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McKechnie AE, Freeman MT, Brigham RM. Avian Heterothermy: A Review of Patterns and Processes. Integr Comp Biol 2023; 63:1028-1038. [PMID: 37156524 DOI: 10.1093/icb/icad029] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/02/2023] [Accepted: 05/05/2023] [Indexed: 05/10/2023] Open
Abstract
Many birds reduce rest-phase energy demands through heterothermy, physiological responses involving facultative, reversible reductions in metabolic rate and body temperature (Tb). Here, we review the phylogenetic distribution and ecological contexts of avian heterothermy. Heterothermy has been reported in 140 species representing 15 orders and 39 families. Recent work supports the view that deep heterothermy is most pronounced in phylogenetically older taxa whereas heterothermy in passerines and other recently diverged taxa is shallower and confined to minimum Tb > 20°C. The reasons why deep heterothermy is absent in passerines remain unclear; we speculate an evolutionary trade-off may exist between the capacity to achieve low heterothermic Tb and the tolerance of hyperthermic Tb. Inter- and intraspecific variation in heterothermy is correlated with factors including foraging ecology (e.g., territoriality and defense of food resources among hummingbirds), food availability and foraging opportunities (e.g., lunar phase predicts torpor use in caprimulgids), and predation risk. Heterothermy also plays a major role before and during migration. Emerging questions include the magnitude of energy savings associated with heterothermy among free-ranging birds, the role phylogenetic variation in the capacity for heterothermy has played in evolutionary radiations into extreme habitats, and how the capacity for heterothermy affects avian vulnerability to rapid anthropogenic climate change.
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Affiliation(s)
- Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
| | - Marc T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
| | - R Mark Brigham
- Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada
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2
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Aharon-Rotman Y, McEvoy JF, Beckmann C, Geiser F. Heterothermy in a Small Passerine: Eastern Yellow Robins Use Nocturnal Torpor in Winter. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.759726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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 (Ts) as a proxy for body temperature. Second, we tested if skin temperature fluctuated in relation to ambient temperature (Ta). We found that the Ts of eastern yellow robins fluctuated during winter by 9.1 ± 3.9°C on average (average minimum Ts 30.1 ± 2.3°C), providing the first evidence of torpor expression in this species. Daily minimum Ts decreased with Ta, 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.
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3
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Aharon-Rotman Y, Körtner G, Wacker CB, Geiser F. Do small precocial birds enter torpor to conserve energy during development? J Exp Biol 2020; 223:jeb231761. [PMID: 32978318 DOI: 10.1242/jeb.231761] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 09/15/2020] [Indexed: 01/24/2023]
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 Coturnix 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 4-5 h with a reduction of metabolism by >40% and another approached the 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 development in small precocial and not only altricial birds.
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Affiliation(s)
- Yaara Aharon-Rotman
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Gerhard Körtner
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Chris B Wacker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
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4
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Ortega-García S, Ferreyra-García D, Schondube JE. Gut reaction! Neotropical nectar-feeding bats responses to direct and indirect costs of extreme environmental temperatures. J Comp Physiol B 2020; 190:655-667. [PMID: 32601952 DOI: 10.1007/s00360-020-01288-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 05/04/2020] [Accepted: 06/18/2020] [Indexed: 10/24/2022]
Abstract
One of the consequences of anthropogenic climate change is an increase in the frequency and intensity of extreme weather events. These events have caused mass mortality of different species of wildlife, including bats. In this study, we exposed two species of neotropical nectar-feeding bats that live in contrasting environmental conditions (A. geoffroyi and L. yerbabuenae) to extreme high and low temperatures while offering them diets with different energy content. This experimental approach allowed us to determine their thermal and behavioral responses, and to identify environmental conditions that impose high physiologic costs to these species. To determine how bats' responded, we monitored both changes in their body masses and skin temperatures. Both bat species responded differently, with L. yerbabuenae spending more time in normothermia at high temperatures than A. geoffroyi. While both species presented torpor, they used it differently. Torpor allowed A. geoffroyi to maintain and increase body mass at intermediate and low ambient temperatures. At the same time, L. yerbabuenae used torpor only when facing cold ambient temperatures and low-quality food. Understanding the mechanisms that allow species to face changes in their environment is essential given the current climate trends and the fact that the loss of these species could have significant negative consequences in tropical and subtropical ecosystems.
