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Fritz Geise - One of the best experts on this subject based on the ideXlab platform.
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precocious Torpor in an altricial mammal and the functional implications of heterothermy during development
Frontiers in Physiology, 2019Co-Authors: Fritz Geise, Gansukh Sukhchuluu, Qingsheng Chi, Dehua WangAbstract:Most mammals and birds are altricial, small and naked at birth/hatching. They attain endothermic thermoregulation at a fraction of their adult size at a vulnerable stage with high heat loss when many could profit from using Torpor for energy conservation. Nevertheless, detailed data on the interrelations between Torpor expression and development of endothermic thermoregulation are currently restricted to 90%, followed by endothermic arousal. Over the next weeks, Torpor depth and duration decreased together with a reduction in resting metabolic rate at Ta 30-32°C. Our data show that development of endothermy and Torpor expression in this altricial hamster is extremely fast. The results suggest that precocious Torpor by juvenile hamsters in autumn and winter is an important survival tool in their vast and harsh Asian desert habitats, but likely also for many other small mammals and birds worldwide.
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Precocious Torpor in an Altricial Mammal and the Functional Implications of Heterothermy During Development
Frontiers Media S.A., 2019Co-Authors: Fritz Geise, Gansukh Sukhchuluu, Qingsheng Chi, Dehua WangAbstract:Most mammals and birds are altricial, small and naked at birth/hatching. They attain endothermic thermoregulation at a fraction of their adult size at a vulnerable stage with high heat loss when many could profit from using Torpor for energy conservation. Nevertheless, detailed data on the interrelations between Torpor expression and development of endothermic thermoregulation are currently restricted to <0.1% of extant endotherms. We investigated at what age and body mass (BM) desert hamsters (Phodopus roborovskii), wild-caught in Inner Mongolia and born in autumn/early winter when environmental temperatures in the wild begin to decrease, are able to defend their body temperature (Tb) at an ambient temperature (Ta) of ∼21°C and how soon thereafter they could express Torpor. Measurements of surface temperatures via infrared thermometer and thermal camera show that although neonate hamsters (BM 0.9 ± 0.1 g) cooled rapidly to near Ta, already on day 15 (BM 5.5 ± 0.2 g) they could defend a high and constant Tb. As soon as day 16 (BM 5.8 ± 0.2 g), when their maximum activity metabolism (measured as oxygen consumption) approached maxima measured in vertebrates, animals were able to enter Torpor for several hours with a reduction of metabolism by >90%, followed by endothermic arousal. Over the next weeks, Torpor depth and duration decreased together with a reduction in resting metabolic rate at Ta 30–32°C. Our data show that development of endothermy and Torpor expression in this altricial hamster is extremely fast. The results suggest that precocious Torpor by juvenile hamsters in autumn and winter is an important survival tool in their vast and harsh Asian desert habitats, but likely also for many other small mammals and birds worldwide
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more functions of Torpor and their roles in a changing world
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2017Co-Authors: Julia Nowack, Clare Stawski, Fritz GeiseAbstract:Increased winter survival by reducing energy expenditure in adult animals is often viewed as the primary function of Torpor. However, Torpor has many other functions that ultimately increase the survival of heterothermic mammals and birds. In this review, we summarize new findings revealing that animals use Torpor to cope with the conditions during and after natural disasters, including fires, storms, and heat waves. Furthermore, we suggest that Torpor, which also prolongs longevity and was likely crucial for survival of mammals during the time of the dinosaur extinctions, will be advantageous in a changing world. Climate change is assumed to lead to an increase in the occurrence and intensity of climatic disasters, such as those listed above and also abnormal floods, droughts, and extreme temperatures. The opportunistic use of Torpor, found in many heterothermic species, will likely enhance survival of these challenges, because these species can reduce energy and foraging requirements. However, many strictly seasonal hibernators will likely face the negative consequences of the predicted increase in temperature, such as range contraction. Overall, available data suggest that opportunistic heterotherms with their flexible energy requirements have an adaptive advantage over homeotherms in response to unpredictable conditions.
