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O'Connor RS, Love OP, Régimbald L, Le Pogam A, Gerson AR, Elliott KH, Hargreaves AL, Vézina F. An arctic breeding songbird overheats during intense activity even at low air temperatures. Sci Rep 2024; 14:15193. [PMID: 38956145 PMCID: PMC11219724 DOI: 10.1038/s41598-024-65208-9] [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: 11/17/2023] [Accepted: 06/18/2024] [Indexed: 07/04/2024] Open
Abstract
Birds maintain some of the highest body temperatures among endothermic animals. Often deemed a selective advantage for heat tolerance, high body temperatures also limits birds' thermal safety margin before reaching lethal levels. Recent modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures, which may require reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. We measured within-individual changes in body temperature in calm birds and then in response to an experimental increase in activity in an outdoor captive population of Arctic, cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying air temperatures (- 15 to 36 °C). Calm buntings exhibited a modal body temperature range from 39.9 to 42.6 °C. However, we detected a significant increase in body temperature within minutes of shifting calm birds to active flight, with strong evidence for a positive effect of air temperature on body temperature (slope = 0.04 °C/ °C). Importantly, by an ambient temperature of 9 °C, flying buntings were already generating body temperatures ≥ 45 °C, approaching the upper thermal limits of organismal performance (45-47 °C). With known limited evaporative heat dissipation capacities in these birds, our results support the recent prediction that free-living buntings operating at maximal sustainable rates will increasingly need to rely on behavioural thermoregulatory strategies to regulate body temperature, to the detriment of nestling growth and survival.
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Affiliation(s)
- Ryan S O'Connor
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada.
- Groupe de Recherche sur les Environnements Nordiques BORÉAS, Rimouski, Canada.
- Centre d'études Nordiques, Rimouski, Canada.
- Centre de la Science de la Biodiversité du Québec, Rimouski, Canada.
| | - Oliver P Love
- Department of Integrative Biology, University of Windsor, Windsor, ON, N9B 3P4, Canada
| | - Lyette Régimbald
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
| | - Audrey Le Pogam
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
- Groupe de Recherche sur les Environnements Nordiques BORÉAS, Rimouski, Canada
- Centre d'études Nordiques, Rimouski, Canada
- Centre de la Science de la Biodiversité du Québec, Rimouski, Canada
| | - Alexander R Gerson
- Department of Biology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Kyle H Elliott
- Department of Natural Resource Sciences, McGill University, Sainte Anne de Bellevue, QC, H9X 3V90, Canada
| | - Anna L Hargreaves
- Department of Biological Sciences, McGill University, Montréal, QC, H3A 1B1, Canada
| | - François Vézina
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
- Groupe de Recherche sur les Environnements Nordiques BORÉAS, Rimouski, Canada
- Centre d'études Nordiques, Rimouski, Canada
- Centre de la Science de la Biodiversité du Québec, Rimouski, Canada
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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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A prenatal acoustic signal of heat affects thermoregulation capacities at adulthood in an arid-adapted bird. Sci Rep 2022; 12:5842. [PMID: 35393484 PMCID: PMC8991222 DOI: 10.1038/s41598-022-09761-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/01/2022] [Indexed: 11/16/2022] Open
Abstract
Understanding animal physiological adaptations for tolerating heat, and the causes of inter-individual variation, is key for predicting climate change impacts on biodiversity. Recently, a novel mechanism for transgenerational heat adaptation was identified in a desert-adapted bird, where parents acoustically signal hot conditions to embryos. Prenatal exposure to “heat-calls” adaptively alters zebra finch development and their thermal preferences in adulthood, suggesting a long-term shift towards a heat-adapted phenotype. However, whether such acoustic experience improves long-term thermoregulatory capacities is unknown. We measured metabolic rate (MR), evaporative water loss (EWL) and body temperature in adults exposed to a stepped profile of progressively higher air temperatures (Ta) between 27 and 44 °C. Remarkably, prenatal acoustic experience affected heat tolerance at adulthood, with heat-call exposed individuals more likely to reach the highest Ta in morning trials. This was despite MR and EWL reaching higher levels at the highest Ta in heat-call individuals, partly driven by a stronger metabolic effect of moderate activity. At lower Ta, however, heat-call exposed individuals had greater relative water economy, as expected. They also better recovered mass lost during morning trials. We therefore provide the first evidence that prenatal acoustic signals have long-term consequences for heat tolerance and physiological adaptation to heat.
