Abstract
Bats in hot roosts experience some of the most thermally challenging environments of any endotherms, but little is known about how heat tolerance and evaporative cooling capacity vary among species. We investigated thermoregulation in three sympatric species (Nycteris thebaica, Taphozous mauritianus and Sauromys petrophilus) in a hot, semi-arid environment by measuring body temperature (T b), metabolic rate and evaporative water loss (EWL) at air temperatures (T a) of 10–42 °C. S. petrophilus was highly heterothermic with no clear thermoneutral zone, and exhibited rapid increases in EWL at high T a to a maximum of 23.7 ± 7.4 mg g−1 h−1 at T a ≈ 42 °C, with a concomitant maximum T b of 43.7 ± 1.0 °C. T. mauritianus remained largely normothermic at T as below thermoneutrality and increased EWL to 14.7 ± 1.3 mg g−1 h−1 at T a ≈ 42 °C, with a maximum T b of 42.9 ± 1.6 °C. In N. thebaica, EWL began increasing at lower T a than in either of the other species and reached a maximum of 18.6 ± 2.1 mg g−1 h−1 at T a = 39.4 °C, with comparatively high maximum T b values of 45.0 ± 0.9 °C. Under the conditions of our study, N. thebaica was considerably less heat tolerant than the other two species. Among seven species of bats for which data on T b as well as roost temperatures in comparison to outside T a are available, we found limited evidence for a correlation between overall heat tolerance and the extent to which roosts are buffered from high T a.
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Acknowledgments
We thank Peter and Jane Phillips for allowing us to conduct this project on Makulu Makete, and for all their support and encouragement. We also thank the following field assistants: Treharne Drury, Veronique Wolfaardt, Phillip Crawford, Cedric and Yvonne Cory Toussaint, Nancy and Dean Barber and Philip Jordaan. Berry Pinshow and two anonymous reviewers provided constructive comments that greatly improved the quality of the manuscript. This study was facilitated by funding from Bat Conservation International, the National Research Foundation and the University of Pretoria. All experimental procedures were approved by the University of Pretoria’s Animal Use and Care Committee (Project EC014-10) and comply with current South African laws.
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Communicated by I.D. Hume.
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Cory Toussaint, D., McKechnie, A.E. Interspecific variation in thermoregulation among three sympatric bats inhabiting a hot, semi-arid environment. J Comp Physiol B 182, 1129–1140 (2012). https://doi.org/10.1007/s00360-012-0683-6
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DOI: https://doi.org/10.1007/s00360-012-0683-6