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a new cue for Torpor induction charcoal ash and smoke
The Journal of Experimental Biology, 2017Co-Authors: Clare Stawski, Gerhard Kortne, Julia Nowack, Fritz GeiseAbstract:ABSTRACT Recent work has shown that the use of Torpor for energy conservation increases after forest fires in heterothermic mammals, probably in response to the reduction of food. However, the specific environmental cues for this increased Torpor expression remain unknown. It is possible that smoke and the novel substrate of charcoal and ash act as signals for an impending period of starvation requiring Torpor. We therefore tested the hypothesis that the combined cues of smoke, a charcoal/ash substrate and food shortage will enhance Torpor expression in a small forest-dwelling marsupial, the yellow-footed antechinus ( Antechinus flavipes ), because like other animals that live in fire-prone habitats they must effectively respond to fires to ensure survival. Activity and body temperature patterns of individuals in outdoor aviaries were measured under natural environmental conditions. All individuals were strictly nocturnal, but diurnal activity was observed shortly after smoke exposure. Overall, Torpor in females was longer and deeper than that in males. Interestingly, while both males and females increased daily Torpor duration during food restriction by >2-fold as anticipated, a combination of food restriction and smoke exposure on a charcoal/ash substrate further increased daily Torpor duration by ∼2-fold in both sexes. These data show that this combination of cues for Torpor induction is stronger than food shortage on its own. Our study provides significant new information on how a small forest-dwelling mammal responds to fire cues during and immediately after a fire and identifies a new, not previously recognised, regulatory mechanism for thermal biology in mammals.
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daily Torpor and hibernation in birds and mammals
Biological Reviews of The Cambridge Philosophical Society, 2015Co-Authors: Thomas Ruf, Fritz GeiseAbstract:Many birds and mammals drastically reduce their energy expenditure during times of cold exposure, food shortage, or drought, by temporarily abandoning euthermia, i.e. the maintenance of high body temperatures. Traditionally, two different types of heterothermy, i.e. hypometabolic states associated with low body temperature (Torpor), have been distinguished: daily Torpor, which lasts less than 24 h and is accompanied by continued foraging, versus hibernation, with Torpor bouts lasting consecutive days to several weeks in animals that usually do not forage but rely on energy stores, either food caches or body energy reserves. This classification of Torpor types has been challenged, suggesting that these phenotypes may merely represent extremes in a continuum of traits. Here, we investigate whether variables of Torpor in 214 species (43 birds and 171 mammals) form a continuum or a bimodal distribution. We use Gaussian-mixture cluster analysis as well as phylogenetically informed regressions to quantitatively assess the distinction between hibernation and daily Torpor and to evaluate the impact of body mass and geographical distribution of species on Torpor traits. Cluster analysis clearly confirmed the classical distinction between daily Torpor and hibernation. Overall, heterothermic endotherms tend to be small; hibernators are significantly heavier than daily heterotherms and also are distributed at higher average latitudes (∼35°) than daily heterotherms (∼25°). Variables of Torpor for an average 30 g heterotherm differed significantly between daily heterotherms and hibernators. Average maximum Torpor bout duration was >30-fold longer, and mean Torpor bout duration >25-fold longer in hibernators. Mean minimum body temperature differed by ∼13°C, and the mean minimum Torpor metabolic rate was ∼35% of the basal metabolic rate (BMR) in daily heterotherms but only 6% of BMR in hibernators. Consequently, our analysis strongly supports the view that hibernators and daily heterotherms are functionally distinct groups that probably have been subject to disruptive selection. Arguably, the primary physiological difference between daily Torpor and hibernation, which leads to a variety of derived further distinct characteristics, is the temporal control of entry into and arousal from Torpor, which is governed by the circadian clock in daily heterotherms, but apparently not in hibernators.
Fritz Geiser - One of the best experts on this subject based on the ideXlab platform.
