Energetics of Hibernation in the Arctic Ground Squirrel (Spermophilus Parryii Kenicotti) PDF Download
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Author: Shawna Karpovich
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 158
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Book Description
"Arctic ground squirrels (Spermophilus parryii kenicotti) hibernate underground; experiencing burrows temperatures of -5 to -25C̊. Hibernation consists of 7-9 months of torpor interrupted every 2-3 weeks by 10-20 h arousal episodes with high body temperatures and metabolic rates. Metabolic rates and body temperatures were measured during arousal episodes under temperate and arctic conditions. No difference in cost of arousal episodes was detected. Yet, when the cost of thermogenesis during torpor was included, proportional cost of arousal episodes decreased from 86 to 27% comparing temperate to arctic conditions. The relationship between metabolic rate and body temperature was examined during the recooling phase of hibernation. As animals entered torpor, body temperature was allowed to either decrease naturally or was experimentally altered at different points along the recooling curve. The changes in metabolic rate can be explained by changes in body temperature and no sign of temperature-independent metabolic suppression was detected"--Leaf iii.
Author: Shawna Karpovich
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 158
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Book Description
"Arctic ground squirrels (Spermophilus parryii kenicotti) hibernate underground; experiencing burrows temperatures of -5 to -25C̊. Hibernation consists of 7-9 months of torpor interrupted every 2-3 weeks by 10-20 h arousal episodes with high body temperatures and metabolic rates. Metabolic rates and body temperatures were measured during arousal episodes under temperate and arctic conditions. No difference in cost of arousal episodes was detected. Yet, when the cost of thermogenesis during torpor was included, proportional cost of arousal episodes decreased from 86 to 27% comparing temperate to arctic conditions. The relationship between metabolic rate and body temperature was examined during the recooling phase of hibernation. As animals entered torpor, body temperature was allowed to either decrease naturally or was experimentally altered at different points along the recooling curve. The changes in metabolic rate can be explained by changes in body temperature and no sign of temperature-independent metabolic suppression was detected"--Leaf iii.
Author: Timothy J. Karels
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Populations of arctic ground squirrels in the boreal forest of the southwest Yukon were studied in order to answer the following questions: (1) What are the mechanisms of population regulation in arctic ground squirrel populations, (2) How does variation among individuals and their environment influence their reproduction and survival, and (3) How does variation in habitat influence hibernating strategies of arctic ground squirrels? In spring 1996, control densities of ground squirrels were 1.6 per ha, and four other populations ranged in density from 3.2 to 30.1 per ha as a result of a 10-year (1987-96) large scale manipulation of food and predators in the boreal forest of the Kluane Boreal Forest Ecosystem Project. When the Kluane project terminated in spring 1996, I measured population densities, reproduction, emigration, and survival in all populations using live-trapping and radio-telemetry techniques until spring 1998. Arctic ground squirrel populations were strongly regulated because all experimental populations declined to control densities within two years after the termination of the experimental manipulations. Two factors proved strongly density-dependent and hence were regulatory: (1) the proportion of females that weaned their litter and (2) overwinter survival. Simultaneous density-independent changes in weaning rate were also detected and were attributed to changes in the previous year's snow accumulation. Female ground squirrels exhibited positive associations of life history traits. Squirrels in better condition at spring emergence were more likely to give birth, wean their litter, survive to the next breeding season, and reproduce once again. Nearly all females who failed during lactation did not survive to the next breeding season. The overwinter survival rate of females that successfully weaned a litter declined at a greater rate with increasing population density than did squirrels that never gave birth, indicating a cost to reproduction. Ground squirrels hibernated distantly (24 m) from their summer burrows in relation to population density and in open or shrubby habitats that were likely to accumulate the most snow. Increased snow accumulation over hibernacula increased the minimum soil temperatures and decreased the rate of mass loss of hibernating squirrels suggesting a selective mechanism for the ability of ground squirrels to identify habitats that minimize their energy expenditure during hibernation.
Author: Trixie Nicole Lee
Publisher:
ISBN:
Category : Marmots
Languages : en
Pages : 240
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The Arctic is home to animals that have taken adaptations to overwintering to extremes. In this dissertation, I have investigated one of these adaptations, hibernation, in two species from the Arctic, the Alaska marmot (Marmota broweri) and the arctic ground squirrel (Urocitellus parryii). The expression of hibernation under natural conditions in these species was compared by collecting body temperature records of free-living individuals. The Alaska marmot, a highly social species, demonstrated extreme synchrony in body temperature patterns among a family group, indicating a strong reliance on social thermoregulation. In contrast, the arctic ground squirrel was confirmed to be a solitary hibernator that reduces body temperature below freezing during torpor. Both species must produce heat when soil temperatures are significantly below freezing for most of the winter. At these subfreezing ambient temperatures, the arctic ground squirrel has shown an increasing reliance on nonlipid fuel during torpor, driving a loss of lean mass during hibernation of ~20%. I calibrated deuterium dilution to repeatedly estimate body composition in this species, which dramatically changes adiposity through its annual cycle, and used this technique to quantify lean mass loss throughout hibernation in a study of tissue metabolism. I also developed and applied the natural abundance of nitrogen and carbon stable isotopes as tools for monitoring differential tissue metabolism and differentiating mixed metabolic fuel use in the arctic ground squirrel. These data clarified the mechanism of change in nitrogen stable isotopes andd, indicated that hibernating ground squirrels rebuild organ tissues while breaking down muscle tissue to meet energetic demands. Furthermore, I corroborated a shift in metabolic fuel use toward nonlipid sources during torpor at low ambient temperatures by using the carbon isotope ratio in exhaled breath in combination with respiratory quotient. This dissertation combines studies of hibernation patterns in free-living animals with experimental data on the tissues and fuels being catabolized at very low temperatures to broaden our understanding of how small mammals successfully hibernate in severe winter conditions. It also presents the development and use of stable isotope ratios as physiological tools in hibernating species.
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Author: Timothy J. (Timothy Jack) Karels
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612538856
Category :
Languages : en
Pages : 366
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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