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Mella VSA, Cooper CE, Karr M, Krockenberger A, Madani G, Webb EB, Krockenberger MB. Hot climate, hot koalas: the role of weather, behaviour and disease on thermoregulation. CONSERVATION PHYSIOLOGY 2024; 12:coae032. [PMID: 38803425 PMCID: PMC11129715 DOI: 10.1093/conphys/coae032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 04/08/2024] [Accepted: 04/30/2024] [Indexed: 05/29/2024]
Abstract
Thermoregulation is critical for endotherms living in hot, dry conditions, and maintaining optimal core body temperature (Tb) in a changing climate is an increasingly challenging task for mammals. Koalas (Phascolarctos cinereus) have evolved physiological and behavioural strategies to maintain homeostasis and regulate their Tb but are thought to be vulnerable to prolonged heat. We investigated how weather, behaviour and disease influence Tb for wild, free-living koalas during summer in north-west New South Wales. We matched Tb with daily behavioural observations in an ageing population where chlamydial disease is prevalent. Each individual koala had similar Tb rhythms (average Tb = 36.4 ± 0.05°C), but male koalas had higher Tb amplitude and more pronounced daily rhythm than females. Disease disrupted the 24-hr circadian pattern of Tb. Koala Tb increased with ambient temperature (Ta). On the hottest day of the study (maximum Ta = 40.8°C), we recorded the highest (Tb = 40.8°C) but also the lowest (Tb = 32.4°C) Tb ever documented for wild koalas, suggesting that they are more heterothermic than previously recognized. This requires individuals to predict days of extreme Ta from overnight and early morning conditions, adjusting Tb regulation accordingly, and it has never been reported before for koalas. The large diel amplitude and low minimum Tb observed suggest that koalas at our study site are energetically and nutritionally compromised, likely due to their age. Behaviour (i.e. tree hugging and drinking water) was not effective in moderating Tb. These results indicate that Ta and koala Tb are strongly interconnected and reinforce the importance of climate projections for predicting the future persistence of koalas throughout their current distribution. Global climate models forecast that dry, hot weather will continue to escalate and drought events will increase in frequency, duration and severity. This is likely to push koalas and other arboreal folivores towards their thermal limit.
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Affiliation(s)
- Valentina S A Mella
- Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales 2006, Australia
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Christine E Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, Western Australia 6102, Australia
| | - Madeline Karr
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Andrew Krockenberger
- Division of Research and Innovation, James Cook University, Cairns, Queensland 4878, Australia
| | - George Madani
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Elliot B Webb
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
- Department of Planning and Environment, Science, Economics and Insights Division, Parramatta, New South Wales 2150, Australia
| | - Mark B Krockenberger
- Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales 2006, Australia
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2
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Pessato A, Udino E, McKechnie AE, Bennett ATD, Mariette MM. Thermal acclimatisation to heatwave conditions is rapid but sex-specific in wild zebra finches. Sci Rep 2023; 13:18297. [PMID: 37880274 PMCID: PMC10600105 DOI: 10.1038/s41598-023-45291-0] [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: 08/16/2023] [Accepted: 10/18/2023] [Indexed: 10/27/2023] Open
Abstract
Under climate change, increasing air temperature average and variability pose substantial thermal challenges to animals. While plasticity in thermoregulatory traits could potentially attenuate this impact, whether thermal acclimatisation can occur quickly enough to track weather variability in hot climates is unknown in any endotherm, and sex differences have never been tested. We investigated acclimatisation responsiveness of male and female wild zebra finches to short-term (< 2 weeks) summer temperature fluctuations in the Australian desert. Hotter weather before respirometry trials triggered a typical acclimatisation response (especially at chamber temperature Tchamb ≥ 40). However, acclimatisation occurred remarkably rapidly: metabolic rate responded within just one day, while body temperature (Tb) and evaporative cooling capacity (EHL/MHP) were best predicted by weather on the trial day; whereas evaporative water loss responded more slowly (1 week). Nonetheless, rapid acclimatisation only occurred in males, and females had higher Tb and lower EHL/MHP than males, potentially increasing hyperthermia risk. Furthermore, acclimatisation did not translate into greater acute heat tolerance (i.e. ability to tolerate Tchamb = 46 °C). Our results therefore reveal surprisingly rapid acclimatisation and even anticipatory adjustments to heat. However, with no changes in acute heat tolerance, and in females, phenotypic flexibility may provide only limited buffering against the detrimental impact of heatwaves.
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Affiliation(s)
- Anaïs Pessato
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong 3216, VIC, Australia
| | - Eve Udino
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong 3216, VIC, Australia
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0001, South Africa
| | - Andrew T D Bennett
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong 3216, VIC, Australia
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, VIC, 3030, Australia
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong 3216, VIC, Australia.
- Doñana Biological Station EBD-CSIC, 41092, Seville, Spain.