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Affiliation(s)
- Stephanie Ortega-García
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Antigua carretera a Pátzcuaro No. 8701 Col Ex hacienda San José de la Huerta, Morelia, Michoacán, Mexico
| | - Daniel Ferreyra-García
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Antigua carretera a Pátzcuaro No. 8701 Col Ex hacienda San José de la Huerta, Morelia, Michoacán, Mexico
| | - Jorge E Schondube
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Antigua carretera a Pátzcuaro No. 8701 Col Ex hacienda San José de la Huerta, Morelia, Michoacán, Mexico.
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5
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Refinetti R. Circadian rhythmicity of body temperature and metabolism. Temperature (Austin) 2020; 7:321-362. [PMID: 33251281 PMCID: PMC7678948 DOI: 10.1080/23328940.2020.1743605] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 12/19/2022] Open
Abstract
This article reviews the literature on the circadian rhythms of body temperature and whole-organism metabolism. The two rhythms are first described separately, each description preceded by a review of research methods. Both rhythms are generated endogenously but can be affected by exogenous factors. The relationship between the two rhythms is discussed next. In endothermic animals, modulation of metabolic activity can affect body temperature, but the rhythm of body temperature is not a mere side effect of the rhythm of metabolic thermogenesis associated with general activity. The circadian system modulates metabolic heat production to generate the body temperature rhythm, which challenges homeothermy but does not abolish it. Individual cells do not regulate their own temperature, but the relationship between circadian rhythms and metabolism at the cellular level is also discussed. Metabolism is both an output of and an input to the circadian clock, meaning that circadian rhythmicity and metabolism are intertwined in the cell.
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Affiliation(s)
- Roberto Refinetti
- Department of Psychology, University of New Orleans, New Orleans, LA, USA
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6
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Boyles JG. A Brief Introduction to Methods for Describing Body Temperature in Endotherms. Physiol Biochem Zool 2019; 92:365-372. [DOI: 10.1086/703420] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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7
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Romano AB, Hunt A, Welbergen JA, Turbill C. Nocturnal torpor by superb fairy-wrens: a key mechanism for reducing winter daily energy expenditure. Biol Lett 2019; 15:20190211. [PMID: 31238856 DOI: 10.1098/rsbl.2019.0211] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Many passerine birds are small and require a high mass-specific rate of resting energy expenditure, especially in the cold. The energetics of thermoregulation is, therefore, an important aspect of their ecology, yet few studies have quantified thermoregulatory patterns in wild passerines. We used miniature telemetry to record the skin temperature ( Tskin) of free-living superb fairy-wrens ( Malurus cyaneus, 8.6 g; n = 6 birds over N = 7-22 days) and determine the importance of controlled reductions in body temperature during resting to their winter energy budgets. Fairy-wrens routinely exhibited large daily fluctuations in Tskin between maxima of 41.9 ± 0.6°C and minima of 30.4 ± 0.7°C, with overall individual minima of 27.4 ± 1.1°C (maximum daily range: 14.7 ± 0.9°C). These results provide strong evidence of nocturnal torpor in this small passerine, which we calculated to provide a 42% reduction in resting metabolic rate at a Ta of 5°C compared to active-phase Tskin. A capacity for energy-saving torpor has important consequences for understanding the behaviour and life-history ecology of superb fairy-wrens. Moreover, our novel field data suggest that torpor could be more widespread and important than previously thought within passerines, the most diverse order of birds.
