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Understanding species thermal niche is critical to predicting how amphibians will respond to climate change. To characterize the thermal niche of European alpine newts (Ichthyosaura alpestris), Gvoždík and Kristin (2017) devised a suite of behavioral and physiological experiments. Using both thermal gradient tracks to calculate preferred temperatures and respirometry trials to monitor aerobic capacity, they tracked food digestion as a measure of thermal performance. Given knowledge of ectotherm physiology one would predict that satiated newts should optimize their aerobic capacity for digestion (i.e., select thermal habitats that maximize their ability to process food). However, the alpine newts in their experiments instead behaved more “economically”, preferring body temperatures that were lower than those required for maximum aerobic capacity. They demonstrate the importance of considering maintenance costs for understanding measures of maximum physiological performance. Here, alpine newts did indeed demonstrate thermoregulatory behavior that maximized their ability to process food, yet they did it relative to the lowest possible energy expense.
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