TY - JOUR
T1 - Thermogenic capacity at subzero temperatures
T2 - How low can a hibernator go?
AU - Richter, M. M.
AU - Williams, C. T.
AU - Lee, T. N.
AU - Tøien,
AU - Florant, G. L.
AU - Barnes, B. M.
AU - Buck, C. L.
N1 - Publisher Copyright:
© 2014 by The University of Chicago. All rights reserved.
PY - 2015
Y1 - 2015
N2 - Hibernation in mammals is a physiological and behavioral adaptation to survive intervals of low resource availability through profound decreases in metabolic rate (MR), core body temperature (Tb), and activity. Most small mammalian hibernators thermoconform, with Tb approximating ambient temperature (Ta); arctic species are an exception, since they must actively defend what can be large thermal gradients between Tb and Ta. Here we compare the thermogenic capacity of the arctic ground squirrel (Urocitellus parryii) to that of the golden-mantled ground squirrel (Callospermophilus lateralis), a temperate-zone montane hibernator. We allowed animals to reenter torpor at sequentially lower Ta’s and found that arctic ground squirrels maintained steady state torpor at Ta’s as low as 26°C, through a 36-fold increase in torpid MR (TMR), compared to their minimum TMR, exhibited at a Ta of 07C. Golden-mantled ground squirrels are able to maintain steady state torpor at Ta’s at least as low as 28°C, through a 13.5-fold increase in MR, compared to their minimum TMR at a Ta of 2°C. In a second experiment, torpid animals were exposed to continuously decreasing Ta’s (0.25°C/30 min); individuals of both species increased their metabolism while remaining torpid at low Ta’s (as low as 23°C for arctic ground squirrels and -10°C for golden-mantled ground squirrels). Although the capacity to hibernate at subfreezing Tas is not unique to arctic ground squirrels, their large body size, greater torpid metabolic scope, and previously ascribed capacity to supercool allow them to occupy much colder hibernacula for prolonged seasons of hibernation.
AB - Hibernation in mammals is a physiological and behavioral adaptation to survive intervals of low resource availability through profound decreases in metabolic rate (MR), core body temperature (Tb), and activity. Most small mammalian hibernators thermoconform, with Tb approximating ambient temperature (Ta); arctic species are an exception, since they must actively defend what can be large thermal gradients between Tb and Ta. Here we compare the thermogenic capacity of the arctic ground squirrel (Urocitellus parryii) to that of the golden-mantled ground squirrel (Callospermophilus lateralis), a temperate-zone montane hibernator. We allowed animals to reenter torpor at sequentially lower Ta’s and found that arctic ground squirrels maintained steady state torpor at Ta’s as low as 26°C, through a 36-fold increase in torpid MR (TMR), compared to their minimum TMR, exhibited at a Ta of 07C. Golden-mantled ground squirrels are able to maintain steady state torpor at Ta’s at least as low as 28°C, through a 13.5-fold increase in MR, compared to their minimum TMR at a Ta of 2°C. In a second experiment, torpid animals were exposed to continuously decreasing Ta’s (0.25°C/30 min); individuals of both species increased their metabolism while remaining torpid at low Ta’s (as low as 23°C for arctic ground squirrels and -10°C for golden-mantled ground squirrels). Although the capacity to hibernate at subfreezing Tas is not unique to arctic ground squirrels, their large body size, greater torpid metabolic scope, and previously ascribed capacity to supercool allow them to occupy much colder hibernacula for prolonged seasons of hibernation.
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U2 - 10.1086/679591
DO - 10.1086/679591
M3 - Article
C2 - 25590595
AN - SCOPUS:84921270086
SN - 1522-2152
VL - 88
SP - 81
EP - 89
JO - Physiological and Biochemical Zoology
JF - Physiological and Biochemical Zoology
IS - 1
ER -