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Affiliation(s)
- Alex B Romano
- 1 Hawkesbury Institute for the Environment, Western Sydney University , Richmond, New South Wales , Australia
| | - Anthony Hunt
- 2 Australian Bird Study Association , 16 Alderson Ave, North Rocks, New South Wales 2151 , Australia
| | - Justin A Welbergen
- 1 Hawkesbury Institute for the Environment, Western Sydney University , Richmond, New South Wales , Australia
| | - Christopher Turbill
- 1 Hawkesbury Institute for the Environment, Western Sydney University , Richmond, New South Wales , Australia
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8
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Jepsen EM, Ganswindt A, Ngcamphalala CA, Bourne AR, Ridley AR, McKechnie AE. Non-invasive monitoring of physiological stress in an afrotropical arid-zone passerine bird, the southern pied babbler. Gen Comp Endocrinol 2019; 276:60-68. [PMID: 30836104 DOI: 10.1016/j.ygcen.2019.03.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 02/01/2019] [Accepted: 03/01/2019] [Indexed: 11/27/2022]
Abstract
Using faecal matter to monitor stress levels in animals non-invasively is a powerful technique for elucidating the effects of biotic and abiotic stressors on free-living animals. To validate the use of droppings for measuring stress in southern pied babblers (Turdoides bicolor) we performed an ACTH challenge on captive individuals and determined the effect of temporary separation from their social group on their faecal glucocorticoid metabolite (fGCM) concentration. Additionally, we compared fGCM concentrations of captive babblers to those of wild conspecifics and examined the effects of dominance rank on fGCM concentration. We found droppings to be a suitable matrix for measuring physiological stress in babblers and that individual separation from the group caused an increase in fGCM levels. In addition, babblers temporarily held in captivity had substantially higher fGCM concentrations than wild individuals, indicating that babblers kept in captivity experience high levels of stress. In wild, free-living individuals, dominant males showed the highest levels of stress, suggesting that being the dominant male of a highly territorial social group is stressful. Non-invasive sampling allows field-based researchers to reduce disturbance related to monitoring adrenocortical function, thereby avoiding artificially increasing circulating corticosterone concentration as it is not necessary to physically restrain study animals.
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Affiliation(s)
- Emma M Jepsen
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria, South Africa; DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa
| | - André Ganswindt
- Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa
| | - Celiwe A Ngcamphalala
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria, South Africa; DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa
| | - Amanda R Bourne
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa
| | - Amanda R Ridley
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa; Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley, Australia
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria, South Africa; DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa.
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9
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Douglas TK, Cooper CE, Withers PC. Avian torpor or alternative thermoregulatory strategies for overwintering? J Exp Biol 2017; 220:1341-1349. [PMID: 28356368 DOI: 10.1242/jeb.154633] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 01/16/2017] [Indexed: 11/20/2022]
Abstract
ABSTRACT
It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (Pomatostomus superciliosus), which has characteristics related to a high probability of torpor use; it is a sedentary, insectivorous, cooperative breeding species, which we studied during winter in a temperate habitat. Wild, free-living babblers maintained normothermy overnight, even at sub-zero ambient temperatures, with a mean minimum body temperature of 38.5±0.04°C that was independent of minimum black bulb temperature. Physiological variables measured in the laboratory revealed that babblers had a low basal metabolic rate and evaporative water loss, but their body temperature and thermal conductance were typical of those of other birds and they had a typical endothermic response to low ambient temperature. Huddling yielded significant energy savings at low temperatures and a roost nest created a microclimate that buffered against low temperatures. Low basal energy requirements, communal roosting and the insulation of a roost nest confer sufficient energetic benefits, allowing babblers to meet energy requirements without resorting to heterothermia, even in their depauperate, low-productivity landscape, suggesting that passerine birds use alternatives to torpor to balance their energy budgets when possible.
