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Tabh JKR, Hartjes M, Burness G. Endotherms trade body temperature regulation for the stress response. Proc Biol Sci 2023; 290:20231251. [PMID: 37909077 PMCID: PMC10618863 DOI: 10.1098/rspb.2023.1251] [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: 06/05/2023] [Accepted: 10/06/2023] [Indexed: 11/02/2023] Open
Abstract
Responding to perceived threats is energetically expensive and can require animals to curtail somatic repair, immunity, and even reproduction to balance energy ledgers. In birds and mammals, energetic demands of thermoregulation are often immense, yet whether homeostatic body temperatures are also compromised to aid the stress response is not known. Using data sourced from over 60 years of literature and 24 endotherm species, we show that exposure to non-thermal challenges (e.g. human interaction, social threats) caused body temperatures to decrease in the cold and increase in the warmth, but particularly when species-specific costs of thermoregulation were high and surplus energy low. Biophysical models revealed that allowing body temperature to change in this way liberated up to 24% (mean = 5%) of resting energy expenditure for use towards coping. While useful to avoid energetic overload, these responses nevertheless heighten risks of cold- or heat-induced damage, particularly when coincident with cold- or heatwaves.
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Affiliation(s)
- Joshua K. R. Tabh
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada K9L 0G2
- Department of Biology, Lund University, Lund, 223 62, Sweden
| | - Mariah Hartjes
- Department of Biology, Trent University, Peterborough, Ontario, Canada K9L 0G2
| | - Gary Burness
- Department of Biology, Trent University, Peterborough, Ontario, Canada K9L 0G2
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2
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Wongsaengchan C, McCafferty DJ, Evans NP, McKeegan DEF, Nager RG. Body surface temperature of rats reveals both magnitude and sex differences in the acute stress response. Physiol Behav 2023; 264:114138. [PMID: 36871696 DOI: 10.1016/j.physbeh.2023.114138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 02/09/2023] [Accepted: 02/24/2023] [Indexed: 03/07/2023]
Abstract
Understanding how biological markers of stress relate to stressor magnitude is much needed and can be used in welfare assessment. Changes in body surface temperature can be measured using infrared thermography (IRT) as a marker of a physiological response to acute stress. While an avian study has shown that changes in body surface temperature can reflect the intensity of acute stress, little is known about surface temperature responses to stressors of different magnitudes and its sex-specificity in mammals, and how they correlate with hormonal and behavioural responses. We used IRT to collect continuous surface temperature measurements of tail and eye of adult male and female rats (Rattus norvegicus), for 30 minutes after exposure to one of three stressors (small cage, encircling handling or rodent restraint cone) for one minute, and cross-validated the thermal response with plasma corticosterone (CORT) and behavioural assessment. To obtain individual baseline temperatures and thermal responses to stress, rats were imaged in a test arena (to which they were habituated) for 30 seconds before and 30 minutes after being exposed to the stressor. In response to the three stressors, tail temperature initially decreased and then recovered to, or overshot the baseline temperature. Tail temperature dynamics differed between stressors; being restrained in the small cage was associated with the smallest drop in temperature, in male rats, and the fastest thermal recovery, in both sexes. Increases in eye temperature only distinguished between stressors early in the response and only in females. The post stressor increase in eye temperature was greater in the right eye of males and the left eye of females. In both sexes encircling may have been associated with the fastest increase in CORT. These results were in line with observed behavioural changes, with greater movement in rats exposed to the small cage and higher immobility after encircling. The female tail and eye temperature, as well as the CORT concentrations did not return to pre-stressor levels in the observation period, in conjunction with the greater occurrence of escape-related behaviours in female rats. These results suggest that female rats are more vulnerable to acute restraint stress compared to male rats and emphasise the importance of using both sexes in future investigations of stressor magnitude. This study demonstrates that acute stress induced changes in mammalian surface temperature measured with IRT relate to the magnitude of restraint stress, indicate sex differences and correlate with hormonal and behavioural responses. Thus, IRT has the potential to become a non-invasive method of continuous welfare assessment in unrestrained mammals.
