1
|
Abarzúa T, Camus I, Ortiz F, Ñunque A, Cubillos FA, Sabat P, Nespolo RF. Modeling heterothermic fitness landscapes in a marsupial hibernator using changes in body composition. Oecologia 2023; 203:79-93. [PMID: 37798536 PMCID: PMC10615951 DOI: 10.1007/s00442-023-05452-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 09/16/2023] [Indexed: 10/07/2023]
Abstract
Hibernation is an adaptive strategy that allows animals to enter a hypometabolic state, conserving energy and enhancing their fitness by surviving harsh environmental conditions. However, addressing the adaptive value of hibernation, at the individual level and in natural populations, has been challenging. Here, we applied a non-invasive technique, body composition analysis by quantitative magnetic resonance (qMR), to calculate energy savings by hibernation in a population of hibernating marsupials (Dromiciops gliroides). Using outdoor enclosures installed in a temperate rainforest, and measuring qMR periodically, we determined the amount of fat and lean mass consumed during a whole hibernation cycle. With this information, we estimated the daily energy expenditure of hibernation (DEEH) at the individual level and related to previous fat accumulation. Using model selection approaches and phenotypic selection analysis, we calculated linear (directional, β), quadratic (stabilizing or disruptive, γ) and correlational (ρ) coefficients for DEEH and fat accumulation. We found significant, negative directional selection for DEEH (βDEEH = - 0.58 ± 0.09), a positive value for fat accumulation (βFAT = 0.34 ± 0.07), and positive correlational selection between both traits (ρDEEH × FAT = 0.24 ± 0.07). Then, individuals maximizing previous fat accumulation and minimizing DEEH were promoted by selection, which is visualized by a bi-variate selection surface estimated by generalized additive models. At the comparative level, results fall within the isometric allometry known for hibernation metabolic rate in mammals. Thus, by a combination of a non-invasive technique for body composition analysis and semi-natural enclosures, we were characterized the heterothermic fitness landscape in a semi-natural population of hibernators.
Collapse
Affiliation(s)
- Tamara Abarzúa
- Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile
| | - Isidora Camus
- Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile
| | - Felipe Ortiz
- Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile
| | - Abel Ñunque
- Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile
- Millenium Nucleus of Patagonian Limit of Life (LiLi), Valdivia, Chile
| | - Francisco A Cubillos
- Departamento de Biología y Química, Universidad de Santiago de Chile, Santiago, Chile
- Millenium Nucleus of Patagonian Limit of Life (LiLi), Valdivia, Chile
- Millennium Institute for Integrative Biology (iBio), Santiago, Chile
| | - Pablo Sabat
- Facultad de Ciencias, Universidad de Chile, Santiago, Chile
- Center for Applied Ecology and Sustainability (CAPES), Departamento de Ecología Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Roberto F Nespolo
- Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile.
- Millenium Nucleus of Patagonian Limit of Life (LiLi), Valdivia, Chile.
- Center for Applied Ecology and Sustainability (CAPES), Departamento de Ecología Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
| |
Collapse
|
2
|
Michel A, Johnson JR, Szeligowski R, Ritchie EG, Sih A. Integrating sensory ecology and predator-prey theory to understand animal responses to fire. Ecol Lett 2023; 26:1050-1070. [PMID: 37349260 DOI: 10.1111/ele.14231] [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: 04/26/2022] [Revised: 01/11/2023] [Accepted: 02/10/2023] [Indexed: 06/24/2023]
Abstract
Fire regimes are changing dramatically worldwide due to climate change, habitat conversion, and the suppression of Indigenous landscape management. Although there has been extensive work on plant responses to fire, including their adaptations to withstand fire and long-term effects of fire on plant communities, less is known about animal responses to fire. Ecologists lack a conceptual framework for understanding behavioural responses to fire, which can hinder wildlife conservation and management. Here, we integrate cue-response sensory ecology and predator-prey theory to predict and explain variation in if, when and how animals react to approaching fire. Inspired by the literature on prey responses to predation risk, this framework considers both fire-naïve and fire-adapted animals and follows three key steps: vigilance, cue detection and response. We draw from theory on vigilance tradeoffs, signal detection, speed-accuracy tradeoffs, fear generalization, neophobia and adaptive dispersal. We discuss how evolutionary history with fire, but also other selective pressures, such as predation risk, should influence animal behavioural responses to fire. We conclude by providing guidance for empiricists and outlining potential conservation applications.
