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Levesque DL, Breit AM, Brown E, Nowack J, Welman S. Non-Torpid Heterothermy in Mammals: Another Category along the Homeothermy-Hibernation Continuum. Integr Comp Biol 2023; 63:1039-1048. [PMID: 37407285 DOI: 10.1093/icb/icad094] [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: 02/27/2023] [Revised: 06/14/2023] [Accepted: 06/29/2023] [Indexed: 07/07/2023] Open
Abstract
Variability in body temperature is now recognized to be widespread among whole-body endotherms with homeothermy being the exception rather than the norm. A wide range of body temperature patterns exists in extant endotherms, spanning from strict homeothermy, to occasional use of torpor, to deep seasonal hibernation with many points in between. What is often lost in discussions of heterothermy in endotherms are the benefits of variations in body temperature outside of torpor. Endotherms that do not use torpor can still obtain extensive energy and water savings from varying levels of flexibility in normothermic body temperature regulation. Flexibility at higher temperatures (heat storage or facultative hyperthermia) can provide significant water savings, while decreases at cooler temperatures, even outside of torpor, can lower the energetic costs of thermoregulation during rest. We discuss the varying uses of the terms heterothermy, thermolability, and torpor to describe differences in the amplitude of body temperature cycles and advocate for a broader use of the term "heterothermy" to include non-torpid variations in body temperature.
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Affiliation(s)
| | - Ana M Breit
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Eric Brown
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Julia Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, L3 3AF Liverpool, UK
| | - Shaun Welman
- Department of Zoology, Nelson Mandela University, Gqeberha 6031, South Africa
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2
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Keicher L, Shipley JR, Schaeffer PJ, Dechmann DKN. Contrasting Torpor Use by Reproductive Male Common Noctule Bats in the Laboratory and in the Field. Integr Comp Biol 2023; 63:1087-1098. [PMID: 37237444 PMCID: PMC10714913 DOI: 10.1093/icb/icad040] [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: 01/26/2023] [Revised: 05/01/2023] [Accepted: 05/23/2023] [Indexed: 05/28/2023] Open
Abstract
Metabolic processes of animals are often studied in controlled laboratory settings. However, these laboratory settings often do not reflect the animals' natural environment. Thus, results of metabolic measurements from laboratory studies must be cautiously applied to free-ranging animals. Recent technological advances in animal tracking allow detailed eco-physiological studies that reveal when, where, and how physiological measurements from the field differ from those from the laboratory. We investigated the torpor behavior of male common noctule bats (Nyctalus noctula) across different life history stages using two approaches: in controlled laboratory experiments and in the field using calibrated heart rate telemetry. We predicted that non-reproductive males would extensively use torpor to conserve energy, whereas reproductive males would reduce torpor use to promote spermatogenesis. We did not expect differences in torpor use between captive and wild animals as we simulated natural temperature conditions in the laboratory. We found that during the non-reproductive phase, both captive and free-ranging bats used torpor extensively. During reproduction, bats in captivity unexpectedly also used torpor throughout the day, while only free-ranging bats showed the expected reduction in torpor use. Thus, depending on life history stage, torpor behavior in the laboratory was markedly different from the wild. By implementing both approaches and at different life history stages, we were able to better explore the limitations of eco-physiological laboratory studies and make recommendations for when they are an appropriate proxy for natural behavior.
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Affiliation(s)
- Lara Keicher
- Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - J Ryan Shipley
- Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, Zürcherstraße 111, Birmensdorf 8903 CH, Switzerland
| | - Paul J Schaeffer
- Department of Biology, Miami University, 700 E. High St., Oxford, OH 45056, USA
| | - Dina K N Dechmann
- Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
- Centre for the Advanced Study of Collective Behaviour, Universitätsstraße 10, 78457 Konstanz, Germany
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3
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Nowack J, Mzilikazi N, Dausmann KH. Saving energy via short and shallow torpor bouts. J Therm Biol 2023; 114:103572. [PMID: 37344030 DOI: 10.1016/j.jtherbio.2023.103572] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/04/2023] [Accepted: 04/05/2023] [Indexed: 06/23/2023]
Abstract
Maintaining a high and stable body temperature as observed in most endothermic mammals and birds is energetically costly and many heterothermic species reduce their metabolic demands during energetic bottlenecks through the use of torpor. With the increasing number of heterotherms revealed in a diversity of habitats, it becomes apparent that triggers and patterns of torpor use are more variable than previously thought. Here, we report the previously overlooked use of, shallow rest-time torpor (body temperature >30 °C) in African lesser bushbabies, Galago moholi. Body core temperature of three adult male bushbabies recorded over five months showed a clear bimodal distribution with an average active modal temperature of 39.2 °C and a resting modal body temperature of 36.7 °C. Shallow torpor was observed in two out of three males (n = 29 torpor bouts) between June and August (austral winter), with body temperatures dropping to an overall minimum of 30.7 °C and calculated energy savings of up to 10%. We suggest that shallow torpor may be an ecologically important, yet mostly overlooked energy-saving strategy employed by heterothermic mammals. Our data emphasise that torpor threshold temperatures need to be used with care if we aim to fully understand the level of physiological plasticity displayed by heterothermic species.