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Affiliation(s)
- Chanakarn Wongsaengchan
- School of Psychology & Neuroscience, University of St Andrews, St Andrews, KY16 9JP, United Kingdom
| | - Dominic J McCafferty
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Scottish Centre for Ecology and the Natural Environment, Rowardennan, G63 0AW, United Kingdom
| | - Neil P Evans
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Jarrett Building, Glasgow, G61 1QH, United Kingdom
| | - Dorothy E F McKeegan
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Jarrett Building, Glasgow, G61 1QH, United Kingdom
| | - Ruedi G Nager
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, United Kingdom.
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Eye Region Surface Temperature and Corticosterone Response to Acute Stress in a High-Arctic Seabird, the Little Auk. Animals (Basel) 2022; 12:ani12040499. [PMID: 35203208 PMCID: PMC8868316 DOI: 10.3390/ani12040499] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/31/2022] [Accepted: 02/12/2022] [Indexed: 02/05/2023] Open
Abstract
Measuring changes in surface body temperature (specifically in eye-region) in vertebrates using infrared thermography is increasingly applied for detection of the stress reaction. Here we investigated the relationship between the eye-region temperature (TEYE; measured with infrared thermography), the corticosterone level in blood (CORT; stress indicator in birds), and some covariates (ambient temperature, humidity, and sex/body size) in a High-Arctic seabird, the Little Auk Alle alle. The birds responded to the capture-restrain protocol (blood sampling at the moment of capturing, and after 30 min of restrain) by a significant TEYE and CORT increase. However, the strength of the TEYE and CORT response to acute stress were not correlated. It confirms the results of a recent study on other species and all together indicates that infrared thermography is a useful, non-invasive measure of hypothalamic-pituitary-adrenal (HPA) axis reactivity under acute activation, but it might not be a suitable proxy for natural variation of circulating glucocorticoid levels.
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Tabh JKR, Mastromonaco GF, Burness G. Stress-induced changes in body surface temperature are repeatable, but do not differ between urban and rural birds. Oecologia 2022; 198:663-677. [PMID: 35138449 DOI: 10.1007/s00442-022-05120-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 01/18/2022] [Indexed: 11/29/2022]
Abstract
Urbanisation can alter local microclimates, thus creating new thermal challenges for resident species. However, urban environments also present residents with frequent, novel stressors (e.g., noise, human interaction) which may demand investment in costly, self-preserving responses (e.g., the fight-or-flight response). One way that urban residents might cope with this combination of demands is by using regional heterothermy to reduce costs of thermoregulation during the stress response. In this study, we used black-capped chickadees (nurban = 9; nrural = 10) to test whether known heterothermic responses to stress exposure (here, at the bare skin around the eye): (1) varied consistently among individuals (i.e., were repeatable), and (2) were most pronounced among urban individuals compared with rural individuals. Further, to gather evidence for selection on stress-induced heterothermic responses in urban settings, we tested: (3) whether repeatability of this response was lower among birds sampled from urban environments compared with those sampled from rural environments. For the first time, we show that heterothermic responses to stress exposures (i.e. changes in body surface temperature) were highly repeatable across chronic time periods (R = 0.58) but not acute time periods (R = 0.13). However, we also show that these responses did not differ between urban and rural birds, nor were our repeatability estimates any lower in our urban sample. Thus, while regional heterothermy during stress exposure may provide energetic benefits to some, but not all, individuals, enhanced use of this response to cope with urban pressures appears unlikely in our study species.
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Affiliation(s)
- Joshua K R Tabh
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, K9L 0G2, Canada. .,Department of Wildlife and Science, Toronto Zoo, Scarborough, ON, M1B 5K7, Canada.