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Affiliation(s)
- Tegan K. Douglas
- Department of Environment and Agriculture, Curtin University, Bentley, WA 6845, Australia
| | - Christine E. Cooper
- Department of Environment and Agriculture, Curtin University, Bentley, WA 6845, Australia
- School of Animal Biology, University of Western Australia, Crawley, WA 6009, Australia
| | - Philip C. Withers
- Department of Environment and Agriculture, Curtin University, Bentley, WA 6845, Australia
- School of Animal Biology, University of Western Australia, Crawley, WA 6009, Australia
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10
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Cunningham SJ, Thompson ML, McKechnie AE. It's cool to be dominant: social status alters short-term risks of heat stress. J Exp Biol 2017; 220:1558-1562. [DOI: 10.1242/jeb.152793] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 02/06/2017] [Indexed: 11/20/2022]
Abstract
Climate change has potential to trigger social change. As a first step towards understanding mechanisms determining the vulnerability of animal societies to rising temperatures, we investigated interactions between social rank and thermoregulation in three arid-zone bird species: fawn-coloured lark (Mirafra africanoides, territorial); African red-eyed bulbul (Pycnonotus nigricans, loosely social) and sociable weaver (Philetairus socius, complex cooperative societies). We assessed relationships between body temperature (Tb), air temperature (Ta) and social rank in captive groups in the Kalahari Desert. Socially dominant weavers and bulbuls had lower mean Tb than subordinate conspecifics, and dominant individuals of all species maintained more stable Tb as Ta increased. Dominant bulbuls and larks tended to monopolise available shade, but dominant weavers did not. Nevertheless, dominant weavers thermoregulated more precisely, despite expending no more behavioural effort on thermoregulation than subordinates. Increasingly unequal risks associated with heat stress may have implications for stability of animal societies in warmer climates.
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Affiliation(s)
- Susan J. Cunningham
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
| | - Michelle L. Thompson
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - Andrew E. McKechnie
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
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11
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Ruf T, Geiser F. Daily torpor and hibernation in birds and mammals. Biol Rev Camb Philos Soc 2015; 90:891-926. [PMID: 25123049 PMCID: PMC4351926 DOI: 10.1111/brv.12137] [Citation(s) in RCA: 484] [Impact Index Per Article: 53.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 07/16/2014] [Accepted: 07/16/2014] [Indexed: 12/11/2022]
Abstract
Many birds and mammals drastically reduce their energy expenditure during times of cold exposure, food shortage, or drought, by temporarily abandoning euthermia, i.e. the maintenance of high body temperatures. Traditionally, two different types of heterothermy, i.e. hypometabolic states associated with low body temperature (torpor), have been distinguished: daily torpor, which lasts less than 24 h and is accompanied by continued foraging, versus hibernation, with torpor bouts lasting consecutive days to several weeks in animals that usually do not forage but rely on energy stores, either food caches or body energy reserves. This classification of torpor types has been challenged, suggesting that these phenotypes may merely represent extremes in a continuum of traits. Here, we investigate whether variables of torpor in 214 species (43 birds and 171 mammals) form a continuum or a bimodal distribution. We use Gaussian-mixture cluster analysis as well as phylogenetically informed regressions to quantitatively assess the distinction between hibernation and daily torpor and to evaluate the impact of body mass and geographical distribution of species on torpor traits. Cluster analysis clearly confirmed the classical distinction between daily torpor and hibernation. Overall, heterothermic endotherms tend to be small; hibernators are significantly heavier than daily heterotherms and also are distributed at higher average latitudes (∼35°) than daily heterotherms (∼25°). Variables of torpor for an average 30 g heterotherm differed significantly between daily heterotherms and hibernators. Average maximum torpor bout duration was >30-fold longer, and mean torpor bout duration >25-fold longer in hibernators. Mean minimum body temperature differed by ∼13°C, and the mean minimum torpor metabolic rate was ∼35% of the basal metabolic rate (BMR) in daily heterotherms but only 6% of BMR in hibernators. Consequently, our analysis strongly supports the view that hibernators and daily heterotherms are functionally distinct groups that probably have been subject to disruptive selection. Arguably, the primary physiological difference between daily torpor and hibernation, which leads to a variety of derived further distinct characteristics, is the temporal control of entry into and arousal from torpor, which is governed by the circadian clock in daily heterotherms, but apparently not in hibernators.
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Affiliation(s)
- Thomas Ruf
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Savoyenstraße 1, A-1160 Vienna, Austria
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
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12
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McAllan BM, Geiser F. Torpor during reproduction in mammals and birds: dealing with an energetic conundrum. Integr Comp Biol 2014; 54:516-32. [PMID: 24973362 DOI: 10.1093/icb/icu093] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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.