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3
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Zuluaga JD, Danner RM. Novel approaches for assessing acclimatization in birds reveal seasonal changes in peripheral heat exchange and thermoregulatory behaviors. J Exp Biol 2023; 226:jeb245772. [PMID: 37665269 DOI: 10.1242/jeb.245772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 08/23/2023] [Indexed: 09/05/2023]
Abstract
Using thermography and behavioral analyses, we found that heat exchange and thermoregulatory behaviors changed seasonally in chipping sparrows (Spizella passerina). Studies on seasonal acclimatization in birds have primarily involved metabolic measurements, few of which have investigated behaviors, and none have investigated changes in peripheral heat exchange. We captured chipping sparrows in the winter and summer of 2022 in Wilmington, North Carolina, USA, and we collected thermal images of these birds at 15.0, 27.5 and 40.0°C. We found that heat dissipation through the bill and legs changed seasonally, but surprisingly both were higher in winter than in summer. We found that heat dissipating behaviors were more common in winter, whereas heat conserving behaviors were more common in summer, and that behaviors associated with resource costs (e.g. panting) or predation risk (e.g. bill tucking) showed the most distinct differences between seasons. Meanwhile, low-cost and low-risk postural adjustments (e.g. feather adjustments and tarsus exposure) did not vary as strongly between seasons but followed similar trends. The seasonal adjustments to behaviors suggest that non-acclimatized birds must use costly thermoregulatory behaviors more frequently than acclimatized birds. The use of thermography resulted in the discovery of one completely novel behavior, and the first detection of a known behavior in a new species. Both novel behaviors aided in evaporative heat loss and occurred more commonly in winter, supporting the presence of seasonal acclimatization as evidenced by behavioral adjustments. These results provide novel insights into the process of acclimatization and suggest a role for behavioral adjustments in seasonal acclimatization.
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Affiliation(s)
- Juan D Zuluaga
- University of North Carolina Wilmington Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403-5915, USA
| | - Raymond M Danner
- University of North Carolina Wilmington Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403-5915, USA
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4
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González-Medina E, Playà-Montmany N, Cabello-Vergel J, Parejo M, Abad-Gómez JM, Sánchez-Guzmán JM, Villegas A, Gutiérrez JS, Masero JA. Mediterranean songbirds show pronounced seasonal variation in thermoregulatory traits. Comp Biochem Physiol A Mol Integr Physiol 2023; 280:111408. [PMID: 36812978 DOI: 10.1016/j.cbpa.2023.111408] [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: 07/31/2022] [Revised: 02/15/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023]
Abstract
Addressing the patterns of variation in thermal traits is crucial to better predict the potential effects of climate change on organisms. Here, we assessed seasonal (winter vs summer) adjustments in key thermoregulatory traits in eight Mediterranean-resident songbirds. Overall, songbirds increased whole-animal (by 8%) and mass-adjusted (by 9%) basal metabolic rate and decreased (by 56%) thermal conductance below the thermoneutral zone during winter. The magnitude of these changes was within the lower values found in songbirds from northern temperate areas. Moreover, songbirds increased (by 11%) evaporative water loss within the thermoneutral zone during summer, while its rate of increase above the inflection point of evaporative water loss (i.e., the slope of evaporative water loss versus temperature) decreased by 35% during summer - a value well above that reported for other temperate and tropical songbirds. Finally, body mass increased by 5% during winter, a pattern similar to that found in many northern temperate species. Our findings support the idea that physiological adjustments might enhance the resilience of Mediterranean songbirds to environmental changes, with short-term benefits by saving energy and water under thermally stressful conditions. Nevertheless, not all species showed the same patterns, suggesting different strategies in their thermoregulatory adaptations to seasonal environments.
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Affiliation(s)
- Erick González-Medina
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain.
| | - Núria Playà-Montmany
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain. https://twitter.com/NuriaPlayaM
| | - Julián Cabello-Vergel
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Manuel Parejo
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - José M Abad-Gómez
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Juan M Sánchez-Guzmán
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; Ecology in the Anthropocene, Associated Unit CSIC-UEX, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Auxiliadora Villegas
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; Ecology in the Anthropocene, Associated Unit CSIC-UEX, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain. https://twitter.com/AuxVil
| | - Jorge S Gutiérrez
- Conservation Biology Research Group, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; Ecology in the Anthropocene, Associated Unit CSIC-UEX, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain. https://twitter.com/JSGutierrez
| | - José A Masero
- Ecology in the Anthropocene, Associated Unit CSIC-UEX, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain. https://twitter.com/jamasero
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5
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Ma L, Conradie SR, Crawford CL, Gardner AS, Kearney MR, Maclean IMD, McKechnie AE, Mi CR, Senior RA, Wilcove DS. Global patterns of climate change impacts on desert bird communities. Nat Commun 2023; 14:211. [PMID: 36639376 PMCID: PMC9839677 DOI: 10.1038/s41467-023-35814-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/03/2023] [Indexed: 01/15/2023] Open
Abstract
The world's warm deserts are predicted to experience disproportionately large temperature increases due to climate change, yet the impacts on global desert biodiversity remain poorly understood. Because species in warm deserts live close to their physiological limits, additional warming may induce local extinctions. Here, we combine climate change projections with biophysical models and species distributions to predict physiological impacts of climate change on desert birds globally. Our results show heterogeneous impacts between and within warm deserts. Moreover, spatial patterns of physiological impacts do not simply mirror air temperature changes. Climate change refugia, defined as warm desert areas with high avian diversity and low predicted physiological impacts, are predicted to persist in varying extents in different desert realms. Only a small proportion (<20%) of refugia fall within existing protected areas. Our analysis highlights the need to increase protection of refugial areas within the world's warm deserts to protect species from climate change.
