ORCID Profile
0000-0001-7621-5049
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University of New England
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Publisher: Royal Zoological Society of New South Wales
Date: 2010
DOI: 10.7882/AZ.2010.009
Publisher: Springer Science and Business Media LLC
Date: 09-03-2010
DOI: 10.1007/S00360-010-0459-9
Abstract: Many small desert dasyurids employ torpor almost daily during winter, because cold nights and low food availability impose high energetic costs. However, in Western Australia the arid zone extends into tropical, coastal regions, where winter temperature conditions are far less severe. We studied the thermal biology and activity patterns of free-ranging kaluta (approximately 27 g), a dasyurid restricted to these tropical spinifex deserts, during the Austral winter (June-July) and in addition quantified activity patterns in captivity. Unlike most dasyurids, wild and captive kalutas were almost exclusively diurnal and retreated into underground burrows during the night. Despite being active during the warmer part of the day, kalutas entered torpor daily. However, torpor patterns differed remarkably between males and females. While females spent most of the night torpid at body temperatures (T (b)) as low as 21 degrees C, close to soil temperature, males entered multiple short and shallow bouts (T (b) > 25 degrees C) during the night. Males also maintained higher T (b)s during the early morning when active, occupied larger home ranges and covered greater distances while foraging than females. Hence, males appear to expend more energy than the similar-sized females both while foraging and during the rest phase. We propose that physiological as well as behavioural preparations for the September mating season that culminate in a complete male die-off might already impose energetic costs on males during winter.
Publisher: Wiley
Date: 11-2016
DOI: 10.1111/JNE.12437
Abstract: Endothermic mammals and birds require intensive energy turnover to sustain high body temperatures and metabolic rates. To cope with the energetic bottlenecks associated with the change of seasons, and to minimise energy expenditure, complex mechanisms and strategies are used, such as daily torpor and hibernation. During torpor, metabolic depression and low body temperatures save energy. However, these bouts of torpor, lasting for hours to weeks, are interrupted by active 'euthermic' phases with high body temperatures. These dynamic transitions require precise communication between the brain and peripheral tissues to defend rheostasis in energetics, body mass and body temperature. The hypothalamus appears to be the major control centre in the brain, coordinating energy metabolism and body temperature. The sympathetic nervous system controls body temperature by adjustments of shivering and nonshivering thermogenesis, with the latter being primarily executed by brown adipose tissue. Over the last decade, comparative physiologists have put forward integrative studies on the ecophysiology, biochemistry and molecular regulation of energy balance in response to seasonal challenges, food availability and ambient temperature. Mammals coping with such environments comprise excellent model organisms for studying the dynamic regulation of energy metabolism. Beyond the understanding of how animals survive in nature, these studies also uncover general mechanisms of mammalian energy homeostasis. This research will benefit efforts of translational medicine aiming to combat emerging human metabolic disorders. The present review focuses on recent advances in the understanding of energy balance and its neuronal and endocrine control during the most extreme metabolic fluctuations in nature: daily torpor and hibernation.
Publisher: Springer Science and Business Media LLC
Date: 05-1986
DOI: 10.1007/BF01946695
Publisher: Springer Science and Business Media LLC
Date: 21-04-2017
Publisher: Informa UK Limited
Date: 12-1997
DOI: 10.1071/MU97046
Publisher: Springer Science and Business Media LLC
Date: 06-12-2005
DOI: 10.1007/S00360-005-0038-7
Abstract: During roosting in summer, reproductive female bats appear to use torpor less frequently and at higher body temperatures (Tb) than male bats, ostensibly to maximise offspring growth. To test whether field observations result from differences in thermal physiology or behavioural thermoregulation during roosting, we measured the thermoregulatory response and energetics of captive pregnant and lactating female and male long-eared bats (Nyctophilus geoffroyi 8.9 g and N. gouldi 11.5 g) during overnight exposure to a constant ambient temperature (Ta) of 15 degrees C. Bats were captured 1-1.5 h after sunset and measurements began at 21:22+/-0:36 h. All N. geoffroyi entered torpor commencing at 23:47+/-01:01 h. For N. gouldi, 10/10 males, 9/10 pregnant females and 7/8 lactating females entered torpor commencing at 01:10+/-01:40 h. The minimum Tb of torpid bats was 15.6+/-1.1 degrees C and torpid metabolic rate (TMR) was reduced to 0.05+/-0.02 ml O2 g(-1) h(-1). Sex or reproductive condition of either species did not affect the timing of entry into torpor (F=1.5, df=2, 19, P=0.24), minimum TMR (F=0.21, df=4, 40, P=0.93) or minimum Tb (F=0.76, df=5, 41, P=0.58). Moreover, sex or reproductive condition did not affect the allometric relationship between minimum resting metabolic rate and body mass (F=1.1, df=4, 37, P=0.37). Our study shows that under identical thermal conditions, thermal physiology of pregnant and lactating female and male bats are indistinguishable. This suggests that the observed reluctance by reproductive females to enter torpor in the field is predominantly because of ecological rather than physiological differences, which reflect the fact that females roost gregariously whereas male bats typically roost solitarily.
Publisher: Springer Science and Business Media LLC
Date: 09-1994
DOI: 10.1007/BF00346446
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1007/BF00692755
Publisher: Springer Science and Business Media LLC
Date: 10-1995
DOI: 10.1007/BF00387311
Publisher: Elsevier BV
Date: 10-2005
Publisher: Springer Science and Business Media LLC
Date: 25-01-2021
DOI: 10.1007/S00114-007-0215-5
Abstract: When food is limited and/or environmental conditions are unfavourable, many mammals reduce activity and use torpor to save energy. Nevertheless, reliable predictors for torpor occurrence, especially in the wild, are currently not available. Interrelations between torpor use and other energy conserving strategies are also poorly understood. We tested the hypothesis that reductions in normothermic body temperature (T(b)) and the period of activity before torpor events could be used as predictors for torpor occurrence in sugar gliders, Petaurus breviceps (body mass, approximately 125 g), known to display daily torpor in the wild. Occurrence of torpor was preceded by significant (approximately 10-25%) reductions of the duration of the activity phase. Moreover, the normothermic resting T(b) fell by an average of 1.2 degrees C over 3 days before a torpor event, relative to in iduals that did not display torpor. Our new findings suggest that before entering torpor, sugar gliders, which appear to use torpor as an emergency measure rather than a routine energy saving strategy, systematically reduce activity times and normothermic resting T(b)s to lower energy expenditure and perhaps to avoid employing torpor. Thus, reduced activity and normothermic T(b) may provide a predictive tool for the occurrence of daily torpor in the wild.
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.CBPA.2010.04.018
Abstract: Giles' planigale (Planigale gilesi) is among the smallest extant marsupials and inhabits deep soil cracks in arid floodplains. We examined whether its physiology shows specific adaptations to its extreme habitat. Metabolic rate, body temperature, evaporative water loss and thermal conductance were measured for eight planigales (average mass 9 g) exposed to four different ambient temperatures ranging from 10 degrees C to 32 degrees C. Water economy and respiratory variables were measured for the first time in this species. All of these standard physiological variables conformed to allometrically-predicted values for a marsupial. All variables were significantly affected by ambient temperature, except tidal volume and dry thermal conductance. Metabolic rate increased substantially at low ambient temperatures, as required to maintain a relatively constant body temperature of about 32-34 degrees C. This increased oxygen demand was accommodated by increased ventilation rather than increased oxygen extraction. Planigales had a comparatively high point of relative water economy of 19.1 degrees C, consistent with their small body size and arid habitat. Torpor reduced energy expenditure by 79% and evaporative water loss by 62%. Our study suggests that torpor use, along with behavioural adaptations, suffice for P. gilesi to live underground in arid habitats without further physiological adaptations.
Publisher: Springer Science and Business Media LLC
Date: 30-03-2000
Abstract: Previous studies have suggested that Australian long-eared bats (Nyctophilus) differ from northern-hemisphere bats with respect to their thermal physiology and patterns of torpor. To determine whether this is a general trait of Australian bats, we characterised the temporal organisation of torpor and quantified metabolic rates and body temperatures of normothermic and torpid Australian bats (Nyctophilus geoffroyi, 7 g and N. gouldi, 10 g) over a range of air temperatures and in different seasons. The basal metabolic rate of normothermic bats was 1.36 +/- 0.17 ml g(-1) h(-1) (N. geoffroyi) and 1.22 +/- 0.13 ml g(-1) h(-1) (N. gouldi), about 65% of that predicted by allometric equations, and the corresponding body temperature was about 36 degrees C. Below an air temperature of about 25 degrees C bats usually remained normothermic for only brief periods and typically entered torpor. Arousal from torpor usually occurred shortly after the beginning of the dark phase and torpor re-entry occurred almost always during the dark phase after normothermic periods of only 111 +/- 48 min (N. geoffroyi) and 115 +/- 66 min (N. gouldi). At air temperatures below 10 degrees C, bats remained torpid for more than 1 day. Bats that were measured overnight had steady-state torpor metabolic rates representing only 2.7% (N. geoffroyi) and 4.2% (N. gouldi) of the basal metabolic rate, and their body temperatures fell to minima of 1.4 and 2.3 degrees C, respectively. In contrast, bats measured entirely during the day, as in previous studies, had torpor metabolic rates that were up to ten times higher than those measured overnight. The steady-state torpor metabolic rate of thermoconforming torpid bats showed an exponential relationship with body temperature (r2 = 0.94), suggesting that temperature effects are important for reduction of metabolic rate below basal levels. However, the 75% reduction of metabolic rate between basal metabolic rate and torpor metabolic rate at a body temperature of 29.3 degrees C suggests that metabolic inhibition also plays an important role. Torpor metabolic rate showed little or no seasonal change. Our study suggests that Australian Nyctophilus bats have a low basal metabolic rate and that their patterns of torpor are similar to those measured in bats from the northern hemisphere. The low basal metabolic rate and the high proclivity of these bats for using torpor suggest that they are constrained by limited energy availability and that heterothermy plays a key role in their natural biology.
Publisher: Oxford University Press (OUP)
Date: 15-04-2011
Publisher: Oxford University Press (OUP)
Date: 24-07-2424
Publisher: Springer Science and Business Media LLC
Date: 1984
DOI: 10.1007/BF00688801
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/ZO20025
Abstract: We aim to summarise what is known about torpor use and patterns in Australian and New Zealand (ANZ) bats from temperate, tropical/subtropical and arid/semiarid regions and to identify whether and how they differ. ANZ bats comprise ~90 species from 10 families. Members of at least nine of these are known to use torpor, but detailed knowledge is currently restricted to the pteropodids, molossids, mystacinids, and vespertilionids. In temperate areas, several species can hibernate (use a sequence of multiday torpor bouts) in trees or caves mostly during winter and continue to use short bouts of torpor for the rest of the year, including while reproducing. Subtropical vespertilionids also use multiday torpor in winter and brief bouts of torpor in summer, which permit a reduction in foraging, probably in part to avoid predators. Like temperate-zone vespertilionids they show little or no seasonal change in thermal energetics during torpor, and observed changes in torpor patterns in the wild appear largely due to temperature effects. In contrast, subtropical blossom-bats (pteropodids) exhibit more pronounced daily torpor in summer than winter related to nectar availability, and this involves a seasonal change in physiology. Even in tropical areas, vespertilionids express short bouts of torpor lasting ~5 h in winter summer data are not available. In the arid zone, molossids and vespertilionids use torpor throughout the year, including during desert heat waves. Given the same thermal conditions, torpor bouts in desert bats are longer in summer than in winter, probably to minimise water loss. Thus, torpor in ANZ bats is used by members of all or most families over the entire region, its regional and seasonal expression is often not pronounced or as expected, and it plays a key role in energy and water balance and other crucial biological functions that enhance long-term survival by in iduals.
Publisher: The Company of Biologists
Date: 15-01-2017
DOI: 10.1242/JEB.146548
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 in iduals in outdoor aviaries were measured under natural environmental conditions. All in iduals 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 & -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.
Publisher: Wiley
Date: 28-07-2007
Publisher: Springer Science and Business Media LLC
Date: 30-08-2013
DOI: 10.1007/S00360-013-0779-7
Abstract: Bats are among the most successful groups of Australian arid-zone mammals and, therefore, must cope with pronounced seasonal fluctuations in ambient temperature (T a), food availability and unpredictable weather patterns. As knowledge about the energy conserving strategies in desert bats is scant, we used temperature-telemetry to quantify the thermal physiology of tree-roosting inland freetail bats (Mormopterus species 3, 8.5 g, n = 8) at Sturt National Park over two summers (2010-2012), when T a was high and insects were relatively abundant. Torpor use and activity were affected by T a. Bats remained normothermic on the warmest days they employed one "morning" torpor bout on most days and typically exhibited two torpor bouts on the coolest days. Overall, animals employed torpor on 67.9 % of bat-days and torpor bout duration ranged from 0.5 to 39.3 h. At any given T a, torpor bouts were longer in Mormopterus than in bats from temperate and subtropical habitats. Furthermore, unlike bats from other climatic regions that used only partial passive rewarming, Mormopterus aroused from torpor using either almost entirely passive (68.9 % of all arousals) or active rewarming (31.1 %). We provide the first quantitative data on torpor in a free-ranging arid-zone molossid during summer. They demonstrate that this desert bat uses torpor extensively in summer and often rewarms passively from torpor to maximise energy and water conservation.
Publisher: Annual Reviews
Date: 03-2004
DOI: 10.1146/ANNUREV.PHYSIOL.66.032102.115105
Abstract: ▪ Abstract Although it is well established that during periods of torpor heterothermic mammals and birds can reduce metabolic rates (MR) substantially, the mechanisms causing the reduction of MR remain a controversial subject. The comparative analysis provided here suggests that MR reduction depends on patterns of torpor used, the state of torpor, and body mass. Daily heterotherms, which are species that enter daily torpor exclusively, appear to rely mostly on the fall of body temperature (T b ) for MR reduction, perhaps with the exception of very small species and at high torpor T b , where some metabolic inhibition may be used. In contrast, hibernators (species capable of prolonged torpor bouts) rely extensively on metabolic inhibition, in addition to T b effects, to reduce MR to a fraction of that observed in daily heterotherms. In small hibernators, metabolic inhibition and the large fall of T b are employed to maximize energy conservation, whereas in large hibernators, metabolic inhibition appears to be employed to facilitate MR and T b reduction at torpor onset. Over the ambient temperature (T a ) range where torpid heterotherms are thermo-conforming, the T b -T a differential is more or less constant despite a decline of MR with T a however, in thermo-regulating torpid in iduals, the T b -T a differential is maintained by a proportional increase of MR as during normothermia, albeit at a lower T b . Thermal conductance in most torpid thermo-regulating in iduals is similar to that in normothermic in iduals despite the substantially lower MR in the former. However, conductance is low when deeply torpid animals are thermo-conforming probably because of peripheral vasoconstriction.
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.JTHERBIO.2016.07.015
Abstract: Although roost choice in bats has been studied previously, little is known about how opposing roost colours affect the expression of torpor quantitatively. We quantified roost selection and thermoregulation in a captive Australian insectivorous bat, Nyctophilus gouldi (n=12) in winter when roosting in black and white coloured boxes using temperature-telemetry. We quantified how roost choice influences torpor expression when food was provided ad libitum or restricted in bats housed together in an outdoor aviary exposed to natural fluctuations of ambient temperature. Black box temperatures averaged 5.1°C (maximum 7.5°C) warmer than white boxes at their maximum daytime temperature. Bats fed ad libitum chose black boxes on most nights (92.9%) and on 100% of nights when food-restricted. All bats used torpor on all study days. However, bats fed ad libitum and roosting in black boxes used shorter torpor and spent more time normothermic/active at night than food-restricted bats and bats roosting in white boxes. Bats roosting in black boxes also rewarmed passively more often and to a higher skin temperature than those in white boxes. Our study suggests that N. gouldi fed ad libitum select warmer roosts in order to passively rewarm to a higher skin temperature and thus save energy required for active midday rewarming as well as to maintain a normothermic body temperature for longer periods at night. This study shows that colour should be considered when deploying bat boxes black boxes are preferable for those bats that use passive rewarming, even in winter when food availability is reduced.
Publisher: American Physiological Society
Date: 08-2011
DOI: 10.1152/AJPREGU.00792.2010
Abstract: Although many tropical and subtropical areas experience pronounced seasonal changes in weather and food availability, few studies have examined and none have compared the thermal physiology and energetics of a hibernating mammal that is restricted to these regions. We quantified thermal energetics of northern long-eared bats ( Nyctophilus bifax body mass ∼10 g) during summer, winter, and spring from a subtropical habitat, and also during winter from a tropical habitat, to determine how N. bifax cope with climate and seasonal changes in weather. We captured bats in the wild and measured metabolic rates via open-flow respirometry. The basal metabolic rate of subtropical bats at an ambient temperature (T a ) of 32.6 ± 0.7°C was 1.28 ± 0.06 ml O 2 ·g −1 ·h −1 during both summer and winter, similar to other species of Nyctophilus. Resting metabolic rates below the thermoneutral zone increased similarly with decreasing T a during all seasons and in both regions. All in iduals showed a high proclivity to enter torpor at T a values below the thermoneutral zone. Metabolic rates in torpid thermoconforming bats fell with T a and body temperature, and mean minimum metabolic rates during torpor were similar during all seasons and in both regions and as predicted from body mass in temperate zone hibernators. At very low T a , torpid N. bifax thermoregulated, and this threshold T a differed significantly between subtropical (T a = 3.5 ± 0.3°C) and tropical (T a = 6.7 ± 0.7°C) in iduals, but not between seasons. Our data show that thermal energetics of N. bifax do not vary seasonally and in many aspects are similar in tropical and subtropical bats however, torpid in iduals from the subtropics allow body temperature to fall to significantly lower values than those from the tropics.
Publisher: Elsevier BV
Date: 02-1999
Publisher: Elsevier
Date: 2010
Publisher: Springer Science and Business Media LLC
Date: 10-06-2016
DOI: 10.1007/S00114-016-1376-X
Abstract: Mammalian fur often shows agouti banding with a proximal dark band near the skin and a lighter distal band. We examined the function of both bands in relation to camouflage, thermal properties of pelts, and thermal energetics of dunnarts (Sminthopsis crassicaudata), which are known to use torpor and basking. Although the distal band of dunnart fur darkened with increasing latitude, which is important for camouflage, it did not affect the thermal properties and the length of the dark band and total hair length were not correlated. In contrast, the length of the proximal dark band of preserved pelts exposed to sunlight was positively correlated (r (2) = 0.59) with the temperature underneath the pelt (T pelt). All dunnarts offered radiant heat basked by exposing the dark band of the hair during both rest and torpor. Basking dunnarts with longer dark bands had lower resting metabolism (r (2) = 0.69), warmed faster from torpor (r (2) = 0.77), required less energy to do so (r (2) = 0.32), and reached a higher subcutaneous temperature (T sub) at the end of rewarming (r (2) = 0.75). We provide the first experimental evidence on the possible dual function of the color banding of mammalian fur. The distal colored band appears to be important for camouflage, whereas the length of the dark proximal hair band facilitates heat gain for energy conservation and allows animals to rewarm quickly and economically from torpor.
Publisher: Springer Science and Business Media LLC
Date: 05-2006
Publisher: Springer Science and Business Media LLC
Date: 29-04-2005
DOI: 10.1007/S00360-005-0488-Y
Abstract: Metabolic rate and evaporative water loss (EWL) were measured for a small, arid-zone marsupial, the stripe-faced dunnart (Sminthopsis macroura), when normothermic and torpid. Metabolic rate increased linearly with decreasing ambient temperature (T(a)) for normothermic dunnarts, and calculated metabolic water production (MWP) ranged from 0.85+/-0.05 (T(a)=30 degrees C) to 3.13+/-0.22 mg H2O g(-1) h(-1) (T(a)=11 degrees C). Torpor at T(a)=11 and 16 degrees C reduced MWP to 24-36% of normothermic values. EWL increased with decreasing T(a), and ranged from 1.81+/-0.37 (T(a)=30 degrees C) to 5.26+/-0.86 mg H2O g(-1) h(-1) (T(a)=11 degrees C). Torpor significantly reduced absolute EWL to 23.5-42.3% of normothermic values, resulting in absolute water savings of 50-55 mg H2O h(-1). The relative water economy (EWL/MWP) of the dunnarts was unfavourable, remaining >1 at all T(a) investigated, and did not improve with torpor. Thus torpor in stripe-faced dunnarts results in absolute, but not relative, water savings.