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daily Torpor and hibernation in birds and mammals
Biological Reviews of The Cambridge Philosophical Society, 2015Co-Authors: Fritz GeiserAbstract:Many birds and mammals drastically reduce their energy expenditure during times of cold exposure, food shortage, or drought, by temporarily abandoning euthermia, i.e., the maintenance of high body temperatures. Traditionally, two different types of heterothermy, i.e., hypometabolic states associated with low body temperatures (Torpor), have been distinguished: Daily Torpor, which lasts less than 24 h and is accompanied by continued foraging, versus hibernation, with Torpor bouts lasting consecutive days to several weeks in animals that usually do not forage but rely on energy stores, either food caches or body energy reserves. This classification of Torpor types has been challenged however, suggesting that these phenotypes may merely represent the extremes in a continuum of traits. Here, we investigate whether variables of Torpor in 214 species, 43 birds and 171 mammals form a continuum or a bimodal distribution. We use Gaussian-mixture cluster analysis as well as phylogenetically informed regressions to quantitatively assess the distinction between hibernation and daily Torpor and to evaluate the impact of body mass and geographical distribution of species on Torpor traits. Cluster analysis clearly confirmed the classical distinction between daily Torpor and hibernation. Overall, heterothermic endotherms are small on average, but hibernators are significantly heavier than daily heterotherms and also are distributed at higher average latitudes (~35°) than daily heterotherms (~25°). Variables of Torpor for an average 30-g heterotherm differed significantly between daily heterotherms and hibernators. Average maximum Torpor bout duration was >30-fold longer, and mean Torpor bout duration >25-fold longer in hibernators. Mean minimum body temperature differed by ~13°C, and the mean minimum Torpor metabolic rate was ~35% of the BMR in daily heterotherms but only 6% of basal metabolic rate in hibernators. Consequently, our analysis strongly supports the view that hibernators and daily heterotherms are functionally distinct groups that probably have been subject to disruptive selection. Arguably, the primary physiological difference between daily Torpor and hibernation, which leads to a variety of derived further distinct characteristics, is the temporal control of entry into and arousal from Torpor, which is governed by the circadian clock in daily heterotherms, but apparently not in hibernators.
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body mass dependent use of hibernation why not prolong the active season if they can
Functional Ecology, 2014Co-Authors: Claudia Bieber, Gabrielle Stalder, Karin Lebl, Fritz GeiserAbstract:Summary 1. Hibernation is the most effective means for energy conservation during winter in mammals. The drawbacks of deep and prolonged Torpor include reduced immunocompetence, and consequently, hibernators should be selected to minimize Torpor expression when climatic conditions or energy availability (e.g. food or fat stores) permit. Therefore, it seems surprising that some hibernators employ extraordinary long hibernation seasons, lasting well beyond periods with unfavourable conditions. 2. Because of their extended use of Torpor, edible dormice (Glis glis) provide an ideal model for scrutinizing interactions between energy reserves (i.e. body fat stores) and thermoregulatory patterns. We used a multimodel inference approach to analyse body temperature data (i.e. use of Torpor) from 42 entire hibernation seasons over 4 years in females in relation to body mass. 3. Body mass prior to hibernation did not affect the duration of the hibernation season, but animals hibernated for c. 8 months, that is, 2 months longer than required by environmental conditions. Fatter individuals aroused significantly more often, had a higher mean minimum body temperature during Torpor and remained euthermic for longer periods than leaner animals. 4. Surplus energy was therefore not used to shorten the hibernation season, but to rewarm more frequently, and to allow shallower Torpor bouts. These adjustments apparently serve to avoid negative effects of Torpor and, perhaps equally importantly, to minimize the time active above-ground. We argue that maintaining a short active season, despite surplus energy reserves, may be explained by known beneficial effects of hibernation on survival rates (via predator avoidance). 5. Our data provide quantitative evidence that hibernation is a flexible tool within life-history strategies. We conclude that, apart from energetic necessities due to harsh environmental conditions, predator avoidance may be an important factor influencing patterns of hibernation and Torpor in mammals. Thus, our study indicates that climatic conditions alone are not a good predictor of hibernation patterns or survival in hibernating species during global climate change.
