Journal of Comparative Physiology B

, Volume 175, Issue 7, pp 479–486 | Cite as

Torpor and thermal energetics in a tiny Australian vespertilionid, the little forest bat (Vespadelus vulturnus)

  • Craig K. R. WillisEmail author
  • Christopher Turbill
  • Fritz Geiser
Original Paper


Data on thermal energetics for vespertilionid bats are under-represented in the literature relative to their abundance, as are data for bats of very small body mass. Therefore, we studied torpor use and thermal energetics in one of the smallest (4 g) Australian vespertilionids, Vespadelus vulturnus. We used open-flow respirometry to quantify temporal patterns of torpor use, upper and lower critical temperatures (T uc and T lc) of the thermoneutral zone (TNZ), basal metabolic rate (BMR), resting metabolic rate (RMR), torpid metabolic rate (TMR), and wet thermal conductance (C wet) over a range of ambient temperatures (T a). We also measured body temperature (T b) during torpor and normothermia. Bats showed a high proclivity for torpor and typically aroused only for brief periods. The TNZ ranged from 27.6°C to 33.3°C. Within the TNZ T b was 33.3±0.4°C and BMR was 1.02±0.29 mlO2 g−1 h−1 (5.60±1.65 mW g−1) at a mean body mass of 4.0±0.69 g, which is 55 % of that predicted for a 4 g bat. Minimum TMR of torpid bats was 0.014±0.006 mlO2 g−1 h−1 (0.079±0.032 mW g−1) at T a=4.6±0.4°C and T b=7.5±1.9. T lc and C wet of normothermic bats were both lower than that predicted for a 4 g bat, which indicates that V. vulturnus is adapted to minimising heat loss at low T a. Our findings support the hypothesis that vespertilionid bats have evolved energy-conserving physiological traits, such as low BMR and proclivity for torpor.


Australian bats Body size BMR Thermal biology Vespertilionidae 



Basal metabolic rate


Wet thermal conductance


Metabolic rate


Resting metabolic rate


Ambient temperature


Body temperature


Lower critical temperature


Torpid metabolic rate


Thermoneutral zone


Upper critical temperature

\(\ifmmode\expandafter\dot\else\expandafter\.\fi{V}O_{2} \)

Rate of oxygen consumption



Our research is funded by a Natural Sciences and Engineering Research Council (Canada) Post-Doctoral Fellowship to CKRW, an Australian Research Council Postgraduate Award to CT, an Australian Research Council (ARC) grant to FG, and the University of New England. All experiments comply with current laws of Australia and were approved by the University of New England Animal Ethics Committee.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Craig K. R. Willis
    • 1
    Email author
  • Christopher Turbill
    • 1
  • Fritz Geiser
    • 1
  1. 1.Centre for Behavioural and Physiological Ecology, ZoologyUniversity of New EnglandArmidaleAustralia

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