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Affiliation(s)
- Julia Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, Byrom Street, Liverpool, United Kingdom; Department of Biology, Institute of Cell and Systems Biology of Animals, Functional Ecology, University Hamburg, Hamburg, Germany.
| | - Nomakwezi Mzilikazi
- Department of Zoology, Nelson Mandela University, Port Elizabeth, South Africa
| | - Kathrin H Dausmann
- Department of Biology, Institute of Cell and Systems Biology of Animals, Functional Ecology, University Hamburg, Hamburg, Germany
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4
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Determining the different phases of torpor from skin- or body temperature data in heterotherms. J Therm Biol 2023; 111:103396. [PMID: 36585072 DOI: 10.1016/j.jtherbio.2022.103396] [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: 06/08/2022] [Revised: 10/28/2022] [Accepted: 11/22/2022] [Indexed: 11/27/2022]
Abstract
Technological innovations have made heat-sensitive data-loggers smaller, more efficient and less expensive, which has led to a growing body of literature that measures the skin- or body temperatures of small animals in their natural environments. Studies of this type on heterothermic endotherms have prompted much debate regarding how to best define 'torpor' expressions from skin- or body temperature data alone. We propose a new quantitative method for defining torpor 'entries', 'arousals' and 'stable torpor periods' whilst comparing the results to 'torpor bout' durations identified using only the torpor cut-off method. By decomposing a torpor bout into 'entries', 'stable torpor periods', and 'active arousals', we avoid biases introduced by using strict threshold temperature values for the onset of torpor, thereby allowing better insight into individual use of torpor. We present our method as an easy-to-use function written in R-code, offering an un-biased and consistent methodology to be applied on skin- or body temperature measurements across datasets and research groups. When testing the function on a large dataset of skin temperature data collected on three bat species in Norway (Plecotus auritus: Nind = 39; Eptesicus nilssonii: Nind = 11; Myotis brandtii: Nind = 10), we identified 461 complete torpor bouts across species. More than 40% of the torpor bouts (Nbouts = 192) did not contain stable torpor periods, because the bats aroused before they had reached a stable skin temperature level. Furthermore, only considering 'torpid' and 'euthermic' temperature values by applying strict cut-off thresholds led to potentially large underestimations of torpor bout durations compared to our quantitative determination of the onset and termination of each torpor bout. We highlight the importance of differentiating between torpor phases, especially for active arousals that can be very energetically expensive and may alter our evaluation of the actual energetic savings gained by an individual employing torpor.
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5
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Chenery M, Geiser F, Stawski C. OUP accepted manuscript. J Mammal 2022; 103:826-834. [PMID: 36110387 PMCID: PMC9469929 DOI: 10.1093/jmammal/gyac022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 02/08/2022] [Indexed: 11/14/2022] Open
Abstract
Insectivorous bats are particularly susceptible to heat loss due to their relatively large surface area to volume ratio. Therefore, to maintain a high normothermic body temperature, bats require large amounts of energy for thermoregulation. This can be energetically challenging for small bats during cold periods as heat loss is augmented and insect prey is reduced. To conserve energy many bats enter a state of torpor characterized by a controlled reduction of metabolism and body temperature in combination with selecting roosts based upon thermal properties. Our study aimed to quantify torpor patterns and roost preferences of free-ranging little forest bats (Vespadelus vulturnus) during winter to identify physiological and behavioral mechanisms used by this species for survival of the cold season. All bats captured were male (body mass 4.9 ± 0.7 g, n = 6) and used torpor on every day monitored, with bouts lasting up to 187.58 h (mean = 35.5 ± 36.7 h, n = 6, total number of samples [N] = 61). Torpor bout duration was significantly correlated with daily minimum and maximum ambient temperature, mean skin temperature, insect mass, and body mass of individuals and the multiday torpor bouts recorded in the cold qualify as hibernation. The lowest skin temperature recorded was 5.2°C, which corresponded to the lowest ambient temperature measurement of −5.8°C. Most bats chose tall, large, live Eucalyptus trees for roosting and to leave their roost for foraging on warmer days. Many individuals often switched roosts (every 3–5 days) and movements increased as spring approached (every 1–2 days). Our data suggest that V. vulturnus are capable of using the environmental temperature to gauge potential foraging opportunities and as a cue to reenter torpor when conditions are unsuitable. Importantly, frequent use of torpor and appropriate roost selection form key roles in the winter survival of these tiny bats.