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Affiliation(s)
- B M McAllan
- *Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia*Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Fritz Geiser
- *Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia
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13
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Vuarin P, Henry PY. Field evidence for a proximate role of food shortage in the regulation of hibernation and daily torpor: a review. J Comp Physiol B 2014; 184:683-97. [DOI: 10.1007/s00360-014-0833-0] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 04/30/2014] [Indexed: 02/06/2023]
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14
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Kronfeld-Schor N, Dayan T. Thermal Ecology, Environments, Communities, and Global Change: Energy Intake and Expenditure in Endotherms. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2013. [DOI: 10.1146/annurev-ecolsys-110512-135917] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To survive, animals must maintain a balance between energy acquisition (foraging) and energy expenditure. This challenge is particularly great for endotherm vertebrates that require high amounts of energy to maintain homeothermy. Many of these endotherms use hibernation or daily torpor as a mechanism to reduce energy expenditure during anticipated or stochastic periods of stress. Although ecological researchers have focused extensively on energy acquisition, physiologists have largely studied thermal ecology and the mechanisms allowing endotherms to regulate energy expenditure, with little research explicitly linking ecology and thermal biology. Nevertheless, theoretical considerations and research conducted so far point to a significant ecological role for torpor in endotherms. Moreover, global-change challenges facing vertebrate endotherms are also considered in view of their ability to regulate their energy expenditure. We review the thermal ecology of endothermic vertebrates and some of its ecological and evolutionary implications.
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Affiliation(s)
| | - Tamar Dayan
- Department of Zoology, Tel Aviv University, Tel Aviv 69978, Israel;,
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15
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Klug BJ, Barclay RMR. Effect of wind on the accuracy of externally attached, temperature-sensitive radiotransmitters. WILDLIFE SOC B 2013. [DOI: 10.1002/wsb.327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Brandon J. Klug
- Department of Biological Sciences; University of Calgary; Calgary AB Canada T2N 1N4
| | - Robert M. R. Barclay
- Department of Biological Sciences; University of Calgary; Calgary AB Canada T2N 1N4
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16
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Noakes MJ, Smit B, Wolf BO, McKechnie AE. Thermoregulation in African Green Pigeons (Treron calvus) and a re-analysis of insular effects on basal metabolic rate and heterothermy in columbid birds. J Comp Physiol B 2013; 183:969-82. [PMID: 23689380 DOI: 10.1007/s00360-013-0763-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/13/2013] [Accepted: 05/03/2013] [Indexed: 10/26/2022]
Abstract
Columbid birds represent a useful model taxon for examining adaptation in metabolic and thermal traits, including the effects of insularity. To test predictions concerning the role of insularity and low predation risk as factors selecting for the use of torpor, and the evolution of low basal metabolic rate in island species, we examined thermoregulation under laboratory and semi-natural conditions in a mainland species, the African Green Pigeon (Treron calvus). Under laboratory conditions, rest-phase body temperature (T b) was significantly and positively correlated with air temperature (T a) between 0 and 35 °C, and the relationship between resting metabolic rate (RMR) and T a differed from typical endothermic patterns. The minimum RMR, which we interpret as basal metabolic rate (BMR), was 0.825 ± 0.090 W. Green pigeons responded to food restriction by significantly decreasing rest-phase T b, but the reductions were small (at most ~5 °C below normothermic values), with a minimum T b of 33.1 °C recorded in a food-deprived bird. We found no evidence of the large reductions in T b and metabolic rate and the lethargic state characteristic of torpor. The absence of torpor in T. calvus lends support to the idea that species restricted to islands that are free of predators are more likely to use torpor than mainland species that face the risk of predation during the rest-phase. We also analysed interspecific variation in columbid BMR in a phylogenetically informed framework and verified the conclusions of an earlier study which found that BMR is significantly lower in island species compared to those that occur on mainlands.