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Affiliation(s)
- Liang Ma
- Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, USA. .,School of Ecology, Shenzhen Campus of SunYat-sen University, Shenzhen, Guangdong, People's Republic of China.
| | - Shannon R Conradie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria, 0184, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria, 0002, South Africa
| | - Christopher L Crawford
- Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, USA
| | - Alexandra S Gardner
- Environment and Sustainability Institute, University of Exeter Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - Michael R Kearney
- School of BioSciences, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Ilya M D Maclean
- Environment and Sustainability Institute, University of Exeter Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria, 0184, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria, 0002, South Africa
| | - Chun-Rong Mi
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Rebecca A Senior
- Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, USA.,Conservation Ecology Group, Department of Biosciences, Durham University, Durham, DH1 3LE, UK
| | - David S Wilcove
- Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, USA.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
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6
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Cabello-Vergel J, González-Medina E, Parejo M, Abad-Gómez JM, Playà-Montmany N, Patón D, Sánchez-Guzmán JM, Masero JA, Gutiérrez JS, Villegas A. Heat tolerance limits of Mediterranean songbirds and their current and future vulnerabilities to temperature extremes. J Exp Biol 2022; 225:285906. [PMID: 36408945 PMCID: PMC9789400 DOI: 10.1242/jeb.244848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 11/09/2022] [Indexed: 11/22/2022]
Abstract
Songbirds are one of the groups most vulnerable to extreme heat events. Although several recent studies have assessed their physiological responses to heat, most of them have focused solely on arid-zone species. We investigated thermoregulatory responses to heat in eight small-sized songbirds occurring in the Mediterranean Basin, where heatwaves are becoming more frequent and intense. Specifically, we determined their heat tolerance limits (HTLs) and evaporative cooling efficiency, and evaluated their current and future vulnerabilities to heat in southwestern Iberia, a Mediterranean climate warming hotspot. To do this, we exposed birds to an increasing profile of air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), evaporative cooling efficiency (the ratio between evaporative heat loss and metabolic heat production) and body temperature (Tb). HTL ranged between 40 and 46°C across species, and all species showed rapid increases in RMR, EWL and Tb in response to increasing Ta. However, only the crested lark (Galerida cristata) achieved an evaporative cooling efficiency greater than 1. The studied songbirds currently experience summer Ta maxima that surpass the upper critical temperatures of their thermoneutral zone and even their HTL. Our estimates indicate that five of the eight species will experience moderate risk of lethal dehydration by the end of the century. We argue that the limited heat tolerance and evaporative cooling efficiency of small-sized Mediterranean songbirds make them particularly vulnerable to heatwaves, which will be exacerbated under future climate change scenarios.
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Affiliation(s)
- Julián Cabello-Vergel
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Author for correspondence ()
| | - Erick González-Medina
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Manuel Parejo
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - José M. Abad-Gómez
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Núria Playà-Montmany
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Daniel Patón
- Ecology Department, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Juan M. Sánchez-Guzmán
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - José A. Masero
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Jorge S. Gutiérrez
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Auxiliadora Villegas
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
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7
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Pandit MM, Bridge ES, Ross JD. Environmental conditions lead to shifts in individual communication, which can cause cascading effects on soundscape composition. Ecol Evol 2022; 12:e9359. [PMID: 36203628 PMCID: PMC9526030 DOI: 10.1002/ece3.9359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 08/03/2022] [Accepted: 08/22/2022] [Indexed: 11/06/2022] Open
Affiliation(s)
- Meelyn M. Pandit
- Oklahoma Biological Survey University of Oklahoma Norman Oklahoma USA
- Department of Biology University of Oklahoma Norman Oklahoma USA
| | - Eli S. Bridge
- Oklahoma Biological Survey University of Oklahoma Norman Oklahoma USA
- Department of Biology University of Oklahoma Norman Oklahoma USA
| | - Jeremy D. Ross
- Oklahoma Biological Survey University of Oklahoma Norman Oklahoma USA
- Department of Biology University of Oklahoma Norman Oklahoma USA
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8
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Monge O, Schulze CH, Dullinger S, Fusani L, Maggini I. Unshaded coffee imposes a heavier load on thermoregulation than shaded coffee for birds in a tropical mountainous region. Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2022.e02117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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9
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Abstract
Physiological performance declines precipitously at high body temperature (Tb), but little attention has been paid to adaptive variation in upper Tb limits among endotherms. We hypothesized that avian maximum tolerable Tb (Tbmax) has evolved in response to climate, with higher Tbmax in species exposed to high environmental heat loads or humidity-related constraints on evaporative heat dissipation. To test this hypothesis, we compared Tbmax and related variables among 53 bird species at multiple sites in South Africa with differing maximum air temperature (Tair) and humidity using a phylogenetically informed comparative framework. Birds in humid, lowland habitats had comparatively high Tbmax (mean ± SD = 45.60 ± 0.58 °C) and low normothermic Tb (Tbnorm), with a significantly greater capacity for hyperthermia (Tbmax - Tbnorm gradient = 5.84 ± 0.77 °C) compared with birds occupying cool montane (4.97 ± 0.99 °C) or hot arid (4.11 ± 0.84 °C) climates. Unexpectedly, Tbmax was significantly lower among desert birds (44.65 ± 0.60 °C), a surprising result in light of the functional importance of hyperthermia for water conservation. Our data reveal a macrophysiological pattern and support recent arguments that endotherms have evolved thermal generalization versus specialization analogous to the continuum among ectothermic animals. Specifically, a combination of modest hyperthermia tolerance and efficient evaporative cooling in desert birds is indicative of thermal specialization, whereas greater hyperthermia tolerance and less efficient evaporative cooling among species in humid lowland habitats suggest thermal generalization.
