WILLIAMS, J. B.*; OSTROWSKI, S.; Ohio State Univerisity; University of Lyon: Heterothermy of free-living Arabian sand gazelles (Gazella subgutturosa marica) in a desert environment

One mechanism, thought to be important in reducing evaporative water loss among large desert ungulates, is heterothermy, the storage of body heat during the day and dissipation of this heat at night, thereby reducing evaporative water loss in maintenance of Tb. Mitchell and colleagues have criticized early studies of heterothermy because test animals were captive and did not have the opportunity to behaviorally thermoregulate. They concluded �we believe that the high Tbs displayed in some heat-exposed antelope, and invoked in support of adaptive heterothermy, are experimental artifacts arising from depriving the animals of their natural local climate and of thermoregulatory behavior.� To test whether desert ungulates employ heterothermy, we have continuously measured the Tb of free-living Arabian sand gazelles (Gazella subgutturosa marica), a small desert antelope (12-20 kg) that lives in the deserts of Saudi Arabia, during both winter and summer. We found that the mean daily Tb varied by 2.6�0.8�C during summer, but only by 1.7�0.3�C during winter. Tb increased during day by more than 2�C when Ta>Tb and declined when Ta