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Torpor in free ranging antechinus does it increase fitness
Naturwissenschaften, 2014Co-Authors: Daniella A Rojas, Gerhard Kortner, Fritz GeiserAbstract:Antechinus are small, insectivorous, heterothermic marsupial mammals that use Torpor from late summer to early winter and reproduce once a year in late winter/early spring. Males die after mating, most females produce only a single litter, but some survive a second winter and produce another litter. As it is not known how these females manage to survive the second winter after the energetically demanding reproductive period and then reproduce a second time, we aimed to provide the first data on thermal biology of free-ranging antechinus by using temperature telemetry. Male Antechinus stuartii and Antechinus flavipes rarely entered Torpor in autumn/early winter in the wild, expressing only shallow bouts of <2 h. Female A. stuartii used Torpor extensively, employing bouts up to 16.7 h with body temperatures as low as 17.8 °C. Interestingly, although first and second year females used similar Torpor patterns, Torpor occurrence was almost twofold in second year (93 % of days) than first year females (49 %), and the proportion of the overall monitoring period animals spent torpid was 3.2-fold longer in the former with a corresponding shorter activity period. Our study suggests that intensive use of Torpor is crucial for second year females for autumn and winter survival and production of a second litter. We provide the first evidence of an age-related pattern in daily Torpor expression in free-ranging mammals and show that Torpor use is a complex process that is affected not only by the current energy availability and thermal conditions but also by the reproductive history and age of individuals.
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The Other Functions of Torpor
Living in a Seasonal World, 2012Co-Authors: Fritz Geiser, R. Mark BrighamAbstract:Although energy conservation by cold-climate adult endotherms in winter is often viewed as the main function of Torpor, recent evidence suggests that this may not always be the case. We examined whether other functions of Torpor may be equally or even more important in some instances. Torpor enhances fat storage during migration, apparently permits prolonged female sperm storage in bats, allows reproduction with limited or fluctuating food supply, and delays parturition until more favorable periods. Torpor appears to increase the efficiency of energy and nutrient use during development. Further, Torpor reduces water requirements, appears to permit persistence during droughts, reduces the load of some parasites, permits co-existence of competing species, and also reduces the risk of predation and mammalian extinctions. Thus, the functions of Torpor are complex and some of these appear to be not just proximate.
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hibernation and Torpor in tropical and subtropical bats in relation to energetics extinctions and the evolution of endothermy
Integrative and Comparative Biology, 2011Co-Authors: Fritz Geiser, Clare StawskiAbstract:Synopsis Torpor, the most effective means of energy conservation available to endotherms, is still widely viewed as a specific adaptation in a few high-latitude, cold-climate endotherms with no adaptive function in warm regions. Nevertheless, a growing number of diverse terrestrial mammals and birds from low latitudes (0–308), including species from tropical and subtropical regions, are heterothermic and employ Torpor. Use of Torpor is especially important for bats because they are small, expend large amounts of energy when active, rely on a fluctuating food supply, and have only a limited capacity for storage of fat. Patterns of Torpor in tropical/subtropical bats are highly variable, but short bouts of Torpor with relatively high body temperatures (Tb) are most common. Hibernation (a sequence of multiday bouts of Torpor) has been reported for free-ranging subtropical tree-dwelling vespertilionids, cave-dwelling hipposiderids, and house-dwelling molossids. The observed range of minimum Tb is � 6–308C, and the reduction of energy expenditure through the use of Torpor, in comparison to normothermic values, ranges from 50 to 99%. Overall, Torpor in the tropics/ subtropics has been reported for 10 out of the currently recognized 18 bat families, which contain 1079 species, or 96.7% of all bats. Although it is unlikely that all of these are heterothermic, the large majority probably will be. Frequent use of Torpor, including hibernation in diverse groups of tropical/subtropical bats, suggests that heterothermy is an ancestral chiropteran trait. Although data especially from the field are still scarce, it is likely that Torpor, highly effective in reducing requirements for energy and water even under warm conditions, plays a crucial role in the long-term survival of the majority of small tropical and subtropical bats. Discovering how bats achieve this provides numerous opportunities for exiting new research.
