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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

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

Stéphane Ostrowski^1,* and Joseph B. Williams²

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 (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°C. We found that the mean daily T_b 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 T_b was 39.5±0.2°C. During the day, in summer, T_b increased by more than 2°C when T_a>T_b and declined at night when T_a<T_b, suggesting that gazelles stored heat during day and dissipated it by non evaporative means during night. The minimum T_b was lower in summer (38.2±0.5°C) than in winter (38.6±0.3°C) despite the fact that the gradient between T_b and T_a was larger and solar radiation was lower in winter. Correlation between daily variation of T_b and mean, maximal T_as 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 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°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 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 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 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.

Key words: Arabian sand gazelle, dehydration, desert, Gazella subgutturosa marica, heterothermy, thermoregulation, water saving

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