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10
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Short JC, Freeman MT, McKechnie AE. Respirometry protocols for avian thermoregulation at high air temperatures: stepped and steady-state profiles yield similar results. J Exp Biol 2022; 225:275927. [PMID: 35730660 DOI: 10.1242/jeb.244166] [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: 02/22/2022] [Accepted: 06/20/2022] [Indexed: 11/20/2022]
Abstract
Relationships between air temperature (Tair) and avian body temperature (Tb), resting metabolic rate (RMR) and evaporative water loss (EWL) during acute heat exposure can be quantified through respirometry using several approaches. One involves birds exposed to a stepped series of progressively increasing Tair setpoints for short periods (< 20-30 min), whereas a second seeks to achieve steady-state conditions by exposing birds to a single Tair for longer periods (> 1-2 h). To compare these two approaches, we measured Tb, RMR and EWL over Tair=28 °C to 44 °C in the dark-capped bulbul (Pycnonotus tricolor). The two protocols yielded indistinguishable values of Tb, RMR and EWL and related variables at most Tair values, revealing that both are appropriate for quantifying avian thermal physiology during heat exposure over the range of Tair in the present study. The stepped protocol, however, has several ethical and practical advantages.
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Affiliation(s)
- James C Short
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, P.O. Box 754, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria 0028, South Africa
| | - Marc T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, P.O. Box 754, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria 0028, South Africa
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, P.O. Box 754, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria 0028, South Africa
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11
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Conradie SR, Woodborne SM, Wolf BO, Pessato A, Mariette MM, McKechnie AE. Global heating poses a serious threat to Australia's birds: reply to Pacheco-Fuentes et al. CONSERVATION PHYSIOLOGY 2022; 10:coac011. [PMID: 35492411 PMCID: PMC9041427 DOI: 10.1093/conphys/coac011] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 02/01/2022] [Accepted: 02/14/2022] [Indexed: 06/14/2023]
Affiliation(s)
- Shannon R Conradie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria 0184, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa
| | - Stephan M Woodborne
- iThemba LABS, 514 Empire Rd, Johannesburg 2193, South Africa
- Mammal Research Institute, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, Albuquerque, NM 87131, USA
| | - Anaïs Pessato
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds VIC 3216, Australia
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds VIC 3216, Australia
- Estación Biológica de Doñana (EBD-CSIC), Calle Américo-Vespucio, Edificio I, 41092 Sevilla, Spain
| | - Andrew E McKechnie
- Corresponding author: South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, South Africa.
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12
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Czenze ZJ, Freeman MT, Kemp R, van Jaarsveld B, Wolf BO, McKechnie AE. Efficient Evaporative Cooling and Pronounced Heat Tolerance in an Eagle-Owl, a Thick-Knee and a Sandgrouse. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.799302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Avian evaporative cooling and the maintenance of body temperature (Tb) below lethal limits during heat exposure has received more attention in small species compared to larger-bodied taxa. Here, we examined thermoregulation at air temperatures (Tair) approaching and exceeding normothermic Tb in three larger birds that use gular flutter, thought to provide the basis for pronounced evaporative cooling capacity and heat tolerance. We quantified Tb, evaporative water loss (EWL) and resting metabolic rate (RMR) in the ∼170-g Namaqua sandgrouse (Pterocles namaqua), ∼430-g spotted thick-knee (Burhinus capensis) and ∼670-g spotted eagle-owl (Bubo africanus), using flow-through respirometry and a stepped Tair profile with very low chamber humidities. All three species tolerated Tair of 56–60°C before the onset of severe hyperthermia, with maximum Tb of 43.2°C, 44.3°C, and 44.2°C in sandgrouse, thick-knees and eagle-owls, respectively. Evaporative scope (i.e., maximum EWL/minimum thermoneutral EWL) was 7.4 in sandgrouse, 12.9 in thick-knees and 7.8 in eagle-owls. The relationship between RMR and Tair varied substantially among species: whereas thick-knees and eagle-owls showed clear upper critical limits of thermoneutrality above which RMR increased rapidly and linearly, sandgrouse did not. Maximum evaporative heat loss/metabolic heat production ranged from 2.8 (eagle-owls) to 5.5 (sandgrouse), the latter the highest avian value yet reported. Our data reveal some larger species with gular flutter possess pronounced evaporative cooling capacity and heat tolerance and, when taken together with published data, show thermoregulatory performance varies widely among species larger than 250 g. Our data for Namaqua sandgrouse reveal unexpectedly pronounced variation in the metabolic costs of evaporative cooling within the genus Pterocles.