Gerhard Kortne - One of the best experts on this subject based on the ideXlab platform.
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a new cue for Torpor induction charcoal ash and smoke
The Journal of Experimental Biology, 2017Co-Authors: Clare Stawski, Gerhard Kortne, Julia Nowack, Fritz GeiseAbstract:ABSTRACT Recent work has shown that the use of Torpor for energy conservation increases after forest fires in heterothermic mammals, probably in response to the reduction of food. However, the specific environmental cues for this increased Torpor expression remain unknown. It is possible that smoke and the novel substrate of charcoal and ash act as signals for an impending period of starvation requiring Torpor. We therefore tested the hypothesis that the combined cues of smoke, a charcoal/ash substrate and food shortage will enhance Torpor expression in a small forest-dwelling marsupial, the yellow-footed antechinus ( Antechinus flavipes ), because like other animals that live in fire-prone habitats they must effectively respond to fires to ensure survival. Activity and body temperature patterns of individuals in outdoor aviaries were measured under natural environmental conditions. All individuals were strictly nocturnal, but diurnal activity was observed shortly after smoke exposure. Overall, Torpor in females was longer and deeper than that in males. Interestingly, while both males and females increased daily Torpor duration during food restriction by >2-fold as anticipated, a combination of food restriction and smoke exposure on a charcoal/ash substrate further increased daily Torpor duration by ∼2-fold in both sexes. These data show that this combination of cues for Torpor induction is stronger than food shortage on its own. Our study provides significant new information on how a small forest-dwelling mammal responds to fire cues during and immediately after a fire and identifies a new, not previously recognised, regulatory mechanism for thermal biology in mammals.
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the key to winter survival daily Torpor in a small arid zone marsupial
Naturwissenschaften, 2009Co-Authors: Gerhard Kortne, Fritz GeiseAbstract:Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active individuals. In contrast, the widely held view is that daily Torpor reduces energy expenditure usually by about 30%, is employed for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on laboratory studies, whereas knowledge on daily Torpor in the field is scant. We used temperature telemetry to quantify thermal biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily Torpor is a crucial survival strategy of this species in winter. All individuals entered Torpor daily with the exception of a single male that remained normothermic for a single day (Torpor on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T a) ranging from approximately −1°C to 36°C. Dunnarts usually entered Torpor during the night and aroused at midday with the daily increase of T a. Torpor was on average about twice as long (mean 11.0 ± 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally omitted activity for several days in sequence. Consequently, we estimate that daily Torpor in this species can reduce daily energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily Torpor is an essential mechanism for overcoming energetic challenges during winter and that Torpor data obtained in the laboratory can substantially underestimate the ecological significance of daily Torpor in the wild.
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winter Torpor in a large bird
Nature, 2000Co-Authors: Gerhard Kortne, Mark R Igham, Fritz GeiseAbstract:Torpor is a natural state in which animals show a substantial and controlled reduction of body temperature to conserve energy1,2. A few small birds (weighing less than 80 g) are known to use it as a survival strategy in winter, but we have discovered that a large bird, the Australian tawny frogmouth, which weighs 500 g, can also enter this state. This surprising finding increases the size of birds known to use natural Torpor by almost tenfold, suggesting that avian Torpor is more widespread than is commonly believed, enabling birds to stay in their territory throughout the year.