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Affiliation(s)
- Melissa Chenery
- 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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6
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Social thermoregulation in Mediterranean greater white-toothed shrews (Crocidura russula). Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03072-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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7
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Haugg E, Herwig A, Diedrich V. Body Temperature and Activity Adaptation of Short Photoperiod-Exposed Djungarian Hamsters ( Phodopus sungorus): Timing, Traits, and Torpor. Front Physiol 2021; 12:626779. [PMID: 34305626 PMCID: PMC8294097 DOI: 10.3389/fphys.2021.626779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 05/24/2021] [Indexed: 11/13/2022] Open
Abstract
To survive the Siberian winter, Djungarian hamsters (Phodopus sungorus) adjust their behavior, morphology, and physiology to maintain energy balance. The reduction of body mass and the improvement of fur insulation are followed by the expression of spontaneous daily torpor, a state of reduced metabolism during the resting phase to save additional energy. Since these complex changes require time, the upcoming winter is anticipated via decreasing photoperiod. Yet, the extent of adaptation and torpor use is highly individual. In this study, adaptation was triggered by an artificially changed light regime under laboratory conditions with 20°C ambient temperature and food and water ad libitum. Two approaches analyzed data on weekly measured body mass and fur index as well as continuously recorded core body temperature and activity during: (1) the torpor period of 60 hamsters and (2) the entire adaptation period of 11 hamsters, aiming to identify parameters allowing (1) a better prediction of torpor expression in individuals during the torpor period as well as (2) an early estimation of the adaptation extent and torpor proneness. In approach 1, 46 torpor-expressing hamsters had a median torpor incidence of 0.3, covering the spectrum from no torpor to torpor every day within one representative week. Torpor use reduced the body temperature during both photo- and scotophase. Torpor was never expressed by 14 hamsters. They could be identified by a high, constant body temperature during the torpor period and a low body mass loss during adaptation to a short photoperiod. Already in the first week of short photoperiod, approach 2 revealed that the hamsters extended their activity over the prolonged scotophase, yet with reduced scotophase activity and body temperature. Over the entire adaptation period, scotophase activity and body temperature of the scoto- and photophases were further reduced, later accompanied by a body mass decline and winter fur development. Torpor was expressed by those hamsters with the most pronounced adaptations. These results provide insights into the preconditions and proximate stimuli of torpor expression. This knowledge will improve experimental planning and sampling for neuroendocrine and molecular research on torpor regulation and has the potential to facilitate acute torpor forecasting to eventually unravel torpor regulation processes.
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Affiliation(s)
- Elena Haugg
- Institute of Neurobiology, Ulm University, Ulm, Germany
| | - Annika Herwig
- Institute of Neurobiology, Ulm University, Ulm, Germany
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8
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Monarchino MN, Johnson JS. Roost elevation and ambient temperature best predict use of summer heterothermy in eastern red bats. J Zool (1987) 2020. [DOI: 10.1111/jzo.12848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - J. S. Johnson
- Department of Biological Sciences Ohio University Athens OH USA
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9
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Czenze ZJ, Dunbar M. Body mass affects short‐term heterothermy in Neotropical bats. Biotropica 2020. [DOI: 10.1111/btp.12807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zenon J. Czenze
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Miranda Dunbar
- Department of Biology Southern Connecticut State University New Haven CT USA
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10
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Geiser F. Seasonal Expression of Avian and Mammalian Daily Torpor and Hibernation: Not a Simple Summer-Winter Affair †. Front Physiol 2020; 11:436. [PMID: 32508673 PMCID: PMC7251182 DOI: 10.3389/fphys.2020.00436] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 04/08/2020] [Indexed: 12/17/2022] Open
Abstract
Daily torpor and hibernation (multiday torpor) are the most efficient means for energy conservation in endothermic birds and mammals and are used by many small species to deal with a number of challenges. These include seasonal adverse environmental conditions and low food/water availability, periods of high energetic demands, but also reduced foraging options because of high predation pressure. Because such challenges differ among regions, habitats and food consumed by animals, the seasonal expression of torpor also varies, but the seasonality of torpor is often not as clear-cut as is commonly assumed and differs between hibernators and daily heterotherms expressing daily torpor exclusively. Hibernation is found in mammals from all three subclasses from the arctic to the tropics, but is known for only one bird. Several hibernators can hibernate for an entire year or express torpor throughout the year (8% of species) and more hibernate from late summer to spring (14%). The most typical hibernation season is the cold season from fall to spring (48%), whereas hibernation is rarely restricted to winter (6%). In hibernators, torpor expression changes significantly with season, with strong seasonality mainly found in the sciurid and cricetid rodents, but seasonality is less pronounced in the marsupials, bats and dormice. Daily torpor is diverse in both mammals and birds, typically is not as seasonal as hibernation and torpor expression does not change significantly with season. Torpor in spring/summer has several selective advantages including: energy and water conservation, facilitation of reproduction or growth during development with limited resources, or minimisation of foraging and thus exposure to predators. When torpor is expressed in spring/summer it is usually not as deep and long as in winter, because of higher ambient temperatures, but also due to seasonal functional plasticity. Unlike many other species, subtropical nectarivorous blossom-bats and desert spiny mice use more frequent and pronounced torpor in summer than in winter, which is related to seasonal availability of nectar or water. Thus, seasonal use of torpor is complex and differs among species and habitats.