Publisher: Wiley
Date: 19-03-2021
DOI: 10.1002/TQEM.21737
Abstract: Developing countries located in the tropics have favorable climates to develop modern agriculture and agriculture‐based industry. Peru and Indonesia are ex les of two developing countries located in the tropics with economies based on the export of agricultural products. The generation of agricultural and forest residues has continuously increased in these countries. In this paper, we analyze the availability of agricultural and forest products in Peru and Indonesia in order to calculate the number of residues that could potentially be used for different applications such as energy generation and composite materials production. A single index taking into account the technical, economic, and environmental performance of these residues‐based products was utilized to compare them. The results showed that, in addition to the generation of energy, the production of plastic bio‐based composites and activated carbon are viable alternatives for the use of these residues.
Publisher: The Royal Society
Date: 05-2017
Abstract: To cope with the post-fire challenges of decreased availability of food and shelter, brown antechinus ( Antechinus stuartii ), a small marsupial mammal, increase the use of energy-conserving torpor and reduce activity. However, it is not known how long it takes for animals to resume pre-fire torpor and activity patterns during the recovery of burnt habitat. Therefore, we tested the hypothesis that antechinus will adjust torpor use and activity after a fire depending on vegetation recovery. We simultaneously quantified torpor and activity patterns for female antechinus from three adjacent areas: (i) the area of a management burn 1 year post-fire, (ii) an area that was burned 2 years prior, and (iii) a control area. In comparison to shortly after the management burn, antechinus in all three groups displayed less frequent and less pronounced torpor while being more active. We provide the first evidence that only 1 year post-fire antechinus resume pre-fire torpor and activity patterns, probably in response to the return of herbaceous ground cover and foraging opportunities.
Publisher: Springer Science and Business Media LLC
Date: 22-09-2006
DOI: 10.1007/S00360-005-0026-Y
Abstract: Altricial mammals and birds become endothermic at about half the size of adults and presumably would benefit energetically from entering torpor at that time. Because little is known about torpor during development in endotherms, we investigated whether after the establishment of endothermic thermoregulation (i.e. the ability to maintain a high body temperature during cold exposure), Sminthopsis macroura, a small (approximately 25 g) insectivorous marsupial, is capable of entering torpor and whether torpor patterns change with growth. Endothermic thermoregulation was established when the nest young reached a body mass of approximately 10 g, and they were capable of entering torpor early during development at approximately 10-12 g, lending some support to the view that torpor is a phylogenetically old mammalian trait. Torpor bout length shortened significantly and the minimum metabolic rate during torpor increased as juveniles approached adult size, and consequently total daily energy expenditure increased steeply with age. Relationships between total daily energy expenditure and body mass during development of S. macroura (slope approximately 1.3) differed substantially from the relationship between basal metabolism and body mass in adult endotherms (slope approximately 0.75) suggesting that the energy expenditure-size relationship during the development differs substantially from that in adults under thermo-neutral conditions. Our study shows that while torpor can substantially reduce energy expenditure during development of endotherms and hence is likely important for survival during energy bottlenecks, it also may enhance somatic growth when food is limited. We therefore hypothesize that torpor during the development in endotherms is far more widespread than is currently appreciated.
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.ENVINT.2013.10.009
Abstract: Exposure to contaminants, often pesticides, has been implicated as a major factor contributing to decreases in bat populations. Bats provide essential ecosystem services and a sustained, thriving population is vital for ecosystem health. Understanding issues threatening their survival is crucial for their protection and conservation. This paper provides the first review for 12years on organic pollutants in bats and aims to investigate trends and any new issues impacting bat resilience. Organochlorine (OC) pesticides have been reported most often, especially in the older literature, with the dichlorodiphenyltrichloroethane (DDT) metabolite, dichlorodiphenyldichloroethylene (DDE), present at highest concentrations in tissues analyzed. The OC pesticide concentrations reported in bat tissues have declined significantly since the late 1970s, presumably as a result of restrictions in use. For ex le, DDE study mean concentrations over time periods 1970-1980, 1981-1999 and 2000-2013 ranged from 2.6-62, 0.05-2.31, 0.08-0.19ppm wet weight, respectively. Exposure, however, still occurs from remaining residues, many years after the compounds have been actively used. In recent years (2000-2013), a range of other organic chemicals have been reported in bat tissues including brominated flame retardants (polybrominated diphenyl ether at a mean concentration of 2.9ppm lipid weight) and perfluorinated compounds (perfluorooctanyl sulfonate at a mean concentration 0.09ppm wet weight). The persistent organic compounds concentrate in tissues with higher fat content notably back-depot fat. Numerous factors influence exposure, residues detected and concentrations in different in iduals, species and tissues which must be understood to provide meaningful assessment of the impacts of exposure. Exposure can lead to not only acute and lethal impacts, but also physiological sub-lethal and chronic effects, often linked to the annual cycle of fat deposition and withdrawal. Current challenges for bat conservation include collation of a more extensive and standardized database of bat exposure, especially to current use pesticides and emerging contaminants, and better prediction and definition of toxicity end points notably for the sub-lethal effects. Understanding sub-lethal effects will be of greater importance for sustaining populations in the longer-term.
Publisher: Springer Science and Business Media LLC
Date: 12-10-2016
DOI: 10.1007/S00360-016-1039-4
Abstract: Wildfires can completely obliterate above-ground vegetation, yet some small terrestrial mammals survive during and after fires. As knowledge about the physiological and behavioural adaptations that are crucial for post-wildfire survival is scant, we investigated the thermal biology of a small insectivorous marsupial (Antechinus flavipes) after a severe forest fire. Some populations of antechinus survived the fire in situ probably by hiding deep in rocky crevices, the only fire-proof sites near where they were trapped. We hypothesised that survival in the post-fire landscape was achieved by decreasing daytime activity and using torpor frequently to save energy. Indeed, daytime activity was less common and torpor expression was substantially higher (≥2-fold) at the post-fire site than observed in an unburnt control site and also in comparison to a laboratory study, both when food was provided ad libitum and withheld. Basking in the post-fire site was also recorded, which was likely used to further reduce energy expenditure. Our data suggest that torpor and basking are used by this terrestrial mammal to reduce energy and foraging requirements, which is important in a landscape where food and shelter are limited and predation pressure typically is increased.
Publisher: Springer Science and Business Media LLC
Date: 07-1996
DOI: 10.1007/BF00263982
Publisher: Wiley
Date: 17-10-2011
Publisher: The Company of Biologists
Date: 15-12-2008
DOI: 10.1242/JEB.023101
Abstract: Daily patterns of body temperature (Tb) and energy expenditure in heterothermic endotherms are affected by changes in ambient temperature (Ta) and selection of suitable microclimates,yet most laboratory studies employ constant Ta to measure metabolic rates. In particular, exposure to a daily temperature cycle, even within rest shelters, may be important in timing of torpor and arousal and determining resting energy costs in wild animals. We tested how captive bats(Nyctophilus geoffroyi 7 g) exposed to a diurnal Ta fluctuation (between 13°C and 27°C), similar to natural conditions in their summer tree roosts, adjusted the timing of daily arousals. To distinguish the effects of Ta and passive rewarming from time of the day, we shifted the heating phase to commence at 06:00 h, 09:00 h or 12:00 h on each day. Bats entered torpor overnight and aroused the next day at a time corresponding to rising Taand passive rewarming. The critical Ta (and torpid Tb) for arousal was not fixed, however, but was lower when heating occurred later in the rest phase, providing the first evidence that the critical arousal Ta is affected by time of the day. Bats re-entered torpor in response to cooling late in the afternoon, yet always aroused at lights off. A period of normothermic thermoregulation was therefore closely synchronised with maximum daily Ta,indicating a trade-off between the benefits and energetic costs of normothermia during resting. Our experiment clearly shows that a daily Ta cycle affects the thermoregulatory behaviour and energetics of these small bats. More generally, these results demonstrate the critical influence of behavioural decisions on the daily energy expenditure of small heterothermic mammals.
Publisher: The Royal Society
Date: 06-2015
Abstract: Wildfires have increased in frequency and intensity worldwide with climate change as a main driving factor. While a number of studies have focused on population changes in regard to fires, there are essentially no quantitative data on behavioural and physiological adjustments that are vital for the persistence of in iduals during and after fires. Here we show that brown antechinus, a small insectivorous marsupial mammal, (i) endured a prescribed fire in situ , (ii) remained in their scorched home range despite unburned areas nearby, and (iii) substantially increased post-fire torpor use and thus reduced foraging requirements and exposure to predators. Hence, torpor is a physiological adaptation that, although not quantified in this context previously, appears to play a key role in post-fire survival for this and other heterothermic species.
Publisher: Springer Science and Business Media LLC
Date: 27-05-2019
DOI: 10.1007/S00114-019-1626-9
Abstract: Torpor in birds is considered to be far less common than in mammals. This is particularly true for passerine birds for which knowledge of torpor expression is scarce, although almost all are small, have high energy expenditure and could profit energetically from using torpor. To assess whether the extent and ersity of avian and especially passerine torpor expression and heterothermy may be currently underestimated because of limited long-term data on free-ranging birds, core body temperature fluctuations were quantified over ~ 4.3 months in a medium-sized honeyeater, the noisy miner (Manorina melanocephala, ~ 75 g), in an open woodland during the cold season in eastern Australia. Miners used shallow nocturnal torpor frequently (63% of days), torpor bouts lasted on average for 6.5 h (maximum 13.5 h) and, unlike during hypothermia, torpor was terminated by endogenous heat production for rewarming. Body temperatures (T
Publisher: Informa UK Limited
Date: 06-2012
DOI: 10.2980/19-2-3464
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.137828
Abstract: Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (& %) when basking at ambient temperatures (Ta) of ∼15 and 0°C. Interestingly, body temperature (Tb) also was significantly reduced from 34.7±0.6°C (Ta 15°C not basking) to 30.4±2.0°C (Ta 0°C basking), which resulted in an extremely low (& % of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at Ta 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average Tb of 22.0±2.6°C movement to the basking l occurred at Tb& .0°C. Energy expenditure for rewarming was significantly reduced (by & %) during radiant heat-assisted rewarming, however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and Tb during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting Tb and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts where basking is common, but also for P. sungorus and likely other cold-climate mammals.
Publisher: American Physiological Society
Date: 12-2014
DOI: 10.1152/AJPREGU.00214.2014
Abstract: Regulated torpor and unregulated hypothermia are both characterized by substantially reduced body temperature (T b ) and metabolic rate (MR), but they differ physiologically. Although the remarkable, medically interesting adaptations accompanying torpor (e.g., tolerance for cold and ischemia, absence of reperfusion injury, and disuse atrophy) often do not apply to hypothermia in homeothermic species such as humans, the terms “torpor” and “hypothermia” are often used interchangeably in the literature. To determine how these states differ functionally and to provide a reliable diagnostic tool for differentiating between these two physiologically distinct states, we examined the interrelations between T b and MR in a mammal ( Sminthopsis macroura) undergoing a bout of torpor with those of the hypothermic response of a similar-sized juvenile rat ( Rattus norvegicus). Our data show that under similar thermal conditions, 1) cooling rates differ substantially (approximately fivefold) between the two states 2) minimum MR is approximately sevenfold higher during hypothermia than during torpor despite a similar T b 3) rapid, endogenously fuelled rewarming occurs in torpor but not hypothermia and 4) the hysteresis between T b and MR during warming and cooling proceeds in opposite directions in torpor and hypothermia. We thus demonstrate clear diagnostic physiological differences between these two states that can be used experimentally to confirm whether torpor or hypothermia has occurred. Furthermore, the data can clarify the results of studies investigating the ability of physiological or pharmacological agents to induce torpor. Consequently, we recommend using the terms “torpor” and “hypothermia” in ways that are consistent with the underlying regulatory differences between these two physiological states.
Publisher: Elsevier BV
Date: 10-2011
Publisher: CSIRO Publishing
Date: 1993
DOI: 10.1071/ZO9930067
Abstract: The pattern of torpor was examined in the eastern pygmy possum, Cercartetus nanus (21 g). Animals displayed torpor regularly in the laboratory, and the occurrence of torpor increased with decreasing air temperature (T(a)). At high T(a) (18-degrees-C) animals usually exhibited daily torpor, but torpor bouts of up to 2 days were observed occasionally. The duration of torpor bouts lengthened with a lowering of T(a) and the mean bout duration at T(a) = 5-degrees-C was 17.0 +/- 2.5 days. The minimum metabolic rate (measured as rate of oxygen consumption) of torpid in iduals was 0.018 +/- 0.003 mL O2 g-1 h-1, which is less than 2% of the basal metabolic rate. The body temperature (T(b)) Of torpid animals fell to a minimum of 1.3 +/- 0.4-degrees-C. These results clearly demonstrate that Cercartetus nanus is a deep hibernator.
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/AM05227
Abstract: THE fat-tailed false antechinus (Pseudantechinus macdonnellensis) is a medium-sized dasyurid marsupial (body mass 18-33 g), that is endemic to central Australia. It is largely confined to rocky environments in the Northern Territory, Western Australia and South Australia (Menkhorst and Knight 2001). Despite its specialised habitat, the species is a generalist insectivore. Ten insect orders and spiders (Araneae) were recorded in faecal s les of a population in West MacDonnell National Park, Northern Territory, during a two and a half year study (Gilfillan 2001). Isoptera, Coleoptera and Orthoptera were the major insect orders in the diet. Here we report the results of the analysis of a small s le of faeces of P. macdonnellensis collected from the same location as the population studied by Gilfillan. Our results are noteworthy because of additions to the prey taken by P. macdonnellensis including three new classes and two new phyla.
Publisher: Springer Science and Business Media LLC
Date: 16-09-2016
DOI: 10.1007/S00360-016-1031-Z
Abstract: Many mammals use torpor throughout the year but the in idual contributions of environmental variables to seasonal changes in torpor expression are often difficult to tease apart. In many mammals, torpor is most often used opportunistically in response to decreased ambient temperature (T
Publisher: Springer International Publishing
Date: 2021
Publisher: Springer International Publishing
Date: 2021
Publisher: Elsevier BV
Date: 02-2018
DOI: 10.1016/J.PHYSBEH.2017.11.020
Abstract: The recent observation that torpor plays a key role in post-fire survival has been mainly attributed to the reduced food resources after fires. However, some of these adjustments can be facilitated or lified by environmental changes associated with fires, such as the presence of a charcoal-ash substrate. In a previous experiment on a small terrestrial mammal the presence of charcoal and ash linked to food restriction intensified torpor use. However, whether fire cues also act as a trigger of torpor use when food is available and whether they affect other species including arboreal mammals remains elusive. To evaluate whether smoke, charcoal and ash can act as proximate triggers for an impending period of food shortage requiring torpor for mammals, we conducted an experiment on captive sugar gliders (Petaurus breviceps), a small, arboreal marsupial, housed in outside aviaries under different food regimes and natural ambient conditions. When food was available, fire simulation via exposure to smoke and charcoal-ash substrate caused a significant earlier start of activity and a significant decrease in resting body temperature. In contrast, only when food was withheld, did smoke and charcoal-ash exposure significantly enhance torpor depth and duration. Thus, our study not only provides evidence that fire simulation does affect arboreal and terrestrial species similarly, but also suggests that smoke and ash were presumably selected as cues for torpor induction because they indicate an impending lack of food.
Publisher: Wiley
Date: 16-01-2014
DOI: 10.1111/JZO.12102
Publisher: Springer Science and Business Media LLC
Date: 2004
DOI: 10.1007/S00360-003-0388-Y
Abstract: The physiological signal for torpor initiation appears to be related to fuel availability. Studies on metabolic fuel inhibition in placental heterotherms show that glucose deprivation via the inhibitor 2-deoxy-D-glucose (2DG) initiates a torpor-like state, whereas fatty acid deprivation via mercaptoacetate (MA) does not. As previous studies using inhibitors were limited to quantifying body temperature in placentals, we investigated whether inhibition of glucose or fatty acids for cellular oxidation induces torpor in the marsupial hibernator Cercartetus nanus, and how the response of metabolic rate is related to body temperature. Glucoprivation initiated a torpor-like state in C. nanus, but animals had much higher minimum body temperatures and metabolic rates than those of torpid food-deprived animals and arousal rates were slower. Moreover, 2DG-treated animals were thermoregulating at ambient temperatures of 20 and 12 degrees C, whereas food-deprived torpid animals were thermo-conforming. We suggest that glucoprivation reduces the hypothalamic body temperature set point, but only by about 8 degrees C rather than the approximately 28 degrees C during natural torpor. Reduced fatty acid availability via MA also induced a torpor-like state in some C. nanus, with physiological variables that did not differ from those of torpid food-deprived animals. We conclude that reduced glucose availability forms only part of the physiological trigger for torpor initiation in C. nanus. Reduced fatty acid availability, unlike for placental heterotherms, may be an important cue for torpor initiation in C. nanus, perhaps because marsupials lack functional brown adipose tissue.
Publisher: The Royal Society
Date: 13-04-2016
Abstract: Fires have occurred throughout history, including those associated with the meteoroid impact at the Cretaceous–Palaeogene (K–Pg) boundary that eliminated many vertebrate species. To evaluate the recent hypothesis that the survival of the K–Pg fires by ancestral mammals was dependent on their ability to use energy-conserving torpor, we studied body temperature fluctuations and activity of an egg-laying mammal, the echidna ( Tachyglossus aculeatus ), often considered to be a ‘living fossil’, before, during and after a prescribed burn. All but one study animal survived the fire in the prescribed burn area and echidnas remained inactive during the day(s) following the fire and substantially reduced body temperature during bouts of torpor. For weeks after the fire, all in iduals remained in their original territories and compensated for changes in their habitat with a decrease in mean body temperature and activity. Our data suggest that heterothermy enables mammals to outlast the conditions during and after a fire by reducing energy expenditure, permitting periods of extended inactivity. Therefore, torpor facilitates survival in a fire-scorched landscape and consequently may have been of functional significance for mammalian survival at the K–Pg boundary.
Publisher: Wiley
Date: 23-01-2014
DOI: 10.1111/JZO.12105
Publisher: Springer Science and Business Media LLC
Date: 07-04-1998
Abstract: Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats showed a large variation in body temperature (Tb) (33 to 37 degrees C) over a wide range of ambient temperatures (Tas) and a relatively low basal metabolic rate (1.29 ml O2 g-1 h-1). Bats entered torpor frequently in the laboratory at Tas between 14 and 25 degrees C. Entry into torpor always occurred when lights were switched on in the morning, independent of Ta. MRs during torpor were reduced to about 20-40% of normothermic bats and Tbs were regulated at a minimum of 23.1 +/- 1.4 degrees C. The duration of torpor bouts increased with decreasing Ta in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum Tb and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the Tb was also about 5 degrees C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected by Ta and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor.
Publisher: Elsevier BV
Date: 07-1984
Publisher: Springer Science and Business Media LLC
Date: 23-02-1999
Abstract: The costs of arousal from induced torpor were measured in the striped-faced dunnart (Sminthopsis macroura, ca. 25 g) under two experimental ambient temperature cycles. The sinusoidal-type temperature cycles were designed to evaluate the effects of passive, ambient temperature heating during arousal from torpor in these insectivorous marsupials. It was hypothesised that diel ambient temperature cycles may offer significant energy savings during arousal in animals that employ daily torpor in summer as a response to unpredictable food availability. The cost of arousal in animal in which passive, exogenous heating occurred was significantly lower than that in animals not exposed to an ambient temperature cycle. The total cost of all three phases of torpor (entry maintenance and arousal) was almost halved when animals were exposed to an ambient heating cycle from 15 degrees C to 25 degrees C over a 24-h period. In all animals, irrespective of the experimental ambient temperature cycle employed, the minimum torpor body temperature was 17-18 degrees C. The body temperature (Tb) of animals exposed to exogenous heating increased from the torpor Tb minimum to a mean value of 22.59 degrees C before endogenous heat production commenced. This relatively small increase in Tb of ca. 5 degrees C through 'free' passive heating was sufficient to account for the significant ca. three-fold decrease in the cost of arousal and may represent an important energetic aid to free-ranging animals.