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4
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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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5
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Tapper S, Nocera JJ, Burness G. Body temperature is a repeatable trait in a free-ranging passerine bird. J Exp Biol 2021; 224:272129. [PMID: 34498672 DOI: 10.1242/jeb.243057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/03/2021] [Indexed: 12/23/2022]
Abstract
Body temperature (Tb) affects animal function through its influence on rates of biochemical and biophysical reactions, the molecular structures of proteins and tissues, and, ultimately, organismal performance. Despite its importance in driving physiological processes, there are few data on how much variation in Tb exists within populations of organisms, and whether this variation consistently differs among individuals over time (i.e. repeatability of a trait). Here, using thermal radio-frequency identification implants, we quantified the repeatability of Tb, both in the context of a fixed average environment (∼21°C) and across ambient temperatures (6-31°C), in a free-living population of tree swallows (Tachycineta bicolor, n=16). By experimentally trimming the ventral plumage of a subset of female swallows (n=8), we also asked whether the repeatability of Tb is influenced by the capacity to dissipate body heat. We found that both female and male tree swallow Tb was repeatable at 21°C (R=0.89-92), but female Tb was less repeatable than male Tb across ambient temperature (Rfemale=0.10, Rmale=0.58), which may be due to differences in parental investment. Trimmed birds had on average lower Tb than control birds (by ∼0.5°C), but the repeatability of female Tb did not differ as a function of heat dissipation capacity. This suggests that trimmed individuals adjusted their Tb to account for the effects of heat loss on Tb. Our study provides a first critical step toward understanding whether Tb is responsive to natural selection, and for predicting how animal populations will respond to climatic warming.
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Affiliation(s)
- Simon Tapper
- Environmental and Life Sciences Graduate Department, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada, K9L 0G2
| | - Joseph J Nocera
- Faculty of Forestry and Environmental Management, University of New Brunswick, 28 Dineen Drive, Fredericton, NB, Canada, E3B 5A3
| | - Gary Burness
- Department of Biology, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada, K9L 0G2
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6
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Noakes MJ, McKechnie AE, Brigham RM. Interspecific variation in heat tolerance and evaporative cooling capacity among sympatric temperate-latitude bats. CAN J ZOOL 2021. [DOI: 10.1139/cjz-2020-0276] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that interspecific variation in chiropteran heat tolerance and evaporative cooling capacity is correlated with day-roost microclimates, using three vespertilionid bats that occur sympatrically during summer in Saskatchewan, Canada. We predicted that hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796); ∼22 g) would have higher heat tolerance than little brown bats (Myotis lucifugus (Le Conte, 1831); ∼7 g) and silver-haired bats (Lasionycteris noctivagans (Le Conte, 1831); ∼13 g), as the latter two species roost in tree crevices or cavities that are more thermally buffered than the foliage roosts of hoary bats. We measured core body temperature (Tb; passive integrated transponder tags), evaporative water loss, and resting metabolic rate (flow-through respirometry) while exposing individuals to a stepped profile of increasing air temperature (Ta) from ∼30 °C in ∼2 °C increments. Experiments were terminated when individuals became hyperthermic (Tb ≈ 42.5 °C), with maximum Ta (Ta,max) ranging from 42.0 to 49.7 °C. As predicted, hoary bats had the highest heat tolerance and evaporative cooling capacity, reaching Ta,max ∼2.4 and 1.2 °C higher than little brown and silver-haired bats, respectively. Our results are consistent with the hypothesis that heat tolerance of bats is correlated with roost microclimates, although interspecific variation in body mass and phylogeny may confound these conclusions.
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Affiliation(s)
- Matthew J. Noakes
- Department of Vertebrate Zoology and Ecology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, ul. Lwowska 1, 87-100 Toruń, Poland
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, Gauteng, 0002, South Africa
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
| | - Andrew E. McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, Gauteng, 0001, South Africa
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, Gauteng, 0002, South Africa
| | - R. Mark Brigham
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
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7
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Heat tolerance in desert rodents is correlated with microclimate at inter- and intraspecific levels. J Comp Physiol B 2021; 191:575-588. [PMID: 33638667 DOI: 10.1007/s00360-021-01352-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 12/14/2020] [Accepted: 01/23/2021] [Indexed: 01/21/2023]
Abstract
Physiological diversity in thermoregulatory traits has been extensively investigated in both endo- and ectothermic vertebrates, with many studies revealing that thermal physiology has evolved in response to selection arising from climate. The majority of studies have investigated how adaptative variation in thermal physiology is correlated with broad-scale climate, but the role of fine-scale microclimate remains less clear . We hypothesised that the heat tolerance limits and evaporative cooling capacity of desert rodents are correlated with microclimates within species-specific diurnal refugia. We tested predictions arising from this hypothesis by comparing thermoregulation in the heat among arboreal black-tailed tree rats (Thallomys nigricauda), Namaqua rock rats (Micaelamys namaquensis) and hairy-footed gerbils (Gerbillurus paeba). Species and populations that occupy hotter diurnal microsites tolerated air temperatures (Ta) ~ 2-4 ℃ higher compared to those species occupying cooler, more thermally buffered microsites. Inter- and intraspecific variation in heat tolerance was attributable to ~ 30% greater evaporative water loss and ~ 44 % lower resting metabolic rates at high Ta, respectively. Our results suggest that microclimates within rodent diurnal refugia are an important correlate of intra- and interspecific physiological variation and reiterate the need to incorporate fine-scale microclimatic conditions when investigating adaptative variation in thermal physiology.