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Torpor and activity patterns in free ranging sugar gliders petaurus breviceps marsupialia
Oecologia, 2000Co-Authors: Gerhard Kortne, Fritz GeiseAbstract:Almost all studies on daily Torpor in mammals have been conducted in the laboratory under constant environmental conditions. We investigated Torpor and activity patterns in free-ranging sugar gliders (Petaurus breviceps, 100 g) using temperature telemetry and compared field data with published information obtained in the laboratory. Body and/or skin temperature and activity patterns of 12 sugar gliders were monitored from autumn to spring. Healthy sugar gliders were active between sunset and sunrise, but on cold or rainy nights activity was substantially reduced. Animals in poor condition occasionally foraged during the day. Eleven gliders were monitored for 8–171 days and all of these entered daily Torpor. Torpor was observed on 103 days (17% of observation days), usually occurred on rainy or cold nights, and frequency of Torpor changed with season. Torpor bouts lasted between 2 and 23 h (average 13 h) and the body temperature fell to a minimum of 10.4°C. Torpor was thus much deeper, longer and more frequent than in laboratory studies on the same species. Our study shows that cold or wet conditions curtail foraging in wild sugar gliders and that they employ daily Torpor regularly during adverse weather. This suggests that minimisation of energy loss by the use of Torpor in sugar gliders is pivotal for their survival in the wild.
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do patterns of Torpor differ between free ranging and captive mammals and birds
2000Co-Authors: Fritz Geise, Joanne C Holloway, Gerhard Kortne, Tracy A Maddocks, Christophe Turbill, Mark R IghamAbstract:Most studies on Torpor in mammals and birds have been conducted in the laboratory. We compared whether patterns of Torpor of several mammals and birds differ between the laboratory and field. Our comparison shows that in most species patterns of Torpor in the laboratory differ substantially from those in the field. Some species, even if they use Torpor extensively in the field, appear most reluctant to enter Torpor in captivity. Moreover, Torpor in the field is often more frequent, deeper, and longer than in captivity. Our comparison suggests that laboratory studies are likely to underestimate use and depth of Torpor in the wild and thus may underestimate its impact on energy expenditure and survival.
Onwy M Mcalla - One of the best experts on this subject based on the ideXlab platform.
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Torpor during reproduction in mammals and birds dealing with an energetic conundrum
Integrative and Comparative Biology, 2014Co-Authors: Onwy M Mcalla, Fritz GeiseAbstract:Torpor and reproduction in mammals and birds are widely viewed as mutually exclusive processes because of opposing energetic and hormonal demands. However, the reported number of heterothermic species that express Torpor during reproduction is ever increasing, to some extent because of recent work on free-ranging animals. We summarize current knowledge about those heterothermic mammals that do not express Torpor during reproduction and, in contrast, examine those heterothermic birds and mammals that do use Torpor during reproduction. Incompatibility between Torpor and reproduction occurs mainly in high-latitude sciurid and cricetid rodents, which live in strongly seasonal, but predictably productive habitats in summer. In contrast, Torpor during incubation, brooding, pregnancy, or lactation occurs in nightjars, hummingbirds, echidnas, several marsupials, tenrecs, hedgehogs, bats, carnivores, mouse lemurs, and dormice. Animals that enter Torpor during reproduction often are found in unpredictable habitats, in which seasonal availability of food can be cut short by changes in weather, or are species that reproduce fully or partially during winter. Moreover, animals that use Torpor during the reproductive period have relatively low reproductive costs, are largely insectivorous, carnivorous, or nectarivorous, and thus rely on food that can be unpredictable or strongly seasonal. These species with relatively unpredictable food supplies must gain an advantage by using Torpor during reproduction because the main cost is an extension of the reproductive period; the benefit is increased survival of parent and offspring, and thus fitness.
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coping with chaos unpredictable food supplies intensify Torpor use in an arid zone marsupial the fat tailed dunnart sminthopsis crassicaudata
Naturwissenschaften, 2010Co-Authors: Onwy M McallaAbstract:The severity, duration and amplitude of extreme weather events are forecast to intensify with current climate trends, over both long (e.g. seasonal) and short (e.g. daily) time-scales. As such, the predictability of food supplies for many small endotherms is likely to become increasingly important. Numerous small mammals and birds combat food shortages using Torpor, a controlled reduction in metabolic rate and body temperature that helps lower their daily energy requirements. As such, Torpor often has been cited as a key feature allowing some small endotherms to survive highly unpredictable climates, such as tropics or dry deserts, but mensurative demonstrations of this are lacking. We have shown here that when a small desert marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata), is offered unpredictable levels of daily food, they increase frequency of daily Torpor and length of bouts compared with animals offered ad libitum food, but this was not found for animals offered a 70% food-restricted diet. Our data suggest that simple food restriction may not be sufficient for evaluating the efficacy of Torpor as a strategy for managing unpredictable climates.