Publisher: Springer Science and Business Media LLC
Date: 30-11-1998
Abstract: Circadian rhythms have been observed in most mammals, but their importance and function remain controversial with respect to daily cycles during hibernation. We investigated the timing of arousals from and entries into hibernation for both free-living and captive mountain pygmy-possums (Burramys parvus). Under both natural and laboratory conditions most arousals and entries were entrained with the light-dark cycle. Entries occurred mainly during the night and arousals preferably around dusk, which coincides with the onset of the normal activity phase for the nocturnal pygmy-possums. This entrainment prevailed throughout the hibernation season although only the laboratory animals were constantly subjected to photoperiodic stimuli, whereas under natural conditions hibernacula are shielded from photic cues and diurnal temperature fluctuations. Nevertheless, possums left their hibernacula frequently throughout winter and were occasionally trapped close to the snow surface suggesting that during the periods of post-arousal normothermia they can be exposed to environmental stimuli. It thus appears that the synchronisation with the photocycle was governed by a temperature-compensated circadian clock which was reset periodically during short activity periods. For the mountain pygmy-possum, entrainment with the photocycle probably has two functions: 1. Entrainment ensures that foraging bouts during the hibernation season remain synchronised with the dark phase. 2. Information about the prevailing climatic conditions s led during short activity periods enables them to time final spring emergence from hibernation when snow melt begins and ensures that the breeding season can commence as early as possible.
Publisher: Springer Science and Business Media LLC
Date: 1992
DOI: 10.1007/BF00257929
Abstract: Theiler's murine encephalomyelitis virus (TMEV) is ided into two subgroups on the basis of their different biological activities. GDVII subgroup strains produce fatal poliomyelitis in mice without virus persistence or demyelination. In contrast, TO subgroup strains induce demyelinating disease with virus persistence in the spinal cords of weanling mice. Two proteins, whose open reading frames are located in the N-terminus of the polyprotein, recently have been reported to be important for TMEV biological activities. One is leader (L) protein and is processed from the most N-terminus of the polyprotein its function is still unknown. Although the homology of capsid proteins between DA (a representative strain of TO subgroup) and GDVII strains is over 94% at the amino acid level, that of L shows only 85%. Therefore, L is thought to be a key protein for the subgroup-specific biological activities of TMEV. Various studies have demonstrated that L plays important roles in the escape of virus from host immune defenses in the early stage of infection. The second protein is a 17-18 kDa protein, L*, which is synthesized out-of-frame with the polyprotein. Only TO subgroup strains produce L* since GDVII subgroup strains have an ACG rather than AUG at the initiation site and therefore do not synthesize L*. 'Loss and gain of function' experiments demonstrate that L* is essential for virus growth in macrophages, a target cell for TMEV persistence. L* also has been demonstrated to be necessary for TMEV persistence and demyelination. Further analysis of L and L* will help elucidate the pathomechanism(s) of TMEV-induced demyelinating disease.
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.231761
Abstract: Precocial birds hatch feathered and mobile, but when they become fully endothermic soon after hatching, their heat loss is high and they may become energy-depleted. These chicks could benefit from using energy-conserving torpor, which is characterised by controlled reductions of metabolism and body temperature (Tb). We investigated at what age the precocial king quail Cortunix chinensis can defend a high Tb under a mild thermal challenge and whether they can express torpor soon after achieving endothermy to overcome energetic and thermal challenges. Measurements of surface temperature (Ts) using an infrared thermometer showed that king quail chicks are partially endothermic at 2–10 days, but can defend high Tb at a body mass of ∼13 g. Two chicks expressed shallow nocturnal torpor at 14 and 17 days for 4 to 5 hours with a reduction of metabolism by& % and one approached torpor threshold. Although chicks were able to rewarm endogenously from the first torpor bout, metabolism and Ts decreased again by the end of the night, but they rewarmed passively when removed from the chamber. The total metabolic rate increased with body mass. All chicks measured showed a greater reduction of nocturnal metabolism than previously reported in quails. Our data show that shallow torpor can be expressed during the early postnatal phase of quails, when thermoregulatory efficiency is still developing, but heat loss is high. We suggest that torpor may be a common strategy for overcoming challenging conditions during the development in small precocial and not only altricial birds.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.CBPA.2007.02.041
Abstract: Endothermic thermoregulation in small, altricial mammals and birds develops at about one third to half of adult size. The small size and consequently high heat loss in these young should result in more pronounced energetic challenges than in adults. Thus, employing torpor (a controlled reduction of metabolic rate and body temperature) during development would allow them to save energy. Although torpor during development in endotherms is likely to occur in many species, it has been documented in only a few. In small, altricial birds (4 orders) and marsupials (1 order), which are poikilothermic at hatching/birth, the development of competent endothermic thermoregulation during cold exposure appears to be concurrent with the capability to display torpor (i.e. poikilothermy is followed by heterothermy), supporting the view that torpor is phylogenetically old and likely plesiomorphic. In contrast, in small, altricial placental mammals (2 orders), poikilothermy at birth is followed first by a homeothermic phase after endothermic thermoregulation is established the ability to employ torpor develops later (i.e. poikilothermy-homeothermy-heterothermy). This suggests that in placentals torpor is a derived trait that evolved secondarily after a homeothermic phase in certain taxa perhaps as a response to energetic challenges. As mammals and birds arose from different reptilian lineages, endothermy likely evolved separately in the two classes, and given that the developmental sequence of torpor differs between marsupials and placentals, torpor seems to have evolved at least thrice.
Publisher: Springer Science and Business Media LLC
Date: 1985
DOI: 10.1007/BF00694585
Abstract: the treatment of proximal humeral fractures in the elderly remains controversial. Options include nonoperative treatment, open reduction with internal fixation (ORIF), and hemiarthroplasty. Locking plate technology has expanded the indications for ORIF for certain fracture types in osteoporotic bone. This study was performed to characterize the incidence, treatment, and revision surgery of proximal humeral fractures according to geographic region both before (1999 to 2000) and after (2004 to 2005) the introduction of locking plates. we used a 20% s le of Medicare Part-B data and the Medicare denominator file for the years 1998 to 2006. Proximal humeral fractures were identified by Common Procedural Terminology codes for treatment, categorized as nonoperative, ORIF, or hemiarthroplasty. Geographic variation in treatment type was determined with use of 306 hospital referral regions. Odds ratios for revision surgery were calculated by the need for repeat surgery within one year of the index procedure. Rates were adjusted for age, sex, race, and comorbidities. there were 14,774 proximal humeral fractures in the 20% s le from 1999 to 2000 (an estimated total of 73,870 fractures) and 16,138 fractures in the s le from 2004 to 2005 (an estimated total of 80,690 fractures). The overall age, sex, and race-adjusted incidence of proximal humeral fractures was unchanged from 1999 to 2005 (2.47 vs. 2.48 per 1000 Medicare beneficiaries p = 0.992). However, the absolute rate of surgically managed proximal humeral fractures rose 3.2 percentage points from 12.5% to 15.7%, a relative increase of 25.6% (p < 0.0001). The relative increase in the percentage of fractures treated with ORIF was 28.5% (p < 0.0001), while the percentage of fractures treated with hemiarthroplasty increased 19.6% (p < 0.0001). There were large regional variations in the proportion treated surgically (range, 0% to 68.18%). The rates of repeat surgery were significantly higher in 2004 to 2005 compared with 1999 to 2000 (odds ratio = 1.47, p = 0.043). although the incidence of proximal humeral fractures in the elderly did not change from 1999 to 2005, the rate of surgical treatment increased significantly. The marked regional variation in the rates of surgical treatment highlights the need for better consensus regarding optimal treatment of proximal humeral fractures. Additional research is needed to help to determine which fractures are best treated operatively in order to maximize outcome and minimize the need for revision surgery. therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.
Publisher: University of Chicago Press
Date: 11-2003
DOI: 10.1086/378915
Publisher: University of Chicago Press
Date: 09-2000
DOI: 10.1086/317755
Abstract: With the exception of some data for common poorwills (Phalaenoptilus nuttallii) and anecdotal reports for a few other species, knowledge about the use of torpor by free-ranging birds is limited. Our study was designed to assess the use of torpor by free-ranging Australian owlet-nightjars (Aegotheles cristatus). We selected this species for study because of their relatively small body size (50 g), arthropod diet, nocturnal sedentary nature, taxonomic affiliation with other birds for whom the use of torpor is well documented, use of cavity roosts, and because of the cold winter (mean July minimum ambient temperature [T(a)] of approximately 0 degrees C) in the study area. We tracked 12 owlet-nightjars carrying temperature-sensitive transmitters for a total of 906 bird-days (range of 15-115 d per in idual). Five different in iduals entered torpor on 96 d in total. Torpor bouts occurred only between May 8 and September 8, the coldest period of the year. The lowest skin temperature (T(skin)) recorded for any bird was 19.6 degrees C, and the lowest core temperature was 22.4 degrees C. Surprisingly, torpor was rarely used at night because birds usually foraged then. Instead, torpor typically began near dawn, even on cold nights. Torpor bouts beginning at dawn lasted approximately 4 h. On 36% of days when torpor was used at dawn, birds reentered torpor later in the day. Torpor was not used during the breeding season, but this period also corresponds to the warm part of the year. There were no distinct daily minimum, maximum, or mean T(a) thresholds that could be used to reliably distinguish days when dawn torpor was used from those when it was not, although torpor was commonly employed when daily minimum T(a) fell below 3.9 degrees C. Our results show that even though Australia is typically thought of as a warm continent, at least some of the avifauna use torpor as a regular means of saving energy. We hypothesise that the reasons for this species' use of torpor include its ability to remain active all night foraging, either for terrestrial arthropods while walking or for flying insects taken on the wing, and/or its habit of roosting in cavities, which allows them to remain hidden in the daytime.
Publisher: Informa UK Limited
Date: 30-03-2016
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/ZO09097
Abstract: We investigated the importance of energy-conserving strategies for free-ranging Planigale gilesi in arid Australia. We monitored torpor use and basking behaviour using internal temperature-sensitive transmitters. Torpor was used every day the maximum torpor bout duration was 18.2 h and the minimum body temperature was 10.5°C. Basking behaviour was observed during rewarming from torpor as well as during normothermia. The use of torpor and basking is likely to reduce the energy requirements of P. gilesi, thus helping it to survive in a harsh and unpredictable environment.
Publisher: University of Chicago Press
Date: 05-1990
Publisher: Springer Science and Business Media LLC
Date: 04-07-2009
DOI: 10.1007/S00114-009-0583-0
Abstract: Small mammals appear to be less vulnerable to extinction than large species, but the underlying reasons are poorly understood. Here, we provide evidence that almost all (93.5%) of 61 recently extinct mammal species were homeothermic, maintaining a constant high body temperature and thus energy expenditure, which demands a high intake of food, long foraging times, and thus exposure to predators. In contrast, only 6.5% of extinct mammals were likely heterothermic and employed multi-day torpor (hibernation) or daily torpor, even though torpor is widespread within more than half of all mammalian orders. Torpor is characterized by substantial reductions of body temperature and energy expenditure and enhances survival during adverse conditions by minimizing food and water requirements, and consequently reduces foraging requirements and exposure to predators. Moreover, because life span is generally longer in heterothermic mammals than in related homeotherms, heterotherms can employ a 'sit-and-wait' strategy to withstand adverse periods and then repopulate when circumstances improve. Thus, torpor is a crucial but hitherto unappreciated attribute of small mammals for avoiding extinction. Many opportunistic heterothermic species, because of their plastic energetic requirements, may also stand a better chance of future survival than homeothermic species in the face of greater climatic extremes and changes in environmental conditions caused by global warming.
Publisher: Springer Science and Business Media LLC
Date: 07-01-2003
DOI: 10.1007/S00360-002-0311-Y
Abstract: The high expenditure of energy required for endogenous rewarming is one of the widely perceived disadvantages of torpor. However, recent evidence demonstrates that passive rewarming either by the increase of ambient temperature or by basking in the sun appears to be common in heterothermic birds and mammals. As it is presently unknown how radiant heat affects energy expenditure during rewarming from torpor and little is known about how it affects normothermic thermoregulation, we quantified the effects of radiant heat on body temperature and metabolic rate of the small (body mass 25 g) marsupial Sminthopsis macroura in the laboratory. Normothermic resting in iduals exposed to radiant heat were able to maintain metabolic rates near basal levels (at 0.91 ml O(2) g(-1) h(-1)) and a constant body temperature down to an ambient temperature of 12 degrees C. In contrast, metabolic rates of in iduals without access to radiant heat were 4.5-times higher at an ambient temperature of 12 degrees C and body temperature fell with ambient temperature. During radiant heat-assisted passive rewarming from torpor, animals did not employ shivering but appeared to maximise uptake of radiant heat. Their metabolic rate increased only 3.2-times with a 15- degrees C rise of body temperature (Q(10)=2.2), as predicted by Q(10) effects. In contrast, during active rewarming shivering was intensive and metabolic rates showed an 11.6-times increase. Although body temperature showed a similar absolute change between the beginning and the end of the rewarming process, the overall energetic cost during active rewarming was 6.3-times greater than that during passive, radiant heat-assisted rewarming. Our study demonstrates that energetic models assuming active rewarming from torpor at low ambient temperatures can substantially over-estimate energetic costs. The low energy expenditure during passive arousal provides an alternative explanation as to why daily torpor is common in sunny regions and suggests that the prevalence of torpor in low latitudes may have been under-estimated in the past.
Publisher: University of Chicago Press
Date: 05-1997
DOI: 10.1086/639610
Abstract: Endothermy allows maintenance of a constant internal thermal milieu for optimal physiological functions but results in high energy expenditure and water loss. Since torpor can reduce both expenditure of energy and loss of water and thus reduces food and water requirements, we determined how different food and water regimes affect torpor occurrence and patterns in the dasyurid marsupial Sminthopsis macroura at ambient temperatures of 18 degrees C (well below the thermoneutral zone) and 28 degrees C (close to the thermoneutral zone). At 18 degrees C, torpor was more frequent and more pronounced than at 28 degrees C. Withdrawal of food reduced the average daily metabolic rate by 20% withdrawal of water alone had little effect. The average daily metabolic rate of in iduals displaying torpor was 20% lower than that of in iduals remaining normothermic. At 28 degrees C, the average daily metabolic rate under food restriction was 85% of that with food available ad lib. However, this reduction of average daily metabolic rate at 28 degrees C seems due not to the use of torpor but mainly to a reduction of the resting metabolic rate. The results suggest that at low temperature, torpor is used to adjust energy expenditure to availability of food, whereas at high temperature, reductions of resting metabolic rate are employed.
Publisher: Wiley
Date: 29-11-2011
Publisher: Springer Science and Business Media LLC
Date: 03-07-2007
DOI: 10.1007/S00114-007-0274-7
Abstract: Many mammals hibernate each year for about 6 months in autumn and winter and reproduce during spring and summer when they are generally not in torpor. I tested the hypothesis that the marsupial pygmy-possum (Cercartetus nanus), an opportunistic nonseasonal hibernator with a capacity for substantial fattening, would continue to hibernate well beyond winter. I also quantified how long they were able to hibernate without access to food before their body fat stores were depleted. Pygmy-possums exhibited a prolonged hibernation season lasting on average for 310 days. The longest hibernation season in one in idual lasted for 367 days. For much of this time, despite periodic arousals after torpor bouts of approximately 12.5 days, energy expenditure was reduced to only approximately 2.5% of that predicted for active in iduals. These observations represent the first report on body-fat-fuelled hibernation of up to an entire year and provide new evidence that prolonged hibernation is not restricted to placental mammals living in the cold.
Publisher: The Company of Biologists
Date: 05-2012
DOI: 10.1242/JEB.069559
Abstract: Climate change is likely to substantially affect the distribution ranges of species. However, little is known about how different mammalian taxa respond morphologically and physiologically to a rapid change of climate. Our objective was to provide the first quantitative data on the effect of continuous cold exposure during development on morphological and functional variables of a marsupial. Fat-tailed dunnarts (Sminthopsis crassicaudata, Dasyuridae) were reared at an ambient temperature (Ta) of 16°C [cold-reared (CR)] or 22°C [warm-reared (WR)] until they reached adult age (& days). Body and head length of CR animals were significantly longer than in WR animals (mean ± s.e.m. body: CR 80.8±6 mm, WR 76.4±5 mm head: CR 29.4±3 mm, WR 27.5±2 mm), but other body attributes were not significantly different. Use of torpor was more frequent, torpor bout duration was longer and average daily metabolic rate and percentage of savings when using torpor were significantly higher (P& .01) in CR than in WR animals at 16°C Ta but not at 24°C. Furthermore, resting metabolic rates measured at 16°C Ta were significantly lower in CR than WR animals at 30°C Ta values were similar. Our results do not conform to Allen’s rule, but to some extent they do conform to Bergmann’s rule. However, the data demonstrate that a relatively moderate cold exposure from birth until adulthood induces marked changes in the morphology and thermal energetics of small marsupials. Such short-term phenotypic responses without the need for long-term selection are likely important for the ability to cope with different climates over a wide range of distribution, but will also play a crucial role in enhancing the survival of species during climate change.
Publisher: CSIRO Publishing
Date: 17-04-2009
DOI: 10.1071/AN20664
Abstract: Context Mice bred to be genetically different in feed efficiency were used in this experiment designed to help improve our knowledge of the biological basis of variation in feed efficiency between in idual animals. Aims This experiment used mice to explore the metabolic basis of genetic variation in feed efficiency in the growing animal. Methods Mice bred to differ in residual feed intake (RFI) recorded over a postweaning test were used. After 11 generations of ergent selection, mice in groups were tested for RFI from 6 to 8, 8 to 10, and 10 to 12 weeks of age, and measured for traits describing the ability to digest feed, body composition, protein turnover, basal and resting metabolic rate, and level of activity. Key results Compared with the low-RFI (high efficiency) line mice, high-RFI mice consumed 28% more feed per day over their RFI-test, were no heavier, were leaner (16% less total fat per unit of bodyweight), did not differ in the fractional synthesis rate of protein in skeletal muscle or in liver, and had similar basal metabolic rates at 33°C. On an energy basis, the selection lines did not differ in energy retained in body tissue gain, which represented only 1.8% of metabolisable energy intake. The remaining 98.2% was lost as heat. Of the processes measured contributing to the higher feed intake by the high-RFI mice, 47% of the extra feed consumed was lost in faeces and urine, activity was 84% higher and accounted for 24%, the cost of protein gain was 6% higher and accounted for 2%, and the energy cost of digesting and absorbing the extra feed consumed and basal heat production could have accounted for 11 and 15% each. Conclusions Selection for low RFI (high efficiency) in mice was accompanied by an increase in body fat, an improvement in the process of digestion, a lower rate of protein turnover and a much lower level of activity. Selection did not result in major change in basal metabolic rate. Implications This experiment with mice provided new information on the biological basis of genetic differences in feed efficiency. The experiment investigated the relative importance of major energy-consuming metabolic processes and was able to quantify the responses in protein turnover and level of activity, being responses in energy-consuming processes that have proven difficult to quantitatively demonstrate in large farm animals.