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8
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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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9
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Ridley AR, Wiley EM, Bourne AR, Cunningham SJ, Nelson-Flower MJ. Understanding the potential impact of climate change on the behavior and demography of social species: The pied babbler (Turdoides bicolor) as a case study. ADVANCES IN THE STUDY OF BEHAVIOR 2021. [DOI: 10.1016/bs.asb.2021.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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10
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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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11
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Phenotypic flexibility in heat production and heat loss in response to thermal and hydric acclimation in the zebra finch, a small arid-zone passerine. J Comp Physiol B 2020; 191:225-239. [PMID: 33070274 PMCID: PMC7819915 DOI: 10.1007/s00360-020-01322-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 09/21/2020] [Accepted: 09/29/2020] [Indexed: 11/28/2022]
Abstract
To maintain constant body temperature (Tb) over a wide range of ambient temperatures (Ta) endothermic animals require large amounts of energy and water. In hot environments, the main threat to endothermic homeotherms is insufficient water to supply that necessary for thermoregulation. We investigated flexible adjustment of traits related to thermoregulation and water conservation during acclimation to hot conditions or restricted water availability, or both, in the zebra finch, Taeniopygia guttata a small arid-zone passerine. Using indirect calorimetry, we measured changes in whole animal metabolic rate (MR), evaporative heat loss (EHL) and Tb before and after acclimation to 23 or 40 °C, with different availability of water. Additionally, we quantified changes in partitioning of EHL into respiratory and cutaneous avenues in birds exposed to 25 and 40 °C. In response to heat and water restriction zebra finches decreased MR, which together with unchanged EHL resulted in increased efficiency of evaporative heat loss. This facilitated more precise Tb regulation in heat-acclimated birds. Acclimation temperature and water availability had no effect on the partitioning of EHL into cutaneous or respiratory avenues. At 25 °C, cutaneous EHL accounted for ~ 60% of total EHL, while at 40 °C, its contribution decreased to ~ 20%. Consistent among-individual differences in MR and EHL suggest that these traits, provided that they are heritable, may be a subject to natural selection. We conclude that phenotypic flexibility in metabolic heat production associated with acclimation to hot, water-scarce conditions is crucial in response to changing environmental conditions, especially in the face of current and predicted climate change.
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12
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Noakes MJ, McKechnie AE. Phenotypic flexibility of metabolic rate and evaporative water loss does not vary across a climatic gradient in an Afrotropical passerine bird. J Exp Biol 2020; 223:jeb220137. [PMID: 32165435 DOI: 10.1242/jeb.220137] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 03/02/2020] [Indexed: 12/30/2022]
Abstract
Small birds inhabiting northern temperate and boreal latitudes typically increase metabolic rates during cold winters or acclimation to low air temperatures (Taccl). Recent studies suggest considerable variation in patterns of seasonal metabolic acclimatization in birds from subtropical and tropical regions with milder winters, but there remains a dearth of acclimation studies investigating metabolic flexibility among lower-latitude birds. We used short-term thermal acclimation experiments to investigate phenotypic flexibility in basal metabolic rate (BMR), thermoneutral evaporative water loss (EWL) and summit metabolism (Msum) in three populations of white-browed sparrow-weavers (Plocepasser mahali) along a climatic and aridity gradient. We allocated individuals to one of three Taccl treatments (5, 20 and 35°C; n=11 per population per Taccl) for 28 days, and measured post-acclimation BMR, EWL and Msum using flow-through respirometry. Our data reveal the expected pattern of lower BMR and EWL (∼12% and 25% lower, respectively) in birds at Taccl=35°C compared with cooler Taccl treatments, as observed in previous acclimation studies on subtropical birds. We found no variation in the reaction norms of BMR and EWL among populations in response to acclimation, suggesting previously documented differences in seasonal BMR acclimatization are the result of phenotypic flexibility. In contrast to higher-latitude species, Msum did not significantly vary in response to thermal acclimation. These findings support the idea that factors other than enhancing cold tolerance may be driving patterns of metabolic variation in subtropical birds.
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Affiliation(s)
- Matthew J Noakes
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa
| | - Andrew E McKechnie
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa
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13
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Noakes MJ, McKechnie AE. Seasonal Metabolic Acclimatization Varies in Direction and Magnitude among Years in Two Arid-Zone Passerines. Physiol Biochem Zool 2020; 93:140-152. [DOI: 10.1086/707679] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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