| | | | - Gary Burness
- Department of Biology, Trent University, Peterborough, ON, K9L 0G2, Canada
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Jirinec V, Rodrigues PF, Amaral BR, Stouffer PC. Light and temperature niches of ground‐foraging Amazonian insectivorous birds. Ecology 2022; 103:e3645. [DOI: 10.1002/ecy.3645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 10/18/2021] [Accepted: 11/15/2021] [Indexed: 11/07/2022]
Affiliation(s)
- Vitek Jirinec
- Biological Dynamics of Forest Fragments Project Instituto Nacional de Pesquisas da Amazônia (INPA), CP 478 Manaus AM Brazil
- School of Renewable Natural Resources, Louisiana State University and LSU AgCenter Baton Rouge Louisiana USA
- Integral Ecology Research Center 239 Railroad Ave Blue Lake California USA
| | - Patricia F. Rodrigues
- Biological Dynamics of Forest Fragments Project Instituto Nacional de Pesquisas da Amazônia (INPA), CP 478 Manaus AM Brazil
- School of Renewable Natural Resources, Louisiana State University and LSU AgCenter Baton Rouge Louisiana USA
| | - Bruna R. Amaral
- Biological Dynamics of Forest Fragments Project Instituto Nacional de Pesquisas da Amazônia (INPA), CP 478 Manaus AM Brazil
- Department of Ecosystem Science and Management Pennsylvania State University, University Park Pennsylvania USA
| | - Philip C. Stouffer
- Biological Dynamics of Forest Fragments Project Instituto Nacional de Pesquisas da Amazônia (INPA), CP 478 Manaus AM Brazil
- School of Renewable Natural Resources, Louisiana State University and LSU AgCenter Baton Rouge Louisiana USA
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Tabh JKR, Burness G, Wearing OH, Tattersall GJ, Mastromonaco GF. Infrared thermography as a technique to measure physiological stress in birds: Body region and image angle matter. Physiol Rep 2021; 9:e14865. [PMID: 34057300 PMCID: PMC8165734 DOI: 10.14814/phy2.14865] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/31/2021] [Accepted: 04/13/2021] [Indexed: 11/24/2022] Open
Abstract
In vertebrates, changes in surface temperature following exposure to an acute stressor are thought to be promising indicators of the physiological stress response that may be captured noninvasively by infrared thermography. However, the efficacy of using stress-induced changes in surface temperature as indicators of physiological stress-responsiveness requires: (1) an understanding of how such responses vary across the body, (2) a magnitude of local, stress-induced thermal responses that is large enough to discriminate and quantify differences among individuals with conventional technologies, and (3) knowledge of how susceptible measurements across different body regions are to systematic error. In birds, temperature of the bare tissues surrounding the eye (the periorbital, or "eye," region) and covering the bill have each been speculated as possible predictors of stress physiological state. Using the domestic pigeon (Columba livia domestica; n = 9), we show that stress-induced changes in surface temperature are most pronounced at the bill and that thermal responses at only the bill have sufficient resolution to detect and quantify differences in responsiveness among individuals. More importantly, we show that surface temperature estimates at the eye region experience greater error due to changes in bird orientation than those at the bill. Such error concealed detection of stress-induced thermal responses at the eye region. Our results highlight that: (1) in some species, bill temperature may serve as a more robust indicator of autonomic stress-responsiveness than eye region temperature, and (2) future studies should account for spatial orientation of study individuals if inference is to be drawn from infrared thermographic images.
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Affiliation(s)
- Joshua K R Tabh
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada.,Department of Wildlife and Science, Toronto Zoo, Scarborough, ON, Canada
| | - Gary Burness
- Department of Biology, Trent University, Peterborough, ON, Canada
| | - Oliver H Wearing
- Department of Biology, McMaster University, Hamilton, ON, Canada
| | - Glenn J Tattersall
- Department of Biological Sciences, Brock University, St Catharines, ON, Canada
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Rogalla S, Shawkey MD, Vanthournout B, D'Alba L. Thermoregulation and heat exchange in ospreys (Pandion haliaetus). J Therm Biol 2021; 96:102857. [PMID: 33627285 DOI: 10.1016/j.jtherbio.2021.102857] [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: 07/10/2020] [Revised: 01/08/2021] [Accepted: 01/12/2021] [Indexed: 10/22/2022]
Abstract
The osprey (Pandion haliaetus) is a cosmopolitan and long-distant migrant, found at all thermal extremes ranging from polar to tropical climates. Since ospreys may have an unusually flexible thermal physiology due to their migration over, and use of, a wide range of habitats, they represent an interesting study system to explore thermoregulatory adaptations in a raptor. In this study, we investigated the efficiency of heat exchange between body and environment in ospreys using micro-computed tomography (μ-CT), infrared thermography and behavioral observations. μ-CT revealed that the osprey bill has its largest potential for heat exchange at the proximal bill region, where arteries are situated most closely under the surface. However, thermal images of 10 juvenile ospreys showed that the bill contributes to only 0.3% of the bird's total heat exchange. The long legs and protruding claws played a more prominent role as heat dissipation areas with a contribution of 6% and 7%, respectively. Operative thresholds, i.e. the ambient temperature below which heat is lost, were high (>38.5 °C) in these body parts. However, we found no indication of active regulation of heat exchange. Instead we observed multiple behavioral adaptations starting at relatively low ambient temperatures. At 26.3 °C ospreys had a 50% probability of showing panting behavior and above 27.9 °C they additionally spread their wings to enable heat dissipation from the less insulated ventral side. The thermal images revealed that at an ambient temperature of 32.1 °C ospreys had a 50% probability of developing a ≥2 °C and up to 7.5 °C colder stripe on the head, which was likely caused by cutaneous evaporation. Our observations suggest that ospreys more strongly rely on behavioral mechanisms than on active thermal windows to cope with heat stress. This study not only improves our understanding of the role of different body parts in ospreys' total heat exchange with the environment but further provides an insight about additional adaptations of this raptor to cope with heat stress.
