Do Patterns of Torpor Differ between Free-ranging and Captive Mammals and Birds?

Geiser, Fritz; Holloway, Joanne C.; Körtner, Gerhard; Maddocks, Tracy A.; Turbill, Christopher; Brigham, R. Mark

doi:10.1007/978-3-662-04162-8_10

Cited by 73 publications

(65 citation statements)

References 22 publications

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“…The former had over ten times the number of species (or measures from different species) than the latter, although the authors admit to only being able to obtain a subset of available T b datasets. The amount of data we have on heterothermy in mammals is heavily skewed towards laboratory data, which often underestimates torpor use [160]. A large number of the 'data deficient' species were also found at the lower latitudes.…”

Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 99%

Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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Global climate change is expected to have strong effects on the world's flora and fauna. As a result, there has been a recent increase in the number of meta-analyses and mechanistic models that attempt to predict potential responses of mammals to changing climates. Many models that seek to explain the effects of environmental temperatures on mammalian energetics and survival assume a constant body temperature. However, despite generally being regarded as strict homeotherms, mammals demonstrate a large degree of daily variability in body temperature, as well as the ability to reduce metabolic costs either by entering torpor, or by increasing body temperatures at high ambient temperatures. Often, changes in body temperature variability are unpredictable, and happen in response to immediate changes in resource abundance or temperature. In this review we provide an overview of variability and unpredictability found in body temperatures of extant mammals, identify potential blind spots in the current literature, and discuss options for incorporating variability into predictive mechanistic models.

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Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 99%

Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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“…Fasting ruminants for longer periods of time is detrimental to rumen symbionts and can thus be hazardous for the animal before a truly postabsorptive state is reached. Furthermore, physiological measurements under artificial experimental or feeding regimes are likely to prevent natural responses of wild animals (19,41).…”

mentioning

confidence: 99%

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Arnold

Ruf

Reimoser

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

126

143

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. Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus). Am J Physiol Regul Integr Comp Physiol 286: R174-R181, 2004. First published September 11, 2003 10.1152/ajpregu.00593.2002Herbivores of temperate and arctic zones are confronted during winter with harsh climatic conditions and nutritional shortness. It is still not fully understood how large ungulates cope with this twofold challenge. We found that red deer, similar to many other northern ungulates, show large seasonal fluctuations of metabolic rate, as indicated by heart rate, with a 60% reduction at the winter nadir compared with the summer peak. A previously unknown mechanism of energy conservation, i.e., nocturnal hypometabolism associated with peripheral cooling, contributed significantly to lower energy expenditure during winter. Predominantly during late winter night and early morning hours, subcutaneous temperature could decrease substantially. Importantly, during these episodes of peripheral cooling, heart rate was not maintained at a constant level, as to be expected from classical models of thermoregulation in the thermoneutral zone, but continuously decreased with subcutaneous temperature, both during locomotor activity and at rest. This indicates that the circadian minimum of basal metabolic rate and of the set-point of body temperature regulation varied and dropped to particularly low levels during late winter. Our results suggest, together with accumulating evidence from other species, that reducing endogenous heat production is not restricted to hibernators and daily heterotherms but is a common and well-regulated physiological response of endothermic organisms to energetically challenging situations. Whether the temperature of all tissues is affected, or the body shell only, may simply be a result of the duration and degree of hypometabolism and its interaction with body size-dependent heat loss. hypometabolism; hypothermia; winter adaptation; body temperature regulation MANY UNGULATES ARE CAPABLE of withstanding long and cold winters with low food availability. Large body size, excellent fur insulation, and countercurrent heat exchange mechanisms contribute to minimize energy requirements under cold load. However, reduced heat loss alone can hardly explain the substantially lowered metabolic rate (MR) of northern ungulates and the apparently ubiquitous decrease of voluntary food intake during winter (4,13,18,28,35,37,42,44,59,63,72). The search for mechanism to explain reduced energy expenditure during winter has so far produced equivocal results. Studies on white-tailed deer [Odocoileus virginianus (66)], moose [Alces alces (56, 57)], roe deer [Capreolus capreolus (69)], and wapiti [Cervus elaphus nelsoni (49)] reported that animals had reduced MRs during winter. However, other studies failed to find any differences between summer and winter basal metabolic rate (BMR) and concluded that seasonal variations in MR were merely consequences of different activity levels and failures to measure animals within thei...

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“…It is known that thermoregulation may differ markedly between captive and free-ranging animals [Geiser et al, 2000]. The aim of this study was therefore to investigate the use of heterothermy (if any) by free-ranging southern lesser bushbabies (G. moholi).…”

Section: Introductionmentioning

confidence: 99%

Lack of Torpor in Free-Ranging Southern Lesser Galagos, Galago moholi: Ecological and Physiological Considerations

Mzilikazi¹,

Masters²,

Lovegrove³

2006

IJFP

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Studies investigating heterothermy under natural conditions are particularly scarce for tropical species. However, heterothermy patterns in tropical and subtropical environments often differ markedly from those observed in arctic and temperate species. The investigation of heterothermy in strepsirhine primates has focussed largely on the Malagasy cheirogaleids. In addition, a physiological verification of torpor occurrence in mainland strepsirhines is important with regard to arguments pertaining to the colonization of Madagascar by strepsirhine primates. We measured body temperatures of 11 free-ranging Galago moholi, between February 2002 and September 2003, for 3 consecutive months for each animal. No incidents of heterothermy were recorded throughout the study period. We considered how physiological and ecological aspects of G. moholi biology might have obviated the use of torpor. It was suggested that the breeding pattern observed in G. moholi prevented torpor use whilst increasing fecundity, and that the ecological costs of torpor far outweighed the energetic costs. This study highlights the need for more studies on free-ranging animals to elucidate the physiological, ecological and phylogenetic constraints and determinants of torpor use. Furthermore, if convincing arguments are to be made regarding the possible role of heterothermy in species dispersal, more data from free-ranging animals are needed.

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Do Patterns of Torpor Differ between Free-ranging and Captive Mammals and Birds?

Cited by 73 publications

References 22 publications

Modelling mammalian energetics: the heterothermy problem

Modelling mammalian energetics: the heterothermy problem

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Lack of Torpor in Free-Ranging Southern Lesser Galagos, Galago moholi: Ecological and Physiological Considerations

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