![]() Duration of a bout of torpor was measured from time of entry to time of arousal and, thus, included both decline in body temperature and the interval of deep torpor when body temperature usually was constant and approximated ambient. The point of initial decline into torpor and the 1st evidence of thermogenesis following torpor were recorded as times of entry and arousal, respectively. A slow decline in nest temperature occurred when an animal entered torpor, but the decline was rapid when an active animal left its nest box. A euthermic animal warmed its nest box several degrees above ambient, and that warming was easily detected in the temperature records. Thermocouples were attached to a data-logging system (Lawson Labs, Inc., Columbia Falls, Montana), and their outputs were recorded on a microcomputer at 15-min intervals. The timing of entrances into and arousals from torpor was determined from records of thermocouples mounted on the floor of each animal's nest box. Five chipmunks with prolonged hibernation seasons eventually were given an additional 200 g of seeds to stimulate them to cease torpor. A covered nest box (15 by 13 by 11.5 cm) made of wood with an entrance in the front was secured in 1 corner of each enclosure, and a water bottle was inserted through the wall adjacent to the nest box.Ĭhipmunks were given cotton nesting material and moved into a cold (5 ± 0.5☌) room with constant dim (2 weeks. Each chipmunk was housed individually in a wooden box (46 by 28 by 29 cm) with a top of hardware cloth and wood shavings on the floor. All animals were kept initially at 22–23☌ at 12L:12D and fed sunflower seeds ad lib. All but 4 animals lacked obvious toothwear and were judged to be young of the year despite their large size. Seventy-two chipmunks were captured in hardwood forests of Broome County, New York, in September and the 1st week of October 1994. Here, I describe patterns of body temperature in eastern chipmunks ( Tamias striatus) given differing amounts of food at the onset of dormancy and provide the 1st test of this hypothesis. A high variability in size of external energy reserves could have led to an ability to vary rate of energy consumption by adjusting time spent in torpor. As a result, stores can be relatively large and potentially quite variable among individuals and from year to year for the same individual. ![]() Those hibernators that rely exclusively on food caches are not constrained by body size in amount of energy they store. The view that thermoregulatory patterns of hibernation are species specific and modified, for the most part, only by changes in ambient temperature may reflect the fact that most studies have been done on species that store energy as body fat. Those species of hibernators that have high rates of metabolism, long dormant seasons, and small energy reserves appear to spend more time in torpor at the same environmental temperatures than do species that are less constrained energetically ( French 1986).Īlthough variations in use of torpor among species are well recognized, there is little evidence of individual flexibility. However, torpor is not used indiscriminately. Reduction of body temperature (torpor) that frequently accompanies this seasonal dormancy is clearly an adaptation for energy conservation. Many mammals remain inactive when food is scarce and the weather inclement, often subsisting for many months on energy stored as body fat or nonperishable food. ![]() Thermoregulatory responses of chipmunks appear more flexible than those of species that store energy as body fat, but the match between use and availability of energy during dormancy is imprecise.Ĭhipmunk, food cache, hibernation, New York, Tamias striatus, torpor Animals given an intermediate ration (1,000 g) hibernated until food was gone (42%) or spontaneously terminated hibernation with abundant food uneaten (58%). In addition, chipmunks given the least amount of food (400 g) continued to hibernate until they consumed all seeds those provided with abundant food (5,000 g) terminated hibernation spontaneously early in the spring phase and remained euthermic thereafter. Duration of bouts of torpor in winter and spring and amount of time animals hibernated before starting the energetically demanding spring phase were related inversely to amount of food provided at the beginning of the experiment. Duration of torpor by eastern chipmunks, Tamias striatus, kept at 5☌ progressively increased at the beginning of hibernation (autumn phase), remained long and relatively constant (winter phase), and then decreased (spring phase) in a fashion similar to that observed in hibernators that store energy as body fat. ![]()
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