Temperature effects on metabolic rate and torpor in southern forest bats (Vespadelus regulus)
Christopher TurbillResearch Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Savoyenstrasse 1, 1160 Vienna, Austria. Email: cturbill@une.edu.au
Australian Journal of Zoology 57(2) 125-127 https://doi.org/10.1071/ZO09029
Submitted: 25 March 2009 Accepted: 13 July 2009 Published: 13 August 2009
Abstract
I measured the metabolic rate (MR) of four male southern forest bats (Vespadelus regulus; 5.5 g) exposed to a diurnal increase in air temperature (Ta) from 13 to 26°C, simulating conditions in natural tree roosts. Three bats remained in torpor throughout the day, despite the rise in Ta, whereas one bat aroused at a Ta of 25.2°C and was normothermic for 108 min until re-entering torpor when Ta declined in the afternoon. All bats aroused shortly after lights off. Torpid MR increased exponentially with rising Ta, yet even at 26°C remained only 16% of minimum resting MR at the same Ta. Rest-phase energy expenditure (12 h), including the estimated cost of an evening arousal, ranged from 0.62 to 1.23 kJ. Thus, torpor provides these small bats with an enormous reduction in energy consumption even at Ta close to their thermoneutral zone.
Additional keywords: energy expenditure, thermoregulation.
Acknowledgements
I thank Rebecca Drury, Gerhard Körtner and Fritz Geiser for their help in this study. All procedures were approved by the Animal Ethics Committee of the University of New England.
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