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology CO2, University of New England, Armidale, NSW, Australia
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11
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Johnson JS, Treanor JJ, Slusher AC, Lacki MJ. Buildings provide vital habitat for little brown myotis (
Myotis lucifugus
) in a high‐elevation landscape. Ecosphere 2019. [DOI: 10.1002/ecs2.2925] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Affiliation(s)
- Joseph S. Johnson
- Department of Biological Sciences Ohio University Athens Ohio 45701 USA
| | - John J. Treanor
- United States National Park Service Yellowstone National Park Wyoming 82190 USA
| | - Alexandra C. Slusher
- Department of Forestry and Natural Resources University of Kentucky Lexington Kentucky 40546 USA
| | - Michael J. Lacki
- Department of Forestry and Natural Resources University of Kentucky Lexington Kentucky 40546 USA
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12
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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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13
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Frequent nocturnal torpor in a free-ranging Australian honeyeater, the noisy miner. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2019; 106:28. [DOI: 10.1007/s00114-019-1626-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 05/14/2019] [Accepted: 05/16/2019] [Indexed: 11/26/2022]
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14
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The avian "hibernation" enigma: thermoregulatory patterns and roost choice of the common poorwill. Oecologia 2018; 189:47-53. [PMID: 30460539 DOI: 10.1007/s00442-018-4306-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Accepted: 11/13/2018] [Indexed: 02/06/2023]
Abstract
Compared to mammals, there are relatively few studies examining heterothermy in birds. In 13 bird families known to contain heterothermic species, the common poorwill (Phalaenoptilus nuttallii) is the only species that ostensibly hibernates. We used temperature-sensitive radio-transmitters to collect roost and skin temperature (Tskin) data, and winter roost preferences for free-ranging poorwills in southern Arizona. Further, to determine the effect of passive rewarming on torpor bout duration and active rewarming (i.e., the use of metabolic heat to increase Tskin), we experimentally shaded seven birds during winter to prevent them from passively rewarming via solar radiation. Poorwills selected winter roosts that were open to the south or southwest, facilitating passive solar warming in the late afternoon. Shaded birds actively rewarmed following at least 3 days of continuous torpor. Average torpor bout duration by shaded birds was 122 h and ranged from 91 to 164 h. Active rewarming by shaded birds occurred on significantly warmer days than those when poorwills remained torpid. One shaded bird remained inactive for 45 days, during which it spontaneously rewarmed actively on eight occasions. Our findings show that during winter poorwills exhibit physiological patterns and active rewarming similar to hibernating mammals.
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Streicher S, Lutermann H, Bennett NC, Bertelsen MF, Mohammed OB, Manger PR, Scantlebury M, Ismael K, Alagaili AN. Living on the edge: Daily, seasonal and annual body temperature patterns of Arabian oryx in Saudi Arabia. PLoS One 2017; 12:e0180269. [PMID: 28854247 PMCID: PMC5576856 DOI: 10.1371/journal.pone.0180269] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 06/13/2017] [Indexed: 11/19/2022] Open
Abstract
Heterothermy, the ability to allow body temperature (Tb) to fluctuate, has been proposed as an adaptive mechanism that enables large ungulates to cope with the high environmental temperatures and lack of free water experienced in arid environments. By storing heat during the daytime and dissipating it during the night, arid-adapted ungulates may reduce evaporative water loss and conserve water. Adaptive heterothermy in large ungulates should be particularly pronounced in hot environments with severely limited access to free water. In the current study we investigated the effects of environmental temperature (ambient, Ta and soil, Ts) and water stress on the Tb of wild, free-ranging Arabian oryx (Oryx leucoryx) in two different sites in Saudi Arabia, Mahazat as-Sayd (MS) and Uruq Bani Ma’arid (UBM). Using implanted data loggers wet took continuous Tb readings every 10 minutes for an entire calendar year and determined the Tb amplitude as well as the heterothermy index (HI). Both differed significantly between sites but contrary to our expectations they were greater in MS despite its lower environmental temperatures and higher rainfall. This may be partially attributable to a higher activity in an unfamiliar environment for translocated animals in UBM. As expected Tb amplitude and HI were greatest during summer. Only minor sex differences were apparent that may be attributable to sex-specific investment into reproduction (e.g. male-male competition) during rut. Our results suggest that the degree of heterothermy is not only driven by extrinsic factors (e.g. environmental temperatures and water availability), but may also be affected by intrinsic factors (e.g. sex and/or behaviour).