Publisher: Elsevier BV
Date: 03-2010
DOI: 10.1016/J.CBPA.2009.11.014
Abstract: Sugar gliders, Petaurus breviceps (average body mass: 120 g) like other small wild mammals must cope with seasonal changes in food availability and weather and therefore thermoregulatory and energetic challenges. To determine whether free-ranging sugar gliders, an arboreal marsupial, seasonally adjust their energy expenditure and water use, we quantified field metabolic rates (FMR) and water flux at a seasonal cool-temperate site in eastern Australia. Thirty six male and female sugar gliders were labelled with doubly labelled water for this purpose in spring, summer and autumn. The mean FMR was 159+/-6 kJ d(-1) (spring), 155+/-8 kJ d(-1) (summer), and 152+/-20 kJ d(-1) (autumn) and the mean FMR for the three seasons combined was 158+/-5 kJ d(-1) (equivalent to 1.33 kJ g(-)(1)d(-1) or 780 kJ kg(-0.)(75)d(-1)). The mean total body water was 83+/-2 g, equal to 68.5% of body weight. Mean water flux was 29+/-1 mL day(-1). Season, ambient temperature or sex did not affect any of the measured and estimated physiological variables, but body mass and total body water differed significantly between sexes and among seasons. Our study is the first to provide evidence for a constant FMR in a small mammal in three different seasons and despite different thermal conditions. This suggests that seasonal changes in climate are compensated for by behavioural and physiological adjustments such as huddling and torpor known to be employed extensively by sugar gliders in the wild.
Publisher: Springer Science and Business Media LLC
Date: 07-2003
DOI: 10.1007/S00360-003-0352-X
Abstract: Marsupials, unlike placental mammals, are believed to be unable to increase heat production and thermal performance after cold-acclimation. It has been suggested that this may be because marsupials lack functional brown fat, a thermogenic tissue, which proliferates during cold-acclimation in many placentals. However, arid zone marsupials have to cope with unpredictable, short-term and occasionally extreme changes in environmental conditions, and thus they would benefit from an appropriate physiological response. We therefore investigated whether a sequential two to four week acclimation in Sminthopsis macroura (body mass approx. 25 g) to both cold (16 degrees C) and warm (26 degrees C) ambient temperatures affects the thermal physiology of the species. Cold-acclimated S. macroura were able to significantly increase maximum heat production (by 27%) and could maintain a constant body temperature at significantly lower effective ambient temperatures (about 9 degrees C lower) than when warm-acclimated. Moreover, metabolic rates during torpor were increased following cold-acclimation in comparison to warm-acclimation. Our study shows that, despite the lack of functional brown fat, short-term acclimation can have significant effects on thermoenergetics of marsupials. It is likely that the rapid response in S. macroura reflects an adaptation to the unpredictability of the climate in their habitat.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1007/BF00693360
Publisher: The Company of Biologists
Date: 08-2010
DOI: 10.1242/JEB.043182
Abstract: Currently, there are no data on the thermal biology of free-ranging pteropodid bats (Chiroptera). Therefore, our aim was to investigate physiological and behavioural strategies employed by the fruit bat Nyctimene robinsoni (body mass ∼50 g) in winter in tropical Northern Queensland in relation to ambient temperature (Ta) and the lunar cycle. Daily body temperature (Tb) fluctuations in free-ranging bats were measured via radio-telemetry and metabolic rate was measured in captivity via open-flow respirometry (Ta, 15–30°C). Free-ranging bats showed a significant 24 h circadian cycle in Tb, with the lowest Tb at the end of the rest phase just after sunset and the highest Tb at the end of the activity phase just before sunrise. Average daily core Tb ranged from 34.7±0.6 to 37.3±0.8°C (mean ± s.d.) over an average daily Ta range of 17.1±1.1 to 23.5±1.8°C. Tb never fell below 30°C but Tb was significantly reduced during the full moon period compared with that during the new moon period. Tb was correlated with Ta during the second half of the rest phase (P& .001) but not during the active phase. Resting metabolic rate of bats was significantly affected by Ta (P& .001, R2=0.856). Our results show that tube-nosed bats exhibit reduced Tb on moonlit nights when they reduce foraging activity, but during our study torpor was not expressed. The energy constraints experienced here by tube-nosed bats with relatively moderate Ta fluctuations, short commuting distances between roosting and feeding locations, and high availability of food were probably not substantial enough to require use of torpor.
Publisher: Frontiers Media SA
Date: 02-11-2017
Publisher: Springer Science and Business Media LLC
Date: 04-1993
DOI: 10.1007/BF00263598
Publisher: Frontiers Media SA
Date: 24-04-2019
Publisher: University of Chicago Press
Date: 07-2008
DOI: 10.1086/589545
Abstract: Little is known about the energy conservation strategies of free-ranging marsupials living in resource-poor Australian deserts. We studied activity patterns and torpor of free-living mulgaras (Dasycercus blythi) in arid central Australia during the winter of 2006. Mulgaras are small (approximately 75 g), nocturnal, insectivorous marsupials, with a patchy distribution in hummock grasslands. Mulgaras (six males, three females) were implanted intraperitoneally with temperature-sensitive transmitters and monitored for 6-55 d. Temperature profiles for different microhabitats and the thermal properties of soil and a number of burrows were also measured. Air temperature ranged from -3 degrees C at night to 30 degrees C during the day. Although burrows buffered temperature extremes, the thermal diffusivity of the sandy soil was high, and many burrows were shallow. Hence, soil and burrow temperatures averaged about 15 degrees C. The activity of mulgaras was often restricted to a few hours after sunset, before they retired into their burrows. Mulgaras employed torpor frequently, often entering torpor during the night and arousing around midday, with arousals occurring later on cooler days. Shallow burrows allowed cooling below mean T(soil). Consequently, body temperatures as low as 10.8 degrees C were observed. The longest torpor bout was 20.8 h. Torpor patterns changed seasonally and differed between males and females. From June to August, females entered torpor almost daily despite mating and gestation, but from the end of the gestation period onward, they remained normothermic. In contrast, males showed only shallow and short torpor during the mating season, but from mid-July, a transition to more frequent and deeper torpor resembling that of females was observed. Apparently, in both sexes, the reproductive effort entails energetic costs, but torpor, as an energy-saving mechanism, and reproduction are not exclusive in mulgaras. In a resource-poor environment during the least productive part of the year, frequent torpor seems to provide the means to compensate for the increased energetic costs associated with reproduction.
Publisher: Springer Science and Business Media LLC
Date: 22-05-2000
Abstract: 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.
Publisher: Elsevier BV
Date: 09-1995
DOI: 10.1016/0300-9629(95)00089-P
Abstract: Daily torpor is an energy-conserving mechanism, used by many small marsupials to reduce energy expenditure during adverse environmental conditions. Since little is known about how much energy is actually saved by torpor in marsupials and how this is related to the duration of torpor bouts, we investigated the effect of ambient temperature (Ta) on different metabolic states and the effect of torpor bout duration in Sminthopsis crassicaudata (16 g) on average daily metabolic rate (ADMR). Ta had a significant effect on the active and resting metabolic rates (MR), both being higher at Ta 12 degrees C than Ta 18 degrees C (P < 0.001, t-test). In contrast, the ADMR at Ta 12 degrees C and Ta 18 degrees C did not differ significantly, and it appears that the increased cost for thermoregulation in normothermic active and resting animals at Ta 12 degrees C was compensated by a decrease in MR during torpor. Torpor bout duration was negatively correlated with ADMR. Torpor bouts of 5 hr reduced ADMR by 12-16%. Torpor bouts of more than 10 hr reduced ADMRs by 30-50%. Our study shows that torpor can significantly reduce daily energy expenditure in S. crassicaudata, and this may be important for the survival of this species in the wild.
Publisher: The Company of Biologists
Date: 2015
DOI: 10.1242/JEB.128926
Abstract: Huddling and torpor are widely used for minimizing heat loss by mammals. Despite the questionable energetic benefits from social heterothermy of mixed groups of warm normothermic and cold torpid in iduals, the heterothermic Australian marsupial sugar glider (Petaurus breviceps) rests in such groups during the cold season. To unravel why they might do so, we examined torpor expression of two sugar glider groups of four in iduals each in outside enclosures during winter. We observed 79 torpor bouts during 50 days of observation and found that torpor bouts were longer and deeper when all in iduals of a group entered torpor together and therefore infer that they would have saved more energy in comparison to short and shallow solitary torpor bouts. However, all gliders of either group only expressed torpor uniformly in response to food restriction, whereas on most occasions at least one in idual per group remained normothermic. On the other hand, the presence of warm gliders in mixed groups also appears to be of energetic advantage for torpid in iduals, because nest box temperature was negatively correlated with the number of torpid gliders and normothermic in iduals kept the nest temperature at a value closer to the threshold for thermoregulatory heat production during torpor. Our study suggests that mixed groups of torpid and normothermic in iduals are observed when environmental conditions are adverse but food is available, leading to intermediate energy savings from torpor. However, under especially challenging conditions and when animals are starving, energy savings are maximized by uniform and pronounced expression of torpor.
Publisher: Elsevier BV
Date: 09-1990
DOI: 10.1016/0005-2760(90)90183-X
Abstract: Dietary lipid composition profoundly influences the hibernation pattern of the chipmunk Eutamias amoenus. The object of the present study was to investigate whether these physiological changes following feeding of saturated and unsaturated lipids were associated by compositional changes of fatty acids of tissues and membranes. Animals were fed with rodent chow (control diet), rodent chow with 10% sunflower seed oil (unsaturated diet) and rodent chow with 10% sheep fat (saturated diet). Diet-induced changes in the fatty acid composition of depot fat and brain total lipids and of mitochondrial phospholipids were determined. The fatty acid unsaturation index was lower in animals on saturated diet than in animals on unsaturated diet (depot fat 86.1 vs. 145.9 heart mitochondria 207.6 vs. 247.1 liver mitochondria 148.4 vs. 173.5). Pronounced differences between dietary groups were also observed in n-3 or n-6 fatty acids or their ratios of depot fat, brain and liver mitochondria. Generally, the diet-induced differences in tissue and membrane fatty acid composition in E. amoenus were more pronounced than those observed previously in non-hibernating species. Selective feeding and incorporation of high amounts of unsaturated fatty acids into tissues and cell membranes may be an important preparation for hibernation of E. amoenus which lowers its body temperature during torpor to about 0 degrees C.
Publisher: Springer Science and Business Media LLC
Date: 06-02-2020
Publisher: Springer Science and Business Media LLC
Date: 17-12-2011
DOI: 10.1007/S00442-011-2214-7
Abstract: Food availability, ambient temperatures (T(a)), and prevailing weather conditions have long been presumed to influence torpor use. To a large extent, this is based on measurements in the laboratory of animals placed on restricted diets and kept at low T (a). Information on the determinants of torpor employment in the field is limited. We assessed winter torpor by insectivorous, free-ranging Australian owlet-nightjars (Aegotheles cristatus 22 birds, 834 bird-days over six winters). Birds in three habitats were investigated to test whether torpor use is affected by annual T(a), rainfall, and arthropod abundance. Owlet-nightjars entered daily torpor regularly at all sites. Torpor frequency, depth and bout duration were greatest during two periods with lower arthropod abundance, providing rare evidence of the link between food availability and torpor patterns of wild birds. Temporal organization of torpor was similar among sites, and nocturnal torpor was more frequent than previously reported. Our findings quantitatively demonstrate that reduced food resources affect torpor usage independently from T(a), and support the view that food availability is a primary ecological determinant of torpor use in the wild.
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1007/BF00378050
Publisher: Elsevier BV
Date: 10-2010
DOI: 10.1016/J.PHYSBEH.2010.07.003
Abstract: Although several mammals have been observed to bask in the sun, little is known about this behaviour or its energetic consequences. We investigated the importance of basking behaviour for one of the smallest marsupials, Planigale gilesi (9g). Metabolic rates of captive planigales (n=6) exposed to simulated natural conditions with access to a radiant heat source were measured. Basking behaviour as a function of food availability was quantified using a video camera installed within the planigales' home cages (n=7). All planigales basked during respirometry measurements, reducing resting energy expenditure by 58% at an ambient temperature of 15 degrees C, which reflects conditions in their nesting sites in the wild during winter. Basking behaviour in home cages was displayed by all but one planigale food withdrawal either triggered basking or it caused a significant increase in basking duration. Our study demonstrates the effectiveness of basking for reducing energy expenditure in one of the smallest marsupials, supporting recent findings on the importance of behavioural thermoregulation in small mammals in general.
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/AM01053
Abstract: TORPOR and reproduction in mammals are widely viewed as mutually exclusive processes. For most mammals, different energetic and hormonal demands appear to require a temporal sequence of torpor and reproduction within the yearly schedule. Torpor is characterised by a pronounced fall in body temperature and metabolic rate, which results in an overall reduction of energy expenditure (Geiser and Ruf 1995) and in most mammals occurs during the non-reproductive season (Goldman et al. 1986 Barnes 1996). Reproduction, on the other hand, requires an increase of energy expenditure for acquiring, processing and transfer of nutrients to the growing offspring (Hoffman 1964 Goldman et al. 1986 Thompson and Nicoll 1986 Kenagy et al. 1989 Barnes 1996).
Publisher: Wiley
Date: 07-1996
Publisher: Springer Science and Business Media LLC
Date: 03-08-2007
DOI: 10.1007/S00360-007-0186-Z
Abstract: Australian deserts are characterized by unpredictability, low primary productivity, and high temperature fluctuations. Despite these adverse conditions the ersity of small insectivorous marsupials of the family Dasyuridae is surprisingly high. We quantified the thermal biology of the dasyurid Pseudantechinus madonnellensis (body mass approximately 30 g) in the wild to gain some understanding of whether the success of dasyurids in the arid zone may be related to some extent to their use of energy conservation strategies. In winter, most free-ranging Pseudantechinus frequently (58.3% of 131 animal days) entered daily torpor after midnight (mean 0157 hours) in rock crevices when outside ambient temperatures (T (a)) were low. Most animals remained torpid until the next morning when they moved while still torpid from rock crevices to sun-exposed basking sites. We visually observed basking during rewarming from torpor (mean commencement at 0943 hours) at body temperatures (T (b)) as low as 19.3 degrees C when radiant heat was high and T (a) was rising. Basking continued for the rest of the day. Torpor use was not strongly correlated with T (a), but the temporal organization of daily torpor and activity were apparently linked to the thermal characteristics of basking sites. Our study suggests that by frequently employing daily torpor and basking and by appropriately coordinating their thermal biology with that of specific locations in their environment, Pseudantechinus can reduce daily energy expenditure and thus can live and reproduce in a challenging environment. It is likely that the success of other small dasyurids and perhaps many other small mammals living in deserts is linked to employment of torpor and basking for energy conservation.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 1989
DOI: 10.1016/0300-9629(89)90046-7
Abstract: 1. The thermal response of isolated perfused hearts of four dasyurid marsupials was determined and compared with that of two rodents. 2. Heart beat rate was strongly temperature dependent in all species. 3. The temperature of cardiac arrest in the species investigated in the present study and of others collected from the literature occurred at a mean of about 13 degrees C in homeotherms, 7 degrees C in daily heterotherms, and 1 degrees C in hibernators. 4. For both marsupials and placentals the temperature of cardiac arrest in hibernators and daily heterotherms correlated with the minimum body temperature during torpor.
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.PHYSBEH.2017.12.019
Abstract: While torpor is a beneficial energy-saving strategy, it may incur costs if an animal is unable to respond appropriately to external stimuli, which is particularly true when it is necessary to escape from threats such as fire. We aimed to determine whether torpid bats, which are potentially threatened because they must fly to escape, can sense smoke and whether respiration rate (RR), heart rate (HR) and reaction time of torpid bats prior to and following smoke introduction is temperature-dependent. To test this we quantified RR and HR of captive Australian tree-roosting bats, Nyctophilus gouldi (n=5, ~10g), in steady-state torpor in response to short-term exposure to smoke from Eucalyptus spp. leaves between ambient temperatures (T
Publisher: Oxford University Press (OUP)
Date: 22-06-2011
DOI: 10.1093/ICB/ICR042
Abstract: 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 erse terrestrial mammals and birds from low latitudes (0-30°), 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 (T(b)) 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 T(b) is ∼6-30 °C, 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 erse 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.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AM18044
Abstract: Faecal hormone monitoring offers a robust tool to non-invasively determine the physiological stress experienced by an in idual when faced with natural or human-driven stressors. Although already quantified for several species, the method needs to be validated for each new species to ensure reliable quantification of the respective glucocorticoids. Here we investigated whether measurement of faecal glucocorticoid metabolite (fGCM) provides a feasible and non-invasive way to assess the physiological state of sugar gliders (Petaurus breviceps), an arboreal marsupial native to Australia, by using both a biological and physiological validation. Our analysis confirmed that the cortisol enzyme immunoassay (EIA) was the most appropriate assay for monitoring fGCM concentrations in sugar gliders. Comparing the fGCM response to the physiological and the biological validation, we found that while the administration of ACTH led to a significant increase in fGCM concentration in all in iduals, only six of eight in iduals showed a considerable fGCM response following the biological validation. Our study identified the most appropriate immunoassay for monitoring fGCM concentrations as an indicator of physiological stress in sugar gliders, but also supports recent suggestions that, if possible, both biological and physiological stressors should be used when testing the suitability of an EIA for a species.
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1007/BF00692726
Abstract: In 1997, supported by experimental work, Argenta published a clinical report describing a variety of complicated wounds whose treatment responded successfully to negative pressure dressings using a vacuum-assisted closure system (VAC) (Kinetic Concepts Inc., San Antonio, TX). This system has been successfully used in the fields of orthopaedics and traumatology, general surgery, plastic and reconstructive surgery and gynaecology/obstetrics for a large variety of complicated wounds located in several regions, particularly in the torso and extremities. To the best of our knowledge, the use of the VAC therapy in treating free flaps surgical wounds has not been discussed in the literature. Since 2009 at the Novara Major Hospital, we have been using the VAC therapy in selected cases for difficult and complicated wounds of the maxillofacial region. The purpose of this study is to describe and discuss three cases undergoing VAC therapy followed by loco-regional flaps in the management of exposed bone after fibular free flap. The advantages and disadvantages of VAC therapy in treating complicated wounds have been reported by several studies compared with conventional wet-to-dry dressings, this system eliminates interstitial oedema, exudates and debrides while increasing blood perfusion leading to a more rapid promotion of wound healing with less bacterial loading. Although surgical debridement, wet-to-dry dressing changes and antibiotic treatment are the mainstay in managing maxillofacial wounds, VAC therapy can be used to obtain primary closure or to prepare the wound bed until definitive reconstruction is carried out. In our opinion, the VAC technique is an innovative therapy, and at our institution represents the standard of care for the majority of complicated wounds.
Publisher: Springer Science and Business Media LLC
Date: 13-02-2015
Abstract: Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O
Publisher: Wiley
Date: 15-10-2013
Publisher: Public Library of Science (PLoS)
Date: 05-08-2015
Publisher: Springer International Publishing
Date: 19-11-2017
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.170894
Abstract: Many hibernating animals thermoregulate during torpor and defend their body temperature (Tb) below 10°C by an increase in metabolic rate. Above a critical temperature (Tcrit) animals usually thermoconform. We investigated the physiological responses above and below Tcrit for a small tree dwelling bat (Chalinolobus gouldii, ∼14 g) that is often exposed to subzero temperatures during winter. Through simultaneous measurement of heart rate (HR) and oxygen consumption (V̇O2) we show that the relationship between oxygen transport and cardiac function is substantially altered in thermoregulating torpid bats between 1 and -2°C, compared with thermoconforming torpid bats at mild ambient temperatures (Ta 5-20°C). Tcrit for this species was Ta 0.7±0.4°C, with a corresponding Tb of 1.8±1.2°C. Below Tcrit animals began to thermoregulate, indicated by a considerable but disproportionate increase in both HR and V̇O2. The maximum increase in HR was only 4-fold greater than the average thermoconforming minimum, compared to a 46-fold increase in V̇O2. The differential response of HR and V̇O2 to low Ta was reflected in a 15-fold increase in oxygen delivery per heart beat (cardiac oxygen pulse). During torpor at low Ta, thermoregulating bats maintained a relatively slow HR and compensated for increased metabolic demands by significantly increasing stroke volume and tissue oxygen extraction. Our study provides new information on the relationship between metabolism and HR in an unstudied physiological state that may occur frequently in the wild and can be extremely costly for heterothermic animals.
