1
|
Wacker CB, Geiser F. The Rate of Cooling during Torpor Entry Drives Torpor Patterns in a Small Marsupial. Physiol Biochem Zool 2023; 96:393-404. [PMID: 38237188 DOI: 10.1086/727975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
AbstractTo maximize energy savings, entry into torpor should involve a fast reduction of metabolic rate and body temperature (Tb); that is, animals should thermoconform. However, animals often defend against the decrease in Tb via a temporary increase in thermoregulatory heat production, slowing the cooling process. We investigated how thermoregulating or thermoconforming during torpor entry affects temporal and thermoenergetic aspects in relation to body mass and age in juvenile and adult fat-tailed dunnarts (Sminthopsis crassicaudata; Marsupialia: Dasyuridae). During torpor entry, juvenile thermoconformers cooled twice as fast as and used less energy during cooling than juvenile thermoregulators. While both juvenile and adult thermoconformers had a lower minimum Tb, a lower torpor metabolic rate, and longer torpor bouts than thermoregulators, these differences were more pronounced in the juveniles. Rewarming from torpor took approximately twice as long for juvenile thermoconformers, and the costs of rewarming were greater. To determine the difference in average daily metabolic rate between thermoconformers and thermoregulators independent of body mass, we compared juveniles of a similar size (∼13 g) and similarly sized adults (∼17 g). The average daily metabolic rate was 7% (juveniles) and 17% (adults) less in thermoconformers than in thermoregulators, even though thermoconformers were active for longer. Our data suggest that thermoconforming during torpor entry provides an energetic advantage for both juvenile and adult dunnarts and may aid growth for juveniles. While thermoregulation during torpor entry is more costly, it still saves energy, and the higher Tb permits greater alertness and mobility and reduces the energetic cost of endogenous rewarming.
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Kerman K, Roggero A, Rolando A, Palestrini C. Sexual horn dimorphism predicts the expression of active personality trait: males perform better only in the sexually horn dimorphic Onthophagus dung beetle. J ETHOL 2023. [DOI: 10.1007/s10164-023-00782-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2023]
|
4
|
Flewwelling LD, Wearing OH, Garrett EJ, Scott GR. Thermoregulatory trade-offs underlie the effects of warming summer temperatures on deer mice. J Exp Biol 2023; 226:287070. [PMID: 36808489 DOI: 10.1242/jeb.244852] [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: 08/05/2022] [Accepted: 02/13/2023] [Indexed: 02/22/2023]
Abstract
Climate warming could challenge the ability of endotherms to thermoregulate and maintain normal body temperature (Tb), but the effects of warming summer temperatures on activity and thermoregulatory physiology in many small mammals remain poorly understood. We examined this issue in deer mice (Peromyscus maniculatus), an active nocturnal species. Mice were exposed in the lab to simulated seasonal warming, in which an environmentally realistic diel cycle of ambient temperature (Ta) was gradually warmed from spring conditions to summer conditions (controls were maintained in spring conditions). Activity (voluntary wheel running) and Tb (implanted bio-loggers) were measured throughout, and indices of thermoregulatory physiology (thermoneutral zone, thermogenic capacity) were assessed after exposure. In control mice, activity was almost entirely restricted to the night-time, and Tb fluctuated ∼1.7°C between daytime lows and night-time highs. Activity, body mass and food consumption were reduced and water consumption was increased in later stages of summer warming. This was accompanied by strong Tb dysregulation that culminated in a complete reversal of the diel pattern of Tb variation, with Tb reaching extreme highs (∼40°C) during daytime heat but extreme lows (∼34°C) at cooler night-time temperatures. Summer warming was also associated with reduced ability to generate body heat, as reflected by decreased thermogenic capacity and decreased mass and uncoupling protein (UCP1) content of brown adipose tissue. Our findings suggest that thermoregulatory trade-offs associated with daytime heat exposure can affect Tb and activity at cooler night-time temperatures, impacting the ability of nocturnal mammals to perform behaviours important for fitness in the wild.
Collapse
Affiliation(s)
- Luke D Flewwelling
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1
| | - Oliver H Wearing
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1
| | - Emily J Garrett
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1
| | - Graham R Scott
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1
| |
Collapse
|
5
|
Glass JR, Harrison JF. The thermal performance curve for aerobic metabolism of a flying endotherm. Proc Biol Sci 2022; 289:20220298. [PMID: 35975442 PMCID: PMC9382204 DOI: 10.1098/rspb.2022.0298] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/28/2022] [Indexed: 12/14/2022] Open
Abstract
Performance benefits of stable, warm muscles are believed to be important for the evolution of endothermy in mammals, birds and flying insects. However, thermal performance curves have never been measured for a free-flying endotherm, as it is challenging to vary body temperatures of these animals, and maximal flight performance is difficult to elicit. We varied air temperatures and gas densities to manipulate thoracic temperatures of flying honeybees from 29°C to 44°C, with low air densities used to increase flight metabolic rates to maximal values. Honeybees showed a clear thermal performance curve with an optimal temperature of 39°C. Maximal flight metabolic rates increased by approximately 2% per 1°C increase in thoracic temperature at suboptimal thoracic temperatures, but decreased approximately 5% per 1°C increase as the bees continued to heat up. This study provides the first quantification of the maximal metabolic performance benefit of thermoregulation in an endotherm. These data directly support aerobic capacity models for benefits of thermoregulation in honeybees, and suggest that improved aerobic capacity probably contributes to the multiple origins of endothermic heterothermy in bees and other insects.
Collapse
Affiliation(s)
- Jordan R. Glass
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Jon F. Harrison
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| |
Collapse
|
6
|
Wang Z, Liu R, Zhang L, Yu S, Nie Y, Deng Y, Liu R, Zhu W, Zhou Z, Diao J. Thermoregulation of Eremias argus alters temperature-dependent toxicity of beta-cyfluthrin: Ecotoxicological effects considering ectotherm behavior traits. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 293:118461. [PMID: 34748886 DOI: 10.1016/j.envpol.2021.118461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 10/27/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
Risk assessments of the ecotoxicological effects insecticides impose on ectotherms have increasingly considered temperature. However, the changes toxicants induce in thermoregulatory behavioral traits may lead to a divergence of thermal selection and temperature-dependent changes of contaminant toxicity. This study demonstrated the interaction of behavioral thermoregulation and temperature-dependent toxicity of beta-cyfluthrin (BC) in the lizard Eremias argus. Based on the negative relationship between temperature and BC toxicity, seeking a warming environment was assumed to represent a self-rescue behavior (and vice versa). The results showed that BC-treated lizards (0-20 μg/g body weight (bw)) showed such self-rescue behavior, while lizards exposed to an extremely high BC dose (200 μg/g bw) sought a cooler environment. Biochemical assays showed that BC affected neurotransmitter systems, caused oxidative stress, and interfered with ion-transport in the central nervous system. Biomarkers of the cholinergic and glutamatergic system, ion-transport function, and oxidative stress were identified as potential biochemical variables related to thermoregulatory behavior. Apparently, seeking a warmer environment is a survival strategy with the aim to neutralize BC toxicity, while seeking a cooler environment aims to attenuate the harmful effects of metabolic and oxidative stress, and to decelerate internal BC diffusion. This phenomenon could be also explained by the concept of the "cooling trap", i.e., a behavior where cooler temperatures are sought. This impairs survival after exposure to BC at it has a negative temperature coefficient, derived from a dysfunction of the central nervous system regarding thermoregulation caused by the high dosage of neurotoxicant and resulting temperature maladaptation. Implications of the interaction between thermoregulatory behavior and temperature-dependent toxicity are presented, which may aid further temperature-dependent risk assessments.
