ABSTRACT

As global climate change persists, ectotherm viability is of concern because of their reliance on the external thermal environment survival. Ecologically relevant data on temperatures inhabitable by a species can be acquired by assessing critical thermal capacities, which are often reflected by the behavior and physiology of an organism. For treefrogs, thermal capacities could be influenced by a variety of important factors and are important for assessing the impact of climate change. Here, we assessed critical thermal tolerance in Cope's Gray Treefrogs (Hyla chrysoscelis) in Cookeville, Tennessee, in relation to capture date by measuring critical thermal maximum (CT_max), minimum (CT_min), and breadth over a season. The CT_max for H. chrysoscelis ranged from 28.2°C to 43.0°C, CT_min ranged from 1.0°C to 22.5°C, and breadth ranged from 8.0°C to 41.0°C. We found that frogs detected later in the season had significantly increased thermal breadths and significantly higher thermal tolerances, with a slight trend of greater cold tolerance. This study demonstrates that variability may exist in thermal tolerances within a population in relation to date, which may be a result of thermal acclimation. Variation in thermal capacity within a population may allow for persistence through climate change and is a useful knowledge for making future predictions.