Summary
Female golden-mantled ground squirrels,Spermophilus lateralis, kept in a cool room (9.5 °C), were food deprived and their hibernation thereby extended by 11 weeks on average compared to undeprived control animals in the same room. The deprived group was then refed. Despite their prolonged hibernation, peak weights and onset of hibernation in the subsequent season were only 2–4 weeks later than in the undeprived controls and this effect was only marginally significant. However, the periods of circannual cycles of both the deprived and undeprived groups in the cool room were significantly longer than those of another group of female ground squirrels kept in a warm room (21 °C). It is argued that warm temperatures are capable of terminating the winter phase of circannual cycles, namely that of hibernation and declining body weight. If animals are kept continuously in a cool environment this phase ends spontaneously. Even many weeks of food deprivation are only capable of extending this phase by a relatively small amount, if at all.
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The author thanks Kirsteen Lang for invaluable help at every phase of this work, Linda Jones and others at the Environmental Sciences Centre, Kananaskis, for heir cooperation, and Janice Farintosh, John Ting and Yasmin Shah for collecting data. Support came from the Natural Sciences and Engineering Research Council of Canada.
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Mrosovsky, N. Circannual cycles in golden-mantled ground squirrels: Experiments with food deprivation and effects of temperature on periodicity. J. Comp. Physiol. 136, 355–360 (1980). https://doi.org/10.1007/BF00657357
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DOI: https://doi.org/10.1007/BF00657357