Collapse
Affiliation(s)
- Zikang Wang
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Ran Liu
- Beijing Food Safety Monitoring and Risk Assessment Center (Beijing Food Inspection Institute), Beijing, China
| | - Luyao Zhang
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Simin Yu
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Yufan Nie
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Yue Deng
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Rui Liu
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Wentao Zhu
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Zhiqiang Zhou
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China
| | - Jinling Diao
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing, 100193, China.
| |
Collapse
|
7
|
Levesque DL, Nowack J, Boyles JG. Body Temperature Frequency Distributions: A Tool for Assessing Thermal Performance in Endotherms? Front Physiol 2021; 12:760797. [PMID: 34721082 PMCID: PMC8551754 DOI: 10.3389/fphys.2021.760797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 09/07/2021] [Indexed: 12/25/2022] Open
Abstract
There is increasing recognition that rather than being fully homeothermic, most endotherms display some degree of flexibility in body temperature. However, the degree to which this occurs varies widely from the relatively strict homeothermy in species, such as humans to the dramatic seasonal hibernation seen in Holarctic ground squirrels, to many points in between. To date, attempts to analyse this variability within the framework generated by the study of thermal performance curves have been lacking. We tested if frequency distribution histograms of continuous body temperature measurements could provide a useful analogue to a thermal performance curve in endotherms. We provide examples from mammals displaying a range of thermoregulatory phenotypes, break down continuous core body temperature traces into various components (active and rest phase modes, spreads and skew) and compare these components to hypothetical performance curves. We did not find analogous patterns to ectotherm thermal performance curves, in either full datasets or by breaking body temperature values into more biologically relevant components. Most species had either bimodal or right-skewed (or both) distributions for both active and rest phase body temperatures, indicating a greater capacity for mammals to tolerate body temperatures elevated above the optimal temperatures than commonly assumed. We suggest that while core body temperature distributions may prove useful in generating optimal body temperatures for thermal performance studies and in various ecological applications, they may not be a good means of assessing the shape and breath of thermal performance in endotherms. We also urge researchers to move beyond only using mean body temperatures and to embrace the full variability in both active and resting temperatures in endotherms.
Collapse
Affiliation(s)
- D L Levesque
- School of Biology and Ecology, University of Maine, Orono, ME, United States
| | - J Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - J G Boyles
- Cooperative Wildlife Research Laboratory, Center for Ecology, and School of Biological Sciences, Southern Illinois University, Carbondale, IL, United States
| |
Collapse
|
8
|
Abstract
Temperature is an important environmental factor governing the ability of organisms to grow, survive and reproduce. Thermal performance curves (TPCs), with some caveats, are useful for charting the relationship between body temperature and some measure of performance in ectotherms, and provide a standardized set of characteristics for interspecific comparisons. Endotherms, however, have a more complicated relationship with environmental temperature, as endothermy leads to a decoupling of body temperature from external temperature through use of metabolic heat production, large changes in insulation and variable rates of evaporative heat loss. This has impeded our ability to model endothermic performance in relation to environmental temperature as well as to readily compare performance between species. In this Commentary, we compare the strengths and weaknesses of potential TPC analogues (including other useful proxies for linking performance to temperature) in endotherms and suggest several ways forward in the comparative ecophysiology of endotherms. Our goal is to provide a common language with which ecologists and physiologists can evaluate the effects of temperature on performance. Key directions for improving our understanding of endotherm thermoregulatory physiology include a comparative approach to the study of the level and precision of body temperature, measuring performance directly over a range of body temperatures and building comprehensive mechanistic models of endotherm responses to environmental temperatures. We believe the answer to the question posed in the title could be 'yes', but only if 'performance' is well defined and understood in relation to body temperature variation, and the costs and benefits of endothermy are specifically modelled.
Collapse
Affiliation(s)
| | - Katie E Marshall
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| |
Collapse
|
9
|
Menzies AK, Studd EK, Majchrzak YN, Peers MJL, Boutin S, Dantzer B, Lane JE, McAdam AG, Humphries MM. Body temperature, heart rate, and activity patterns of two boreal homeotherms in winter: Homeostasis, allostasis, and ecological coexistence. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13640] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Allyson K. Menzies
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
| | - Emily K. Studd
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
- Department of Biological Sciences University of Alberta Edmonton AB Canada
| | | | | | - Stan Boutin
- Department of Biological Sciences University of Alberta Edmonton AB Canada
| | - Ben Dantzer
- Department of Psychology University of Michigan Ann Arbor MI USA
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor MI USA
| | - Jeffrey E. Lane
- Department of Biology University of Saskatchewan Saskatoon SK Canada
| | - Andrew G. McAdam
- Department of Ecology and Evolutionary Biology University of Colorado Boulder CO USA
| | - Murray M. Humphries
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
| |
Collapse
|
10
|
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.
Collapse
Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology CO2, University of New England, Armidale, NSW, Australia
| |
Collapse
|
11
|
Nowack J, Tarmann I, Hoelzl F, Smith S, Giroud S, Ruf T. Always a price to pay: hibernation at low temperatures comes with a trade-off between energy savings and telomere damage. Biol Lett 2019; 15:20190466. [PMID: 31573426 PMCID: PMC6832184 DOI: 10.1098/rsbl.2019.0466] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 09/10/2019] [Indexed: 12/16/2022] Open
Abstract
We experimentally tested the costs of deep torpor at low temperatures by comparing telomere dynamics in two species of rodents hibernating at either 3 or 14°C. Our data show that hibernators kept at the warmer temperature had higher arousal frequencies, but maintained longer telomeres than individuals hibernating at the colder temperature. We suggest that the high-energy demand of frequent arousals is counteracted by a lower temperature differential between torpid and euthermic body temperature and that telomere length is restored during arousals when the body temperature is returned to normothermic values. Taken together, our study shows that hibernation at low body temperatures comes with costs on a cellular level and that hibernators need to actively counterbalance the shortening of telomeres.