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Affiliation(s)
- S. Streicher
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - H. Lutermann
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - N. C. Bennett
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - M. F. Bertelsen
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
- Copenhagen Zoo, Centre for Zoo and Wild Animal Health, Frederiksberg, Denmark
| | - O. B. Mohammed
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - P. R. Manger
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Copenhagen Zoo, Centre for Zoo and Wild Animal Health, Frederiksberg, Denmark
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - M. Scantlebury
- School of Biological Sciences, Institute for Global Food Security, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - K. Ismael
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
- Prince Saud Al- Faisal Wildlife Research Centre, Taif, Saudi Arabia
| | - A. N. Alagaili
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
- Saudi Wildlife Authority, Riyadh, Saudi Arabia
- * E-mail:
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Theimer TC, Williams CT, Johnson SR, Gilbert AT, Bergman DL, Buck CL. Den use and heterothermy during winter in free-living, suburban striped skunks. J Mammal 2017. [DOI: 10.1093/jmammal/gyx009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Barclay RMR, Jacobs DS, Harding CT, McKechnie AE, McCulloch SD, Markotter W, Paweska J, Brigham RM. Thermoregulation by captive and free-ranging Egyptian rousette bats (Rousettus aegyptiacus) in South Africa. J Mammal 2017. [DOI: 10.1093/jmammal/gyw234] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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18
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Stawski C, Nowack J, Körtner G, Geiser F. A new cue for torpor induction: charcoal, ash and smoke. J Exp Biol 2017; 220:220-226. [DOI: 10.1242/jeb.146548] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/20/2016] [Indexed: 12/13/2022]
Abstract
ABSTRACT
Recent work has shown that the use of torpor for energy conservation increases after forest fires in heterothermic mammals, probably in response to the reduction of food. However, the specific environmental cues for this increased torpor expression remain unknown. It is possible that smoke and the novel substrate of charcoal and ash act as signals for an impending period of starvation requiring torpor. We therefore tested the hypothesis that the combined cues of smoke, a charcoal/ash substrate and food shortage will enhance torpor expression in a small forest-dwelling marsupial, the yellow-footed antechinus (Antechinus flavipes), because like other animals that live in fire-prone habitats they must effectively respond to fires to ensure survival. Activity and body temperature patterns of individuals in outdoor aviaries were measured under natural environmental conditions. All individuals were strictly nocturnal, but diurnal activity was observed shortly after smoke exposure. Overall, torpor in females was longer and deeper than that in males. Interestingly, while both males and females increased daily torpor duration during food restriction by >2-fold as anticipated, a combination of food restriction and smoke exposure on a charcoal/ash substrate further increased daily torpor duration by ∼2-fold in both sexes. These data show that this combination of cues for torpor induction is stronger than food shortage on its own. Our study provides significant new information on how a small forest-dwelling mammal responds to fire cues during and immediately after a fire and identifies a new, not previously recognised, regulatory mechanism for thermal biology in mammals.
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Affiliation(s)
- Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Gerhard Körtner
- 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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Descovich KA, Johnston S, Lisle A, Nicolson V, Janssen T, Brooks P, Phillips CJC. Long-term measurement of body temperature in the southern hairy-nosed wombat (Lasiorhinus latifrons). AUSTRALIAN MAMMALOGY 2017. [DOI: 10.1071/am15041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The southern hairy-nosed wombat (Lasiorhinus latifrons) is a nocturnal, fossorial marsupial that has evolved a range of physiological and behavioural adaptations to its semiarid environment. This study describes long-term core body temperature (Tb) of L. latifrons in a population with opportunities for behavioural thermoregulation through burrow use. Tb was measured hourly in 12 captive L. latifrons using implanted dataloggers over a 9-month period from late winter to late autumn. Data were examined for daily patterns, seasonal changes, sex differences and the relationship with environmental conditions (ambient temperature, den temperature and relative humidity). Tb ranged from 30.9 to 38.8°C, and had a distinct nychthemeral rhythm, with peak temperatures occurring at night in line with nocturnal activity. Females had a higher mean Tb (34.9°C) than males (34.4°C). The relationship between external ambient temperature and body temperature was negative, with body temperature decreasing as ambient temperature increased. This study is an important step towards a comprehensive picture of thermoregulation in L. latifrons, which may become vulnerable in the future if environmental temperatures rise and water availability decreases.