Collapse
Affiliation(s)
- Alice Michel
- Animal Behavior Graduate Group, University of California, Davis, California, USA
| | - Jacob R Johnson
- Animal Behavior Graduate Group, University of California, Davis, California, USA
| | - Richard Szeligowski
- Department of Environmental Science & Policy, University of California, Davis, California, USA
| | - Euan G Ritchie
- School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Burwood, Victoria, Australia
| | - Andrew Sih
- Department of Environmental Science & Policy, University of California, Davis, California, USA
| |
Collapse
|
3
|
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
|
4
|
Lizards' response to the sound of fire is modified by fire history. Anim Behav 2023. [DOI: 10.1016/j.anbehav.2022.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
5
|
Reher S, Rabarison H, Nowack J, Dausmann KH. Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.779381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Rapid environmental changes are challenging for endothermic species because they have direct and immediate impacts on their physiology by affecting microclimate and fundamental resource availability. Physiological flexibility can compensate for certain ecological perturbations, but our basic understanding of how species function in a given habitat and the extent of their adaptive scope is limited. Here we studied the effect of acute, experimental microclimate change on the thermal physiology of two populations of the widespread Malagasy bat, Macronycteris commersoni. Populations of this species are found roosting under contrasting conditions, i.e., in a constant hot and humid cave or below foliage unprotected from fluctuations in ambient conditions. We exposed free-ranging individuals of each population to the respective opposite condition and thus to novel microclimate within an ecologically realistic scope while measuring metabolic rate and skin temperature. Cave bats in forest setting had a limited capacity to maintain euthermia to the point that two individuals became hypothermic when ambient temperature dropped below their commonly experienced cave temperature. Forest bats on the other hand, had difficulties to dissipate heat in the humid cave set-up. The response to heat, however, was surprisingly uniform and all bats entered torpor combined with hyperthermia at temperatures exceeding their thermoneutral zone. Thus, while we observed potential for flexible compensation of heat through “hot” torpor, both populations showed patterns suggestive of limited potential to cope with acute microclimate changes deviating from their typically occupied roosts. Our study emphasizes that intraspecific variation among populations could be misleading when assessing species’ adaptive scopes, as variation may arise from genetic adaptation, developmental plasticity or phenotypic flexibility, all of which allow for compensatory responses at differing time scales. Disentangling these mechanisms and identifying the basis of variation is vital to make accurate predictions of species’ chances for persisting in ever rapidly changing habitats and climates.
Collapse
|
6
|
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
|
7
|
Webb JK, Jolly CJ, Hinds M, Adams C, Cuartas‐Villa S, Lapwong Y, Letnic M. Effects of the Australian 2019–2020 megafires on a population of endangered broad‐headed snakes
Hoplocephalus bungaroides. AUSTRAL ECOL 2021. [DOI: 10.1111/aec.13118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jonathan K. Webb
- School of Life Sciences University of Technology Sydney Broadway New South Wales 2007Australia
| | - Chris J. Jolly
- School of Environmental Science Institute for Land, Water, and Society Charles Sturt University Albury New South WalesAustralia
| | - Meagan Hinds
- NSW Department of Planning Industry and Environment Ecosystems and Threatened Species Parramatta New South WalesAustralia
| | - Craig Adams
- School of Life Sciences University of Technology Sydney Broadway New South Wales 2007Australia
| | - Santiago Cuartas‐Villa
- School of Life Sciences University of Technology Sydney Broadway New South Wales 2007Australia
| | - Yingyod Lapwong
- School of Life Sciences University of Technology Sydney Broadway New South Wales 2007Australia
| | - Mike Letnic
- School of Biological, Earth and Environmental Sciences University of New South Wales Sydney New South Wales Australia
| |
Collapse
|
8
|
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]
|
9
|
Álvarez-Ruiz L, Belliure J, Pausas JG. Fire-driven behavioral response to smoke in a Mediterranean lizard. Behav Ecol 2021. [DOI: 10.1093/beheco/arab010] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
The evolutionary role of fire in animals has been poorly explored. Reptiles use sensory cues, such as smell (chemoreception), to detect threats and flee. In Mediterranean ecosystems, fire is a threat faced by reptiles. We hypothesized that the Mediterranean lizard Psammodromus algirus recognizes the threat of fire by detecting the smoke, which triggers a behavioral response that enhances survival in fire-prone ecosystems. We predicted that lizards from fire-prone ecosystems will be more sensitive to fire stimulus than those from ecosystems that rarely burn. We conducted a terrarium experiment in which lizards from habitats with contrasted fire regimes (fire-prone vs. non-fire-prone) were exposed to smoke versus control (false smoke) treatment. We found that, in populations from fire-prone habitats, more lizards reacted to smoke, and their behavioral response was more intense than in lizard populations from non-fire-prone habitats. Our results suggest that an enhanced response to smoke may be adaptive in lizards from fire-prone ecosystems as it increases the chance for survival. We provide evidence that fire is likely an evolutionary driver shaping behavioral traits in lizard populations exposed to frequent wildfires. Understanding ecological and evolutionary processes shaping animal populations is relevant for species conservation in a changing fire regime world.