Collapse
Affiliation(s)
- Julia Nowack
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Iris Tarmann
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Franz Hoelzl
- Department of Interdisciplinary Life Sciences, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, Austria
| | - Steve Smith
- Department of Interdisciplinary Life Sciences, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, Austria
| | - Sylvain Giroud
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Thomas Ruf
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| |
Collapse
|
12
|
Turbill C, Stojanovski L. Torpor reduces predation risk by compensating for the energetic cost of antipredator foraging behaviours. Proc Biol Sci 2018; 285:20182370. [PMID: 30963890 PMCID: PMC6304060 DOI: 10.1098/rspb.2018.2370] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 11/27/2018] [Indexed: 11/12/2022] Open
Abstract
Foraging activity is needed for energy intake but increases the risk of predation, and antipredator behavioural responses, such as reduced activity, generally reduce energy intake. Hence, the mortality and indirect effects of predation risk are dependent on the energy requirements of prey. Torpor, a controlled reduction in resting metabolism and body temperature, is a common energy-saving mechanism of small mammals that enhances their resistance to starvation. Here we test the hypothesis that torpor could also reduce predation risk by compensating for the energetic cost of antipredator behaviours. We measured the foraging behaviour and body temperature of house mice in response to manipulation of perceived predation risk by adjusting levels of ground cover and starvation risk by 24 h food withdrawal every third day. We found that a voluntary reduction in daily food intake in response to lower cover (high predation risk) was matched by the extent of a daily reduction in body temperature. Our study provides the first experimental evidence of a close link between energy-saving torpor responses to starvation risk and behavioural responses to perceived predation risk. By reducing the risk of starvation, torpor can facilitate stronger antipredator behaviours. These results highlight the interplay between the capacity for reducing metabolic energy expenditure, optimal decisions about foraging behaviour and the life-history ecology of prey.
Collapse
Affiliation(s)
- Christopher Turbill
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, New South Wales, Australia
| | | |
Collapse
|
13
|
Geiser F, Stawski C, Doty AC, Cooper CE, Nowack J. A burning question: what are the risks and benefits of mammalian torpor during and after fires? CONSERVATION PHYSIOLOGY 2018; 6:coy057. [PMID: 30323932 PMCID: PMC6181253 DOI: 10.1093/conphys/coy057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/11/2018] [Accepted: 10/08/2018] [Indexed: 06/08/2023]
Abstract
Although wildfires are increasing globally, available information on how mammals respond behaviourally and physiologically to fires is scant. Despite a large number of ecological studies, often examining animal diversity and abundance before and after fires, the reasons as to why some species perform better than others remain obscure. We examine how especially small mammals, which generally have high rates of energy expenditure and food requirements, deal with fires and post-fire conditions. We evaluate whether mammalian torpor, characterised by substantial reductions in body temperature, metabolic rate and water loss, plays a functional role in survival of mammals impacted by fires. Importantly, torpor permits small mammals to reduce their activity and foraging, and to survive on limited food. Torpid small mammals (marsupials and bats) can respond to smoke and arouse from torpor, which provides them with the possibility to evade direct exposure to fire, although their response is often slowed when ambient temperature is low. Post-fire conditions increase expression of torpor with a concomitant decrease in activity for free-ranging echidnas and small forest-dwelling marsupials, in response to reduced cover and reduced availability of terrestrial insects. Presence of charcoal and ash increases torpor use by captive small marsupials beyond food restriction alone, likely in anticipation of detrimental post-fire conditions. Interestingly, although volant bats use torpor on every day after fires, they respond by decreasing torpor duration, and increasing activity, perhaps because of the decrease in clutter and increase in foraging opportunities due to an increase in aerial insects. Our summary shows that torpor is an important tool for post-fire survival and, although the physiological and behavioural responses of small mammals to fire are complex, they seem to reflect energetic requirements and mode of foraging. We make recommendations on the conditions during management burns that are least likely to impact heterothermic mammals.
Collapse
Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Anna C Doty
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- Department of Biological Sciences, Arkansas State University, Jonesboro, AR, USA
| | - Christine E Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, Western Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- School of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool, UK
| |
Collapse
|
14
|
Doty AC, Currie SE, Stawski C, Geiser F. Can bats sense smoke during deep torpor? Physiol Behav 2018; 185:31-38. [DOI: 10.1016/j.physbeh.2017.12.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 11/24/2017] [Accepted: 12/14/2017] [Indexed: 12/28/2022]
|
15
|
Nowack J, Stawski C, Körtner G, Geiser F. Physiological and behavioral responses of an arboreal mammal to smoke and charcoal-ash substrate. Physiol Behav 2018; 184:116-121. [DOI: 10.1016/j.physbeh.2017.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 11/08/2017] [Accepted: 11/16/2017] [Indexed: 10/18/2022]
|
16
|
Geiser F, Stawski C, Wacker CB, Nowack J. Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy. Front Physiol 2017; 8:842. [PMID: 29163191 PMCID: PMC5673639 DOI: 10.3389/fphys.2017.00842] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/09/2017] [Indexed: 12/02/2022] Open
Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Chris B Wacker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia.,Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| |
Collapse
|
17
|
Mayberry HW, McGuire LP, Willis CKR. Body temperatures of hibernating little brown bats reveal pronounced behavioural activity during deep torpor and suggest a fever response during white-nose syndrome. J Comp Physiol B 2017; 188:333-343. [PMID: 28766065 DOI: 10.1007/s00360-017-1119-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 07/18/2017] [Accepted: 07/25/2017] [Indexed: 01/06/2023]
Abstract
Hibernating animals use torpor [reduced body temperature (T b) and metabolic rate] to reduce energy expenditure during winter. Periodic arousals to normal T b are energetically expensive, so hibernators trade off arousal benefits against energetic costs. This is especially important for bats with white-nose syndrome (WNS), a fungal disease causing increased arousal frequency. Little brown bats (Myotis lucifugus) with WNS show upregulation of endogenous pyrogens and sickness behaviour. Therefore, we hypothesized that WNS should cause a fever response characterized by elevated T b. Hibernators could also accrue some benefits of arousals with minimal T b increase, thus avoiding full arousal costs. We compared skin temperature (T sk) of captive Myotis lucifugus inoculated with the WNS-causing fungus to T sk of sham-inoculated controls. Infected bats re-warmed to higher T sk during arousals which is consistent with a fever response. Torpid T sk did not differ. During what we term "cold arousals", bats exhibited movement following T sk increases of only 2.2 ± 0.3 °C, compared to >20 °C increases during normal arousals. Cold arousals occurred in both infected and control bats, suggesting they are not a pathophysiological consequence of WNS. Fever responses are energetically costly and could exacerbate energy limitation and premature fat depletion for bats with WNS. Cold arousals could represent an energy-saving mechanism for both healthy and WNS-affected bats when complete arousals are unnecessary or too costly. A few cold arousals were observed mid-hibernation, typically in response to disturbances. Cold arousals may, therefore, represent a voluntary restriction of arousal temperature instead of loss of thermoregulatory control.