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Matthews JK, Stawski C, Körtner G, Parker CA, Geiser F. Torpor and basking after a severe wildfire: mammalian survival strategies in a scorched landscape. J Comp Physiol B 2016; 187:385-393. [DOI: 10.1007/s00360-016-1039-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 09/14/2016] [Accepted: 09/30/2016] [Indexed: 11/24/2022]
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Abstract
Many environmental conditions can constrain the ability of animals to obtain sufficient food energy, or transform that food energy into useful chemical forms. To survive extended periods under such conditions animals must suppress metabolic rate to conserve energy, water, or oxygen. Amongst small endotherms, this metabolic suppression is accompanied by and, in some cases, facilitated by a decrease in core body temperature-hibernation or daily torpor-though significant metabolic suppression can be achieved even with only modest cooling. Within some ectotherms, winter metabolic suppression exceeds the passive effects of cooling. During dry seasons, estivating ectotherms can reduce metabolism without changes in body temperature, conserving energy reserves, and reducing gas exchange and its inevitable loss of water vapor. This overview explores the similarities and differences of metabolic suppression among these states within adult animals (excluding developmental diapause), and integrates levels of organization from the whole animal to the genome, where possible. Several similarities among these states are highlighted, including patterns and regulation of metabolic balance, fuel use, and mitochondrial metabolism. Differences among models are also apparent, particularly in whether the metabolic suppression is intrinsic to the tissue or depends on the whole-animal response. While in these hypometabolic states, tissues from many animals are tolerant of hypoxia/anoxia, ischemia/reperfusion, and disuse. These natural models may, therefore, serve as valuable and instructive models for biomedical research.
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Affiliation(s)
- James F Staples
- Department of Biology, University of Western Ontario, London, Ontario, Canada
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22
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Brigham RM, Geiser F. Do red squirrels (Tamiasciurus hudsonicus) use daily torpor during winter? ECOSCIENCE 2015. [DOI: 10.2980/19-2-3464] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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23
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Physiological and behavioural responses of a small heterothermic mammal to fire stimuli. Physiol Behav 2015; 151:617-22. [DOI: 10.1016/j.physbeh.2015.09.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 07/16/2015] [Accepted: 09/01/2015] [Indexed: 01/06/2023]
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Hetem RS, Maloney SK, Fuller A, Mitchell D. Heterothermy in large mammals: inevitable or implemented? Biol Rev Camb Philos Soc 2014; 91:187-205. [PMID: 25522232 DOI: 10.1111/brv.12166] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 10/24/2014] [Accepted: 11/11/2014] [Indexed: 11/26/2022]
Abstract
Advances in biologging techniques over the past 20 years have allowed for the remote and continuous measurement of body temperatures in free-living mammals. While there is an abundance of literature on heterothermy in small mammals, fewer studies have investigated the daily variability of body core temperature in larger mammals. Here we review measures of heterothermy and the factors that influence heterothermy in large mammals in their natural habitats, focussing on large mammalian herbivores. The mean 24 h body core temperatures for 17 species of large mammalian herbivores (>10 kg) decreased by ∼1.3°C for each 10-fold increase in body mass, a relationship that remained significant following phylogenetic correction. The degree of heterothermy, as measured by the 24 h amplitude of body core temperature rhythm, was independent of body mass and appeared to be driven primarily by energy and water limitations. When faced with the competing demands of osmoregulation, energy acquisition and water or energy use for thermoregulation, large mammalian herbivores appear to relax the precision of thermoregulation thereby conserving body water and energy. Such relaxation may entail a cost in that an animal moves closer to its thermal limits for performance. Maintaining homeostasis requires trade-offs between regulated systems, and homeothermy apparently is not accorded the highest priority; large mammals are able to maintain optimal homeothermy only if they are well nourished, hydrated, and not compromised energetically. We propose that the amplitude of the 24 h rhythm of body core temperature provides a useful index of any compromise experienced by a free-living large mammal and may predict the performance and fitness of an animal.
