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First published online March 30, 2006
Journal of Experimental Biology 209, 1421-1429 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02151
Heterothermy of free-living Arabian sand gazelles (Gazella subgutturosa marica) in a desert environment
1 National Wildlife Research Center, PO Box 1086, Taif, Saudi
Arabia
2 Department of Evolution, Ecology and Organismal Biology, Ohio State
University, 300 Aronoff Lab, 318 W 12th Avenue, Columbus, OH 43210,
USA
* Author for correspondence at present address: UMR 5123, Université Claude Bernard Lyon 1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France (e-mail: stephane.ostrowski{at}laposte.net)
Accepted 7 February 2006
To test whether free-living desert ungulates employ heterothermy to reduce water loss, we measured core body temperature (Tb) 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 (Ta) often exceeds 40°C. We found that the mean daily Tb varied by 2.6±0.8°C during summer (June–July) and 1.7±0.3°C during winter (January–February); over both seasons, mean Tb was 39.5±0.2°C. During the day, in summer, Tb increased by more than 2°C when Ta>Tb and declined at night when Ta<Tb, suggesting that gazelles stored heat during day and dissipated it by non evaporative means during night. The minimum Tb was lower in summer (38.2±0.5°C) than in winter (38.6±0.3°C) despite the fact that the gradient between Tb and Ta was larger and solar radiation was lower in winter. Correlation between daily variation of Tb and mean, maximal Tas were significant in summer, but not in winter. To dissipate the amount of heat stored by gazelles would require an evaporative water loss of 33.5 ml H2O day–1 in summer and 23.2 ml H2O day–1 in winter.
We tested whether the amplitude of daily variation in Tb was influenced by the level of water provided to six captive sand gazelles maintained under controlled conditions in summer. The daily amplitude of Tb was increased by 1.4°C when gazelles were denied drinking water but supplied with pre-formed water in food, and by 1.1°C when they were denied both water and food. Gazelles denied only drinking water increased the amplitude of variation in Tb, whereas when denied both food and water, they seemed to undergo a dehydration-hyperthermia, with increased mean and maximal Tb values but no decrease of minimal Tb.
Free-ranging and captive gazelles surviving on pre-formed 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 Tb 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 Tb.
Key words: Arabian sand gazelle, dehydration, desert, Gazella subgutturosa marica, heterothermy, thermoregulation, water saving
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