Collapse
Affiliation(s)
- Heather W Mayberry
- Department of Biology, University of Winnipeg, 515 Portage Ave, Winnipeg, MB, R3B 2E9, Canada. .,Department of Ecology and Evolutionary Biology, University of Toronto Mississauga, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6, Canada.
| | - Liam P McGuire
- Department of Biology, University of Winnipeg, 515 Portage Ave, Winnipeg, MB, R3B 2E9, Canada.,Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA
| | - Craig K R Willis
- Department of Biology, University of Winnipeg, 515 Portage Ave, Winnipeg, MB, R3B 2E9, Canada
| |
Collapse
|
18
|
Rusch TW, Angilletta MJ. Competition during thermoregulation altered the body temperatures and hormone levels of lizards. Funct Ecol 2017. [DOI: 10.1111/1365-2435.12869] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Travis W. Rusch
- School of Life Sciences Arizona State University Tempe AZ85287 USA
| | | |
Collapse
|
19
|
More functions of torpor and their roles in a changing world. J Comp Physiol B 2017; 187:889-897. [PMID: 28432393 PMCID: PMC5486538 DOI: 10.1007/s00360-017-1100-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/26/2016] [Accepted: 02/26/2017] [Indexed: 02/06/2023]
Abstract
Increased winter survival by reducing energy expenditure in adult animals is often viewed as the primary function of torpor. However, torpor has many other functions that ultimately increase the survival of heterothermic mammals and birds. In this review, we summarize new findings revealing that animals use torpor to cope with the conditions during and after natural disasters, including fires, storms, and heat waves. Furthermore, we suggest that torpor, which also prolongs longevity and was likely crucial for survival of mammals during the time of the dinosaur extinctions, will be advantageous in a changing world. Climate change is assumed to lead to an increase in the occurrence and intensity of climatic disasters, such as those listed above and also abnormal floods, droughts, and extreme temperatures. The opportunistic use of torpor, found in many heterothermic species, will likely enhance survival of these challenges, because these species can reduce energy and foraging requirements. However, many strictly seasonal hibernators will likely face the negative consequences of the predicted increase in temperature, such as range contraction. Overall, available data suggest that opportunistic heterotherms with their flexible energy requirements have an adaptive advantage over homeotherms in response to unpredictable conditions.
Collapse
|
20
|
Wacker CB, McAllan BM, Körtner G, Geiser F. The role of basking in the development of endothermy and torpor in a marsupial. J Comp Physiol B 2017; 187:1029-1038. [PMID: 28283794 DOI: 10.1007/s00360-017-1060-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 01/02/2017] [Accepted: 01/18/2017] [Indexed: 10/20/2022]
Abstract
Marsupials have a slow rate of development and this allows a detailed examination of thermoregulatory developmental changes and stages. We quantified the cooling rates of marsupial dunnarts (Sminthopsis crassicaudata) at 40-56 days (d) old, and torpor and basking behaviour in animals given the option to bask in four age groups from 60 to 150 d. The development of thermoregulation was a continuum, but was characterised by three major thermoregulatory stages: (1) at 40 d, animals were unable to maintain a constant high body temperature during short-term cold exposure; (2) at 60 d, animals could maintain a high T b for the first part of the night at an ambient temperature of 15.0 ± 0.7 °C; later in the night, they entered an apparent torpor bout but could only rewarm passively when basking under a heat lamp; (3) from ~90 d, they expressed prolonged torpor bouts and were able to rewarm endogenously. Young newly weaned 60 d animals were able to avoid hypothermia by basking. In this case, basking was not an optional behavioural method of reducing the cost of rewarming from torpor, but was essential for thermoregulation independent of the nest temperature. Results from our study suggest that basking is a crucial behavioural trait that permits young marsupials and perhaps other juvenile altricial mammals to overcome the developmental stage between poikilothermy early in development and full endothermy later in life.
Collapse
Affiliation(s)
- Chris B Wacker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.
| | - Bronwyn M McAllan
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.,Physiology, School of Medical Sciences, Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - 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
| |
Collapse
|
21
|
Galván I, Palacios D, Negro JJ. The bare head of the Northern bald ibis ( Geronticus eremita) fulfills a thermoregulatory function. Front Zool 2017; 14:15. [PMID: 28265294 PMCID: PMC5333446 DOI: 10.1186/s12983-017-0201-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 02/24/2017] [Indexed: 11/18/2022] Open
Abstract
Background Dark pigments provide animals with several adaptive benefits such as protection against ultraviolet (UV) radiation and mechanical abrasion, but may also impose several constraints like a high absorbance of solar radiation. Endotherms, with relatively constant and high body temperatures, may be especially prone to thermoregulatory limitations if dark coloured and inhabiting hot environments. It is therefore expected that adaptations have specifically evolved because of these limitations. Bare, highly vascularised head skin may have evolved in birds with dark plumage from hot geographical regions because of favouring heat dissipation. Using the Northern bald ibis (Geronticus eremita) as a model species, we measured the surface temperature (Tsurf) of the head, the bill and the black feathered body of 11 birds along ambient temperatures (Ta) ranging from 21 to 42.5 °C employing thermal imaging. Results While Tsurf of the bill and the feathered body was only slightly above Ta, head Tsurf was considerably higher, by up to 12 °C. Estimated values of heat loss followed similar variations. We also found that the red colour intensity of the head of ibises increased with head Tsurf, suggesting that birds are capable of controlling blood flow and the thermoregulatory function of the head. Conclusions These findings are consistent with the hypothesis that bare skin has evolved in dark pigmented birds inhabiting hot environments because of their ability to dissipate heat. Electronic supplementary material The online version of this article (doi:10.1186/s12983-017-0201-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Ismael Galván
- Department of Evolutionary Ecology, Doñana Biological Station - CSIC, 41092 Sevilla, Spain
| | - Daniel Palacios
- Department of Zoology, University of Córdoba, 14071 Córdoba, Spain
| | - Juan José Negro
- Department of Evolutionary Ecology, Doñana Biological Station - CSIC, 41092 Sevilla, Spain
| |
Collapse
|
22
|
Nowack J, Cooper CE, Geiser F. Cool echidnas survive the fire. Proc Biol Sci 2016; 283:rspb.2016.0382. [PMID: 27075255 DOI: 10.1098/rspb.2016.0382] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 03/18/2016] [Indexed: 11/12/2022] Open
Abstract
Fires have occurred throughout history, including those associated with the meteoroid impact at the Cretaceous-Palaeogene (K-Pg) boundary that eliminated many vertebrate species. To evaluate the recent hypothesis that the survival of the K-Pg fires by ancestral mammals was dependent on their ability to use energy-conserving torpor, we studied body temperature fluctuations and activity of an egg-laying mammal, the echidna (Tachyglossus aculeatus), often considered to be a 'living fossil', before, during and after a prescribed burn. All but one study animal survived the fire in the prescribed burn area and echidnas remained inactive during the day(s) following the fire and substantially reduced body temperature during bouts of torpor. For weeks after the fire, all individuals remained in their original territories and compensated for changes in their habitat with a decrease in mean body temperature and activity. Our data suggest that heterothermy enables mammals to outlast the conditions during and after a fire by reducing energy expenditure, permitting periods of extended inactivity. Therefore, torpor facilitates survival in a fire-scorched landscape and consequently may have been of functional significance for mammalian survival at the K-Pg boundary.