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13
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Czenze ZJ, Smit B, Jaarsveld B, Freeman MT, McKechnie AE. Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Zenon J. Czenze
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Ben Smit
- Department of Zoology and Entomology Rhodes University Makhanda South Africa
| | - Barry Jaarsveld
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Marc T. Freeman
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Andrew E. McKechnie
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
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14
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Playà‐Montmany N, González‐Medina E, Cabello‐Vergel J, Parejo M, Abad‐Gómez JM, Sánchez‐Guzmán JM, Villegas A, Masero JA. The thermoregulatory role of relative bill and leg surface areas in a Mediterranean population of Great tit ( Parus major). Ecol Evol 2021; 11:15936-15946. [PMID: 34824801 PMCID: PMC8601919 DOI: 10.1002/ece3.8263] [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: 05/26/2021] [Revised: 09/15/2021] [Accepted: 10/07/2021] [Indexed: 11/07/2022] Open
Abstract
There is growing evidence on the role of legs and bill as 'thermal windows' in birds coping with heat stress. However, there is a lack of empirical work examining the relationship between the relative bill and/or leg surface areas and key thermoregulatory traits such as the limits of the thermoneutral zone (TNZ) or the cooling efficiency at high temperatures. Here, we explored this relationship in a Mediterranean population of Great tit (Parus major) facing increasing thermal stress in its environment. The lower and upper critical limits of the TNZ were found to be 17.7 ± 1.6ºC and 34.5 ± 0.7°C, respectively, and the basal metabolic rate was 0.96 ± 0.12 ml O2 min-1 on average. The evaporative water loss (EWL) inflection point was established at 31.85 ± 0.27°C and was not significantly different from the value of the upper critical limit. No significant relationship was observed between the relative bill or tarsi size and TNZ critical limits, breadth, mass-independent VO2, or mass-independent EWL at any environmental temperature (from 10 to 40°C). However, Great tit males (but not females) with larger tarsi areas (a proxy of leg surface area) showed higher cooling efficiencies at 40°C. We found no support for the hypothesis that the bill surface area plays a significant role as a thermal window in Great tits, but the leg surface areas may play a role in males' physiological responses to high temperatures. On the one hand, we argue that the studied population occupies habitats with available microclimates and fresh water for drinking during summer, so active heat dissipation by EWL might be favored instead of dry heat loss through the bill surface. Conversely, male dominance behaviors could imply a greater dependence on cutaneous EWL through the upper leg surfaces as a consequence of higher exposure to harsh environmental conditions than faced by females.
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Affiliation(s)
- Núria Playà‐Montmany
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Erick González‐Medina
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Julián Cabello‐Vergel
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Manuel Parejo
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - José M. Abad‐Gómez
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Juan M. Sánchez‐Guzmán
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Auxiliadora Villegas
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - José A. Masero
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
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15
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Urohidrosis as an overlooked cooling mechanism in long-legged birds. Sci Rep 2021; 11:20018. [PMID: 34625581 PMCID: PMC8501033 DOI: 10.1038/s41598-021-99296-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 09/22/2021] [Indexed: 11/08/2022] Open
Abstract
Behavioural thermoregulation could buffer the impacts of climate warming on vertebrates. Specifically, the wetting of body surfaces and the resulting evaporation of body fluids serves as a cooling mechanism in a number of vertebrates coping with heat. Storks (Ciconiidae) frequently excrete onto their legs to prevent overheating, a phenomenon known as urohidrosis. Despite the increasingly recognised role of bare and highly vascularised body parts in heat exchange, the ecological and evolutionary determinants of urohidrosis have been largely ignored. We combine urohidrosis data from a scientifically curated media repository with microclimate and ecological data to investigate the determinants of urohidrosis in all extant stork species. Our phylogenetic generalised linear mixed models show that high temperature, humidity and solar radiation, and low wind speed, promote the use of urohidrosis across species. Moreover, species that typically forage in open landscapes exhibit a more pronounced use of urohidrosis than those mainly foraging in waterbodies. Substantial interspecific variation in temperature thresholds for urohidrosis prevalence points to different species vulnerabilities to high temperatures. This integrated approach that uses online data sources and methods to model microclimates should provide insight into animal thermoregulation and improve our capacity to make accurate predictions of climate change's impact on biodiversity.
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16
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Paces B, Waringer BM, Domer A, Burns D, Zvik Y, Wojciechowski MS, Shochat E, Sapir N, Maggini I. Evaporative Water Loss and Stopover Behavior in Three Passerine Bird Species During Autumn Migration. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.704676] [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
Migratory birds are often not specifically adapted to arid conditions, yet several species travel across deserts during their journeys, and often have more or less short stopovers there. We investigated whether differences in thermoregulatory mechanisms, specifically evaporative cooling, explain the different behavior of three passerine species while stopping over in the Negev desert, Israel. We measured cutaneous water loss (CWL) under ambient conditions and the temperature of panting onset in an experimental setup. In addition, we performed behavioral observations of birds at a stopover site where we manipulated water availability. Blackcaps had slightly higher CWL at relatively low temperatures than Willow Warblers and Lesser Whitethroats. When considered relative to total body mass, however, Willow Warblers had the highest CWL of the three species. Blackcaps started panting at lower ambient temperature than the other two species. Taken together, these results suggest that Willow Warblers are the most efficient in cooling their body, possibly with the cost of needing to regain water by actively foraging during their staging. Lesser Whitethroats had a similar pattern, which was reflected in their slightly higher levels of activity and drinking behavior when water was available. However, in general the behavior of migratory species was not affected by the availability of water, and they were observed drinking rather rarely. Our results indicate that differences in thermoregulatory mechanisms might be at the basis of the evolution of different stopover strategies of migratory birds while crossing arid areas such as deserts.
