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Journal of Comparative Physiology B

, Volume 176, Issue 2, pp 165–172 | Cite as

Thermal physiology of pregnant and lactating female and male long-eared bats, Nyctophilus geoffroyi and N. gouldi

  • Christopher TurbillEmail author
  • Fritz Geiser
Original Paper

Abstract

During roosting in summer, reproductive female bats appear to use torpor less frequently and at higher body temperatures (T b) than male bats, ostensibly to maximise offspring growth. To test whether field observations result from differences in thermal physiology or behavioural thermoregulation during roosting, we measured the thermoregulatory response and energetics of captive pregnant and lactating female and male long-eared bats (Nyctophilus geoffroyi 8.9 g and N. gouldi 11.5 g) during overnight exposure to a constant ambient temperature (T a) of 15°C. Bats were captured 1–1.5 h after sunset and measurements began at 21:22±0:36 h. All N. geoffroyi entered torpor commencing at 23:47±01:01 h. For N. gouldi, 10/10 males, 9/10 pregnant females and 7/8 lactating females entered torpor commencing at 01:10±01:40 h. The minimum T b of torpid bats was 15.6±1.1°C and torpid metabolic rate (TMR) was reduced to 0.05±0.02 ml O2 g−1 h−1. Sex or reproductive condition of either species did not affect the timing of entry into torpor (F=1.5, df=2, 19, P=0.24), minimum TMR (F=0.21, df=4, 40, P=0.93) or minimum T b (F=0.76, df=5, 41, P=0.58). Moreover, sex or reproductive condition did not affect the allometric relationship between minimum resting metabolic rate and body mass (F=1.1, df=4, 37, P=0.37). Our study shows that under identical thermal conditions, thermal physiology of pregnant and lactating female and male bats are indistinguishable. This suggests that the observed reluctance by reproductive females to enter torpor in the field is predominantly because of ecological rather than physiological differences, which reflect the fact that females roost gregariously whereas male bats typically roost solitarily.

Keywords

Bats Energy use Reproduction Thermoregulation Torpor 

Abbreviations

MR

Metabolic rate

RMR

Resting metabolic rate

Ta

Ambient temperature

Tb

Body temperature

TMR

Torpid metabolic rate

TNZ

Thermoneutral zone

Notes

Acknowledgements

We would like to thank Dr. Mark Brigham for his assistance in the field and Dr. Stuart Cairns for statistical guidance. This study was conducted in accordance with procedures approved by the Animal Ethics Committee of the University of New England, and was supported by an Australian Postgraduate Award to CT and a grant from the Australian Research Council to FG.

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Centre for Behavioural and Physiological Ecology, ZoologyUniversity of New EnglandArmidaleAustralia

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