Deep, prolonged torpor by pregnant, free-ranging bats
- 485 Downloads
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.
KeywordsTorpor Bout Reproductive Individual Passive Warming Harsh Weather Prolonged Torpor
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.
- Bell GP (1990) Birds and mammals on an insect diet: a primer on diet composition analysis in relation to ecological energetics. Stud Avian Biol 13:416–422Google Scholar
- Geiser F (1996) Torpor in reproductive endotherms. In: Geiser F, Hulbert AJ, Nicol SC (eds) Adaptations to the cold: 10th international hibernation symposium. University of New England Press, Armidale, pp 81–86Google Scholar
- 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
- McKechnie AE, Wolf BO (2004) The energetics of the rewarming phase of avian torpor. In: Barnes BM, Carey HV (eds) Life in the cold: evolution, mechanisms, adaptation and application. Institute of Arctic Biology, University of Alaska, Fairbanks, pp 265–267Google Scholar
- Wang LCH (1989) Ecological, physiological and biochemical aspects of torpor in mammals and birds. In: Wang LCH (ed) Advances in comparative and environmental physiology. Springer, Berlin Heidelberg New York, pp 361–401Google Scholar
- Willis CKR, Lane JE, Liknes ET, Swanson DL, Brigham RM (2004) A technique for modeling thermoregulatory energy expenditure in mammals and birds. In: Barnes BM, Carey HV (eds) Life in the cold: evolution, mechanism, adaptation, and application. Institute of Arctic Biology, University of Alaska, Fairbanks, pp 209–220Google Scholar