, Mathieu; Blaimont, Pauline; et al (May 2021, Journal of Animal Ecology)

   Abstract In the past decades, nocturnal temperatures have been playing a disproportionate role in the global warming of the planet. Yet, they remain a neglected factor in studies assessing the impact of global warming on natural populations.Here, we question whether an intense augmentation of nocturnal temperatures is beneficial or deleterious to ectotherms. Physiological performance is influenced by thermal conditions in ectotherms and an increase in temperature by only 2°C is sufficient to induce a disproportionate increase in metabolic expenditure. Warmer nights may expand ectotherms' species thermal niche and open new opportunities for prolonged activities and improve foraging efficiency. However, increased activity may also have deleterious effects on energy balance if exposure to warmer nights reduces resting periods and elevates resting metabolic rate.We assessed whether warmer nights affected an individual's growth, dorsal skin colouration, thermoregulation behaviour, oxidative stress status and parasite load by exposing yearling common lizards (Zootoca vivipara) from four populations to either ambient or high nocturnal temperatures for approximately 5 weeks.Warmer nocturnal temperatures increased the prevalence of ectoparasitic infestation and altered allocation of resources towards structural growth rather than storage. We found no change in markers for oxidative stress. The thermal treatment did not influence thermal preferences, but influenced dorsal skin brightness and luminance, in line with a predicted acclimation response in colder environments to enhance heat gain from solar radiation.Altogether, our results highlight the importance of considering nocturnal warming as an independent factor affecting ectotherms' life history in the context of global climate change. ​ 

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