, Volume 93, Issue 2, pp 80–83 | Cite as

Deep, prolonged torpor by pregnant, free-ranging bats

  • Craig K. R. Willis
  • R. Mark Brigham
  • Fritz Geiser
Short Communication


Many mammals save energy during food shortage or harsh weather using controlled reductions in body temperature and metabolism called torpor. However, torpor slows offspring growth, and reproductive individuals are thought to avoid using it because of reduced fitness resulting from delayed offspring development. We tested this hypothesis by investigating torpor during reproduction in hoary bats (Lasiurus cinereus, Vespertilionidae) in southern Canada. We recorded deep, prolonged torpor bouts, which meet the definition for hibernation, by pregnant females. Prolonged torpor occurred during spring storms. When conditions improved females aroused and gave birth within several days. Our observations imply a fitness advantage of torpor in addition to energy conservation because reduced foetal growth rate could delay parturition until conditions are more favourable for lactation and neonatal survival.


Torpor Bout Reproductive Individual Passive Warming Harsh Weather Prolonged Torpor 
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We thank C. Turbill for comments and R. Fisher, Q. Fletcher, A. Karst, K. Kolar, S. Martinez, M. Ranalli and C. Voss for help in the field. This work was supported by the Natural Sciences and Engineering Research Council (Canada), Mountain Equipment Co-op, Saskatchewan Environment and Resource Management and the American Society of Mammalogists.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Craig K. R. Willis
    • 1
  • R. Mark Brigham
    • 2
  • Fritz Geiser
    • 1
  1. 1.Centre for Behavioural and Physiological Ecology, ZoologyUniversity of New EnglandArmidaleAustralia
  2. 2.Department of BiologyUniversity of ReginaReginaCanada

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