Persistent Link:
http://hdl.handle.net/10150/185449
Title:
Adaptive heterothermy in desert mammals.
Author:
Osborn, Scott Donald.
Issue Date:
1991
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Endothermic homeothermy is a major feature of the adaptive suites of tachymetabolic animals such as mammals and birds. The advantages homeothermy confers on birds and mammals include relative independence from the environment, a stable internal milieu, and possibly the ability to sustain high aerobic activity (Bennett and Ruben 1979). Some mammals in situations of limited water or energy availability, however, depart markedly from homeothermy and instead display patterns of heterothermy. Torpor is a lowering of body temperature (T(b)) to conserve energy and/or water. I studied the energetics of arousal from torpor in two desert pocket mice species. The species differed in warming rates and arousal durations, but used similar amounts of energy to arouse. The smaller species, Perognathus amplus, lost mass more quickly while fasting in the cold, yet waited as long as the larger species, Chaetodipus baileyi, before entering torpor. P. amplus maintained a lower T(b) during topor than C. baileyi. The thermodynamics of arousal indicated that metabolic rate during arousal was a function of T(b) but not ambient temperature (Tₐ), that the animals changed thermal conductance to increase heat gain when Tₐ was greater than T(b), and that Q₁₀ decreased during arousals. In contrast to torpor, adaptive hyperthermia provides desert mammals in dry, hot environments a means to conserve water that would normally be used for evaporative cooling. I modeled the effects of body size on adaptive hyperthermia and discovered that small mammals gain the most in terms of water savings using this strategy, and that small and large mammals can spend larger fractions of the day active than do medium size mammals. I demonstrated that two desert ground squirrel species make use of adaptive hyperthermia during the summer near Tucson, Arizona by following free-ranging squirrels implanted with temperature-sensitive radio transmitters. Ground squirrel T(b) fluctuated almost continuously, ranging from about 35°C to over 42°C, and rarely approached steady state. Of the two species studied, Ammospermophilus harrisii had higher mean T(b), similar maximum T(b), and lower T(b) variability compared to Spermophilus tereticaudus. These results are consistent with the more wide-ranging foraging style of A. harrisii compared to S. tereticaudus.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic; Desert animals -- Adaptation; Body temperature -- Regulation.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Ecology and Evolutionary Biology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Vleck, David

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAdaptive heterothermy in desert mammals.en_US
dc.creatorOsborn, Scott Donald.en_US
dc.contributor.authorOsborn, Scott Donald.en_US
dc.date.issued1991en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractEndothermic homeothermy is a major feature of the adaptive suites of tachymetabolic animals such as mammals and birds. The advantages homeothermy confers on birds and mammals include relative independence from the environment, a stable internal milieu, and possibly the ability to sustain high aerobic activity (Bennett and Ruben 1979). Some mammals in situations of limited water or energy availability, however, depart markedly from homeothermy and instead display patterns of heterothermy. Torpor is a lowering of body temperature (T(b)) to conserve energy and/or water. I studied the energetics of arousal from torpor in two desert pocket mice species. The species differed in warming rates and arousal durations, but used similar amounts of energy to arouse. The smaller species, Perognathus amplus, lost mass more quickly while fasting in the cold, yet waited as long as the larger species, Chaetodipus baileyi, before entering torpor. P. amplus maintained a lower T(b) during topor than C. baileyi. The thermodynamics of arousal indicated that metabolic rate during arousal was a function of T(b) but not ambient temperature (Tₐ), that the animals changed thermal conductance to increase heat gain when Tₐ was greater than T(b), and that Q₁₀ decreased during arousals. In contrast to torpor, adaptive hyperthermia provides desert mammals in dry, hot environments a means to conserve water that would normally be used for evaporative cooling. I modeled the effects of body size on adaptive hyperthermia and discovered that small mammals gain the most in terms of water savings using this strategy, and that small and large mammals can spend larger fractions of the day active than do medium size mammals. I demonstrated that two desert ground squirrel species make use of adaptive hyperthermia during the summer near Tucson, Arizona by following free-ranging squirrels implanted with temperature-sensitive radio transmitters. Ground squirrel T(b) fluctuated almost continuously, ranging from about 35°C to over 42°C, and rarely approached steady state. Of the two species studied, Ammospermophilus harrisii had higher mean T(b), similar maximum T(b), and lower T(b) variability compared to Spermophilus tereticaudus. These results are consistent with the more wide-ranging foraging style of A. harrisii compared to S. tereticaudus.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectDesert animals -- Adaptationen_US
dc.subjectBody temperature -- Regulation.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorVleck, Daviden_US
dc.contributor.committeememberBraun, Eldon J.en_US
dc.contributor.committeememberCalder, William A.en_US
dc.contributor.committeememberDantzler, William H.en_US
dc.contributor.committeememberVleck, Carol Mastersen_US
dc.identifier.proquest9124157en_US
dc.identifier.oclc710140485en_US
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