干旱区生态环境知识资源中心

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

We tested whether the amplitude of daily variation in T-b was influenced by the level of water provided to six captive sand gazelles maintained under controlled conditions in summer. The daily amplitude of T-b was increased by 1.4 degrees C when gazelles were denied drinking water but supplied with pre-formed water in food, and by 1.1 degrees C when they were denied both water and food. Gazelles denied only drinking water increased the amplitude of variation in T-b, whereas when denied both food and water, they seemed to undergo a dehydration-hyperthermia, with increased mean and maximal T-b values but no decrease of minimal T-b.

Free-ranging and captive gazelles surviving on preformed water in natural food used heterothermy during summer with no elevation of plasma osmolality, indicating that they were not in a state of dehydration. Our data on variation in T-b of gazelles provide an example of a small desert ungulate employing heterothermy to reduce evaporative water loss that would otherwise be required to maintain normothermic T-b.