Publisher: Springer Science and Business Media LLC
Date: 16-02-2007
DOI: 10.1007/S00360-007-0147-6
Abstract: Most studies on animal physiology and behaviour are conducted in captivity without verification that data are representative of free-ranging animals. We provide the first quantitative comparison of daily torpor, thermal biology and activity patterns, conducted on two groups of sugar gliders (Petaurus breviceps, Marsupialia) exposed to similar thermal conditions, one in captivity and the other in the field. Our study shows that activity in captive gliders in an outdoor aviary is restricted to the night and largely unaffected by weather, whereas free-ranging gliders omit foraging on cold/wet nights and may also forage in the afternoon. Torpor occurrence in gliders was significantly lower in captivity (8.4% after food deprivation 1.1% for all observations) than in the field (25.9%), mean torpor bout duration was shorter in captivity (6.9 h) than in the field (13.1 h), and mean body temperatures during torpor were higher in captivity (25.3 degrees C) than in the field (19.6 degrees C). Moreover, normothermic body temperature as a function of air temperature differed between captive and free-ranging gliders, with a >3 degrees C difference at low air temperatures. Our comparison shows that activity patterns, thermal physiology, use of torpor and patterns of torpor may differ substantially between the laboratory and field, and provides further evidence that functional and behavioural data on captive in iduals may not necessarily be representative of those living in the wild.
Publisher: Springer Science and Business Media LLC
Date: 21-08-2011
DOI: 10.1007/S00114-011-0835-7
Abstract: Australian owlet-nightjars (Aegotheles cristatus ∼50 g) are one of only a few avian species that roost in cavities year-round and regularly enter torpor. Cavity roosts act as thermal buffers, and roost type likely affects energy expenditure of small birds. We used radiotelemetry to locate diurnal winter roost sites of owlet-nightjars in central Australia and to measure body (T (b)) and skin (T (skin)) temperature. We also recorded ambient temperature inside (T (IN)) and outside roosts. In idual owlet-nightjars used one to seven different roosts (tracking time 3-10 weeks), selecting either rock crevices (four birds) or tree hollows (four birds), or switching between the two roost types (seven birds). Rock crevices (T (IN) +9°C to +33°C) were warmer and thermally more stable than tree hollows (T (IN) -4.0°C to +37°C). Torpor, often expressed by a reduction of T (skin)/T (b) by >10°C for 3-4 h at dawn, was influenced by roost selection torpor use in tree hollows was almost twice that in rock crevices. Despite the potential energy savings accrued from roosting in well-insulated cavities, owlet-nightjars roosted in tree hollows more often (65% bird days, n = 398) than in rock crevices (35% bird days, n = 211). Lower costs of arousal from torpor via passive rewarming and basking and decreased risk of predation are two possible explanations for the preference to roost in tree hollows. We provide the first evidence for the influence of cavity roost selection on torpor use in a free-ranging bird and show that roost selection and thermal biology are strongly interrelated in determining energy expenditure.
Publisher: Wiley
Date: 07-1988
Publisher: Wiley
Date: 10-1998
Publisher: The Company of Biologists
Date: 02-2010
DOI: 10.1242/JEB.038224
Abstract: Seasonal changes in weather and food availability differ vastly between temperate and subtropical climates, yet knowledge on how free-ranging subtropical insectivorous bats cope with such changes is limited. We quantified ambient temperatures, torpor patterns and thermal physiology of subtropical insectivorous northern long-eared bats, Nyctophilus bifax, during summer (n=13) and winter (n=8) by temperature telemetry. As predicted, ambient conditions varied significantly between seasons, with warmer weather during summer. All bats used torpor on 85% of observation days during summer in comparison to 100% during winter. During summer, patterns of torpor varied and the duration of torpor bouts was not significantly affected by ambient temperature, whereas during winter torpor bout duration was negatively correlated with mean ambient temperature. Mean torpor bout duration in summer was 3.2±1.3 h and in winter was 26.8±11.3 h. Mean arousal time during summer was in the early afternoon and during winter in the late afternoon, and throughout both seasons arousals for possible foraging periods occurred near sunset. Skin temperature was positively correlated with ambient temperatures in both seasons, but the relationship differed between seasons. We show that torpor is used regularly throughout the year in a free-ranging subtropical bat and provide the first evidence demonstrating that torpor patterns and thermal physiology change with season.
Publisher: University of Chicago Press
Date: 11-2001
DOI: 10.1086/324097
Abstract: Several small caprimulgiform birds (<80 g) are known to enter torpor, apparently to cope with a fluctuating supply of insect prey. Since the large Australian tawny frogmouth (Podargus strigoides 381-556 g) is also insectivorous, we investigated its thermoregulatory behaviour and thermal biology to determine whether this species is also heterothermic. In an open woodland at approximately 1,000 m altitude, we equipped eight free-ranging birds with external temperature-sensitive radio transmitters attached to an elastic harness to measure skin temperature (T(skin)). Core body temperature (T(b)) was measured in three of these birds fitted with an additional intraperitoneal transmitter. T(skin) was closely correlated with T(b), although T(skin) was usually several degrees below T(b). During the three coldest months of the year (June-August), shallow torpor with T(b) as low as 29.1 degrees C occurred frequently, whereas during spring and summer, torpor was not recorded. Torpor occurred either during the night and/or during the first half of the day. Night torpor bouts were initiated after a short activity period around dusk and lasted on average for about 7 h. Torpid birds always aroused before sunrise to either commence a second short foraging period or to fly directly to a day roost tree. After birds roosted, T(b) fell again around sunrise, and birds occasionally entered a second dawn torpor bout however, in most cases, T(b) increased rapidly not long after entry, most likely due to passive heating by the sun. We conclude that despite their large body size and energetically conservative hunting strategy, tawny frogmouths, like several related caprimulgiform species, frequently enter shallow torpor when low T(a) demands high energetic costs for normothermic thermoregulation and likely reduces insect availability.
Publisher: Oxford University Press (OUP)
Date: 07-11-2023
DOI: 10.1093/ICB/ICAD067
Abstract: Torpor was traditionally seen as a winter survival mechanism employed by animals living in cold and highly seasonal habitats. Although we now know that torpor is also used by tropical and subtropical species, and in response to a variety of triggers, torpor is still largely viewed as a highly controlled, seasonal mechanism shown by Northern hemisphere species. To scrutinize this view, we report data from a macroanalysis in which we characterized the type and seasonality of torpor use from mammal species currently known to use torpor. Our findings suggest that predictable, seasonal torpor patterns reported for Northern temperate and polar species are highly derived forms of torpor expression, whereas the more opportunistic and variable forms of torpor that we see in tropical and subtropical species are likely closer to the patterns expressed by ancestral mammals. Our data emphasize that the torpor patterns observed in the tropics and subtropics should be considered the norm and not the exception.
Publisher: Springer Science and Business Media LLC
Date: 03-2005
Publisher: Elsevier BV
Date: 04-2003
Publisher: BMJ
Date: 12-09-2018
DOI: 10.1136/BJOPHTHALMOL-2017-311746
Abstract: To estimate the prevalence and causes of blindness and vision impairment for distance and near in Latin America and the Caribbean (LAC) in 2015 and to forecast trends to 2020. A meta-analysis from a global systematic review of 283 cross-sectional, population-representative studies from published and unpublished sources from 1980 to 2014 in the Global Vision Database included 17 published and 6 unpublished studies from LAC. In 2015, across LAC, age-standardised prevalence was 0.38% in all ages and 1.56% in those over age 50 for blindness 2.06% in all ages and 7.86% in those over age 50 for moderate and severe vision impairment (MSVI) 1.89% in all ages and 6.93% in those over age 50 for mild vision impairment and 39.59% in all ages and 45.27% in those over 50 for near vision impairment (NVI). In 2015, 117.86 million persons were vision impaired of those 2.34 million blind, 12.46 million with MSVI, 11.34 million mildly impaired and 91.72 million had NVI. Cataract is the most common cause of blindness. Undercorrected refractive-error is the most common cause of vision impairment. These prevalence estimates indicate that one in five persons across LAC had some degree of vision loss in 2015. We predict that from 2015 to 2020, the absolute numbers of persons with vision loss will increase by 12% to 132.33 million, while the all-age age-standardised prevalence will decrease for blindness by 15% and for other distance vision impairment by 8%. All countries need epidemiologic research to establish accurate national estimates and trends. Universal eye health services must be included in universal health coverage reforms to address disparities, fragmentation and segmentation of healthcare
Publisher: Elsevier BV
Date: 07-2012
Publisher: Informa UK Limited
Date: 02-07-2016
Publisher: The Company of Biologists
Date: 08-2020
DOI: 10.1242/JEB.229518
Publisher: Springer Science and Business Media LLC
Date: 10-2001
Abstract: Studies on the physiology of mammals and birds are often conducted using captive-bred in iduals and it is commonly assumed that the resulting data are representative of in iduals living in the field. To investigate whether these assumptions are justified, we quantified morphological, behavioural, and physiological variables of the small marsupial feathertail glider (Acrobates pygmaeus). We compared three populations: (i) in iduals from a cool-temperate, montane area, (ii) in iduals form a subtropical, coastal area, and (iii) captive-bred in iduals. Captive-bred gliders differed from the montane field gliders in morphology (longer tails and snouts), behaviour (longer activity periods) and physiology (less frequent torpor, shorter torpor, shallower torpor, higher metabolic rates during rest and torpor, and slower rates of rewarming). Most of these differences were also apparent between the captive-bred and the coastal field gliders. Unlike both field populations, captive-bred gliders often became hypothermic and were unable to rewarm. In contrast to the other physiological variables, the minimum body temperatures defended during torpor and the corresponding air temperatures differed between the montane and coastal field gliders, but were similar in coastal field and captive-bred gliders. Our study shows that morphology, behaviour and physiology can be strongly affected by breeding in or acclimation to captivity. The poor expression of torpor and thermal performance of the captive-bred gliders raises the question of whether they possess the physiological capability for survival in the wild. Even though captive breeding appears to have only minor effects on some physiological variables, data from captive-bred in iduals should only be extrapolated to the field with caution.
Publisher: Springer Science and Business Media LLC
Date: 18-09-2013
DOI: 10.1007/S00114-013-1098-2
Abstract: Hibernation and daily torpor are two distinct forms of torpor, and although they are related, it is not known how and in which sequence they evolved. As the pattern of torpor expressed by the oldest marsupial order the opossums (Didelphimorphia) may provide insights into the evolution of torpor, we aimed to provide the first quantitative data on the thermal biology and torpor expression of the rare Patagonian opossum (Lestodelphys halli). It is the opossum with the southernmost distribution, has a propensity of autumnal fattening, and therefore, is likely to hibernate. We captured two male Lestodelphys, which while in captivity displayed strong daily fluctuations of body temperatures (Tb) measured with implanted miniature data loggers even when they remained normothermic. In autumn and early winter, torpor was expressed occasionally when food was available, but cold exposure and food withdrawal increased torpor use. The mean Tb throughout the study was 32.2 ± 1.4 °C, the minimum Tb measured in torpid Lestodelphys was 7.7 °C, average torpor bout duration was 10.3 h, and the maximum torpor bout duration was 42.5 h. Thus, the pattern of torpor expressed by Lestodelphys was intermediate between that of daily heterotherms and hibernators suggesting that it may represent an ancestral opportunistic torpor pattern from which the derived patterns of daily torpor and seasonal hibernation erged.
Publisher: Springer Science and Business Media LLC
Date: 09-01-1998
Abstract: The hibernating marsupial mountain pygmy-possum (Burramys parvus, 40 g) has to raise its slow-growing offspring during a short alpine summer. Only females provide parental care, while after mating males emigrate to marginal habitats often at lower altitudes which can sustain only low possum densities. We predicted that the hibernation strategies in mountain pygmy-possums are distinct from those of similar-sized placental hibernators, because of the developmental constraints in marsupials and because hibernation differs between the sexes. Using temperature-sensitive radio transmitters, we studied the hibernation patterns of free-living male and female mountain pygmy-possums living in a north- and a south-facing boulder field (Kosciusko National Park) for two consecutive winters. In idual possums commenced hibernation several months before the snow season. As in other hibernators, torpor in the mountain pygmy-possum was interrupted by periodic arousals which occurred most often during the late afternoon. Torpor bouts initially lasted a few days when the hibernacula temperature (T
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/AM13025
Abstract: We quantified activity patterns, foraging times and roost selection in the eastern blossom-bat (Syconycteris australis) (body mass 17.6 g) in coastal northern New South Wales in winter using radio-telemetry. Bats roosted either in rainforest near their foraging site of flowering coast banksia (Banksia integrifolia) and commuted only 0.3 ± 0.1 km (n = 8), whereas others roosted 2.0 ± 0.2 km (n = 4) away in wet sclerophyll forest. Most bats roosted in rainforest foliage, but in the wet sclerophyll forest cabbage palm leaves (Livistonia australis) were preferred roosts, which likely reflects behavioural thermoregulation by bats. Foraging commenced 44 ± 22 min after sunset in rainforest-roosting bats, whereas bats that roosted further away and likely flew over canopies/open ground to reach their foraging site left later, especially a female roosting with her likely young (~4 h after sunset). Bats returned to their roosts 64 ± 12 min before sunrise. Our study shows that S. australis is capable of commuting considerable distances between appropriate roost and foraging sites when nectar is abundant. Bats appear to vary foraging times appropriately to minimise exposure to predators and to undertake parental care.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2001
Abstract: Laboratory studies have shown that high levels of dietary unsaturated fatty acids prolong torpor and lower body temperatures in hibernating herbivorous rodents, which may in turn improve winter survival. The importance of nutritional ecology in relation to hibernation in insectivorous hibernators is unknown. We therefore studied fatty acid composition of dietary insects and the depot fat of echidnas Tachyglossus aculeatus (Monotremata) during the pre-hibernation season and compared depot fat fatty acid composition before and after hibernation. Echidna depot fat fatty acid composition during the pre-hibernation season was almost identical to that of the most abundant prey species, the ant Iridomyrmex sp. Oleic acid (C18:1) was by far the most common fatty acid in both Iridomyrmex sp. (60%) and echidna depot fat (62%). After about 5 months of hibernation and an 18% loss of body mass, echidna fatty acid composition had changed significantly. The percentage of the monounsaturated oleic acid (C18:1) and palmitoleic acid (C16:1) had declined, whereas that of the saturated fatty acids (C12:0, C16:0, C18:0) and the polyunsaturated linoleic acid (C18:2) had increased. Our study suggests that, unlike herbivorous rodent hibernators, echidnas rely to a large extent on monounsaturated fatty acids as fuel for hibernation, reflecting the most common fatty acid in their food. Moreover, it appears that the high concentration of monounsaturated fatty acids compensates for the moderate availability of polyunsaturates and enables them to hibernate at low body temperatures.
Publisher: Springer Science and Business Media LLC
Date: 22-08-2016
DOI: 10.1007/S00114-016-1396-6
Abstract: Increased habitat fragmentation, global warming and other human activities have caused a rise in the frequency of wildfires worldwide. To reduce the risks of uncontrollable fires, prescribed burns are generally conducted during the colder months of the year, a time when in many mammals torpor is expressed regularly. Torpor is crucial for energy conservation, but the low body temperatures (T b) are associated with a decreased responsiveness and torpid animals might therefore face an increased mortality risk during fires. We tested whether hibernators in deep torpor (a) can respond to the smell of smoke and (b) can climb to avoid fires at T bs below normothermic levels. Our data show that torpid eastern pygmy-possums (Cercartetus nanus) are able to detect smoke and also can climb. All males aroused from torpor when the smoke stimulus was presented at an ambient temperature (T a) of 15 °C (T b ∼18 °C), whereas females only raised their heads. The responses were less pronounced at T a 10 °C. The first coordinated movement of possums along a branch was observed at a mean T b of 15.6 °C, and animals were even able to climb their prehensile tail when they reached a mean T b of 24.4 °C. Our study shows that hibernators can sense smoke and move at low T b. However, our data also illustrate that at T b ≤13 °C, C. nanus show decreased responsiveness and locomotor performance and highlight that prescribed burns during winter should be avoided on very cold days to allow torpid animals enough time to respond.
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/AM08114
Abstract: Eastern pygmy-possums (Cercartetus nanus) are known to be conservative with energy use probably because they rely on food that varies in availability. We quantified how nest use, huddling, and torpor contribute to a reduction of energy expenditure in C. nanus during mild cold exposure. In comparison to normothermic resting C. nanus at the same ambient temperature, nest use reduced energy expenditure on average by ~17%, huddling as a pair in a nest by ~50%, whereas torpor, which was employed by all seven in iduals, lowered energy expenditure by %. Our study shows that while all energy-conserving strategies employed by these possums can contribute significantly to reducing energy expenditure, torpor is by far the most effective because it not only reduces thermoregulatory energy costs, but also energy expenditure required for maintenance processes.
Publisher: Springer International Publishing
Date: 2021
Publisher: The Royal Society
Date: 06-06-2012
Abstract: Mammalian torpor saves enormous amounts of energy, but a widely assumed cost of torpor is immobility and therefore vulnerability to predators. Contrary to this assumption, some small marsupial mammals in the wild move while torpid at low body temperatures to basking sites, thereby minimizing energy expenditure during arousal. Hence, we quantified how mammalian locomotor performance is affected by body temperature. The three small marsupial species tested, known to use torpor and basking in the wild, could move while torpid at body temperatures as low as 14.8–17.9°C. Speed was a sigmoid function of body temperature, but body temperature effects on running speed were greater than those in an ectothermic lizard used for comparison. We provide the first quantitative data of movement at low body temperature in mammals, which have survival implications for wild heterothermic mammals, as directional movement at low body temperature permits both basking and predator avoidance.
Publisher: Springer Science and Business Media LLC
Date: 09-07-2014
DOI: 10.1007/S00114-014-1202-2
Abstract: Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures (T a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed (Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats (Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T a was ∼45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures (T skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death.
Publisher: Springer International Publishing
Date: 2021
Publisher: IEEE
Date: 09-2013
Publisher: Elsevier BV
Date: 07-1981
Publisher: Elsevier BV
Date: 10-1996
Publisher: Springer International Publishing
Date: 2021
Publisher: Springer International Publishing
Date: 2021
Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.YGCEN.2012.08.024
Abstract: Seasonal cycles of reproduction are common in many mammals and these are combined with the necessary energy budgeting for thermoregulatory challenges. Many mammals meet the challenge of changing environmental temperatures in winter by using torpor, a controlled reduction in body temperature and metabolic rate. We aimed to determine the effects of photoperiod and reproductive hormones on the seasonal cycles of reproduction and torpor use in a marsupial that commences reproduction in winter, the stripe-faced dunnart, Sminthopsis macroura. Males and females were placed under LD 14:10 and natural reproductive hormones blocked by either flutamide (males) or mifepristone (females) or tamoxifen (females). Reproductive parameters, metabolic rate and torpor variables were determined. The same animals were then placed under LD 10:14 and given testosterone (males) or progesterone (females) or oestrogen (females). Reproductive parameters, metabolic rate and torpor variables were measured. Body mass and tail widths (fattening indicator) in males were significantly affected by testosterone, and the effects were reversed by hormone blockers. Reproductive parameters were unaffected. Resting metabolic rate and ability to use torpor were not affected by treatment in males, however torpor characteristics, especially torpor bout duration, were affected by presence of testosterone in males. In females, body mass was unaffected by hormone presence, although tail widths were affected. Disruption of reproductive cycles occurred with hormone blockers in females, however, resting metabolic rate was not affected, and only presence of progesterone affected torpor characteristics in females. Our results differ from those found for rodents, where presence of testosterone abolishes the use of torpor in males, and oestrogen inhibits torpor use in females. Our study suggests that, in this mammal, metabolic responses to the presence or absence of reproductive hormones differs between males and females, and there is no absolute endocrinologically-driven reproductive season demarcated from the torpor season.
