Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator

C. Loren Buck, Brian M. Barnes

Research output: Contribution to journalArticlepeer-review

242 Scopus citations


Arctic ground squirrels (Spermophilus parryii) overwinter in hibernaculum conditions that are substantially below freezing. During torpor, captive arctic ground squirrels displayed ambient temperature (T(a))-dependent patterns of core body temperature (T(b)), metabolic rate (TMR), and metabolic fuel use, as determined by respiratory quotient (RQ). At T(a) 0 to -16°C, T(b) remained relatively constant, and TMR rose proportionally with the expanding gradient between T(b) and T(a), increasing >15-fold from a minimum of 0.0115 ± 0.0012 ml O2 · g-1 · h-1. At T(a) 0-20°C, T(b) increased with T(a); however, TMR did not change significantly from T(b) 0 to 12°C, indicating temperature-independent inhibition of metabolic rate. The overall change in TMR from T(b) 4 to 20°equates to a Q10 of 2.4, but within this range of T(b), Q10 changed from 1.0 to 14.1. During steady-state torpor at T(a) 4 and 8°C, RQ averaged 0.70 ± 0.013, indicating exclusive lipid catabolism. At T(a) -16 and 20°C, RQ increased significantly to >0.85, consistent with recruitment of nonlipid fuels. RQ was negatively correlated with maximum torpor bout length. For T(a) values <0°C, this relationship supports the hypothesis that availability of nonlipid metabolic fuels limits torpor duration in hibernating mammals; for T(a) values >0°C, hypotheses linked to body temperature are supported. Because anterior body temperatures differ from core, overall, the duration torpor can be extended in hibernating mammals may be dependent on brain temperature.

Original languageEnglish (US)
Pages (from-to)R255-R262
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number1 48-1
StatePublished - 2000
Externally publishedYes


  • Arctic ground squirrel
  • Hibernation
  • Metabolic fuel
  • Metabolism

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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