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Affiliation(s)
- Robyn S Hetem
- Brain Function Research Group, School of Physiology, Faculty of Health Science, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa
| | - Shane K Maloney
- Brain Function Research Group, School of Physiology, Faculty of Health Science, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa.,School of Anatomy, Physiology, and Human Biology, University of Western Australia, Crawley, 6009, Australia
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, Faculty of Health Science, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, Faculty of Health Science, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa
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Vuarin P, Henry PY, Guesnet P, Alessandri JM, Aujard F, Perret M, Pifferi F. Shallow hypothermia depends on the level of fatty acid unsaturation in adipose and liver tissues in a tropical heterothermic primate. J Therm Biol 2014; 43:81-8. [DOI: 10.1016/j.jtherbio.2014.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 05/09/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
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26
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Johnson JS, Lacki MJ. Effects of reproductive condition, roost microclimate, and weather patterns on summer torpor use by a vespertilionid bat. Ecol Evol 2013; 4:157-66. [PMID: 24558571 PMCID: PMC3925379 DOI: 10.1002/ece3.913] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 11/05/2013] [Accepted: 11/13/2013] [Indexed: 11/22/2022] Open
Abstract
A growing number of mammal species are recognized as heterothermic, capable of maintaining a high-core body temperature or entering a state of metabolic suppression known as torpor. Small mammals can achieve large energetic savings when torpid, but they are also subject to ecological costs. Studying torpor use in an ecological and physiological context can help elucidate relative costs and benefits of torpor to different groups within a population. We measured skin temperatures of 46 adult Rafinesque's big-eared bats (Corynorhinus rafinesquii) to evaluate thermoregulatory strategies of a heterothermic small mammal during the reproductive season. We compared daily average and minimum skin temperatures as well as the frequency, duration, and depth of torpor bouts of sex and reproductive classes of bats inhabiting day-roosts with different thermal characteristics. We evaluated roosts with microclimates colder (caves) and warmer (buildings) than ambient air temperatures, as well as roosts with intermediate conditions (trees and rock crevices). Using Akaike's information criterion (AIC), we found that different statistical models best predicted various characteristics of torpor bouts. While the type of day-roost best predicted the average number of torpor bouts that bats used each day, current weather variables best predicted daily average and minimum skin temperatures of bats, and reproductive condition best predicted average torpor bout depth and the average amount of time spent torpid each day by bats. Finding that different models best explain varying aspects of heterothermy illustrates the importance of torpor to both reproductive and nonreproductive small mammals and emphasizes the multifaceted nature of heterothermy and the need to collect data on numerous heterothermic response variables within an ecophysiological context.
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Affiliation(s)
- Joseph S Johnson
- Department of Biology, Bucknell University Lewisburg, 17837, Pennsylvania
| | - Michael J Lacki
- Department of Forestry, University of Kentucky Lexington, 40546, Kentucky
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27
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Muñoz-Garcia A, Ben-Hamo M, Korine C, Pinshow B, Williams JB. A new thermoregulatory index for heterothermy. Methods Ecol Evol 2013. [DOI: 10.1111/2041-210x.12131] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Agustí Muñoz-Garcia
- Department of Evolution; Ecology and Organismal Biology; Ohio State University, Aronoff Laboratory; 318 W 12th Ave., Columbus, OH 43210 USA
| | - Miriam Ben-Hamo
- Mitrani Department of Desert Ecology; Jacob blaustein Institutes for desert Research; Ben-Gurion University of the Negev 84900 Midreshet Ben-Gurion Israel
| | - Carmi Korine
- Mitrani Department of Desert Ecology; Jacob blaustein Institutes for desert Research; Ben-Gurion University of the Negev 84900 Midreshet Ben-Gurion Israel
| | - Berry Pinshow
- Mitrani Department of Desert Ecology; Jacob blaustein Institutes for desert Research; Ben-Gurion University of the Negev 84900 Midreshet Ben-Gurion Israel
| | - Joseph B. Williams
- Department of Evolution; Ecology and Organismal Biology; Ohio State University, Aronoff Laboratory; 318 W 12th Ave., Columbus, OH 43210 USA
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Superina M, Jahn GA. Effect of low-quality diet on torpor frequency and depth in the pichi Zaedyus pichiy (Xenarthra, Dasypodidae), a South American armadillo. J Therm Biol 2013. [DOI: 10.1016/j.jtherbio.2013.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Klug BJ, Barclay RMR. Thermoregulation during reproduction in the solitary, foliage-roosting hoary bat (Lasiurus cinereus). J Mammal 2013. [DOI: 10.1644/12-mamm-a-178.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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30
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Johnson JS, Lacki MJ. Summer heterothermy in Rafinesque's big-eared bats (Corynorhinus rafinesquii) roosting in tree cavities in bottomland hardwood forests. J Comp Physiol B 2012; 183:709-21. [PMID: 23269613 DOI: 10.1007/s00360-012-0728-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 11/13/2012] [Accepted: 11/18/2012] [Indexed: 11/26/2022]
Abstract
Many small mammals are heterothermic endotherms capable of maintaining an elevated core body temperature or reducing their thermoregulatory set point to enter a state of torpor. Torpor can confer substantial energy savings, but also incurs ecological costs, such as hindering allocation of energy towards reproduction. We placed temperature-sensitive radio transmitters on 44 adult Rafinesque's big-eared bats (Corynorhinus rafinesquii) and deployed microclimate dataloggers inside 34 day roosts to compare the use of torpor by different sex and reproductive classes of bats during the summer. We collected 324 bat-days of skin-temperature data from 36 females and 4 males. Reproductive females employed fewer torpor bouts per day than non-reproductive females and males (P < 0.0001), and pregnant and lactating females had higher average (P < 0.0001) and minimum (P < 0.0001) skin temperatures than non-reproductive females. Pregnant females spent less time torpid (P < 0.0001) than non-reproductive females, but lactating females used relatively deep, long torpor bouts. Microclimates varied inside tree species with different configurations of entrances to the roost cavity (P < 0.0001). Bats spent more time torpid when roosting in water tupelo (Nyssa aquatica) trees possessing only a basal entrance to the cavity (P = 0.001). Of the tree species used as roosts, water tupelo cavities exhibited the least variable daytime and nighttime temperatures. These data demonstrate that use of summer torpor is not uniform among sex and reproductive classes in Rafinesque's big-eared bat, and variation in microclimate among tree roosts due to species and structural characteristics facilitates the use of different thermoregulatory strategies in these bats.