Publisher: Springer International Publishing
Date: 2021
Publisher: Wiley
Date: 04-1991
Publisher: Springer International Publishing
Date: 2021
Publisher: CSIRO Publishing
Date: 1990
DOI: 10.1071/WR9900535
Publisher: Springer International Publishing
Date: 2021
Publisher: Wiley
Date: 10-01-2013
DOI: 10.1111/BRV.12016
Abstract: A large number of analyses have examined how basal metabolic rate (BMR) is affected by body mass in mammals. By contrast, the critical ambient temperatures that define the thermo-neutral zone (TNZ), in which BMR is measured, have received much less attention. We provide the first phylogenetic analyses on scaling of lower and upper critical temperatures and the breadth of the TNZ in 204 mammal species from erse orders. The phylogenetic signal of thermal variables was strong for all variables analysed. Most allometric relationships between thermal variables and body mass were significant and regressions using phylogenetic analyses fitted the data better than conventional regressions. Allometric exponents for all mammals were 0.19 for the lower critical temperature (expressed as body temperature - lower critical temperature), -0.027 for the upper critical temperature, and 0.17 for the breadth of TNZ. The small exponents for the breadth of the TNZ compared to the large exponents for BMR suggest that BMR per se affects the influence of body mass on TNZ only marginally. However, the breadth of the TNZ is also related to the apparent thermal conductance and it is therefore possible that BMR at different body masses is a function of both the heat exchange in the TNZ and that encountered below and above the TNZ to permit effective homeothermic thermoregulation.
Publisher: Wiley
Date: 15-08-2014
DOI: 10.1111/BRV.12137
Publisher: Springer International Publishing
Date: 2021
Publisher: Springer International Publishing
Date: 2021
Publisher: Oxford University Press (OUP)
Date: 28-08-1990
DOI: 10.2307/1381938
Publisher: Springer Science and Business Media LLC
Date: 18-01-2014
DOI: 10.1007/S00114-013-1136-0
Abstract: 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 in iduals.
Publisher: Oxford University Press (OUP)
Date: 15-07-2016
Publisher: Oxford University Press (OUP)
Date: 27-06-2014
DOI: 10.1093/ICB/ICU093
Abstract: 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.
Publisher: Springer Science and Business Media LLC
Date: 1994
DOI: 10.1007/BF00714571
Publisher: Springer Berlin Heidelberg
Date: 2012
Publisher: Springer Science and Business Media LLC
Date: 08-12-2007
DOI: 10.1007/S00114-006-0193-Z
Abstract: 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 ( approximately 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 approximately 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.
Publisher: Elsevier BV
Date: 2005
DOI: 10.1016/J.NEUROSCIENCE.2005.06.087
Abstract: We have previously shown that following unilateral nodose ganglionectomy, [125I] CGP42112 binds to a non-angiotensin II (Ang II) related binding site in rat dorsal motor nucleus of the vagus nerve, ambiguus nucleus and nucleus of the solitary tract. Furthermore, this up-regulated binding site localizes with activated microglia. Given that some tetracyclines may inhibit microglia activation in brain, we examined the effect of minocycline treatment on the binding of [125I] CGP42112 and [3H] PK11195 (an established radioligand for microglia), as well as OX-42 immunoreactivity (an immunomarker for activated microglia), following nodose ganglionectomy. Male Wistar Kyoto rats underwent unilateral nodose ganglionectomy or sham operation and were treated with saline or minocycline (50 mg/kg i.p.) 12 h before surgery and twice daily after surgery (each 50mg/kg i.p.) for 3 days. Subsequent to nodose ganglionectomy, [125I] CGP42112 binding (insensitive to PD123319 or Ang II) was increased approximately two-fold in the ipsilateral nucleus of the solitary tract and was also induced in the ipsilateral dorsal motor nucleus of the vagus nerve and ambiguus nucleus of saline-treated rats. Treatment with minocycline reduced this non-angiotensin II [125I] CGP42112 binding (40-50% reduction) in the nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve and ambiguus nucleus. Analogous experiments using [3H] PK11195 also revealed up-regulated binding in the ipsilateral nucleus of the solitary tract ( approximately 205%), dorsal motor nucleus of the vagus nerve (approximately 80%) and ambiguus nucleus (approximately 210%) of saline-treated rats following nodose ganglionectomy, which was reduced by 40-100% with minocycline treatment. Immunoreactivity to OX-42 confirmed an increase in microglia activation and accumulation of macrophages in these brain stem nuclei following nodose ganglionectomy, which was also attenuated following treatment with minocycline. These data demonstrate that non-Ang II [125I] CGP42112 binding following nodose ganglionectomy is attenuated by minocycline treatment. This minocycline-induced effect was associated with reduced activation of microglia and an apparent reduction in the number of macrophages in the abovementioned nuclei. This evidence suggests that a non-Ang II [125I] CGP42112 binding site is located on, or associated with, activated microglia and macrophages, providing a useful tool with which to quantitate the neuroprotective effects of centrally acting anti-inflammatory compounds.
Publisher: Springer Science and Business Media LLC
Date: 15-08-2007
Publisher: Springer Berlin Heidelberg
Date: 2012
Publisher: American Physiological Society
Date: 2015
DOI: 10.1152/AJPREGU.00341.2014
Abstract: Endothermic arousal from torpor is an energetically costly process and imposes enormous demands on the cardiovascular system, particularly during early stage arousal from low body temperature (T b ). To minimize these costs many bats and other heterothermic endotherms rewarm passively from torpor using solar radiation or fluctuating ambient temperature (T a ). Because the heart plays a critical role in the arousal process in terms of blood distribution and as a source of heat production, it is desirable to understand how the function of this organ responds to passive rewarming and how this relates to changes in metabolism and T b . We investigated heart rate (HR) in hibernating long-eared bats ( Nyctophilus gouldi) and its relationship to oxygen consumption (V̇o 2 ) and subcutaneous temperature (T sub ) during exposure to increasing T a compared with endogenous arousals at constant low T a . During passive rewarming, HR and V̇o 2 remained low over a large T sub range and increased concurrently with increasing T a (Q 10 2.4 and 2.5, respectively). Absolute values were higher than during steady-state torpor but below those measured during torpor entry. During active arousals, mean HR and V̇o 2 were substantially higher than during passive rewarming at corresponding T sub . In addition, partial passive rewarming reduced the cost of arousal from torpor by 53% compared with entirely active arousal. Our data show that passive rewarming considerably reduces arousal costs and arousal time we suggest this may also contribute to minimizing exposure to oxidative stresses as well as demands on the cardiovascular system.
Publisher: Springer Science and Business Media LLC
Date: 16-09-2009
DOI: 10.1007/S00114-009-0606-X
Abstract: 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, in iduals 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.
Publisher: Springer Science and Business Media LLC
Date: 11-1985
DOI: 10.1007/BF00692935
Publisher: Elsevier BV
Date: 03-2013
DOI: 10.1016/J.CUB.2013.01.062
Abstract: Hibernation (multiday torpor) and daily torpor in heterothermic mammals and birds are characterized by pronounced temporal reductions in body temperature, energy expenditure, water loss, and other physiological functions and are the most effective means for energy conservation available to endotherms. Hibernators express multiday torpor predominately throughout winter, which substantially enhances winter survival. In contrast, daily heterotherms use daily torpor lasting for several hours during the rest phase. Although torpor is still widely considered to be a specific adaptation of cold-climate species, as we will see in this primer, it is used by many erse species from all climate zones, including the tropics. While energy conservation during adverse conditions is an important function of torpor, it is also employed to permit energy-demanding processes such as reproduction and growth, especially when food supply is limited. Even migrating birds enter torpor to conserve energy for the next stage of migration. Although many heterothermic species will be challenged by anthropogenic influences such as habitat destruction, introduced species, novel pathogens and specifically global warming, not all are likely to be affected in the same way. In fact, as argued here, it is likely that opportunistic heterotherms may be better equipped to deal with these challenges than homeotherms because heterotherms have highly flexible energy requirements, can limit foraging and reduce the risk of predation, and often are also long-lived. In contrast, strongly seasonal hibernators, especially those restricted to mountain tops, and those that have to deal with new diseases that are difficult to combat at low body temperatures, are likely to be adversely affected.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/ZO9940001
Abstract: Most heterothermic marsupials appear to display one of the two patterns of torpor that have been described in placental mammals. During shallow, daily torpor body temperature (T(b)) falls for several hours from about 35-degrees-C to values between 11 and 28-degrees-C, depending on the species, and metabolic rates fall to about 10-60% of the basal metabolic rate (BMR). In contrast during deep and prolonged torpor (hibernation), T(b) falls to about 1-5-degrees-C, metabolic rates to about 2-6% of BMR and torpor bouts last for 5-23 days. Shallow, daily torpor has been observed in the opossums (Didelphidae), the carnivorous marsupials (Dasyuridae) and the small possums (Petauridae). Daily torpor may also occur in the numbat (Myrmecobiidae) and the marsupial mole (Notoryctidae). Deep and prolonged torpor (hibernation) has been observed in the pygmy possums (Burramyidae), feathertail glider (Acrobatidae) and Dromiciops australis (Microbiotheriidae). The patterns of torpor in marsupials are paralleled by those of monotremes, placentals and even birds. These similarities in torpor patterns provide some support to the hypothesis that torpor may be plesiomorphic. However, as endothermy and torpor in birds apparently has evolved separately from that in mammals and as torpor occurrence in mammals can change within only a few generations it appears more likely that torpor in endotherms is convergent.
Publisher: Springer Science and Business Media LLC
Date: 05-08-1997
Abstract: Dietary cholesterol can affect both body lipid composition and steroid hormone concentration. We investigated whether a diet rich in cholesterol influences torpor patterns of hibernating chipmunks (Tamias amoenus) and, if so, whether these changes are better explained by diet-induced changes in body lipid composition or the concentration of testosterone, which at high levels inhibits torpor. Two groups of chipmunks were maintained either on a cholesterol diet (rodent chow containing 10% cholesterol) or a control diet (rodent chow) during pre-hibernation fattening and throughout the hibernation season. Torpid chipmunks on the cholesterol diet had significantly lower minimum body temperatures (-0.2 +/- 0.2 vs -0.6 +/- 0.2 degree C), lower metabolic rates (0.029 +/- 0.002 ml O2 g-1 h-1 vs 0.035 +/- 0.001 ml O2 g-1 h-1), and longer torpor bouts at -1 degree C (6.8 +/- 0.5 vs 4.1 +/- 1.0 days) than chipmunks on the control diet. Dietary cholesterol resulted in a significant increase in blood plasma cholesterol (sevenfold), liver cholesterol content (6.9-fold) and liver triglyceride content (3.5-fold) in comparison to controls. In contrast, dietary cholesterol had no detectable effect on the concentration of plasma testosterone, which was very low in both groups. Since torpor was deeper and longer in animals on the cholesterol diet our study suggests that torpor patterns of chipmunks were either directly affected by the dietary cholesterol or via changes in body lipid composition.
Publisher: Elsevier BV
Date: 05-2016
DOI: 10.1016/J.PHYSBEH.2016.03.009
Abstract: Ecosystems can change rapidly and sometimes irreversibly due to a number of anthropogenic and natural factors, such as deforestation and fire. How in idual animals exposed to such changes respond behaviourally and physiologically is poorly understood. We quantified the phenotypic plasticity of activity patterns and torpor use - a highly efficient energy conservation mechanism - in brown antechinus (Antechinus stuartii), a small Australian marsupial mammal. We compared groups in densely vegetated forest areas (pre-fire and control) with a group in a burned, open habitat (post-fire). Activity and torpor patterns differed among groups and sexes. Females in the post-fire group spent significantly less time active than the other groups, both during the day and night. However, in males only daytime activity declined in the post-fire group, although overall activity was also reduced on cold days in males for all groups. The reduction in total or diurnal activity in the post-fire group was made energetically possible by a ~3.4-fold and ~2.2-fold increase in the proportion of time females and males, respectively, used torpor in comparison to that in the pre-fire and control groups. Overall, likely due to reproductive needs, torpor was more pronounced in females than in males, but low ambient temperatures increased torpor bout duration in both sexes. Importantly, for both male and female antechinus and likely other small mammals, predator avoidance and energy conservation - achieved by reduced activity and increased torpor use - appear to be vital for post-fire survival where ground cover and refuges have been obliterated.
Publisher: Springer Berlin Heidelberg
Date: 25-09-2009
DOI: 10.1007/978-3-642-02421-4_5
Abstract: Aestivation, which in the context of this paper refers to avian and mammalian torpor in summer/at high ambient temperatures (T (a)), does not appear to differ functionally from other forms of torpor, and to a large extent reflects the higher body temperatures (T (b)) caused by high T (a). However, from an ecological point of view, aestivation results in different challenges and requirements than does torpor use in winter, because heat can cause reduced food and water availability in many regions, but without the access to low T (a) for a substantial reduction of T (b). Aestivation is used by a ersity of adult mammals and birds both in the field and laboratory, as well as by growing young to reduce thermoregulatory energy expenditure. Torpor occurs at high T (a) including the thermo-neutral zone and even under these conditions the reduction in energy expenditure and water requirements or water loss is substantial. Although data from the laboratory and, especially, from the field are limited, they show that torpor at high T (a) is an effective survival strategy and suggest that it is employed by many mammals and birds in a ersity of habitats.
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.155879
Abstract: The eastern pygmy-possum (Cercartetus nanus) is a small marsupial that can express spontaneous short bouts of torpor, as well as multi-day bouts of deep hibernation. To examine heart rate (HR) control at various stages of torpor in a marsupial hibernator, and to see whether HR variability differs from deep placental hibernators, we used radiotelemetry to measure ECG and Tb while measuring the rate of O2 consumption and ventilation. The HR and rate of O2 consumption during euthermia was at its minimum (321±34 bpm, 0.705±0.048 ml O2/g*h) at an ambient temperature (Ta) of 31°C. HR had an inverse linear relationship with Ta to a maximum of 630±19 bpm at a Ta of 20°C. During entry into torpor at an Ta of 20°C, HR slowed primarily as a result of episodic periods of cardiac activity where electrical activity of the heart occurred in groups of 3 or 4 heart beats. When Tb was stable at 24°C in these torpor bouts, the episodic nature of HR had disappeared (i.e. no asystoles) with a rate of 34±3 bpm. For multi-day bouts of deep torpor, Ta was lowered to 6.6±0.8°C. During these deep bouts of torpor, Tb reached a minimum of 8.0±1.0°C, with a minimum HR of 8 bpm and a minimum rate of O2 consumption of 0.029±0.07 ml O2/g*h. Shivering bouts occurred in deep torpor about every 8 minutes, during which ventilation occurred, and HR was elevated to 40 bpm. The duration of the QRS complex increased from 12ms during euthermia to 69 ms at a Tb of 8°C. These findings demonstrate the dynamic functioning range of heart rate to be about 600 bpm (∼80 fold), one of the largest known ranges in mammals. Our study shows that despite a separation of ∼160 million years the control and function of the cardiac system seems indistinguishable in marsupial and placental hibernating mammals.
Publisher: Springer Science and Business Media LLC
Date: 10-03-2017
DOI: 10.1007/S00360-017-1060-2
Abstract: Marsupials have a slow rate of development and this allows a detailed examination of thermoregulatory developmental changes and stages. We quantified the cooling rates of marsupial dunnarts (Sminthopsis crassicaudata) at 40-56 days (d) old, and torpor and basking behaviour in animals given the option to bask in four age groups from 60 to 150 d. The development of thermoregulation was a continuum, but was characterised by three major thermoregulatory stages: (1) at 40 d, animals were unable to maintain a constant high body temperature during short-term cold exposure (2) at 60 d, animals could maintain a high T
Publisher: Oxford University Press (OUP)
Date: 02-1997
DOI: 10.2307/1370228
Publisher: Springer Science and Business Media LLC
Date: 11-2001
Abstract: Little information is available on seasonal changes in thermal physiology and energy expenditure in marsupials. To provide new information on the subject, we quantified how body mass, body composition, metabolic rate, maximum heat production, body temperature and thermal conductance change with season in sugar gliders (Petaurus breviceps) held in outdoor aviaries. Sugar gliders increased body mass in autumn to a peak in May/June, which was caused to a large extent by an increase in body fat content. Body mass then declined to minimum values in August/September. Resting metabolic rate both below and above the thermoneutral zone (TNZ) was higher in summer than in winter and the lower critical temperature of the TNZ occurred at a higher ambient temperature (Ta) in summer. The basal metabolic rate was as much as 45% below that predicted from allometric equations for placental mammals and was about 15% lower in winter than in summer. In contrast, maximum heat production was raised significantly by about 20% in winter. This, together with an approximately 20% decrease in thermal conductance, resulted in a 13 degrees C reduction of the minimum effective Ta gliders were able to withstand. Our study provides the first evidence that, despite the apparent lack of functional brown adipose tissue, sugar gliders are able to significantly increase heat production in winter. Moreover, the lower thermoregulatory heat production at most TaS in winter, when food in the wild is scarce, should allow them to reduce energy expenditure.
Publisher: Oxford University Press (OUP)
Date: 02-2002
Publisher: Springer Science and Business Media LLC
Date: 12-1991
DOI: 10.1007/BF00260749
Abstract: Postprandial lipemia plays an important role in the development of coronary heart disease through an elevation of triglyceride-rich lipoproteins. In type 2 diabetic male subjects, our aim was to compare postprandial lipemia in a high-risk population with former myocardial infarction (MI) with that of a lower risk population free of clinically detectable heart disease. 32 male type 2 diabetic subjects were included in the study. We matched 17 cases with a verified history of MI with 15 controls according to age, BMI, HbA1c, diabetes duration, smoking, and treatment of diabetes. Ongoing metformin, insulin, or lipid lowering pharmacological treatment were exclusion criteria. After a maximal exercise tolerance test and echocardiography, the subjects underwent a hyperinsulinemic, euglycemic cl and a vitamin A fat loading test. Plasma triglyceride levels in the case group were significantly higher after 360 minutes (4.6 +/- 3.1 vs. 2.8 +/- 1.8 mmol/l, p = 0.04) and 480 minutes (3.6 +/- 2.2 vs. 2.4 +/- 2.4 mmol/l, p = 0.03), as was the incremental Area Under the Curve (iAUC) for the whole period (560 +/- 452 vs. 297 +/- 214 mmol x 480 min./l p = 0.048). In addition, the retinyl palmitate responses in the chylomicron-fraction from the case group were significantly higher (iAUC 311,502 +/- 194,933 vs. 187,004 +/- 102,928 ng x 480 min./ml p = 0.035). Type 2 diabetic males with prior MI had higher postprandial triglyceride-rich lipoprotein responses than those without MI, indicating that high responses may be a marker for a high-risk population.
Publisher: Oxford University Press (OUP)
Date: 02-2008
Publisher: Informa UK Limited
Date: 09-1999
DOI: 10.1071/MU99024
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/ZO19061
Abstract: Mammalian and avian torpor is widely viewed as an adaptation for survival of cold winters. However, in recent years it has been established that torpor can also be expressed in summer and that the functions of torpor are manyfold, including survival of adverse environmental events such as fires, storms, heat waves and droughts. Here we provide the first evidence on (1) torpor induction via an accidental flooding event in mammals (in captivity) and (2) expression of multiday torpor by spiny mice, lasting & times as long as usually observed for this desert rodent. Our data suggest yet another function of mammalian torpor, as a response to flood, in addition to many other adverse environmental events, and not just in response to cold.