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Affiliation(s)
- Svana Rogalla
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, K. L. Ledeganckstraat 35, 9000, Ghent, Belgium.
| | - Matthew D Shawkey
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, K. L. Ledeganckstraat 35, 9000, Ghent, Belgium
| | - Bram Vanthournout
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, K. L. Ledeganckstraat 35, 9000, Ghent, Belgium
| | - Liliana D'Alba
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, K. L. Ledeganckstraat 35, 9000, Ghent, Belgium
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Robertson JK, Mastromonaco GF, Burness G. Social hierarchy reveals thermoregulatory trade-offs in response to repeated stressors. J Exp Biol 2020; 223:jeb229047. [PMID: 32967999 DOI: 10.1242/jeb.229047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 09/09/2020] [Indexed: 11/20/2022]
Abstract
Coping with stressors can require substantial energetic investment, and when resources are limited, such investment can preclude simultaneous expenditure on other biological processes. Among endotherms, energetic demands of thermoregulation can also be immense, yet our understanding of whether a stress response is sufficient to induce changes in thermoregulatory investment is limited. Using the black-capped chickadee as a model species, we tested a hypothesis that stress-induced changes in surface temperature (Ts), a well-documented phenomenon across vertebrates, stem from trade-offs between thermoregulation and stress responsiveness. Because social subordination is known to constrain access to resources in this species, we predicted that Ts and dry heat loss of social subordinates, but not social dominants, would fall under stress exposure at low ambient temperatures (Ta), and rise under stress exposure at high Ta, thus permitting a reduction in total energetic expenditure toward thermoregulation. To test our predictions, we exposed four social groups of chickadees to repeated stressors and control conditions across a Ta gradient (n=30 days/treatment/group), whilst remotely monitoring social interactions and Ts Supporting our hypothesis, we show that: (1) social subordinates (n=12), who fed less than social dominants and alone experienced stress-induced mass-loss, displayed significantly larger changes in Ts following stress exposure than social dominants (n=8), and (2) stress-induced changes in Ts significantly increased heat conservation at low Ta and heat dissipation at high Ta among social subordinates alone. These results suggest that chickadees adjust their thermoregulatory strategies during stress exposure when resources are limited by ecologically relevant processes.