Collapse
Affiliation(s)
- Lola Álvarez-Ruiz
- Departamento de Ecología, Centro de Investigaciones sobre Desertificación (CIDE-CSIC), Ctra. Náquera Km. 4.5, 46113 Moncada, Valencia, Spain
| | - Josabel Belliure
- Departamento de Ciencias de la Vida, U.D. Ecología, A.P. 20 Campus Universitario, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
| | - Juli G Pausas
- Departamento de Ecología, Centro de Investigaciones sobre Desertificación (CIDE-CSIC), Ctra. Náquera Km. 4.5, 46113 Moncada, Valencia, Spain
| |
Collapse
|
10
|
Nowack J, Dill V, Dausmann KH. Open-flow respirometry under field conditions: How does the airflow through the nest influence our results? J Therm Biol 2020; 92:102667. [PMID: 32888570 DOI: 10.1016/j.jtherbio.2020.102667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 07/01/2020] [Accepted: 07/06/2020] [Indexed: 11/26/2022]
Abstract
Open-flow respirometry is a common method to measure oxygen-uptake as a proxy of energy expenditure of organisms in real-time. Although most often used in the laboratory it has seen increasing application under field conditions. Air is drawn or pushed through a metabolic chamber or the nest with the animal, and the O2 depletion and/or CO2 accumulation in the air is analysed to calculate metabolic rate and energy expenditure. Under field conditions, animals are often measured within the microclimate of their nest and in contrast to laboratory work, the temperature of the air entering the nest cannot be controlled. Thus, the aim of our study was to determine the explanatory power of respirometry in a set-up mimicking field conditions. We measured O2 consumption of 14 laboratory mice (Mus musculus) using three different flow rates [50 L*h-1 (834 mL*min-1), 60 L*h-1 (1000 mL*min-1) and 70 L*h-1 (1167 mL*min-1)] and two different temperatures of the inflowing air; either the same as the temperature inside the metabolic chamber (no temperature differential; 20 °C), or cooler (temperature differential of 10 °C). Our results show that the energy expenditure of the mice did not change significantly in relation to a cooler airflow, nor was it affected by different flow rates, despite a slight, but significant decrease of about 1.5 °C in chamber temperature with the cooler airflow. Our study emphasises the validity of the results obtained by open-flow respirometry when investigating energy budgets and physiological responses of animals to ambient conditions. Nevertheless, subtle changes in chamber temperature in response to changes in the temperature and flow rate of the air pulled or pushed through the system were detectable. Thus, constant airflow during open-flow respirometry and consequent changes in nest/chamber temperature should be measured.
Collapse
Affiliation(s)
- Julia Nowack
- Institute of Zoology, Animal Ecology and Conservation, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany; School of Biological and Environmental Sciences, Liverpool John Moores University, Byrom Street, L3 3AF, Liverpool, UK.
| | - Veronika Dill
- Institute of Zoology, Animal Ecology and Conservation, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany; Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald, Insel Riems, Germany
| | - Kathrin H Dausmann
- Institute of Zoology, Animal Ecology and Conservation, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| |
Collapse
|
11
|
A wake-up call for sleepy lizards: the olfactory-driven response of Tiliqua rugosa (Reptilia: Squamata: Sauria) to smoke and its implications for fire avoidance behavior. J ETHOL 2019. [DOI: 10.1007/s10164-019-00628-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
12
|
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
|
13
|
Stress-induced changes in body temperature of silver-haired bats (Lasionycteris noctivagans). Physiol Behav 2018; 194:356-361. [PMID: 29894759 DOI: 10.1016/j.physbeh.2018.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 06/05/2018] [Accepted: 06/05/2018] [Indexed: 01/21/2023]
Abstract
Acute stressors such as capture and handling can elicit physiological responses in endothermic animals. One example of such a response is an increase in body temperature (Tb) commonly referred to as stress-induced hyperthermia (SIH). For species that employ torpor, typically an inactive state characterized by a controlled reduction in Tb and metabolic rate, a rapid increase in Tb could be advantageous, especially in the context of escape from predators. We quantified SIH in silver-haired bats (Lasionycteris noctivagans) because they readily enter torpor and often roost in exposed places where they could be vulnerable to predators. We tested the hypothesis that handling stress causes SIH in three separate contexts: a) during the nocturnal, active phase immediately following capture during flight, b) during the diurnal, inactive phase of normothermic bats, and c) during pronounced torpor immediately following exposure to cold ambient temperature. We used a standardized protocol during which Tb was measured (as rectal temperature) immediately upon handling and, again, several minutes later. We found that SIH occurred for inactive, normothermic bats held at a warm temperature. Surprisingly, however, handling stress caused a reduction in Tb for normothermic bats following the active, flight phase and, although in the opposite direction, this cooling rate was indistinguishable from the rate of SIH for normothermic bats during the rest phase. As expected, we observed a large change in Tb during rewarming from torpor following handling. This warming rate was greater than that previously reported in the literature for any heterothermic endotherm. Rapid rewarming by silver-haired bats could reflect their tendency to roost in relatively exposed locations that may be vulnerable to predators. This study provides new information on SIH in an under-studied group of animals and illustrates the need to evaluate the hypothesis that SIH and rewarming from torpor are influenced by predation risk and activity state.
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
|
|
17
|
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
|
18
|
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.
Collapse
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
| |
Collapse
|
19
|
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]
|
20
|
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]
|