Publisher: Public Library of Science (PLoS)
Date: 16-11-2011
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CBPA.2015.08.007
Abstract: Prolonged and remote measurement of body temperature (Tb) in undisturbed small hibernators was not possible in the past because of technological limitations. Although passive integrated transponders (PITs) have been used previously to measure subcutaneous temperature (Tsub) during daily torpor in a small marsupial, no study has attempted to use these devices at Tbs below 10°C. Therefore, we investigated whether subcutaneous interscapular PITs can be used as a viable tool for measuring Tb in a small hibernating bat (Nyctophilus gouldi Ng) and compared it with measurements of Tb during daily torpor in a heterothermic bat (Syconycteris australis Sa). The precision of transponders was investigated as a function of ambient temperature (Ta) and remote Tsub readings enabled us to quantify Tsub-Tb differentials during steady-state torpor and arousal. Transponders functioned well outside the manufacturer's recommended range, down to ~5°C. At rest, Tsub and rectal Tb (Trec) were strongly correlated for both bat species (Ng r(2)=0.88 Sa r(2)=0.95) and this was also true for N. gouldi in steady-state torpor (r(2)=0.93). During induced rewarming Tsub increased faster than Trec in both species. Our results demonstrate that transponders can be used to provide accurate remote measurement of Tb in two species of bats during different physiological states, both during steady-state conditions and throughout dynamic phases such as rewarming from torpor. We show that, at least during rewarming, regional heterothermy common to larger hibernators and other hibernating bats is also present in bats capable of daily torpor.
Publisher: Wiley
Date: 05-1992
Publisher: Springer Science and Business Media LLC
Date: 08-08-2007
DOI: 10.1007/S00114-007-0293-4
Abstract: The high energetic cost associated with endothermic rewarming from torpor is widely seen as a major disadvantage of torpor. We tested the hypothesis that small arid zone marsupials, which have limited access to energy in the form of food but le access to solar radiation, employ basking to facilitate arousal from torpor and reduce the costs of rewarming. We investigated torpor patterns and basking behaviour in free-ranging fat-tailed dunnarts Sminthopsis crassicaudata (10 g) in autumn and winter using small, internal temperature-sensitive transmitters. Torpid animals emerged from their resting sites in cracking soil at approximately 1000 h with body temperatures as low as 14.6 degrees C and positioned themselves in the sun throughout the rewarming process. On average, torpor duration in autumn was shorter, and basking was less pronounced in autumn than in winter. These are the first observations of basking during rewarming in S. crassicaudata and only the second direct evidence of basking in a torpid mammal for the reduction of energetic costs during arousal from torpor and normothermia. Our findings suggest that although overlooked in the past, basking may be widely distributed amongst heterothermic mammals. Therefore, the energetic benefits from torpor use in wild animals may currently be underestimated.
Publisher: Springer Science and Business Media LLC
Date: 02-2006
DOI: 10.1007/S00114-005-0063-0
Abstract: Many mammals save energy during food shortage or harsh weather using controlled reductions in body temperature and metabolism called torpor. However, torpor slows offspring growth, and reproductive in iduals are thought to avoid using it because of reduced fitness resulting from delayed offspring development. We tested this hypothesis by investigating torpor during reproduction in hoary bats (Lasiurus cinereus, Vespertilionidae) in southern Canada. We recorded deep, prolonged torpor bouts, which meet the definition for hibernation, by pregnant females. Prolonged torpor occurred during spring storms. When conditions improved females aroused and gave birth within several days. Our observations imply a fitness advantage of torpor in addition to energy conservation because reduced foetal growth rate could delay parturition until conditions are more favourable for lactation and neonatal survival.
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.PHYSBEH.2015.09.002
Abstract: The predicted increase of the frequency and intensity of wildfires as a result of climate change could have a devastating impact on many species and ecosystems. However, the particular physiological and behavioural adaptions of animals to survive fires are poorly understood. We aimed to provide the first quantitative data on physiological and behavioural mechanisms used by a small heterothermic marsupial mammal, the fat-tailed dunnart (Sminthopsis crassicaudata), that may be crucial for survival during and immediately after a fire. Specifically, we aimed to determine (i) whether captive torpid animals are able to respond to fire stimuli and (ii) which energy saving mechanisms are used in response to fires. The initial response of torpid dunnarts to smoke exposure was to arouse immediately and therefore express shorter and shallower torpor bouts. Dunnarts also increased activity after smoke exposure when food was provided, but not when food was withheld. A charcoal/ash substrate, imitating post-fire conditions, resulted in a decrease in torpor use and activity, but only when food was available. Our novel data suggests that heterothermic mammals are able to respond to fire stimuli, such as smoke, to arouse from torpor as an initial response to fire and adjust torpor use and activity levels according to food availability modulated by fire cues.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/ZO14053
Abstract: Prescribed fires for fuel reduction affect wildlife in several ways. We observed a marked increase in superb lyrebird (Menura novaehollandiae) numbers after a controlled burn in Guy Fawkes River National Park, New South Wales, in April and May 2014. The fire occurred during the winter breeding season however, congregations of males were often seen together in the burnt landscape, indicating an opportunistic prioritisation of foraging. The low-intensity fire cleared brush and low-level vegetation, thus decreasing foraging effort and potentially attracting the species despite the need to seek mating partners. Controlled burns therefore have the potential to attract superb lyrebirds immediately after fire due to ease of movement and foraging effort.
Publisher: Royal Zoological Society of New South Wales
Date: 2012
DOI: 10.7882/FS.2012.018
Publisher: University of Chicago Press
Date: 03-2001
DOI: 10.1086/319666
Abstract: Helox (79% helium and 21% oxygen) has often been used for thermobiological studies, primarily because helium is thought to be metabolically inert and to produce no adverse effects other than increasing heat loss. However, these assumptions have been questioned. As basal metabolic rate (BMR) represents maintenance energy requirements for vital body functions, potential physiological effects of helox should be reflected in changes of BMR. In this study, sugar gliders were subjected to both air and helox atmospheres over a wide range of T(a)'s, including the thermoneutral zone (TNZ), to determine (1) whether helox has any influence other than on heat loss and (2) the maximum heat production (HP(max)) and thermal limits of this species. Although thermal conductance in the TNZ increased in helox, BMR was similar in air and helox (0.55+/-0.07 and 0.57+/-0.06 mL g(-1) h(-1), respectively). The TNZ in helox, however, was shifted upwards by about 3 degrees C. Below the TNZ, sugar gliders were able to withstand an effective temperature of -24.7+/-7.3 degrees C with an HP(max) of 3.14+/-0.36 mL g(-1) h(-1). The low effective temperature tolerated by sugar gliders shows that they are competent thermoregulators despite their apparent lack of functional brown fat. Similarities of BMRs in air and helox suggest that the effect of helox is restricted to an increase of heat loss, and, consequently, helox represents a useful tool for thermal physiologists. Moreover, the lack of increase of BMR in helox despite an increase in thermal conductance of sugar gliders suggests that BMR is not a function of body surface.
Publisher: Springer Science and Business Media LLC
Date: 17-03-2011
DOI: 10.1007/S00114-011-0779-Y
Abstract: Bats are most erse in the tropics, but there are no quantitative data on torpor use for energy conservation by any tropical bat in the wild. We examined the thermal biology, activity patterns and torpor use of two tree-roosting long-eared bats (Nyctophilus geoffroyi, 7.8 g) in tropical northern Australia in winter using temperature telemetry. Bats commenced activity about 20 min after sunset, ended activity about 2.5 h before sunrise and entered torpor everyday in the early morning even when minimum ambient temperatures (T (a)) were as high as 23°C. On average, bats remained torpid for almost 5 h, mean minimum skin temperature (T (skin)) measured was 22.8 ± 0.1°C and daily T (skin) minima were correlated with T(a). Our study shows that even in the tropics, torpor is frequently employed by bats, suggesting that worldwide most bat species are heterothermic and use torpor for energy conservation. We propose that the ability of employing torpor and the resulting highly plastic energy requirements may partially explain why these small insectivorous bats can inhabit almost the entire Australian continent despite vastly different climatic and likely trophic conditions. Reduced energy requirements also may permit survival in degraded or modified habitats, reduce the need for foraging and reduce exposure to predators. Thus, the ability to employ torpor may be one important reason for why most Australian bats and other heterothermic mammals have not gone extinct whereas many obligatory homeothermic mammals that cannot employ torpor and have high energy and foraging requirements have suffered high rates of extinctions.
Publisher: CSIRO Publishing
Date: 1988
DOI: 10.1071/ZO9880473
Abstract: Torpor in endotherms has only been observed in small species, suggesting that body mass determines the occurrence of torpor. The present study investigates the influence of body mass on the occurrence of torpor and also the pattern of torpor (i.e. minimum body temperature, metabolic rate, and the duration of torpor). The two small dasyurid marsupials Planigale gilesi (8.3 g) and Ningaui yvonneae (11.6 g) entered torpor frequently when food was available withdrawal of food increased the occurrence of torpor to almost 100%. Minimum body temperatures during torpor in both species were lower and the torpor duration was longer than for most larger dasyurid species studied so far. These findings suggest that the thermal stress on these very small species exerts a strong selective pressure to enhance daily torpor episodes for reduction of heat loss to the environment.
Publisher: Wiley
Date: 08-1999
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.CBPA.2008.07.025
Abstract: Many birds living in regions with seasonal fluctuations in ambient temperatures (T(a)) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ 31.3 to 34.8 degrees C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2+/-0.3 degrees C) than winter-acclimatized (37.1+/-0.5 degrees C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing T(a), and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O(2) g(-1) h(-1)) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter T(a), which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.
Publisher: Informa UK Limited
Date: 12-1999
DOI: 10.1071/MU99031
Publisher: Elsevier BV
Date: 12-2005
Publisher: Springer Science and Business Media LLC
Date: 10-12-2008
DOI: 10.1007/S00114-008-0492-7
Abstract: Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active in iduals. 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 in iduals 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 degrees C to 36 degrees 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.
Publisher: Informa UK Limited
Date: 2000
Abstract: Mammals and birds have evolved the ability to maintain a high and constant body temperature Tb over a wide range of ambient temperatures Ta using endogenous heat production. In many, especially small endotherms, cost for thermoregulatory heat production can exceed available energy to overcome these energetic bottlenecks, they enter a state of torpor (a regulated reduction of Tb and metabolic rate). Since the occurrence of torpor in many species is a seasonal event and occurs at certain times of the day, we review whether circadian and circannual rhythms, important in the timing of biological events in active animals, also play an important role during torpor when Tb is reduced substantially and may even fall below 0 degrees C. The two distinct patterns of torpor, hibernation (prolonged torpor) and daily torpor, differ substantially in their interaction with the circadian system. Daily torpor appears to be integrated into the normal circadian rhythm of activity and rest, although torpor is not restricted only to the normal rest phase of an animal. In contrast, hibernation can last for several days or even weeks, although torpor never spans the entire hibernation season, but is interrupted by periodic arousals and brief normothermic periods. Clearly, a day is no longer ided in activity and rest, and at first glance the role of the circadian system appears negligible. However, in several hibernators, arousals not only follow a regular pattern consistent with a circadian rhythm, but also are entrainable by external stimuli such as photoperiod and Ta. The extent of the interaction between the circadian and circannual system and hibernation varies among species. Biological rhythms of hibernators for which food availability appears to be predictable seasonally and that hibernate in deep and sealed burrows show little sensitivity to external stimuli during hibernation and hence little entrainability of arousal events. In contrast, opportunistic hibernators, which some times use arousals for foraging and hibernate in open and accessible hibernacula, are susceptible to external zeitgebers. In opportunistic hibernators, the circadian system plays a major role in maintaining synchrony between the normal day-night cycle and occasional foraging. Although the daily routine of activity and rest is abandoned during hibernation, the circadian system appears to remain functional, and there is little evidence it is significantly affected by low Tb.
Publisher: Frontiers Media SA
Date: 16-12-2021
Abstract: Torpor is a controlled reduction of metabolism and body temperature, and its appropriate use allows small birds to adapt to and survive challenging conditions. However, despite its great energy conservation potential, torpor use by passerine birds is understudied although they are small and comprise over half of extant bird species. Here, we first determined whether a free-living, small ∼20 g Australian passerine, the eastern yellow robin ( Eopsaltria australis ), expresses torpor by measuring skin temperature (T s ) as a proxy for body temperature. Second, we tested if skin temperature fluctuated in relation to ambient temperature (T a ). We found that the T s of eastern yellow robins fluctuated during winter by 9.1 ± 3.9°C on average (average minimum T s 30.1 ± 2.3°C), providing the first evidence of torpor expression in this species. Daily minimum T s decreased with T a , reducing the estimated metabolic rate by as much as 32%. We hope that our results will encourage further studies to expand our knowledge on the use of torpor in wild passerines. The implications of such studies are important because species with highly flexible energy requirements may have an advantage over strict homeotherms during the current increasing frequency of extreme and unpredictable weather events, driven by changing climate.
Publisher: Springer Science and Business Media LLC
Date: 31-05-2016
DOI: 10.1007/S00360-016-1003-3
Abstract: Historical patterns of wildfires are being altered as a result of changing climate and therefore are becoming an increasingly pressing global issue. How small mammals deal physiologically with changes in landscape and food availability due to fire remains largely unknown, although recent studies on small heterothermic terrestrial mammals have shown an increase in post-fire torpor use to reduce energy and foraging requirements. However, data on the behavioural and physiological responses of bats after fires are scarce, although potentially these volant species may differ from terrestrial mammals. Therefore, we investigated the post-fire thermal biology and activity of lesser long-eared bats (Nyctophilus geoffroyi) using temperature-telemetry in Warrumbungle National Park, NSW, which experienced a devastating wildfire in 2013. The study comprised two field seasons, one in 2013 within 4 months after the fire, and one in 2015 two years after the fire to identify potential changes in behaviour and physiology. Interestingly, soon after the fire, bats showed significantly shorter torpor bout duration (11.8 ± 12.5 h) and longer normothermia duration (8.7 ± 4.6 h) in comparison to those in 2015 (torpor bout duration: 24.1 ± 23.5 h normothermia duration: 2.5 ± 1.5 h). Insect availability was significantly (20-fold) higher in 2013 than in 2015, which was likely an important factor resulting in the short average torpor bout duration by N. geoffroyi after the fire. Our data indicate that volant bats appear to show the opposite post-fire behavioural and physiological responses to small terrestrial mammals, showing longer normothermic and active periods and shorter torpor bouts to capitalise on an increase in available post-fire resources.
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.DIABRES.2006.03.012
Abstract: We examined the association of quality of life with glucose tolerance status in an Australian population to determine the stage in the development of diabetes that quality of life is impaired. The Australian Diabetes, Obesity and Lifestyle study (AusDiab) was a population-based study of 11,247 people from randomly selected areas of Australia. As part of the study, participants underwent an oral glucose tolerance test and completed the SF-36 quality of life questionnaire. Previously diagnosed diabetes was associated with a significantly greater risk of being in the lowest quartile of each dimension of the SF-36 scale (except for mental health) and this association was only partially attenuated by adjustment for age, sex, body mass index (BMI), physical activity and treatment for hypertension and lipid abnormalities (adjusted odds ratios [95% CI]: bodily pain, 1.51 [1.18-1.94] general health, 2.20 [1.64-2.95] physical functioning, 1.50 [1.10-2.05] role limitation (emotional), 1.43 [1.07-1.91] role limitation (physical), 1.57 [1.13-2.18] social functioning, 1.93 [1.46-2.54] and vitality, 2.24 [1.56-3.22]. Among those with newly diagnosed diabetes (NDM) and impaired glucose tolerance (IGT), there was also evidence of reduced quality of life on some dimensions of the SF-36 scale (NDM, general health, physical functioning and role limitation (physical) IGT, physical functioning and social functioning) after adjustment for confounders. These findings show that diabetes is associated with a reduced quality of life and that this is evident in the early stage of the disease, particularly in relation to the ability to perform physical activities.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/ZO08032
Abstract: Several mammal species bask to passively rewarm during arousal from torpor, a strategy that can decrease energetic costs. Nothing is known about basking behaviour in these species or the trade-offs between energetic benefits of basking and potential costs associated with changes in activity patterns and increased predation risk. We assessed basking during winter in Pseudantechinus macdonnellensis, an Australian arid-zone marsupial that belongs to a family (Dasyuridae) that is typically nocturnal. Animals were implanted with temperature-sensitive transmitters to assess body temperatures and to assist in visually locating animals active during the day. Tagged animals regularly exhibited diurnal foraging. Foraging bouts occurred throughout the day however, most bouts were observed within 3 h of sunset. By comparison, basking occurred much more frequently in the morning. Basking and a shift towards diurnal foraging in winter is associated with a decrease in richness and abundance of predators. P. macdonnellensis appears to compensate for the occurrence of torpor during the active phase (i.e. night) in winter by changing activity patterns such that foraging commences during what is usually the rest phase. These activity patterns are not expected to occur during the remainder of the year.
Publisher: Springer International Publishing
Date: 2021
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JEB.098970
Abstract: While heart rate (fH) has been used as an indicator of energy expenditure, quantitative data showing the relationship between these variables are only available for normothermic animals. To determine whether fH also predicts oxygen consumption (VO2) during torpor we simultaneously measured VO2, fH and subcutaneous body temperature (Tsub) of a hibernator, Gould's long-eared bats (Nyctophilus gouldi, 9 g, n=18), at ambient temperatures (Ta) between 0 and 25°C. At rest, fH of normothermic resting bats was negatively correlated with Ta, with maximum fH of 803 bpm (Ta=5°C). During torpor the relationship between fH and Ta was curvilinear, and at low Tsub (~6°C) fH fell to a minimum average of 8 bpm. The minimum average values for both VO2 and fH in torpor reported here were among the lowest recorded for bats. The relationship between fH and VO2 was significant for both resting (r2=0.64, p& .001) and torpid bats (r2=0.84, p& .001), with no overlap between the two states. These variables were also significantly correlated (r2=0.44, p& .001) for entire torpor bouts. Moreover, estimates of VO2 from fH did not differ significantly from measured values during the different physiological states. Our study is the first to investigate the accuracy of fH as a predictor of VO2 during torpor and indicates the reliability of this method as a potential measure of energy expenditure in the field. Nevertheless, fH should only be used to predict VO2 within the range of activities for which robust correlations have been established.
Publisher: Elsevier
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 23-03-1999
Abstract: Blossom-bats, Syconycteris australis (18 g) are known to be highly active throughout the night. Since this species frequently enters torpor, we postulated that their use of heterothermy may be related to a high energy expenditure in the field. To test this hypothesis we measured field metabolic rates (FMR) of S. australis at a subtropical site using the doubly labelled water (DLW) method. We also measured DLW turnover in captive animals held at constant ambient temperature (Ta) with ad libitum food to estimate whether Ta and food availability affect energy expenditure under natural conditions. The FMR of S. australis was 8.55 ml CO2 g-1 h-1 or 76.87 kJ day-1 which is 7.04 times the basal metabolic rate (BMR) and one of the highest values reported for endotherms to date. Mass-specific energy expenditure by bats in the laboratory was about two-thirds of that of bats in the field, but some of this difference was explained by the greater body mass in captive bats. This suggests that foraging times in the field and laboratory were similar, and daily energy expenditure was not strongly affected by Ta or ad libitum food. Water uptake in the field was significantly higher than in the laboratory, most likely because nectar contained more water than the laboratory diet. Our study shows that S. australis has a FMR that is about double that predicted for its size although its BMR is lower than predicted. This supports the view that caution must be used in making assumptions from measurements of BMR in the laboratory about energy and other biological requirements in free-ranging animals.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/ZO20036
Abstract: Small insectivorous bats commonly use torpor while day-roosting, even in summer. However, reproductive female bats are believed to benefit from avoiding torpor because a constant, elevated body temperature maximises the rate of offspring growth, which could increase offspring survival. We used temperature-sensitive radio-transmitters to locate roosts and document the thermal biology of pregnant and lactating females of Nyctophilus geoffroyi (9 g) and N. gouldi (11 g) at a woodland in a cool temperate climate. Unlike males, reproductive female Nyctophilus spp. roosted as small groups (& ) within insulated tree cavities. Roost switching occurred every 3.7 ± 1.5 (N. geoffroyi) or 1.7 ± 0.8 days (N. gouldi), and radio-tagged in iduals roosted together and apart on different days. Skin temperature during roosting was most often between 32 and 36°C, and torpor was used infrequently. Male Nyctophilus have been shown in previous studies to use torpor daily during summer. These contrasting torpor patterns likely reflect the warmed cavities occupied by maternity colonies and the thermally unstable shallow crevices occupied by in idual males. Our results support the hypothesis that availability of thermally suitable roosts will influence thermoregulatory patterns of reproductive females and hence the growth rates and survival of their offspring. Thus, it is important to conserve woodland habitat with trees in a range of decay stages to provide opportunities for selection and movement among roost trees by reproductive female bats.