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17
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Bourne AR, Ridley AR, Spottiswoode CN, Cunningham SJ. Direct and indirect effects of high temperatures on fledging in a cooperatively breeding bird. Behav Ecol 2021. [DOI: 10.1093/beheco/arab087] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Abstract
High temperatures and low rainfall consistently constrain reproduction in arid-zone bird species. Understanding the mechanisms underlying this pattern is critical for predicting how climate change will influence population persistence and to inform conservation and management. In this study, we analyzed Southern Pied Babbler Turdoides bicolor nestling survival, daily growth rate and adult investment behavior during the nestling period over three austral summer breeding seasons. High temperatures were associated with lower body mass, shorter tarsi, and reduced daily growth rates of nestlings. Our piecewise structural equation models suggested that direct impacts of temperature had the strongest influence on nestling size and daily growth rates for both 5-day-old and 11-day-old nestlings, followed by temperature-related adjustments to provisioning rates by adults. Rainfall and group size influenced the behavior of provisioning adults but did not influence nestling growth or survival. Adjustments to adult provisioning strategies did not compensate for direct negative effects of high air temperatures on nestling size or daily growth rates. Detailed mechanistic data like these allow us to model the pathways by which high temperature causes nest failure. In turn, this could allow us to design targeted conservation action to effectively mitigate climate effects.
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Affiliation(s)
- Amanda R Bourne
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa
| | - Amanda R Ridley
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Hackett Drive, Crawley, Perth WA, Australia
| | - Claire N Spottiswoode
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Susan J Cunningham
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa
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18
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Choy ES, O'Connor RS, Gilchrist HG, Hargreaves AL, Love OP, Vézina F, Elliott KH. Limited heat tolerance in a cold-adapted seabird: implications of a warming Arctic. J Exp Biol 2021; 224:270771. [PMID: 34232314 PMCID: PMC8278010 DOI: 10.1242/jeb.242168] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 06/02/2021] [Indexed: 02/01/2023]
Abstract
The Arctic is warming at approximately twice the global rate, with well-documented indirect effects on wildlife. However, few studies have examined the direct effects of warming temperatures on Arctic wildlife, leaving the importance of heat stress unclear. Here, we assessed the direct effects of increasing air temperatures on the physiology of thick-billed murres (Uria lomvia), an Arctic seabird with reported mortalities due to heat stress while nesting on sun-exposed cliffs. We used flow-through respirometry to measure the response of body temperature, resting metabolic rate, evaporative water loss and evaporative cooling efficiency (the ratio of evaporative heat loss to metabolic heat production) in murres while experimentally increasing air temperature. Murres had limited heat tolerance, exhibiting: (1) a low maximum body temperature (43.3°C); (2) a moderate increase in resting metabolic rate relative that within their thermoneutral zone (1.57 times); (3) a small increase in evaporative water loss rate relative that within their thermoneutral zone (1.26 times); and (4) a low maximum evaporative cooling efficiency (0.33). Moreover, evaporative cooling efficiency decreased with increasing air temperature, suggesting murres were producing heat at a faster rate than they were dissipating it. Larger murres also had a higher rate of increase in resting metabolic rate and a lower rate of increase in evaporative water loss than smaller murres; therefore, evaporative cooling efficiency declined with increasing body mass. As a cold-adapted bird, murres' limited heat tolerance likely explains their mortality on warm days. Direct effects of overheating on Arctic wildlife may be an important but under-reported impact of climate change.
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Affiliation(s)
- Emily S Choy
- Department of Natural Resource Sciences, McGill University, Ste Anne de Bellevue, QC, CanadaH9X 3V9
| | - Ryan S O'Connor
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Groupe de recherche sur les environnements nordiques BORÉAS, Institut nordique du Québec, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Centre d'études Nordiques, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Centre de la Science de la Biodiversité du Québec, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1
| | - H Grant Gilchrist
- National Wildlife Research Centre, Environment and Climate Change Canada, 1125 Colonel By Dr, Ottawa, ON, CanadaK1S 5B6
| | - Anna L Hargreaves
- Department of Biology, McGill University, Montreal, QC, CanadaH3G 0B1
| | - Oliver P Love
- Department of Integrative Biology, University of Windsor, Windsor, ON, CanadaN9B 3P4
| | - François Vézina
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Groupe de recherche sur les environnements nordiques BORÉAS, Institut nordique du Québec, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Centre d'études Nordiques, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1.,Centre de la Science de la Biodiversité du Québec, Université du Québec à Rimouski, Rimouski, QC, Canada95L 3A1
| | - Kyle H Elliott
- Department of Natural Resource Sciences, McGill University, Ste Anne de Bellevue, QC, CanadaH9X 3V9
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19
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McKechnie AE, Gerson AR, Wolf BO. Thermoregulation in desert birds: scaling and phylogenetic variation in heat tolerance and evaporative cooling. J Exp Biol 2021; 224:224/Suppl_1/jeb229211. [PMID: 33627461 DOI: 10.1242/jeb.229211] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Evaporative heat dissipation is a key aspect of avian thermoregulation in hot environments. We quantified variation in avian thermoregulatory performance at high air temperatures (T a) using published data on body temperature (T b), evaporative water loss (EWL) and resting metabolic rate (RMR) measured under standardized conditions of very low humidity in 56 arid-zone species. Maximum T b during acute heat exposure varied from 42.5±1.3°C in caprimulgids to 44.5±0.5°C in passerines. Among passerines, both maximum T b and the difference between maximum and normothermic T b decreased significantly with body mass (M b). Scaling exponents for minimum thermoneutral EWL and maximum EWL were 0.825 and 0.801, respectively, even though evaporative scope (ratio of maximum to minimum EWL) varied widely among species. Upper critical limits of thermoneutrality (T uc) varied by >20°C and maximum RMR during acute heat exposure scaled to M b 0.75 in both the overall data set and among passerines. The slope of RMR at T a>T uc increased significantly with M b but was substantially higher among passerines, which rely on panting, compared with columbids, in which cutaneous evaporation predominates. Our analysis supports recent arguments that interspecific within-taxon variation in heat tolerance is functionally linked to evaporative scope and maximum ratios of evaporative heat loss (EHL) to metabolic heat production (MHP). We provide predictive equations for most variables related to avian heat tolerance. Metabolic costs of heat dissipation pathways, rather than capacity to increase EWL above baseline levels, appear to represent the major constraint on the upper limits of avian heat tolerance.