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Affiliation(s)
- Matthew J Noakes
- Department of Zoology and Entomology, DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Pretoria, Pretoria, 0002, South Africa
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Flower TP, Child MF, Ridley AR. The ecological economics of kleptoparasitism: pay-offs from self-foraging versus kleptoparasitism. J Anim Ecol 2012; 82:245-55. [DOI: 10.1111/j.1365-2656.2012.02026.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 07/06/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Tom P. Flower
- Department of Zoology; University of Cambridge; Downing Street Cambridge CB2 3EJ UK
- DST/NRF Centre of Excellence at the Percy FitzPatrick Institute; University of Cape Town; Rondebosch 7701 South Africa
| | - Matthew F. Child
- DST/NRF Centre of Excellence at the Percy FitzPatrick Institute; University of Cape Town; Rondebosch 7701 South Africa
| | - Amanda R. Ridley
- DST/NRF Centre of Excellence at the Percy FitzPatrick Institute; University of Cape Town; Rondebosch 7701 South Africa
- Department of Biological Sciences; Macquarie University; Macquarie NSW 2122 Australia
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Boyles JG, Smit B, McKechnie AE. Variation in body temperature is related to ambient temperature but not experimental manipulation of insulation in two small endotherms with different thermoregulatory patterns. J Zool (1987) 2012. [DOI: 10.1111/j.1469-7998.2012.00909.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- J. G. Boyles
- Department of Zoology and Entomology; Mammal Research Institute; University of Pretoria; Pretoria; South Africa
| | - B. Smit
- Department of Zoology and Entomology; Mammal Research Institute; University of Pretoria; Pretoria; South Africa
| | - A. E. McKechnie
- Department of Zoology and Entomology; Mammal Research Institute; University of Pretoria; Pretoria; South Africa
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Heterothermy in two mole-rat species subjected to interacting thermoregulatory challenges. ACTA ACUST UNITED AC 2011; 317:73-82. [DOI: 10.1002/jez.723] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 08/12/2011] [Accepted: 10/04/2011] [Indexed: 11/07/2022]
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Streicher S, Boyles JG, Oosthuizen MK, Bennett NC. Body temperature patterns and rhythmicity in free-ranging subterranean Damaraland mole-rats, Fukomys damarensis. PLoS One 2011; 6:e26346. [PMID: 22028861 PMCID: PMC3196572 DOI: 10.1371/journal.pone.0026346] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 09/25/2011] [Indexed: 11/25/2022] Open
Abstract
Body temperature (Tb) is an important physiological component that affects endotherms from the cellular to whole organism level, but measurements of Tb in the field have been noticeably skewed towards heterothermic species and seasonal comparisons are largely lacking. Thus, we investigated patterns of Tb patterns in a homeothermic, free-ranging small mammal, the Damaraland mole-rat (Fukomys damarensis) during both the summer and winter. Variation in Tb was significantly greater during winter than summer, and greater among males than females. Interestingly, body mass had only a small effect on variation in Tb and there was no consistent pattern relating ambient temperature to variation in Tb. Generally speaking, it appears that variation in Tb patterns varies between seasons in much the same way as in heterothermic species, just to a lesser degree. Both cosinor analysis and Fast Fourier Transform analysis revealed substantial individual variation in Tb rhythms, even within a single colony. Some individuals had no Tb rhythms, while others appeared to exhibit multiple rhythms. These data corroborate previous laboratory work showing multiplicity of rhythms in mole-rats and suggest the variation seen in the laboratory is a true indicator of the variation seen in the wild.
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Affiliation(s)
- Sonja Streicher
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Justin G. Boyles
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- * E-mail:
| | - Maria K. Oosthuizen
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Department of Zoology, King Saud University, Riyadh, Saudi Arabia
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Does use of the torpor cut-off method to analyze variation in body temperature cause more problems than it solves? J Therm Biol 2011. [DOI: 10.1016/j.jtherbio.2011.07.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Smit B, Boyles JG, Brigham RM, McKechnie AE. Torpor in dark times: patterns of heterothermy are associated with the lunar cycle in a nocturnal bird. J Biol Rhythms 2011; 26:241-8. [PMID: 21628551 DOI: 10.1177/0748730411402632] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Many studies have shown that endotherms become more heterothermic when the costs of thermoregulation are high and/or when limited energy availability constrains thermoregulatory capacity. However, the roles of many ecological variables, including constraints on foraging opportunities and/or success, remain largely unknown. To test the prediction that thermoregulatory patterns should be related to foraging opportunities in a heterothermic endotherm, we examined the relationship between the lunar cycle and heterothermy in Freckled Nightjars (Caprimulgus tristigma), which are visually orienting, nocturnal insectivores that are dependent on ambient light to forage. This model system provides an opportunity to assess whether variation in foraging opportunities influences the expression of heterothermy. The nightjars were active and foraged for insects when moonlight was available but became inactive and heterothermic in the absence of moonlight. Lunar illumination was a much stronger predictor of the magnitude of heterothermic responses than was air temperature (T(a)). Our data suggest that heterothermy was strongly related to variation in foraging opportunities associated with the lunar cycle, even though food abundance appeared to remain relatively high throughout the study period. Patterns of thermoregulation in this population of Freckled Nightjars provide novel insights into the environmental and ecological determinants of heterothermy, with the lunar cycle, and not T(a), being the strongest predictor of torpor use.
