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Expenditure freeze: the metabolic response of small mammals to cold environments
Author(s) -
Humphries Murray M.,
Boutin Stan,
Thomas Donald W.,
Ryan John D.,
Selman Colin,
McAdam Andrew G.,
Berteaux Dominique,
Speakman John R.
Publication year - 2005
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1111/j.1461-0248.2005.00839.x
Subject(s) - homeothermy , basal metabolic rate , biology , ecology , metabolic rate , energy expenditure , abundance (ecology) , thermoregulation , population , energetics , niche , torpor , endocrinology , demography , sociology
There is renewed focus on the ecological determinants of animal metabolism and recent comparative analyses support the physiological expectation that the field metabolic rate (FMR) of homeotherms should increase with declining ambient temperature. However, sustained elevation of FMR during prolonged, seasonal cold could be prevented by intrinsic limits constraining FMR to some multiple of basal metabolic rate (BMR) or extrinsic limits on resource abundance. We analysed previous measures of mammalian FMR and BMR to establish the effect of ambient temperature on both traits and found no support for intrinsic limitation. We also measured the FMR of a northern population of red squirrels ( Tamiasciurus hudsonicus ) exposed to ambient temperatures much colder than all but one previous study of mammal FMR. These measurements revealed levels of energy expenditure that are, unexpectedly, among the lowest ever recorded in homeotherms and that actually decrease as it gets colder. Collectively, these results suggest the metabolic niche space of cold climate endotherms may be much larger than previously recognized.