Strategic (adaptive) hypothermia in bull dromedary camels during rut; could it increase reproductive success? |
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Authors: | Gordon Grigg Lyn Beard Birgit D?rges Jürgen Heucke Jocelyn Coventry Alex Coppock Simon Blomberg |
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Institution: | 1.School of Biological Sciences, University of Queensland, Queensland 4072, Australia;2.Gutshof 2B, Lucklum 38173, Germany;3.NT Department of Primary Industry, Fisheries and Mines, Alice Springs, Northern Territory 0870, Australia;4.65 Elder Street, Alice Springs, Northern Territory 0870, Australia |
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Abstract: | In this study of body temperatures (Tb) in free ranging dromedary camels, we found that bulls in rut start the days cooler. Daily minima during rut averaged 0.6°C lower than at other times (95% CI 0.27–0.94°C) and daily maxima averaged 0.45°C higher (95% CI −0.01 to –0.91°C), increasing the daily Tb cycle. Knut Schmidt-Nielsen described a similar pattern in captive dromedaries deprived of water in hot conditions, which he interpreted as a strategy to conserve water. Our observations were made in winter and with water freely available. Dromedaries can apparently employ heterothermy for more than just water conservation. In the strenuous daily contests between rival bulls in rut, a lower Tb early in the day should extend the time for which a contestant can challenge or defend before heat stress becomes a problem. Calculations show that lowering Tb by even 0.6°C extends that time by more than 30 min, and many daily minima during rut were lower than that. Because the eventual winner of contests gains or retains a herd of females, we speculate that cooler Tb at the start of daily contests confers an advantage which translates directly into increased reproductive success. |
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Keywords: | adaptive heterothermy camels rut reproductive fitness |
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