Behavioral Temperature Regulation in the Bullfrog, Rana catesbeiana

of body temperature during normal diurnal activity was 26--33 C, and the mean was approximately 300 C. The critical thermal maximum was 38.20 C. Body temperatures corresponded more closely to dry than to wet bulb air temperatures. Behavioral thermoregulation is achieved by changes in location and alterations in posture. Radiant energy is used as a heat source, and pond water is used either as a heat source or as a heat sink. Cooling is augmented by postural adjustments which increase the amount of surface area exposed to evaporation. Postural thermoregulation was observed more frequently in young bullfrogs (which often occupy the warmest microenvironments available) than in adults. Temperatures of the surface and shallow waters of small ponds may influence frogs to emerge onto the bank where they are exposed to insolation. While out of water bullfrogs may heat, cool, or maintain a relatively constant body temperature depending on prevailing environmental conditions and related postural adjustments.