Collapse
Affiliation(s)
- Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia Department of Environment and Agriculture, Curtin University, Perth, Western Australia 6845, Australia
| | - Christine Elizabeth Cooper
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia 6845, Australia School of Animal Biology M092, University of Western Australia, Crawley 6009, Western Australia, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| |
Collapse
|
23
|
Bartonička T, Bandouchova H, Berková H, Blažek J, Lučan R, Horáček I, Martínková N, Pikula J, Řehák Z, Zukal J. Deeply torpid bats can change position without elevation of body temperature. J Therm Biol 2016; 63:119-123. [PMID: 28010809 DOI: 10.1016/j.jtherbio.2016.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 12/01/2016] [Accepted: 12/01/2016] [Indexed: 10/20/2022]
Abstract
Because body temperature is tightly coupled to physiological function, hibernating animals entering deep torpor are typically immobile. We analysed thermal behaviour and locomotory activity of hibernating greater mouse-eared bats Myotis myotis and found two types of movement behaviour related to body temperature, i.e. movement at high fur temperature and at low fur temperatures (Tflow; <5°C). First Tflow movements appeared at the beginning of March and often occurred during long torpor bouts. In most cases, Tflow events represented slow displacements between clusters of bats. In several cases, however, departure or arrivals from and into clusters was also recorded without any elevation in body temperature. Distance travelled, flight duration and speed of locomotion during Tflow events was lower than in high fur temperature events. Such behaviour could allow bats to save energy long-term and prolong torpor bouts. Tflow movement in torpid bats significantly changes our understanding of basic hibernation principles and we strongly recommend further studies on the subject.
Collapse
Affiliation(s)
- Tomáš Bartonička
- Department of Botany and Zoology, Masaryk University, Brno, Czechia.
| | - Hana Bandouchova
- Department of Ecology and Diseases of Game, Fish and Bees; University of Veterinary and Pharmaceutical Sciences, Brno, Czechia
| | - Hana Berková
- Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czechia
| | - Ján Blažek
- Department of Botany and Zoology, Masaryk University, Brno, Czechia
| | - Radek Lučan
- Faculty of Science, Charles University in Prague, Prague, Czechia
| | - Ivan Horáček
- Faculty of Science, Charles University in Prague, Prague, Czechia
| | - Natália Martínková
- Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czechia; Institute of Biostatistics and Analyses, Masaryk University, Brno, Czech Republic
| | - Jiri Pikula
- Department of Ecology and Diseases of Game, Fish and Bees; University of Veterinary and Pharmaceutical Sciences, Brno, Czechia
| | - Zdeněk Řehák
- Department of Botany and Zoology, Masaryk University, Brno, Czechia; Faculty of Education, Masaryk University, Brno, Czech Republic
| | - Jan Zukal
- Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czechia
| |
Collapse
|
24
|
Levesque DL, Nowack J, Stawski C. Modelling mammalian energetics: the heterothermy problem. ACTA ACUST UNITED AC 2016. [DOI: 10.1186/s40665-016-0022-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
25
|
Nowack J, Delesalle M, Stawski C, Geiser F. Can hibernators sense and evade fires? Olfactory acuity and locomotor performance during deep torpor. Naturwissenschaften 2016; 103:73. [DOI: 10.1007/s00114-016-1396-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 07/27/2016] [Accepted: 07/29/2016] [Indexed: 10/21/2022]
|
26
|
Wacker CB, McAllan BM, Körtner G, Geiser F. The functional requirements of mammalian hair: a compromise between crypsis and thermoregulation? Naturwissenschaften 2016; 103:53. [PMID: 27287044 DOI: 10.1007/s00114-016-1376-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 05/20/2016] [Accepted: 05/23/2016] [Indexed: 11/28/2022]
Abstract
Mammalian fur often shows agouti banding with a proximal dark band near the skin and a lighter distal band. We examined the function of both bands in relation to camouflage, thermal properties of pelts, and thermal energetics of dunnarts (Sminthopsis crassicaudata), which are known to use torpor and basking. Although the distal band of dunnart fur darkened with increasing latitude, which is important for camouflage, it did not affect the thermal properties and the length of the dark band and total hair length were not correlated. In contrast, the length of the proximal dark band of preserved pelts exposed to sunlight was positively correlated (r (2) = 0.59) with the temperature underneath the pelt (T pelt). All dunnarts offered radiant heat basked by exposing the dark band of the hair during both rest and torpor. Basking dunnarts with longer dark bands had lower resting metabolism (r (2) = 0.69), warmed faster from torpor (r (2) = 0.77), required less energy to do so (r (2) = 0.32), and reached a higher subcutaneous temperature (T sub) at the end of rewarming (r (2) = 0.75). We provide the first experimental evidence on the possible dual function of the color banding of mammalian fur. The distal colored band appears to be important for camouflage, whereas the length of the dark proximal hair band facilitates heat gain for energy conservation and allows animals to rewarm quickly and economically from torpor.
Collapse
Affiliation(s)
- Chris B Wacker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales, 2351, Australia.
| | - Bronwyn M McAllan
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales, 2351, Australia.,Physiology, School of Medical Sciences, Bosch Institute, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Gerhard Körtner
- 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
| |
Collapse
|
27
|
Geiser F, Gasch K, Bieber C, Stalder GL, Gerritsmann H, Ruf T. Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor. ACTA ACUST UNITED AC 2016; 219:2166-72. [PMID: 27207637 DOI: 10.1242/jeb.137828] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/02/2016] [Indexed: 01/22/2023]
Abstract
Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (>30%) when basking at ambient temperatures (Ta) of ∼15 and 0°C. Interestingly, body temperature (Tb) also was significantly reduced from 34.7±0.6°C (Ta 15°C, not basking) to 30.4±2.0°C (Ta 0°C, basking), which resulted in an extremely low (<50% of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at Ta 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average Tb of 22.0±2.6°C; movement to the basking lamp occurred at Tb<20.0°C. Energy expenditure for rewarming was significantly reduced (by >50%) during radiant heat-assisted rewarming; however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and Tb during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting Tb and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts, where basking is common, but also for P. sungorus and probably other cold-climate mammals.