Publisher: Springer Science and Business Media LLC
Date: 15-06-2015
DOI: 10.1038/SREP11243
Abstract: Although storms provide an extreme environmental challenge to organisms and are predicted to increase in frequency and intensity due to climate change, there are no quantitative observations on the behaviour and physiology of animals during natural disasters. We provide the first data on activity and thermal biology of a free-ranging, arboreal mammal during a storm with heavy rain and category 1 cyclone wind speeds. We studied a population of sugar gliders ( Petaurus breviceps ), a species vulnerable to bad weather due to their small body size and mode of locomotion, in a subtropical habitat during spring when storms are common. Although torpor is generally rare in this species, sugar gliders remained inactive or reduced foraging times during the storm and further minimized energy demands by entering deep torpor. All animals survived the storm and reverted to normal foraging activity during the following night(s). It thus appears that heterothermic mammals have a crucial adaptive advantage over homeothermic species as they can outlast challenging weather events, such as storms and floods, by reducing metabolism and thus energetic needs.
Publisher: Springer Science and Business Media LLC
Date: 24-02-2009
DOI: 10.1007/S00114-009-0516-Y
Abstract: One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and, therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing torpor or whether differences in prey composition among in iduals influence torpor characteristics. Here, we test the hypothesis that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara (Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates (mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass among in iduals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal.
Publisher: Wiley
Date: 10-1997
Publisher: Springer Science and Business Media LLC
Date: 04-11-2009
DOI: 10.1007/S00360-009-0417-6
Abstract: Limited information is available on basking behaviour in torpid mammals and its energetic consequences. We investigated the effects of physiological and behavioural strategies on the energetics of the fat-tailed dunnart (Sminthopsis crassicaudata). Metabolic rate and body temperature during torpor, basking and rest were measured over 24 h in response to simulated environmental conditions: (a) constant ambient temperature (T(a)) of 15 degrees C, (b) constant T(a) of 15 degrees C with access to a radiant heat l , (c) a T(a) cycle (range 15-31 degrees C), and (d) a T(a) cycle with access to a radiant heat l . When a radiant heat source was provided, all dunnarts (n = 16) basked during all measurements, which resulted in energy savings of up to 74% during rest. Overall, torpor was used on 59% of measurements with a maximum duration of 16.2 h and reductions in metabolic rate of 90% compared to normothermic values. Torpid dunnarts actively moved from a shaded area to position themselves under the heat l with body temperatures as low as 17.5 degrees C and thereby reduced rewarming costs by 66%. We demonstrated, for the first time in the laboratory, that torpid animals actively move to a heat source to bask, and that this behaviour results in considerable energy savings. Our finding supports the view that basking during normothermia and rewarming from torpor substantially reduces energetic requirements, which may be important for the survival of small dasyurids living on limited resources in the Australian arid zone.
Publisher: Wiley
Date: 29-10-2010
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.CBPA.2016.05.019
Abstract: Daily torpor is frequently expressed in small rodents when facing energetically unfavorable ambient conditions. Desert hamsters (Phodopus roborovskii, ~20g) appear to be an exception as they have been described as homeothermic. However, we hypothesized that they can use torpor because we observed reversible decreases of body temperature (Tb) in fasted hamsters. To test this hypothesis we (i) randomly exposed fasted summer-acclimated hamsters to ambient temperatures (Tas) ranging from 5 to 30°C or (ii) supplied them with different rations of food at Ta 23°C. All desert hamsters showed heterothermy with the lowest mean Tb of 31.4±1.9°C (minimum, 29.0°C) and 31.8±2.0°C (minimum, 29.0°C) when fasted at Ta of 23°C and 19°C, respectively. Below Ta 19°C, the lowest Tb and metabolic rate increased and the proportion of hamsters using heterothermy declined. At Ta 5°C, nearly all hamsters remained normothermic by increasing heat production, suggesting that the heterothermy only occurs in moderately cold conditions, perhaps to avoid freezing at extremely low Tas. During heterothermy, Tbs below 31°C with metabolic rates below 25% of those during normothermia were detected in four in iduals at Ta of 19°C and 23°C. Consequently, by definition, our observations confirm that fasted desert hamsters are capable of shallow daily torpor. The negative correlation between the lowest Tbs and amount of food supply shows that heterothermy was mainly triggered by food shortage. Our data indicate that summer-acclimated desert hamsters can express fasting-induced shallow daily torpor, which may be of significance for energy conservation and survival in the wild.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2007
DOI: 10.1007/S00360-007-0193-0
Abstract: According to the concept of the "minimal boundary curve for endothermy", mammals and birds with a basal metabolic rate (BMR) that falls below the curve are obligate heterotherms and must enter torpor. We examined the reliability of the boundary curve (on a double log plot transformed to a line) for predicting torpor as a function of body mass and BMR for birds and several groups of mammals. The boundary line correctly predicted heterothermy in 87.5% of marsupials (n = 64), 94% of bats (n = 85) and 82.3% of rodents (n = 157). Our analysis shows that the boundary line is not a reliable predictor for use of torpor. A discriminate analysis using body mass and BMR had a similar predictive power as the boundary line. However, there are sufficient exceptions to both methods of analysis to suggest that the relationship between body mass, BMR and heterothermy is not a causal one. Some homeothermic birds (e.g. silvereyes) and rodents (e.g. hopping mice) fall below the boundary line, and there are many ex les of heterothermic species that fall above the boundary line. For marsupials and bats, but not for rodents, there was a highly significant phylogenetic pattern for heterothermy, suggesting that taxonomic affiliation is the biggest determinant of heterothermy for these mammalian groups. For rodents, heterothermic species had lower BMRs than homeothermic species. Low BMR and use of torpor both contribute to reducing energy expenditure and both physiological traits appear to be a response to the same selective pressure of fluctuating food supply, increasing fitness in endothermic species that are constrained by limited energy availability. Both the minimal boundary line and discriminate analysis were of little value for predicting the use of daily torpor or hibernation in heterotherms, presumably as both daily torpor and hibernation are precisely controlled processes, not an inability to thermoregulate.
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/WR03005
Abstract: We studied home-range size, range length and spatial organisation of fat-tailed false antechinus, Pseudantechinus macdonnellensis, at Ormiston Creek, central Australia. Animals were tracked using transmitters implanted into the body cavity. Mean home-range size was 0.76 ha based on the minimum convex polygon (MCP) method and 1.14 ha based on the fixed kernel method (95% contour). Mean size of core areas of the home range was 0.07 ha based on the 50% kernel contour. Mean maximum range length was 148.83 m. Males occupied larger home-range areas than females (MCP: 0.98 v. 0.31 ha, 95% fixed kernel: 1.50 v. 0.43 ha) and also had greater maximum range lengths (180 v. 86 m). Home-range areas showed little overlap within the sexes however, ranges of males overlapped those of females by an average of 37.95%. By comparison with data from a previous mark–recapture study at the same site, radio-tracking produced home-range estimates (MCP) that were greater by a factor of 24.5 for males and 15.5 for females, whereas maximum range lengths were lower for females, but similar for males. The results of this study support the proposition that the rock-dwelling P. macdonnellensis has a more stable home range and undergoes fewer long-range movements than similar-sized arid-zone dasyurids that occupy open environments. These differences likely result from the stability in resources provided by rocky habitats, specifically year-round availability of insects, availability of plentiful shelter sites that are very effective thermal buffers in both summer and winter, and a ersity of accessible microclimates.
Publisher: Elsevier BV
Date: 07-1995
DOI: 10.1016/0031-9384(94)00384-H
Abstract: To determine whether locomotor activity and body temperature (Tb) rhythms change during the mating season of male Antechinus stuartii and whether that could contribute to postmating die-off, we measured both variables in in iduals kept in the laboratory under natural photoperiod. Before the mating season Antechinus were mainly nocturnal. However, during the mating period (end of August) males showed a markedly elevated activity level and some animals extended their activity period well into the light phase. After about 2 weeks, normal activity patterns were restored. Activity was always accompanied by elevated TbS, whereas resting phases were characterized by low TbS. During the mating season the average daily Tb was increased because animals maintained high TbS for longer time periods and because the resting Tb was also elevated. The rise of both Tb and locomotor activity during the mating season indicate an enhanced energy expenditure even when agonistic encounters between males and mating are excluded. However, under laboratory conditions without severe cold stress, food ad lib, and without social interaction males were able to avert postmating die-off.
Publisher: Springer Science and Business Media LLC
Date: 09-08-2005
DOI: 10.1007/S00360-005-0008-0
Abstract: Data on thermal energetics for vespertilionid bats are under-represented in the literature relative to their abundance, as are data for bats of very small body mass. Therefore, we studied torpor use and thermal energetics in one of the smallest (4 g) Australian vespertilionids, Vespadelus vulturnus. We used open-flow respirometry to quantify temporal patterns of torpor use, upper and lower critical temperatures (T (uc) and T (lc)) of the thermoneutral zone (TNZ), basal metabolic rate (BMR), resting metabolic rate (RMR), torpid metabolic rate (TMR), and wet thermal conductance (C (wet)) over a range of ambient temperatures (T (a)). We also measured body temperature (T (b)) during torpor and normothermia. Bats showed a high proclivity for torpor and typically aroused only for brief periods. The TNZ ranged from 27.6 degrees C to 33.3 degrees C. Within the TNZ T (b) was 33.3+/-0.4 degrees C and BMR was 1.02+/-0.29 ml O(2) g(-1) h(-1) (5.60+/-1.65 mW g(-1)) at a mean body mass of 4.0+/-0.69 g, which is 55 % of that predicted for a 4 g bat. Minimum TMR of torpid bats was 0.014+/-0.006 ml O(2) g(-1) h(-1) (0.079+/-0.032 mW g(-1)) at T (a)=4.6+/-0.4 degrees C and T (b)=7.5+/-1.9. T (lc) and C (wet) of normothermic bats were both lower than that predicted for a 4 g bat, which indicates that V. vulturnus is adapted to minimising heat loss at low T (a). Our findings support the hypothesis that vespertilionid bats have evolved energy-conserving physiological traits, such as low BMR and proclivity for torpor.
Publisher: University of Chicago Press
Date: 11-1995
Publisher: Oxford University Press (OUP)
Date: 16-12-2010
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/AM10052
Abstract: Since little information is available on the spatial ecology of small arid-zone marsupials, we used radio-tracking to investigate the small-scale activity patterns of three dasyurid species in semiarid Australia. Sminthopsis crassicaudata, Planigale gilesi and S. macroura were equipped with miniature radio-transmitters to monitor choice of resting sites and daily movements. Resting sites were located within an area of 1.27 ± 0.36 ha, 0.12 ± 0.02 ha and 3.60 ± 0.95 ha, respectively and in iduals returned to previously used resting sites regularly. We also analysed scat s les of S. crassicaudata and P. gilesi, and identified Araneae, Hymenoptera and Orthoptera as the major prey taxa for both species. Our study presents the first radio-tracking-based information on movements for these species in semiarid habitat, which indicates that, over a period of several weeks, resting sites are situated within small and defined areas.
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/ZO9950373
Abstract: The long-term pattern of hibernation was studied in free-living mountain pygmy-possums, Burramys parvus, using temperature-sensitive radio-collars. Most males and females began to hibernate in early June within one week of their release. Hibernation was interrupted by spontaneous arousals that were followed by short normothermic periods and re-entry into torpor. The duration of multiday torpor bouts averaged 8 . 0 days (range 3-17 days) and arousal periods averaged 19 . 1 h. Single-day torpor bouts were observed occasionally. The duration of torpor bouts lengthened with the progress of the hibernation season and normothermic periods became shorter. The pattern of hibernation in free-living B. parvus was similar to that of captive in iduals maintained under temperature regimes that were similar to those in the wild.
Publisher: Public Library of Science (PLoS)
Date: 22-05-2013
Publisher: Elsevier BV
Date: 07-1998
DOI: 10.1016/S0031-9384(98)00136-X
Abstract: Many small mammals display daily torpor to minimize energy expenditure during the rest phase when faced with unfavorable environmental conditions. However, given a choice of thermal environments, it is not clear whether these daily heterotherms select ambient temperatures that minimize metabolic rates during torpor or ambient temperatures that minimize metabolic rates during normothermia. It is also not clear whether they prefer being normothermic or torpid. In this study, we investigated temperature selection, activity patterns, body temperature patterns, and the use of torpor in Sminthopsis macroura in a thermal gradient when food was freely available or restricted. Animals employed torpor regularly immediately after cessation of activity even when excess food was provided. Nevertheless, they selected high ambient temperature near the zone of thermoneutrality during both normothermia and torpor. Reduced food supply did not affect either temperature preference or total activity, but it did result in significantly prolonged torpor bouts. In addition, it lowered the daily minimum body temperature during torpor by about 2 degrees C. Our study shows that S. macroura selected a high ambient temperature to reduce energy costs during normothermia. Nevertheless, daily torpor was frequently employed at the high temperature, especially when food was restricted.
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.CBPA.2012.03.017
Abstract: Torpor is usually associated with low ambient temperatures (T(a)) in winter, but in some species it is also used in summer, often in response to limited food availability. Since the seasonal expression of torpor of both placental and marsupial hibernators in the wild is poorly documented by quantitative data, we investigated torpor and activity patterns of the eastern pygmy-possum Cercartetus nanus (17.4 g) over two seasons. We used radio telemetry to track animals during winter (n=4) and summer (n=5) in a warm-temperate habitat and found that torpor was used in both seasons. In winter all animals entered periods of short-term hibernation (from 5 to 20 days) containing in idual torpor bouts of up to 5.9 days. In summer, torpor bouts were always <1 day in duration, only used by males and were not related to daily mean T(a). Pygmy-possums entered torpor at night as T(a) cooled, and rewarmed during the afternoon as T(a) increased. In iduals interspersed torpor bouts with nocturnal activity and the percentage of the night animals were active was the same in summer and winter. Our study provides the first information on torpor patterns in free-ranging C. nanus, and shows that the use of torpor throughout the year is important for energy management in this species.
Publisher: Springer Science and Business Media LLC
Date: 09-2002
DOI: 10.1007/S00114-002-0349-4
Abstract: The first mammals were small, nocturnal, and presumably had low metabolic rates and were therefore probably unable to maintain a constant high body temperature throughout cool nights. How these animals, without sufficient heat production for endogenous rewarming, were able to become warm and active again before the next activity period remains unresolved. However, we discovered that, similar to reptiles, the carnivorous marsupial mammal Pseudantechinus macdonnellensis (body mass 30.8 +/- 5.0 g) uses the morning sun to rewarm from low (26.3 +/- 4.5 degrees C) body temperatures during torpor. Our findings provide the first evidence of basking during rewarming from torpor in mammals and may provide an alternative explanation as to how ancestral mammals could have become nocturnal to avoid diurnal predators despite their small size and a low endogenous heat production.
Publisher: The Company of Biologists
Date: 15-07-2016
DOI: 10.1242/JEB.129171
Publisher: Elsevier BV
Date: 02-1994
Publisher: Springer Science and Business Media LLC
Date: 09-1995
DOI: 10.1007/BF00367312
Publisher: Springer Science and Business Media LLC
Date: 22-01-2008
DOI: 10.1007/S00360-007-0249-1
Abstract: In summer, long-eared bats (Nyctophilus spp.) roost under bark and in tree cavities, where they appear to benefit from diurnal heating of roosts. In contrast, hibernation is thought to require a cool stable temperature, suggesting they should prefer thermally insulated tree cavities during winter. To test this prediction, we quantified the winter thermoregulatory physiology and ecology of hibernating tree-roosting bats, Nyctophilus geoffroyi and N. gouldi in the field. Surprisingly, bats in winter continued to roost under exfoliating bark (65%) on the northern, sunny side of trees and in shallow tree cavities (35%). Despite passive re-warming of torpid bats by 10-20 degrees C per day, torpor bouts lasted up to 15 days, although shorter bouts were also common. Arousals occurred more frequently and subsequent activity lasted longer on warmer nights, suggesting occasional winter foraging. We show that, because periodic arousals coincide with maximum roost temperatures, when costs of rewarming and normothermic thermoregulation are minimal, exposure to a daily temperature cycle could largely reduce energy expenditure during hibernation. Our study provides further evidence that models of torpor patterns and energy expenditure from hibernators in cold temperate climates are not directly applicable in milder climates, where prolonged torpor can be interspersed with more frequent arousals and occasional foraging.
Publisher: Public Library of Science (PLoS)
Date: 03-07-2012
Publisher: Elsevier BV
Date: 1985
DOI: 10.1016/0300-9629(85)91009-6
Abstract: The minimum body temperatures and the longest torpor bouts recorded for pygmy possums (family Burramyidae) are compared with hibernating representatives from the insectivores, rodents and Australian bats. The lowest body temperatures of pygmy possums are around 6 degrees C which is within the range of the other mammalian groups. The torpor bouts of the pygmy possums last up to two weeks and the durations are similar to those of eutherian hibernators.
Publisher: Elsevier BV
Date: 1986
DOI: 10.1016/0305-0491(86)90345-7
Abstract: The concentration and composition of brain gangliosides of 17 mammalian species belonging to the subclasses of Prototheria (monotremes), Metatheria (marsupials), and Eutheria (placentals) were investigated. The mean concentration of brain gangliosides ranges from 525 to 610 micrograms NeuAc/g wet wt in monotremes, 445-900 micrograms in marsupials and from 630 to 1130 micrograms in the placentals. In the phylogenetic series of mammals, a decrease in the complexity of brain ganglioside composition becomes obvious: a drastic reduction in the number of in idual ganglioside fractions particularly those of the c-pathway of biosynthesis, took place from the level of monotremes to that of the marsupials and placentals. In monotremes, marsupials and "lower" placentals (insectivores) the percentage of alkali-labile gangliosides is relatively low (between traces and 5%), whereas in the higher evolved mammals it amounts to about 20% of all gangliosides. The ratio of the contents of the two major mammalian ganglioside fractions GD1a and GT1b is generally in the range of 1.0 and even higher in the heterothermic platypus from the monotremes and in hibernators among the placental mammals, however, it is much lower (about 0.8). These data support the hypothesis that the brain ganglioside composition not only depends on the phylogenetic level of nervous organization (cephalization) but is additionally correlated with the state of thermal adaptation.
Publisher: Springer Science and Business Media LLC
Date: 27-12-2008
DOI: 10.1007/S00360-008-0328-Y
Abstract: Knowledge about torpor in free-ranging subtropical bats is scarce and it is widely believed that low and stable ambient temperatures are necessary for prolonged torpor. We present temperature-telemetry data from free-ranging male (n = 4) and female (n = 4) subtropical vespertilionid bats, Nyctophilus bifax (approximately 10 g), exposed to pronounced daily fluctuations of ambient temperature. All bats used torpor on every day in winter and both males and females exhibited multi-day torpor bouts of up to 5.4 days. Although females were larger than males, patterns of torpor were similar in both sexes. Torpor use was correlated with prevailing weather conditions and, on days when bats remained torpid, maximum ambient temperature was significantly lower than on days when bats aroused. Moreover, the duration of interbout normothermic periods at night increased with increasing average nightly ambient temperature. Skin temperature of torpid bats varied by 10.2 +/- 3.6 degrees C day(-1) (n = 8, N = 47) and daily minimum skin temperature was positively correlated with the daily minimum ambient temperature. Our study shows that prolonged torpor is an important component of the winter ecology of a subtropical bat and that torpor and activity patterns of N. bifax predominantly reflect prevailing weather conditions.
Publisher: Wiley
Date: 02-1995
No related grants have been discovered for Fritz Geiser.