Heterothermy of free-living Arabian sand gazelles (Gazella subgutturosa marica) in a desert environment.

To test whether free-living desert ungulates employ heterothermy to reduce water loss, we measured core body temperature (T(b)) of six free-living Arabian sand gazelles (Gazella subgutturosa marica), a small desert antelope (12-20 kg) that lives in the deserts of Saudi Arabia, where air temperature (T(a)) often exceeds 40 degrees C. We found that the mean daily T(b) varied by 2.6+/-0.8 degrees C during summer (June-July) and 1.7+/-0.3 degrees C during winter (January-February); over both seasons, mean T(b) was 39.5+/-0.2 degrees C. During the day, in summer, T(b) increased by more than 2 degrees C when T(a)>T(b) and declined at night when T(a)