Collapse
Affiliation(s)
- Fritz Geiser
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Kristina Gasch
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Claudia Bieber
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Gabrielle L Stalder
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Hanno Gerritsmann
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Thomas Ruf
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| |
Collapse
|
28
|
Oliveira FG, Tapisso JT, Monarca RI, Cerveira AM, Mathias ML. Phenotypic flexibility in the energetic strategy of the greater white-toothed shrew, Crocidura russula. J Therm Biol 2016; 56:10-7. [PMID: 26857972 DOI: 10.1016/j.jtherbio.2015.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/11/2015] [Accepted: 12/11/2015] [Indexed: 10/22/2022]
Abstract
The balance between energetic acquisition and expenditure depends on the amount of energy allocated to biological functions such as thermoregulation, growth, reproduction and behavior. Ambient temperature has a profound effect on this balance, with species inhabiting colder climates often needing to invest more energy in thermoregulation to maintain body temperature. This leads to local behavioral and physiological adaptations that increase energetic efficiency. In this study, we investigated the role of activity, behavior and thermogenic capacity in the ability of the greater white-toothed shrew, Crocidura russula, to cope with seasonal changes. Individuals were captured in the Sintra-Cascais Natural Park, a Mediterranean region, and separated into three experimental groups: a control group, acclimated to a 12L:12D photoperiod and temperature of 18-20°C; a winter group, acclimatized to natural winter fluctuations of light and temperature; and a summer group, acclimatized to natural summer fluctuations of light and temperature. No differences were found in resting metabolic rate and nonshivering thermogenesis between the three groups. However, winter shrews significantly reduced their activity, particularly at night, compared to the control and summer groups. Differences in torpor use were also found between groups, with winter shrews entering torpor more frequently and during shorter periods of time than summer and control shrews. Our results indicate C. russula from Sintra relies on the flexibility of energy saving mechanisms, namely daily activity level and torpor use, to cope with seasonal changes in a Mediterranean climate, rather than mechanisms involving body heat production.
Collapse
Affiliation(s)
- Flávio G Oliveira
- CESAM - Centre for Environmental and Marine Studies, Department of Animal Biology, Faculty of Sciences, University of Lisbon, C2 building, 3rd floor, Campo Grande, 1749-016 Lisbon, Portugal.
| | - Joaquim T Tapisso
- CESAM - Centre for Environmental and Marine Studies, Department of Animal Biology, Faculty of Sciences, University of Lisbon, C2 building, 3rd floor, Campo Grande, 1749-016 Lisbon, Portugal.
| | - Rita I Monarca
- CESAM - Centre for Environmental and Marine Studies, Department of Animal Biology, Faculty of Sciences, University of Lisbon, C2 building, 3rd floor, Campo Grande, 1749-016 Lisbon, Portugal
| | - Ana M Cerveira
- CESAM - Centre for Environmental and Marine Studies, Department of Animal Biology, Faculty of Sciences, University of Lisbon, C2 building, 3rd floor, Campo Grande, 1749-016 Lisbon, Portugal
| | - Maria L Mathias
- CESAM - Centre for Environmental and Marine Studies, Department of Animal Biology, Faculty of Sciences, University of Lisbon, C2 building, 3rd floor, Campo Grande, 1749-016 Lisbon, Portugal
| |
Collapse
|
29
|
Nowack J, Geiser F. Friends with benefits: the role of huddling in mixed groups of torpid and normothermic animals. ACTA ACUST UNITED AC 2015; 219:590-6. [PMID: 26685170 DOI: 10.1242/jeb.128926] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 12/01/2015] [Indexed: 12/24/2022]
Abstract
Huddling and torpor are widely used for minimizing heat loss by mammals. Despite the questionable energetic benefits from social heterothermy of mixed groups of warm normothermic and cold torpid individuals, the heterothermic Australian sugar glider (Petaurus breviceps) rests in such groups during the cold season. To unravel why they might do so, we examined torpor expression of two sugar glider groups of four individuals each in outside enclosures during winter. We observed 79 torpor bouts during 50 days of observation and found that torpor bouts were longer and deeper when all individuals of a group entered torpor together, and therefore infer that they would have saved more energy in comparison to short and shallow solitary torpor bouts. However, all gliders of either group only expressed torpor uniformly in response to food restriction, whereas on most occasions at least one individual per group remained normothermic. Nevertheless, the presence of warm gliders in mixed groups also appears to be of energetic advantage for torpid individuals, because nest box temperature was negatively correlated with the number of torpid gliders, and normothermic individuals kept the nest temperature at a value closer to the threshold for thermoregulatory heat production during torpor. Our study suggests that mixed groups of torpid and normothermic individuals are observed when environmental conditions are adverse but food is available, leading to intermediate energy savings from torpor. However, under especially challenging conditions and when animals are starving, energy savings are maximized by uniform and pronounced expression of torpor.
Collapse
Affiliation(s)
- Julia Nowack
- 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
| |
Collapse
|
30
|
Levin E, Plotnik B, Amichai E, Braulke LJ, Landau S, Yom-Tov Y, Kronfeld-Schor N. Subtropical mouse-tailed bats use geothermally heated caves for winter hibernation. Proc Biol Sci 2015; 282:20142781. [PMID: 25740890 DOI: 10.1098/rspb.2014.2781] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We report that two species of mouse-tailed bats (Rhinopoma microphyllum and R. cystops) hibernate for five months during winter in geothermally heated caves with stable high temperature (20°C). While hibernating, these bats do not feed or drink, even on warm nights when other bat species are active. We used thermo-sensitive transmitters to measure the bats' skin temperature in the natural hibernacula and open flow respirometry to measure torpid metabolic rate at different ambient temperatures (Ta, 16-35°C) and evaporative water loss (EWL) in the laboratory. Bats average skin temperature at the natural hibernacula was 21.7 ± 0.8°C, and no arousals were recorded. Both species reached the lowest metabolic rates around natural hibernacula temperatures (20°C, average of 0.14 ± 0.01 and 0.16 ± 0.04 ml O2 g(-1) h(-1) for R. microphyllum and R. cystops, respectively) and aroused from torpor when Ta fell below 16°C. During torpor the bats performed long apnoeas (14 ± 1.6 and 16 ± 1.5 min, respectively) and had a very low EWL. We hypothesize that the particular diet of these bats is an adaptation to hibernation at high temperatures and that caves featuring high temperature and humidity during winter enable these species to survive this season on the northern edge of their world distribution.