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photoperiod affects daily Torpor and tissue fatty acid composition in deer mice
Naturwissenschaften, 2007Co-Authors: Fritz Geise, Onwy M Mcalla, G J Kenagy, Sara M HiebeAbstract:Photoperiod and dietary lipids both influence thermal physiology and the pattern of Torpor of heterothermic mammals. The aim of the present study was to test the hypothesis that photoperiod-induced physiological changes are linked to differences in tissue fatty acid composition of deer mice, Peromyscus maniculatus (∼18-g body mass). Deer mice were acclimated for >8 weeks to one of three photoperiods (LD, light/dark): LD 8:16 (short photoperiod), LD 12:12 (equinox photoperiod), and LD 16:8 (long photoperiod). Deer mice under short and equinox photoperiods showed a greater occurrence of Torpor than those under long photoperiods (71, 70, and 14%, respectively). The duration of Torpor bouts was longest in deer mice under short photoperiod (9.3 ± 2.6 h), intermediate under equinox photoperiod (5.1 ± 0.3 h), and shortest under long photoperiod (3.7 ± 0.6 h). Physiological differences in Torpor use were associated with significant alterations of fatty acid composition in ∼50% of the major fatty acids from leg muscle total lipids, whereas white adipose tissue fatty acid composition showed fewer changes. Our results provide the first evidence that physiological changes due to photoperiod exposure do result in changes in lipid composition in the muscle tissue of deer mice and suggest that these may play a role in survival of low body temperature and metabolic rate during Torpor, thus, enhancing favourable energy balance over the course of the winter.
Clare Stawski - One of the best experts on this subject based on the ideXlab platform.
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more functions of Torpor and their roles in a changing world
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2017Co-Authors: Julia Nowack, Clare Stawski, Fritz GeiseAbstract:Increased winter survival by reducing energy expenditure in adult animals is often viewed as the primary function of Torpor. However, Torpor has many other functions that ultimately increase the survival of heterothermic mammals and birds. In this review, we summarize new findings revealing that animals use Torpor to cope with the conditions during and after natural disasters, including fires, storms, and heat waves. Furthermore, we suggest that Torpor, which also prolongs longevity and was likely crucial for survival of mammals during the time of the dinosaur extinctions, will be advantageous in a changing world. Climate change is assumed to lead to an increase in the occurrence and intensity of climatic disasters, such as those listed above and also abnormal floods, droughts, and extreme temperatures. The opportunistic use of Torpor, found in many heterothermic species, will likely enhance survival of these challenges, because these species can reduce energy and foraging requirements. However, many strictly seasonal hibernators will likely face the negative consequences of the predicted increase in temperature, such as range contraction. Overall, available data suggest that opportunistic heterotherms with their flexible energy requirements have an adaptive advantage over homeotherms in response to unpredictable conditions.
