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First published online February 15, 2008
Journal of Experimental Biology 211, 749-756 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013946

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Thermoregulation in pronghorn antelope (Antilocapra americana, Ord) in winter

J. Hébert¹, A. Lust¹, A. Fuller², S. K. Maloney³, D. Mitchell² and G. Mitchell^1,*

¹ Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
² Department of Physiology, University of the Witwatersrand, Johannesburg, South Africa
³ Physiology, School of Biomedical and Chemical Sciences, University of Western Australia, Perth, Australia

^* Author for correspondence (e-mail: mitchg{at}uwyo.edu)

Accepted 24 December 2007

Conservation of energy is a prerequisite thermoregulatory strategy for survival in northern hemisphere winters. We have used thermistor/data logger assemblies to measure temperatures in the brain, carotid artery, jugular vein and abdominal cavity, in pronghorn antelope to determine their winter body temperature and to investigate whether the carotid rete has a survival role. Over the study period mean black globe and air temperature were –0.5±3.2°C and –2.0±3.4°C, respectively, and mean daytime solar radiation was 186 W m^–2. Brain temperature (T_brain, 39.3±0.3°C) was higher than carotid blood temperature (T_carotid, 38.5±0.4°C), and higher than jugular temperature (T_jugular, 37.9±0.7°C). Minimum T_brain (38.5±0.4°C) and T_carotid (37.8±0.2°C) in winter were higher than the minimum T_brain (37.7±0.5°C) and T_carotid (36.4±0.8°C) in summer that we have reported previously. Compared with summer, winter body temperature patterns were characterized by an absence of selective brain cooling (SBC), a higher range of T_brain, a range of T_carotid that was significantly narrower (1.8°C) than in summer (3.1°C), and changes in T_carotid and T_brain that were more highly correlated (r=0.99 in winter vs r=0.83 in summer). These findings suggest that in winter the effects of the carotid rete are reduced, which eliminates SBC and prevents independent regulation of T_brain, thus coupling T_brain to T_carotid. The net effect is that T_carotid varies little. A possible consequence is depression of metabolism, with the survival advantage of conservation of energy. These findings also suggest that the carotid rete has wider thermoregulatory effects than its traditional SBC function.

Key words: pronghorn, winter thermoregulation, carotid rete