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Affiliation(s)
- Ben Smit
- DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
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Boyles JG, Smit B, McKechnie AE. A new comparative metric for estimating heterothermy in endotherms. Physiol Biochem Zool 2011; 84:115-23. [PMID: 20979498 DOI: 10.1086/656724] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A major focus in the study of endothermic thermoregulation has been the description of thermoregulatory patterns used by various species and/or populations. Compared with ectotherms, relatively few attempts have been made to study the thermoregulation of endotherms in an adaptive framework. We believe that one of the main factors limiting this area of research has been the lack of an appropriate metric to directly compare body temperature (T(b)) variation across all endothermic species. Thus, we present a simple comparative metric, the heterothermy index (HI), to quantify the expression of heterothermy by endotherms during a given time frame. Key advantages of HI are that (1) it represents a new analytical technique that has different strengths than the metrics commonly used to describe variation in T(b), (2) it allows for evaluation of nonenergetic costs and benefits that affect the expression of heterothermy, and (3) it has the potential to unify research on homeotherms and heterotherms through quantitative comparative analyses that examine the entire continuum of thermoregulatory patterns. In short, we suggest that our metric provides a means to overcome one of the hurdles presently slowing the advancement of research on endothermic thermoregulation beyond the simple description of thermoregulatory patterns.
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Affiliation(s)
- Justin G Boyles
- DST/NRF Centre of Excellence,Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
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McKechnie AE, Mzilikazi N. Heterothermy in Afrotropical mammals and birds: a review. Integr Comp Biol 2011; 51:349-63. [PMID: 21705792 DOI: 10.1093/icb/icr035] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recent years have seen a rapid increase in the number of Afrotropical endotherms known to avoid mismatches between energy supply and demand by using daily torpor and/or hibernation. Among mammals, heterothermy has been reported in 40 species in six orders, namely Macroscelidea, Afrosoricida, Rodentia, Eulipotyphla, Primates and Chiroptera. These species span a range in body mass of 7-770 g, with minimum heterothermic body temperatures ranging from 1-27°C and bout length varying from 1 h to 70 days. Daily torpor is the most common form of heterothermy, with true hibernation being observed in only seven species, Graphiurus murinus, Graphiurus ocularis, Atelerix frontalis, Cheirogaleus medius, Cheirogaleus major, Microcebus murinus and Microcebus griseorufus. The traditional distinction between daily torpor and hibernation is blurred in some species, with free-ranging individuals exhibiting bouts of > 24 h and body temperatures < 16 °C, but none of the classical behaviours associated with hibernation. Several species bask in the sun during rewarming. Among birds, heterothermy has been reported in 16 species in seven orders, and is more pronounced in phylogenetically older taxa. Both in mammals and birds, patterns of heterothermy can vary dramatically among species occurring at a particular site, and even among individuals of a single species. For instance, patterns of heterothermy among cheirogalid primates in western Madagascar vary from daily torpor to uninterrupted hibernation for up to seven months. Other examples of variation among closely-related species involve small owls, elephant shrews and vespertilionid bats. There may also be variation in terms of the ecological correlates of torpor within a species, as is the case in the Freckled Nightjar Caprimulgus tristigma.
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Affiliation(s)
- Andrew E McKechnie
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
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