Collapse
Affiliation(s)
- Eran Levin
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | - Brit Plotnik
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | - Eran Amichai
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | - Luzie J Braulke
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | - Shmulik Landau
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | - Yoram Yom-Tov
- Department of Zoology, Tel-Aviv University, Tel-Aviv, Israel
| | | |
Collapse
|
31
|
Measuring subcutaneous temperature and differential rates of rewarming from hibernation and daily torpor in two species of bats. Comp Biochem Physiol A Mol Integr Physiol 2015; 190:26-31. [PMID: 26300411 DOI: 10.1016/j.cbpa.2015.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/07/2015] [Accepted: 08/11/2015] [Indexed: 01/11/2023]
Abstract
Prolonged and remote measurement of body temperature (Tb) in undisturbed small hibernators was not possible in the past because of technological limitations. Although passive integrated transponders (PITs) have been used previously to measure subcutaneous temperature (Tsub) during daily torpor in a small marsupial, no study has attempted to use these devices at Tbs below 10°C. Therefore, we investigated whether subcutaneous interscapular PITs can be used as a viable tool for measuring Tb in a small hibernating bat (Nyctophilus gouldi; Ng) and compared it with measurements of Tb during daily torpor in a heterothermic bat (Syconycteris australis; Sa). The precision of transponders was investigated as a function of ambient temperature (Ta) and remote Tsub readings enabled us to quantify Tsub-Tb differentials during steady-state torpor and arousal. Transponders functioned well outside the manufacturer's recommended range, down to ~5°C. At rest, Tsub and rectal Tb (Trec) were strongly correlated for both bat species (Ng r(2)=0.88; Sa r(2)=0.95) and this was also true for N. gouldi in steady-state torpor (r(2)=0.93). During induced rewarming Tsub increased faster than Trec in both species. Our results demonstrate that transponders can be used to provide accurate remote measurement of Tb in two species of bats during different physiological states, both during steady-state conditions and throughout dynamic phases such as rewarming from torpor. We show that, at least during rewarming, regional heterothermy common to larger hibernators and other hibernating bats is also present in bats capable of daily torpor.
Collapse
|
32
|
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.
Collapse
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
| |
Collapse
|
33
|
Thermal dependence of sprint performance in the lizard Psammodromus algirus along a 2200-meter elevational gradient: Cold-habitat lizards do not perform better at low temperatures. J Therm Biol 2015; 52:90-6. [DOI: 10.1016/j.jtherbio.2015.06.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 06/01/2015] [Accepted: 06/08/2015] [Indexed: 11/18/2022]
|
34
|
Effects of reproductive status and high ambient temperatures on the body temperature of a free-ranging basoendotherm. J Comp Physiol B 2014; 184:1041-53. [PMID: 25155185 DOI: 10.1007/s00360-014-0858-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 06/30/2014] [Accepted: 08/13/2014] [Indexed: 10/24/2022]
Abstract
Tenrecs (Order Afrosoricida) exhibit some of the lowest body temperatures (T b) of any eutherian mammal. They also have a high level of variability in both active and resting T bs and, at least in cool temperatures in captivity, frequently employ both short- and long-term torpor. The use of heterothermy by captive animals is, however, generally reduced during gestation and lactation. We present data long-term T b recordings collected from free-ranging S. setosus over the course of two reproductive seasons. In general, reproductive females had slightly higher (~32 °C) and less variable T b, whereas non-reproductive females and males showed both a higher propensity for torpor as well as lower (~30.5 °C) and more variable rest-phase T bs. Torpor expression defined using traditional means (using a threshold or cut-off T b) was much lower than predicted based on the high degree of heterothermy in captive tenrecs. However, torpor defined in this manner is likely to be underestimated in habitats where ambient temperature is close to T b. Our results caution against inferring metabolic states from T b alone and lend support to the recent call to define torpor in free-ranging animals based on mechanistic and not descriptive variables. In addition, lower variability in T b observed during gestation and lactation confirms that homeothermy is essential for reproduction in this species and probably for basoendothermic mammals in general. The relatively low costs of maintaining homeothermy in a sub-tropical environment might help shed light on how homeothermy could have evolved incrementally from an ancestral heterothermic condition.
Collapse
|
35
|
Busse S, Lutter D, Heldmaier G, Jastroch M, Meyer CW. Torpor at high ambient temperature in a neotropical didelphid, the grey short-tailed opossum (Monodelphis domestica). Naturwissenschaften 2014; 101:1003-6. [PMID: 25142634 DOI: 10.1007/s00114-014-1226-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Revised: 08/08/2014] [Accepted: 08/11/2014] [Indexed: 10/24/2022]
Abstract
The grey short-tailed opossum, Monodelphis domestica, has been an established research animal for more than five decades, but relatively, little is known about its thermophysiology. Here we studied core body temperature (T b) and metabolic rate (MR) of female adult M. domestica housed in the laboratory at an ambient temperature (T a) of 26 °C. In expanding previous reports, the average recorded core T b of M. domestica was 34.3 °C. The T b of an individual M. domestica can drop below 30 °C (minimal T b: 28.6 °C) accompanied by a reduction in MR of up to 52 % even while having ad libitum access to food. These findings demonstrate for the first time the presence of spontaneous torpor in M. domestica. Metabolic suppression at relatively high T a and T b furthermore broadens our perspective on the use of torpor as a metabolic strategy not just restricted to cold climates.
Collapse
Affiliation(s)
- Sebastian Busse
- Animal Physiology, Philipps-Universität Marburg, Karl-von Frisch Str. 8, 35032, Marburg, Germany
| | | | | | | | | |
Collapse
|
36
|
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.