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Affiliation(s)
- Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, P.O. Box 754, Pretoria 0001, South Africa .,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria 0028, South Africa
| | - Alexander R Gerson
- Department of Biology, University of Massachusetts, Amherst, MA 01003-9297, USA
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
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20
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van Jaarsveld B, Bennett NC, Czenze ZJ, Kemp R, van de Ven TMFN, Cunningham SJ, McKechnie AE. How hornbills handle heat: sex-specific thermoregulation in the southern yellow-billed hornbill. J Exp Biol 2021; 224:jeb.232777. [PMID: 33504586 DOI: 10.1242/jeb.232777] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 01/06/2021] [Indexed: 12/22/2022]
Abstract
At a global scale, thermal physiology is correlated with climatic variables such as temperature and aridity. There is also evidence that thermoregulatory traits vary with fine-scale microclimate, but this has received less attention in endotherms. Here, we test the hypothesis that avian thermoregulation varies with microclimate and behavioural constraints in a non-passerine bird. Male and female southern yellow-billed hornbills (Tockus leucomelas) experience markedly different microclimates while breeding, with the female sealing herself into a tree cavity and moulting all her flight feathers during the breeding attempt, becoming entirely reliant on the male for provisioning. We examined interactions between resting metabolic rate (RMR), evaporative water loss (EWL) and core body temperature (T b) at air temperatures (T a) between 30°C and 52°C in male and female hornbills, and quantified evaporative cooling efficiencies and heat tolerance limits. At thermoneutral T a, neither RMR, EWL nor T b differed between sexes. At T a >40°C, however, RMR and EWL of females were significantly lower than those of males, by ∼13% and ∼17%, respectively, despite similar relationships between T b and T a, maximum ratio of evaporative heat loss to metabolic heat production and heat tolerance limits (∼50°C). These sex-specific differences in hornbill thermoregulation support the hypothesis that avian thermal physiology can vary within species in response to fine-scale microclimatic factors. In addition, Q 10 for RMR varied substantially, with Q 10 ≤2 in some individuals, supporting recent arguments that active metabolic suppression may be an underappreciated aspect of endotherm thermoregulation in the heat.
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Affiliation(s)
- Barry van Jaarsveld
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa .,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa
| | - Zenon J Czenze
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Ryno Kemp
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Tanja M F N van de Ven
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.,Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
| | - Susan J Cunningham
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
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21
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Grosiak M, Koteja P, Bauchinger U, Sadowska ET. Age-Related Changes in the Thermoregulatory Properties in Bank Voles From a Selection Experiment. Front Physiol 2020; 11:576304. [PMID: 33329026 PMCID: PMC7711078 DOI: 10.3389/fphys.2020.576304] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/09/2020] [Indexed: 01/21/2023] Open
Abstract
As with many physiological performance traits, the capacity of endotherms to thermoregulate declines with age. Aging compromises both the capacity to conserve or dissipate heat and the thermogenesis, which is fueled by aerobic metabolism. The rate of metabolism, however, not only determines thermogenic capacity but can also affect the process of aging. Therefore, we hypothesized that selection for an increased aerobic exercise metabolism, which has presumably been a crucial factor in the evolution of endothermic physiology in the mammalian and avian lineages, affects not only the thermoregulatory traits but also the age-related changes of these traits. Here, we test this hypothesis on bank voles (Myodes glareolus) from an experimental evolution model system: four lines selected for high swim-induced aerobic metabolism (A lines), which have also increased the basal, average daily, and maximum cold-induced metabolic rates, and four unselected control (C) lines. We measured the resting metabolic rate (RMR), evaporative water loss (EWL), and body temperature in 72 young adult (4 months) and 65 old (22 months) voles at seven ambient temperatures (13-32°C). The RMR was 6% higher in the A than in the C lines, but, regardless of the selection group or temperature, it did not change with age. However, EWL was 12% higher in the old voles. An increased EWL/RMR ratio implies either a compromised efficiency of oxygen extraction in the lungs or increased skin permeability. This effect was more profound in the A lines, which may indicate their increased vulnerability to aging. Body temperature did not differ between the selection and age groups below 32°C, but at 32°C it was markedly higher in the old A-line voles than in those from other groups. As expected, the thermogenic capacity, measured as the maximum cold-induced oxygen consumption, was decreased by about 13% in the old voles from both selection groups, but the performance of old A-line voles was the same as that of the young C-line ones. Thus, the selection for high aerobic exercise metabolism attenuated the adverse effects of aging on cold tolerance, but this advantage has been traded off by a compromised coping with hot conditions by aged voles.