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Affiliation(s)
- Joshua K Robertson
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada K9L 0G2
- Department of Wildlife and Science, Toronto Zoo, Scarborough, ON, Canada M1B 5K7
| | | | - Gary Burness
- Department of Biology, Trent University, Peterborough, ON, Canada K9L 0G2
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Burnett K, Zipple MN, Phillips LT, Panwar P, Mcguire LP, Boyle WA. Nocturnal reductions in body temperature in high-elevation Neotropical birds. Trop Ecol 2019. [DOI: 10.1007/s42965-019-00051-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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10
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Jerem P, Jenni-Eiermann S, McKeegan D, McCafferty DJ, Nager RG. Eye region surface temperature dynamics during acute stress relate to baseline glucocorticoids independently of environmental conditions. Physiol Behav 2019; 210:112627. [PMID: 31348931 PMCID: PMC6739691 DOI: 10.1016/j.physbeh.2019.112627] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/22/2019] [Accepted: 07/22/2019] [Indexed: 02/06/2023]
Abstract
Reactions to acute stressors are critical for survival. Yet, the challenges of assessing underlying physiological processes in the field limit our understanding of how variation in the acute stress response relates to fitness in free-living animals. Glucocorticoid secretion during acute stress can be measured from blood plasma concentrations, but each blood sample can only provide information for one point in time. Also, the number of samples that can be extracted from an individual in the field is usually limited to avoid compromising welfare. This restricts capacity for repeated assessment, and therefore temporal resolution of findings within- and between-acute stress responses - both of which are important for determining links between acute stress and fitness. Acute stress induces additional body surface temperature changes that can be measured non-invasively, and at high frequencies using thermal imaging, offering opportunities to overcome these limitations. But, this method's usefulness in the field depends on the extent that environmental conditions affect the body surface temperature response, which remains poorly understood. We assessed the relative importance of individual physiology (baseline glucocorticoid concentrations) and environmental conditions (air temperature and relative humidity) in determining the eye region surface temperature (Teye) response to acute stress, in wild blue tits (Cyanistes caeruleus) during trapping, handling and blood sampling. When controlling for between-individual baseline variation, Teye initially dropped rapidly below, and then recovered above baseline, before declining more slowly until the end of the test, 160 s after trap closure. One measure of the amplitude of this response - the size of the initial drop in Teye - was dependent on environmental conditions, but not baseline corticosterone. Whereas, two properties defining response dynamics - the timing of the initial drop, and the slope of the subsequent recovery - were related to baseline corticosterone concentrations, independently of environmental conditions. This suggests inferring the acute stress response using thermal imaging of Teye will be practical under fluctuating environmental conditions in the field.
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Affiliation(s)
- Paul Jerem
- Department of Evolution, Behaviour and Environment, School of Life Sciences, University of Sussex, Falmer, UK.
| | | | - Dorothy McKeegan
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Dominic J McCafferty
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Ruedi G Nager
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
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Nord A, Folkow LP. Ambient temperature effects on stress-induced hyperthermia in Svalbard ptarmigan. Biol Open 2019; 8:bio.043497. [PMID: 31182628 PMCID: PMC6602330 DOI: 10.1242/bio.043497] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Stress-induced hyperthermia (SIH) is commonly observed during handling in homeotherms. However, in birds, handling in cold environments typically elicits hypothermia. It is unclear whether this indicates that SIH is differently regulated in this taxon or if it is due to size, because body temperature changes during handling in low temperatures have only been measured in small birds <0.03 kg (that are more likely to suffer high heat loss when handled). We have therefore studied thermal responses to handling stress in the intermediate-sized (0.5-1.0 kg) Svalbard ptarmigan (Lagopus muta hyperborea) in 0°C and -20°C, in winter and spring. Handling caused elevated core body temperature and peripheral vasoconstriction that reduced back skin temperature. Core temperature increased less, and back skin temperature decreased more, in -20°C than in 0°C, probably because of higher heat-loss rate at the lower temperature. Responses were qualitatively consistent between seasons, despite higher body condition/insulation in winter and dramatic seasonal changes in photoperiod, both of which could possibly affect stress responsiveness. Our study supports the notion that SIH is a general thermoregulatory reaction to acute stressors in endotherms, but also suggests that body size and thermal environment should be taken into account when evaluating this response in birds.