Collapse
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
| |
Collapse
|
37
|
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]
|
38
|
Levesque DL, Lovegrove BG. Increased homeothermy during reproduction in a basal placental mammal. ACTA ACUST UNITED AC 2014; 217:1535-42. [PMID: 24501138 DOI: 10.1242/jeb.098848] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Homeothermic endothermy, the maintenance of a high and stable body temperature (Tb) using heat produced by elevated metabolism, is energetically expensive. There is increasing evidence that the earliest endotherms were heterotherms that, rather than maintaining strict homeothermy, allowed Tb to fluctuate with large variations between active and rest-phase Tb. The high level of homeothermy observed in modern mammals is therefore likely to have evolved from an ancestral heterothermic state. One of the hypotheses for the evolution of endothermy is that homeothermy allows for greater energetic output during reproduction (parental care model). We tested this hypothesis by measuring metabolic rates over a range of ambient temperatures in both reproductive and non-reproductive greater hedgehog tenrecs (Setifer setosus), a physiologically primitive mammal from Madagascar. Tenrecs have some of the lowest metabolic rates and highest levels of Tb variability of any mammal and are therefore good models of the ancestral eutherian state. During pregnancy and lactation, there was an increase in metabolism and Tb below the thermoneutral zone, accompanied by a decrease in Tb variability. The lower critical limit of the thermoneutral zone was estimated at ~25°C. However, whereas increases in resting metabolism were substantial below 20°C (up to 150% higher during reproduction), daytime rest-phase ambient temperatures at the study site rarely reached equivalent low levels. Thus, S. setosus provide an example for how relatively low-cost increases in homeothermy could have led to substantial increases in fitness by allowing for the faster production of young. The mechanisms necessary for increases in thermogenesis during reproduction would have further benefited the development of homeothermy in mammals.
Collapse
Affiliation(s)
- Danielle L Levesque
- School of Life Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville 3209, South Africa
| | | |
Collapse
|
39
|
Affiliation(s)
- C. Stawski
- Institute of Environmental Sciences; Jagiellonian University; Kraków Poland
- Centre for Behavioural and Physiological Ecology, Zoology; University of New England; Armidale NSW Australia
| | - C. K. R. Willis
- Department of Biology and Centre for Forest Interdisciplinary Research; University of Winnipeg; Winnipeg Canada
| | - F. Geiser
- Centre for Behavioural and Physiological Ecology, Zoology; University of New England; Armidale NSW Australia
| |
Collapse
|
40
|
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
| |
Collapse
|
41
|
Carr JM, Lima SL. Nocturnal hypothermia impairs flight ability in birds: a cost of being cool. Proc Biol Sci 2013; 280:20131846. [PMID: 24107528 DOI: 10.1098/rspb.2013.1846] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many birds use regulated drops in night-time body temperature (Tb) to conserve energy critical to winter survival. However, a significant degree of hypothermia may limit a bird's ability to respond to predatory attack. Despite this likely energy-predation trade-off, the behavioural costs of avian hypothermia have yet to be examined. We thus monitored the nocturnal hypothermia of mourning doves (Zenaida macroura) in a laboratory setting in response to food deprivation. Nocturnal flight tests were used to quantify the flight ability of hypothermic doves. Many hypothermic doves (39% of tests) could not fly while carrying a small weight, but could do so after quickly warming up to typical daytime Tb. Doves that were unable to fly during their first test were more hypothermic than those that could fly, with average Tb reductions of 5.3°C and 3.3°C, respectively, but there was no overall indication of a threshold Tb reduction beyond which doves were consistently incapable of flight. These results suggest that energy-saving hypothermia interferes with avian antipredator behaviour via a reduction in flight ability, likely leading to a trade-off between energy-saving hypothermia and the risk of predation.
Collapse
Affiliation(s)
- Jennie M Carr
- Department of Biology, Indiana State University, , Terre Haute, IN 47809, USA
| | | |
Collapse
|
42
|
Abstract
Hibernation (multiday torpor) and daily torpor in heterothermic mammals and birds are characterized by pronounced temporal reductions in body temperature, energy expenditure, water loss, and other physiological functions and are the most effective means for energy conservation available to endotherms. Hibernators express multiday torpor predominately throughout winter, which substantially enhances winter survival. In contrast, daily heterotherms use daily torpor lasting for several hours during the rest phase. Although torpor is still widely considered to be a specific adaptation of cold-climate species, as we will see in this primer, it is used by many diverse species from all climate zones, including the tropics. While energy conservation during adverse conditions is an important function of torpor, it is also employed to permit energy-demanding processes such as reproduction and growth, especially when food supply is limited. Even migrating birds enter torpor to conserve energy for the next stage of migration. Although many heterothermic species will be challenged by anthropogenic influences such as habitat destruction, introduced species, novel pathogens and specifically global warming, not all are likely to be affected in the same way. In fact, as argued here, it is likely that opportunistic heterotherms may be better equipped to deal with these challenges than homeotherms because heterotherms have highly flexible energy requirements, can limit foraging and reduce the risk of predation, and often are also long-lived. In contrast, strongly seasonal hibernators, especially those restricted to mountain tops, and those that have to deal with new diseases that are difficult to combat at low body temperatures, are likely to be adversely affected.
Collapse
Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale NSW 2351, Australia.
| |
Collapse
|
43
|
Cory Toussaint D, Brigham RM, McKechnie AE. Thermoregulation in free-ranging Nycteris thebaica (Nycteridae) during winter: No evidence of torpor. Mamm Biol 2013. [DOI: 10.1016/j.mambio.2012.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
44
|
Geiser F, Klingenspor M, McAllan BM. A functional nexus between photoperiod acclimation, torpor expression and somatic fatty acid composition in a heterothermic mammal. PLoS One 2013; 8:e63803. [PMID: 23717487 PMCID: PMC3661731 DOI: 10.1371/journal.pone.0063803] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 04/05/2013] [Indexed: 11/18/2022] Open
Abstract
The seasonal changes in thermal physiology and torpor expression of many heterothermic mammals are controlled by photoperiod. As function at low body temperatures during torpor requires changes of tissue lipid composition, we tested for the first time whether and how fatty acids are affected by photoperiod acclimation in hamsters, Phodopus sungorus, a strongly photoperiodic species. We also examined changes in fatty acid composition in relation to those in morphology and thermal biology. Hamsters in short photoperiod had smaller reproductive organs and most had a reduced body mass in comparison to those in long photoperiod. Pelage colour of hamsters under short photoperiod was almost white while that of long photoperiod hamsters was grey-brown and black. Short photoperiod acclimation resulted in regular (28% of days) torpor use, whereas all hamsters in long photoperiod remained normothermic. The composition of total fatty acids differed between acclimation groups for brown adipose tissue (5 of 8 fatty acids), heart muscle (4 of 7 fatty acids) and leg muscle (3 of 11 fatty acids). Importantly, 54% of all fatty acids detected were correlated (r2 = 0.60 to 0.87) with the minimum surface temperature of individuals, but the responses of tissues differed. While some of the compositional changes of fatty acids were consistent with a ‘homeoviscous’ response, this was not the case for all, including the sums of saturated and unsaturated fatty acids, which did not differ between acclimation groups. Our data identify a possible nexus between photoperiod acclimation, morphology, reproductive biology, thermal biology and fatty acid composition. They suggest that some of the changes in thermal physiology are linked to the composition of tissue and organ fatty acids.
Collapse
Affiliation(s)
- Fritz Geiser
- Biologie-Zoologie, Philipps-University, Marburg, Germany.
| | | | | |
Collapse
|