scholarly journals Seasonal Expression of Avian and Mammalian Daily Torpor and Hibernation: Not a Simple Summer-Winter Affair†

2020 ◽  
Vol 11 ◽  
Author(s):  
Fritz Geiser
Keyword(s):  
Daily Torpor

Torpor and hibernation

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Body Temperature ◽  
Small Mammals ◽  
Energy Input ◽  
The Arctic ◽  
Arid Areas ◽  
Daily Torpor ◽  
High Latitudes ◽  
Small Species ◽  
Universal Feature ◽  
Deep Hibernation

A diurnal (circadian) rhythm in body temperature is a widespread, and possibly universal, feature of endotherms. Some mammals and birds down-regulate their metabolic rate significantly by night, allowing their body temperature to drop sufficiently that they become inactive and enter torpor. Both the minimum temperature achieved and the duration of torpor are highly variable. Daily torpor is principally a response to reduced energy intake, and a drop in ambient temperature. Hibernation is essentially an extreme form of torpor. Small mammals hibernating at high latitudes have regular arousals during which they urinate and may feed. Bears hibernate with relatively high body temperature, and do not undergo arousal. Only one bird, the poorwill, is known to hibernate. Rewarming during arousal may be fuelled exclusively by metabolism (for example in small mammals in the Arctic) or with significant energy input from basking (for example in subtropical arid areas). The capacity for torpor appears to be an ancestral character in both mammals and birds, possibly related to the origin of endothermy in small species subject to marked diurnal and/or seasonal variation in body temperature. Both deep hibernation and strict endothermy are probably derived characteristics.

Control of torpor and body weight patterns by a seasonal timer in Siberian hamsters

1989 ◽  
Vol 257 (1) ◽  
pp. R142-R149 ◽  
Author(s):  
T. J. Bartness ◽  
J. A. Elliott ◽  
B. D. Goldman
Keyword(s):  
Body Weight ◽  
Food Intake ◽  
Implant Removal ◽  
Daily Torpor ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Preparatory Phase ◽  
Pelage Color ◽  
Seasonal Responses

Two experiments were designed to assess whether the short-day-induced patterns of shallow daily torpor, body weight, and other seasonal responses (food intake and pelage pigmentation) exhibited by Siberian hamsters (Phodopus sungorus sungorus) are under the control of a "seasonal timekeeping mechanism" that is independent of reproductive status [testosterone, (T)]. We examined whether the patterning and expression of these seasonal responses were altered by decreases in serum T that accompany gonadal regression during the first 8 wk of short-day exposure (i.e., the "preparatory phase" of the torpor season) or by experimental increases in serum T after this phase. Short-day-housed, castrated hamsters bearing T implants had long-day levels of the hormone and did not exhibit torpor. Appropriate seasonal patterns and levels of torpor, body weight, pelage color stage, and food intake were exhibited after T implant removal although serum T was clamped to long-day levels during the preparatory phase. In animals that were gonad intact during the preparatory phase and were subsequently castrated and given T implants, torpor did not occur as long as the implants were in place. However, the patterns and levels of daily torpor, food intake, and body weight rapidly returned to appropriate seasonal values compared with the castrated, blank-implanted controls on T implant removal; these effects occurred whether the T implants were removed when torpor frequency was increasing, at its peak, or decreasing across the torpor season. T did not affect pelage color stage under any condition.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The Chemistry of Cold: Mechanisms of Torpor Regulation in the Siberian Hamster

Physiology ◽  
2016 ◽  
Vol 31 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Ceyda Cubuk ◽  
Jonathan H. H. Bank ◽  
Annika Herwig
Keyword(s):  
Physiological State ◽  
Daily Torpor ◽  
Brain Areas ◽  
Siberian Hamster ◽  
Siberian Hamsters ◽  
Save Energy

Siberian hamsters use spontaneous daily torpor, a state of hypometabolism and hypothermia, to save energy during winter. Multiple neuroendocrine signals set the scene for spontaneous torpor to occur, and several brain areas have been identified as potential sites for torpor regulation. Here, we summarize the known mechanisms of a fascinating physiological state in the Siberian hamster.

Seasonal Study of Spontaneous Daily Torpor in the White-Footed Mouse, Peromyscus leucopus

1978 ◽  
Vol 51 (3) ◽  
pp. 289-299 ◽  
Author(s):  
G. Robert Lynch ◽  
F. Daniel Vogt ◽  
Harvey R. Smith
Keyword(s):  
Peromyscus Leucopus ◽  
Daily Torpor ◽  
Seasonal Study ◽  
White Footed Mouse

Magnitude of food overabundance affects expression of daily torpor

2015 ◽  
Vol 139 ◽  
pp. 519-523 ◽  
Author(s):  
Takeshi Eto ◽  
Rintaroh Hayashi ◽  
Yoshinobu Okubo ◽  
Atsushi Kashimura ◽  
Chihiro Koshimoto ◽  
...  
Keyword(s):  
Daily Torpor
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