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Affiliation(s)
- Andreas Nord
- Department of Biology, Section for Evolutionary Ecology, Lund University, SE-223 62 Lund, Sweden .,Department of Arctic and Marine Biology, University of Tromsø-the Arctic University of Norway, NO-9037 Tromsø, Norway.,Institute for Biodiversity, Animal Health and Comparative Medicine, Scottish Centre for Ecology and the Natural Environment, University of Glasgow, Rowardennan G63 0AW, United Kingdom
| | - Lars P Folkow
- Department of Arctic and Marine Biology, University of Tromsø-the Arctic University of Norway, NO-9037 Tromsø, Norway
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12
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Beauchamp G. External body temperature and vigilance to a lesser extent track variation in predation risk in domestic fowls. BMC ZOOL 2019. [DOI: 10.1186/s40850-019-0039-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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13
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Surface temperature elevated by chronic and intermittent stress. Physiol Behav 2018; 191:47-55. [PMID: 29630961 PMCID: PMC5945995 DOI: 10.1016/j.physbeh.2018.04.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/03/2018] [Accepted: 04/03/2018] [Indexed: 11/24/2022]
Abstract
Stress in homeothermic animals is associated with raised body core temperature and altered patterns of peripheral blood flow. During acute stress, peripheral vasoconstriction causes a short-lived drop in surface temperature that can be detected non-invasively using infrared thermography (IRT). Whether and how skin temperature changes under chronic stress, and hence the potential of IRT in chronic stress detection, is unknown. We explored the impact of withdrawing environmental enrichments and intermittent routine handling on long-term skin temperature in laying hens (Gallus gallus domesticus). Immediately following enrichment withdrawal, comb, face and eye temperature dropped, suggesting this was acutely stressful. In the 3 weeks that followed, barren-housed hens displayed behavioural markers of frustration. Whilst control birds, housed in enriched conditions, showed a decline over weeks in both comb temperature and baseline corticosterone levels, barren-housed hens had no change in comb temperature and an increase in corticosterone. By the trial end, comb temperature (but not corticosterone) was significantly higher in barren-housed hens. This change in parameters over time may reflect cumulative impacts of enrichment withdrawal in barren pens and/or, as hens were young and maturing, age-related changes in controls. Comb, face and eye temperature were also higher on days following routine handling, and comb temperature higher on other days in hens that were regularly handled for blood sampling than for a less intensive weighing protocol. Together, these data support comb, face and eye surface temperature increase as a long-term marker of stress exposure in laying hens. It is important to recognise that the strength and even direction of these effects may vary with thermoregulatory and energetic context. However, in laboratory and indoor-reared farm animals that live in carefully managed environments, IRT of the skin can potentially be used to non-invasively monitor chronic and intermittent stress exposure. We measured surface temperature (ST) profile in hens subject to long term and intermittent stress. The impact of stressors was validated using established behavioural and hormonal markers. Enrichment withdrawal caused a short term drop in ST but living in a barren environment increased ST. Hens also had higher ST on days following handling or when subject to more intense handling methods. Thermal imaging of ST offers a non-invasive approach toward chronic stress monitoring.
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Brodin A, Nilsson JÅ, Nord A. Adaptive temperature regulation in the little bird in winter: predictions from a stochastic dynamic programming model. Oecologia 2017; 185:43-54. [PMID: 28776203 PMCID: PMC5596050 DOI: 10.1007/s00442-017-3923-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 07/23/2017] [Indexed: 11/21/2022]
Abstract
Several species of small birds are resident in boreal forests where environmental temperatures can be −20 to −30 °C, or even lower, in winter. As winter days are short, and food is scarce, winter survival is a challenge for small endothermic animals. A bird of this size will have to gain almost 10% of its lean body mass in fat every day to sustain overnight metabolism. Birds such as parids (titmice and chickadees) can use facultative hypothermia, a process in which body temperature is actively down-regulated to a specific level, to reduce heat loss and thus save energy. During cold winter nights, these birds may decrease body temperature from the normal from 42 ° down to 35 °C, or even lower in some species. However, birds are unable to move in this deep hypothermic state, making it a risky strategy if predators are around. Why, then, do small northern birds enter a potentially dangerous physiological state for a relatively small reduction in energy expenditure? We used stochastic dynamic programming to investigate this. Our model suggests that the use of nocturnal hypothermia at night is paramount in these biomes, as it would increase winter survival for a small northern bird by 58% over a winter of 100 days. Our model also explains the phenomenon known as winter fattening, and its relationship to thermoregulation, in northern birds.
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Affiliation(s)
- Anders Brodin
- Department of Biology, Lund University, Lund, Sweden.
| | | | - Andreas Nord
- Department of Biology, Lund University, Lund, Sweden.,Department of Arctic and Marine Biology, University of Tromsø, Tromsø, Norway
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