Body Temperature in Free-Ranging Green Tree Frogs (Hyla cinerea): A Comparison with "Typical" Frogs

• Published in: Herpetologica 1991-09, Vol.47 (3), p.328-335
• Main Authors: Wygoda, Mark L., Avery A. Williams
• Format: Article
• Language: English
• Subjects: Amphibians; Biological and medical sciences; Body temperature; Frogs; Fundamental and applied biological sciences. Psychology; Herpetology; Modeling; Plasters; Thermoregulation. Hibernation. Estivation. Ecophysiology and environmental effects; Trees; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Water loss; Water temperature; Water vapor
• ISSN: 0018-0831; 1938-5099

Body temperature of free-ranging Hyla cinerea was compared with that of water-saturated plaster frog models placed in the exact microhabitat occupied by the living frogs. The temperature of frogs at night was significantly higher than the temperature of models, but the mean difference was only 0.8 C. During the day, frog temperature was considerably higher than model temperature, with excess temperatures ranging from 0.9-6.8 C ($\overline{x}_{\text{difference}}$= 3.8 C). Air temperature explained more of the variation in frog body temperature than any other measured environmental variable both during the day (R2= 0.73) and at night (R2= 0.86). The best predictor of diurnal body temperature is a multiple regression equation based on air temperature and water vapor density, whereas nocturnal body temperature is best predicted by a simple regression equation based on model temperature. The elevated body temperatures of Hyla cinerea are best explained by the presence of reduced evaporative water loss relative to typical frogs. Reduction in water loss may have evolved in heliothermic arboreal frogs as an adaptation permitting long-term occupancy of elevated perch sites.