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Affiliation(s)
- Joseph S Johnson
- Department of Forestry, University of Kentucky, Lexington, KY 40546, USA.
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31
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Jonasson KA, Willis CKR. Hibernation energetics of free-ranging little brown bats. ACTA ACUST UNITED AC 2012; 215:2141-9. [PMID: 22623203 DOI: 10.1242/jeb.066514] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hibernation physiology and energy expenditure have been relatively well studied in large captive hibernators, especially rodents, but data from smaller, free-ranging hibernators are sparse. We examined variation in the hibernation patterns of free-ranging little brown bats (Myotis lucifugus) using temperature-sensitive radio-transmitters. First, we aimed to test the hypothesis that age, sex and body condition affect expression of torpor and energy expenditure during hibernation. Second, we examined skin temperature to assess whether qualitative differences in the thermal properties of the hibernacula of bats, compared with the burrows of hibernating rodents, might lead to different patterns of torpor and arousal for bats. We also evaluated the impact of carrying transmitters on body condition to help determine the potential impact of telemetry studies. We observed large variation in the duration of torpor bouts within and between individuals but detected no effect of age, sex or body condition on torpor expression or estimates of energy expenditure. We observed the use of shallow torpor in the midst of periodic arousals, which may represent a unique adaptation of bats for conservation of energy during the most costly phase of hibernation. There was no difference in the body condition of hibernating bats outfitted with transmitters compared with that of control bats captured from the same hibernaculum at the same time. This study provides new information on the energetics of hibernation in an under-represented taxon and baseline data important for understanding how white-nose syndrome, a new disease devastating populations of hibernating bats in North America, may alter the expression of hibernation in affected bats.
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Affiliation(s)
- Kristin A Jonasson
- Department of Biology and Centre for Forest Inter-disciplinary Research, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB, Canada R3B 2E9
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32
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Seasonal changes in thermogenesis of a free-ranging afrotherian small mammal, the Western rock elephant shrew (Elephantulus rupestris). J Comp Physiol B 2012; 182:715-27. [PMID: 22349624 DOI: 10.1007/s00360-012-0647-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Revised: 01/15/2012] [Accepted: 01/26/2012] [Indexed: 01/04/2023]
Abstract
We report on the seasonal metabolic adjustments of a small-sized member of the phylogenetically ancient Afrotheria, the Western rock elephant shrew (Elephantulus rupestris). We recorded body temperature (T (b)) patterns and compared the capacity for adrenergically induced nonshivering thermogenesis (NST) in E. rupestris captured in the wild in summer and winter. Noradrenaline (NA) treatment (0.4-0.5 mg/kg, s.c.) induced a pronounced elevation in oxygen consumption compared to controls (saline), and the increase in oxygen consumption following injection of NA was 1.8-fold higher in winter compared to summer. This suggests that the smaller members of Afrotheria possess functional brown adipose tissue, which changes in thermogenic capacity depending on the season. Torpor was recorded in both seasons, but in winter the incidence of torpor was higher (n = 205 out of 448 observations) and minimal T (b) during torpor was lower (T (b)min: 11.9°C) than in summer (n = 24 out of 674 observations; T (b)min: 26°C). In addition to cold, high air humidity emerged as a likely predictor for torpor entry. Overall, E. rupestris showed a high degree of thermoregulatory plasticity, which was mainly reflected in a variable timing of torpor entry and arousal. We conclude that E. rupestris exhibits seasonal metabolic adjustments comparable to what has been long known for many Holarctic rodents.
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