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1 June 2012 Do Red Squirrels (Tamiasciurus hudsonicus) Use Daily Torpor During Winter?
R. Mark Brigham, Fritz Geiser
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Given their relatively small body size, high thermoregulatory costs, and low metabolic rate, we tested the hypothesis that red squirrels (Tamiasciurus hudsonicus) would employ bouts of daily torpor to save energy during winter. We collected data on body temperature (Tb) using surgically implanted data loggers for squirrels in the Cypress Hills region of Saskatchewan, where extended periods of cold snowy weather make foraging difficult and should lead to high levels of energy expenditure. Based on over 8000 measurements from 4 animals over 3 winters, we found no evidence for torpor use. However, Tb was lowest in January and highest in September and May, and mean monthly Tb was correlated with mean monthly ambient temperature (Ta). Given that taxonomically related species can and do use torpor, it remains to be determined what makes heterothermy in this species costly to the extent that its use is precluded.

R. Mark Brigham and Fritz Geiser "Do Red Squirrels (Tamiasciurus hudsonicus) Use Daily Torpor During Winter?," Ecoscience 19(2), 127-132, (1 June 2012).
Received: 11 April 2011; Accepted: 1 February 2012; Published: 1 June 2012

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