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Affiliation(s)
- Marta Grosiak
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Paweł Koteja
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
| | - Ulf Bauchinger
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Edyta T. Sadowska
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Kraków, Poland
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22
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Pessato A, McKechnie AE, Buchanan KL, Mariette MM. Vocal panting: a novel thermoregulatory mechanism for enhancing heat tolerance in a desert-adapted bird. Sci Rep 2020; 10:18914. [PMID: 33144650 PMCID: PMC7609653 DOI: 10.1038/s41598-020-75909-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/15/2020] [Indexed: 01/06/2023] Open
Abstract
Animals thriving in hot deserts rely on extraordinary adaptations and thermoregulatory capacities to cope with heat. Uncovering such adaptations, and how they may be favoured by selection, is essential for predicting climate change impacts. Recently, the arid-adapted zebra finch was discovered to program their offspring’s development for heat, by producing ‘heat-calls’ during incubation in hot conditions. Intriguingly, heat-calls always occur during panting; and, strikingly, avian evaporative cooling mechanisms typically involve vibrating an element of the respiratory tract, which could conceivably produce sound. Therefore, we tested whether heat-call emission results from a particular thermoregulatory mechanism increasing the parent’s heat tolerance. We repeatedly measured resting metabolic rate, evaporative water loss (EWL) and heat tolerance in adult wild-derived captive zebra finches (n = 44) at increasing air temperatures up to 44 °C. We found high within-individual repeatability in thermoregulatory patterns, with heat-calling triggered at an individual-specific stage of panting. As expected for thermoregulatory mechanisms, both silent panting and heat-calling significantly increased EWL. However, only heat-calling resulted in greater heat tolerance, demonstrating that “vocal panting” brings a thermoregulatory benefit to the emitter. Our findings therefore not only improve our understanding of the evolution of passerine thermal adaptations, but also highlight a novel evolutionary precursor for acoustic signals.
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Affiliation(s)
- Anaïs Pessato
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia.
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa.,DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0001, South Africa
| | - Katherine L Buchanan
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia.
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23
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Borowiec BG. Drinking desert birds keep cool. J Exp Biol 2020. [DOI: 10.1242/jeb.214494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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24
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Freeman MT, Czenze ZJ, Schoeman K, McKechnie AE. Extreme hyperthermia tolerance in the world's most abundant wild bird. Sci Rep 2020; 10:13098. [PMID: 32753751 PMCID: PMC7403380 DOI: 10.1038/s41598-020-69997-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 06/26/2020] [Indexed: 11/09/2022] Open
Abstract
The thermal tolerances of vertebrates are generally restricted to body temperatures below 45–47 °C, and avian and mammalian critical thermal maxima seldom exceed 46 °C. We investigated thermoregulation at high air temperatures in the red-billed quelea (Quelea quelea), an African passerine bird that occurs in flocks sometimes numbering millions of individuals. Our data reveal this species can increase its body temperature to extremely high levels: queleas exposed to air temperature > 45 °C increased body temperature to 48.0 ± 0.7 °C without any apparent ill-effect, with individual values as high as 49.1 °C. These values exceed known avian lethal limits, with tolerance of body temperature > 48 °C unprecedented among birds and mammals.
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Affiliation(s)
- M T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Z J Czenze
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - K Schoeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - A E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa. .,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
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Conradie SR, Woodborne SM, Wolf BO, Pessato A, Mariette MM, McKechnie AE. Avian mortality risk during heat waves will increase greatly in arid Australia during the 21st century. CONSERVATION PHYSIOLOGY 2020; 8:coaa048. [PMID: 32523698 PMCID: PMC7271765 DOI: 10.1093/conphys/coaa048] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/15/2020] [Accepted: 05/03/2020] [Indexed: 05/05/2023]
Abstract
Intense heat waves are occurring more frequently, with concomitant increases in the risk of catastrophic avian mortality events via lethal dehydration or hyperthermia. We quantified the risks of lethal hyperthermia and dehydration for 10 Australian arid-zone avifauna species during the 21st century, by synthesizing thermal physiology data on evaporative water losses and heat tolerance limits. We evaluated risks of lethal hyperthermia or exceedance of dehydration tolerance limits in the absence of drinking during the hottest part of the day under recent climatic conditions, compared to those predicted for the end of this century across Australia. Increases in mortality risk via lethal dehydration and hyperthermia vary among the species modelled here but will generally increase greatly, particularly in smaller species (~10-42 g) and those inhabiting the far western parts of the continent. By 2100 CE, zebra finches' potential exposure to acute lethal dehydration risk will reach ~ 100 d y-1 in the far northwest of Australia and will exceed 20 d y-1 over > 50% of this species' current range. Risks of dehydration and hyperthermia will remain much lower for large non-passerines such as crested pigeons. Risks of lethal hyperthermia will also increase substantially for smaller species, particularly if they are forced to visit exposed water sources at very high air temperatures to avoid dehydration. An analysis of atlas data for zebra finches suggests that population declines associated with very hot conditions are already occurring in the hottest areas. Our findings suggest that the likelihood of persistence within current species ranges, and the potential for range shifts, will become increasingly constrained by temperature and access to drinking water. Our model adds to an increasing body of literature suggesting that arid environments globally will experience considerable losses of avifauna and biodiversity under unmitigated climate change scenarios.
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Affiliation(s)
- Shannon R Conradie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria 0184, South Africa
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa
| | - Stephan M Woodborne
- iThemba LABS, Johannesburg, 514 Empire Rd, Johannesburg 2193, South Africa
- Mammal Research Institute, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, Albuquerque, NM 87131, U.S.A
| | - Anaïs Pessato
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds VIC 3216, Australia
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds VIC 3216, Australia
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria 0184, South Africa
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa
- Corresponding author: South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, South Africa.
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