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a new cue for Torpor induction charcoal ash and smoke
The Journal of Experimental Biology, 2017Co-Authors: Clare Stawski, Gerhard Kortne, Julia Nowack, Fritz GeiseAbstract:ABSTRACT Recent work has shown that the use of Torpor for energy conservation increases after forest fires in heterothermic mammals, probably in response to the reduction of food. However, the specific environmental cues for this increased Torpor expression remain unknown. It is possible that smoke and the novel substrate of charcoal and ash act as signals for an impending period of starvation requiring Torpor. We therefore tested the hypothesis that the combined cues of smoke, a charcoal/ash substrate and food shortage will enhance Torpor expression in a small forest-dwelling marsupial, the yellow-footed antechinus ( Antechinus flavipes ), because like other animals that live in fire-prone habitats they must effectively respond to fires to ensure survival. Activity and body temperature patterns of individuals in outdoor aviaries were measured under natural environmental conditions. All individuals were strictly nocturnal, but diurnal activity was observed shortly after smoke exposure. Overall, Torpor in females was longer and deeper than that in males. Interestingly, while both males and females increased daily Torpor duration during food restriction by >2-fold as anticipated, a combination of food restriction and smoke exposure on a charcoal/ash substrate further increased daily Torpor duration by ∼2-fold in both sexes. These data show that this combination of cues for Torpor induction is stronger than food shortage on its own. Our study provides significant new information on how a small forest-dwelling mammal responds to fire cues during and immediately after a fire and identifies a new, not previously recognised, regulatory mechanism for thermal biology in mammals.
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hibernation and Torpor in tropical and subtropical bats in relation to energetics extinctions and the evolution of endothermy
Integrative and Comparative Biology, 2011Co-Authors: Fritz Geiser, Clare StawskiAbstract:Synopsis Torpor, the most effective means of energy conservation available to endotherms, is still widely viewed as a specific adaptation in a few high-latitude, cold-climate endotherms with no adaptive function in warm regions. Nevertheless, a growing number of diverse terrestrial mammals and birds from low latitudes (0–308), including species from tropical and subtropical regions, are heterothermic and employ Torpor. Use of Torpor is especially important for bats because they are small, expend large amounts of energy when active, rely on a fluctuating food supply, and have only a limited capacity for storage of fat. Patterns of Torpor in tropical/subtropical bats are highly variable, but short bouts of Torpor with relatively high body temperatures (Tb) are most common. Hibernation (a sequence of multiday bouts of Torpor) has been reported for free-ranging subtropical tree-dwelling vespertilionids, cave-dwelling hipposiderids, and house-dwelling molossids. The observed range of minimum Tb is � 6–308C, and the reduction of energy expenditure through the use of Torpor, in comparison to normothermic values, ranges from 50 to 99%. Overall, Torpor in the tropics/ subtropics has been reported for 10 out of the currently recognized 18 bat families, which contain 1079 species, or 96.7% of all bats. Although it is unlikely that all of these are heterothermic, the large majority probably will be. Frequent use of Torpor, including hibernation in diverse groups of tropical/subtropical bats, suggests that heterothermy is an ancestral chiropteran trait. Although data especially from the field are still scarce, it is likely that Torpor, highly effective in reducing requirements for energy and water even under warm conditions, plays a crucial role in the long-term survival of the majority of small tropical and subtropical bats. Discovering how bats achieve this provides numerous opportunities for exiting new research.
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Fat and fed: frequent use of summer Torpor in a subtropical bat
Naturwissenschaften, 2010Co-Authors: Clare Stawski, Fritz GeiserAbstract:A widely held view is that Torpor is avoided by mammals whenever possible because of potential costs associated with reduced body temperatures and slowed metabolic processes. We examined this hypothesis by quantifying use of Torpor in relation to body condition of free-ranging northern long-eared bats ( Nyctophilus bifax , approximately 10 g), a species known to hibernate, from a subtropical region during the austral summer when insects were abundant. Temperature-telemetry revealed that bats used Torpor on 85% of observation days and on 38% of all nights. Torpor bouts ranged from 0.7 to 21.2 h, but the relationship between duration of Torpor bouts and ambient temperature was not significant. However, skin temperature of torpid bats was positively correlated with ambient temperature. Against predictions, individuals with a high body condition index (i.e., good fat/energy reserves) expressed longer and deeper Torpor bouts and also employed Torpor more often during the activity phase at night than those with low body condition index. We provide the first evidence that use of Torpor in a free-ranging subtropical mammal is positively related with high body condition index. This suggests that employment of Torpor is maximised and foraging minimised not because of food shortages or low energy stores but likely to avoid predation when bats are not required to feed.
