Advertisement

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

Abstract

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.

Keywords

Australian bats Body size BMR Thermal biology Vespertilionidae 

Abbreviations

BMR

Basal metabolic rate

Cwet

Wet thermal conductance

MR

Metabolic rate

RMR

Resting metabolic rate

Ta

Ambient temperature

Tb

Body temperature

Tlc

Lower critical temperature

TMR

Torpid metabolic rate

TNZ

Thermoneutral zone

Tuc

Upper critical temperature

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

Rate of oxygen consumption

Notes

Acknowledgements

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.

References

  1. Anthony EL (1988) Age determination in bats. In: Kunz TH (ed) Ecological and behavioral methods for the Study of Bats. Smithsonian Institution, Washington DC, pp 47–58Google Scholar
  2. Bradley SR, Deavers DR (1980) A re-examination of the relationship between thermal conductance and body weight in mammals. Comp Biochem Physiol A 65:465–476CrossRefGoogle Scholar
  3. Churchill S (1998) Australian bats. Reed New Holland, Sydney AustraliaGoogle Scholar
  4. Cryan PM, Wolf BO (2003) Sex differences in the thermoregulation and evaporative water loss of a heterothermic bat, Lasiurus cinereus, during its spring migration. J Exp Biol 206:3381–3390CrossRefPubMedGoogle Scholar
  5. Geiser F (1988) Reduction of metabolism during hibernation and daily torpor in mammals and birds: temperature effect or physiological inhibition? J Comp Physiol B 158:25–37PubMedCrossRefGoogle Scholar
  6. Geiser F (1998) Evolution of daily torpor and hibernation in birds and mammals: importance of body size. Clin Exp Pharmacol Physiol 25:736–740PubMedCrossRefGoogle Scholar
  7. Geiser F (2004) Metabolic rate and body temperature reduction during hibernation and daily torpor. Annu Rev Physiol 66:239–274CrossRefPubMedGoogle Scholar
  8. Geiser F (2005) Energetics, thermal biology, and torpor in Australian bats. In: Akbar Z, McCracken GF, Kunz TH (eds) Functional and evolutionary ecology of bats: Proceedings of the 12th international bat research conference. Oxford University Press, New York (in press)Google Scholar
  9. Geiser F, Brigham RM (2000) Torpor, thermal biology and energetics in Australian long-eared bats (Nyctophilus). J Comp Physiol B 170:153–162CrossRefPubMedGoogle Scholar
  10. Geiser F, Drury RL (2003) Radiant heat affects thermoregulation and energy expenditure during rewarming from torpor. J Comp Physiol B 173:55–60PubMedCrossRefGoogle Scholar
  11. Geiser F, Holloway JC, Körtner G, Maddocks TA, Turbill C, Brigham RM (2000) Do patterns of torpor differ between captive and free-ranging mammals and birds? In: Heldmaier G, Klingenspor M (eds) Life in the cold: Proceedings of the 11th international hibernation symposium. Springer, Berlin Heidelberg, New york, pp 95–102Google Scholar
  12. Geiser F, Körtner G, Schmidt I (1998) Leptin increases energy expenditure of a marsupial by inhibition of daily torpor. Am J Physiol 275:R1627–R1632PubMedGoogle Scholar
  13. Geiser F, Ruf T (1995) Hibernation versus daily torpor in mammals and birds: physiological variables and classification of torpor patterns. Physiol Zool 68:935–966Google Scholar
  14. Henshaw RE (1968) Thermoregulation during hibernation: application of Newton’s law of cooling. J Theor Biol 20:79–90PubMedCrossRefGoogle Scholar
  15. Henshaw RE (1970) Thermoregulation in bats. In: Slaughter BH, Walton DW (eds) About bats. Southern Methodist University Press, Dallas, pp 188–232Google Scholar
  16. Hosken DJ (1997) Thermal biology and metabolism of the greater long-eared bat, Nyctophilus major (Chiroptera: Vespertilionidae). Aust J Zool 45:145–156CrossRefGoogle Scholar
