Behavioral models of hydrothermal regulation in anurans: A field study in the Atlantic Forest, Brazil

Anurans rely on different microhabitats and microclimates for hydro-thermoregulation, which is an important physiological property for locomotor performance, body temperature, water flux, and pathogen defense. We ask whether microhabitat scouting is related to physiological states, specifically if microhabitat choice benefits the production of behavioral fever (e.g., increasing body temperature by selecting warmer places) or sickness behavior (e.g., inactivity and anorexia). We investigated how thermoregulatory behaviors affect hydro-thermoregulation in anurans, using agar models as a sampling unit, simulating four behaviors related to behavioral fever and sickness behavior. We compared the models' hydro-thermal balance in two different environments (wet and transitional forests). We showed that the wet forest was warmer and more stable than transitional forest and the agar models in the wet forest were warmer. Still, the four behavioral simulations exhibited similar average temperatures during the five-day study period in both forests. However, the apathetic behavior models had the lowest daily temperatures. The percentage hydration across models was higher in the wet forest, and daily variation in water loss for each behavioral simulation was higher in the transitional forest. Nevertheless, when limiting the analysis to the warmest times (1000-1600 h), apathetic behavior models lost less water than the others in both forests. We showed that different forests provide microclimatic variation for understory anurans, but different thermoregulatory behaviors may lead to similar body temperatures. Therefore, the Atlantic Forest offers different microclimates and thermoregulation options for anurans, as some species could develop behavioral fever while others demonstrate sickness behavior.Abstract in Portuguese is available with online material.