Meeting Abstract

P3.78  Monday, Jan. 6 15:30  Differential use of hyperthermia as a thermoregulatory strategy in birds exposed to high temperature GERSON, AR*; SMITH, EK; TALBOT, W; O’NEILL, JJ; MCKECHNIE, A; WOLF, BO; University of New Mexico; University of New Mexico; University of New Mexico; University of New Mexico; University of Pretoria; University of New Mexico agerson@unm.edu

Desert dwelling birds regularly experience exceedingly high air temperatures, sometimes far in excess of standard body temperature. In order to thermoregulate under such extreme conditions, desert birds have evolved a suite of behavioral and physiological strategies. One such strategy is the use of hyperthermia. It was the goal of this study to investigate the use of hyperthermia and its potential benefits to thermoregulation among a number of desert birds ranging in size from 7 g to 150 g. We measured metabolic rate and evaporative water loss using flow through respirometry. Body temperature was continuously monitored using implanted temperature sensitive PIT tags while birds were exposed to temperatures from 30°C up to 60°C in some species. We found the use of hyperthermia depended greatly on air temperature, body size, and the evaporative strategy used. Species that primarily utilize cutaneous evaporation maintained much lower body temperatures, metabolic rates, and rates of water loss and were able to maintain much greater gradients between Tb and Ta than birds that rely primarily on respiratory evaporation. The use of hyperthermia by birds that rely primarily on respiratory evaporative water loss may have evolved as a means to increase respiratory evaporative water loss rates, without concomitant increases in breathing frequency, reducing the potential for alkalemia.