  17. Hosken DJ, Withers PC (1999) Metabolic physiology of euthermic and torpid lesser long-eared bats, Nyctophilus geoffroyi (Chiroptera: Vespertilionidae). J Mammal 80:42–52CrossRefGoogle Scholar
  18. Lausen CL, Barclay RMR (2003) Thermoregulation and roost selection by reproductive female big brown bats (Eptesicus fuscus) roosting in rock crevices. J Zool (Lond) 260:235–244CrossRefGoogle Scholar
  19. Levy A (1964) The accuracy of the bubble meter method for gas flow measurements. J Sci Instrum 41:449–453CrossRefGoogle Scholar
  20. Maloney SK, Bronner GN, Buffenstein R (1999) Thermoregulation in the Angolan free-tailed bat, Mops condylurus: a small mammal that uses hot roosts. Physiol Biochem Zool 72:385–396CrossRefPubMedGoogle Scholar
  21. McNab BK (1989) Temperature regulation and rate of metabolism in three Bornean bats. J Mammal 70:153–161CrossRefGoogle Scholar
  22. McNab BK (1992) A statistical analysis of mammalian rates of metabolism. Funct Ecol 6:672–679CrossRefGoogle Scholar
  23. McNab BK (2003) Sample size and the estimation of physiological parameters in the field. Funct Ecol 17:82–86CrossRefGoogle Scholar
  24. Menkhorst P, Knight F (2001) A field guide to the mammals of Australia. Oxford University Press, Melbourne, AustraliaGoogle Scholar
  25. Nickerson DM, Facey DE, Grossman GD (1989) Estimating physiological thresholds with continuous two-phase regression. Physiol Zool 62:866–887Google Scholar
  26. Nowak RM (1991) Walker’s bats of the world. John Hopkins University Press, BaltimoreGoogle Scholar
  27. Schmidt-Nielsen K (1984) Scaling: why is animal size so important. Cambridge University Press, New YorkGoogle Scholar
  28. Smith FA, Lyons SK, Morgan Ernest SK, Jones KE, Kauffman DM, Dayan T, Marquet PA, Brown JH, Haskell JP (2003) Body mass of late quaternary mammals. Ecol 84:3403CrossRefGoogle Scholar
  29. Speakman JR, Thomas DW (2003) Physiological ecology and energetics of bats. In: Kunz TH, Fenton MB (eds) Bat ecology. University of Chicago Press, Chicago, pp 430–490Google Scholar
  30. Turbill C, Körtner G, Geiser F (2003a) Natural use of heterothermy by a small, tree-roosting bat during summer. Physiol Biochem Zool 76:868–876CrossRefPubMedGoogle Scholar
  31. Turbill C, Law BS, Geiser F (2003b) Summer torpor in a free-ranging bat from subtropical Australia. J Therm Biol 28:223–226CrossRefGoogle Scholar
  32. Turbill C, Körtner G, Geiser F (2004) Daily temperature cycles affect energy expenditure and arousal from torpor in a small tree-roosting bat (Nyctophilus geoffroyi). In: Proceedings of the 21st Annual Meeting of the Australian and New Zealand Society for Comparative Physiology and Biochemistry, Dec 9–12, Wollongong, Australia, p 24Google Scholar
  33. Willis CKR (2005) Daily heterothermy in temperate bats using natural roosts. In: Akbar Z, McCracken GF, Kunz TH (eds) Functional and evolutionary ecology of bats: In: Proceedings of the 12th International Bat Research Conference. Oxford University Press, New York (in press)Google Scholar
  34. Willis CKR, Brigham RM (2003) Defining torpor in free-ranging bats: experimental evaluation of external temperature-sensitive radiotransmitters and the concept of active temperature. J Comp Physiol B 173:379–389PubMedCrossRefGoogle Scholar
  35. Willis CKR, Lane JE, Liknes ET, Swanson DL, Brigham RM (2005) Thermal energetics of female big brown bats (Eptesicus fuscus). Can J Zool (in press)Google Scholar
  36. Withers PC (1977) Measurement of VO2, VCO2, and evaporative water loss with a flow-through mask. J Appl Physiol 42:120–123PubMedGoogle Scholar
  37. Withers PC (2001) Design, calibration and calculation for flow-through respirometry systems. Aust J Zool 49:445–461CrossRefGoogle Scholar
  38. Zar JH (1999) Biostatistical Analysis. Prentice Hall, Englewood CliffsGoogle Scholar

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

Personalised recommendations