1
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Freeman MT, Coulson B, Short JC, Ngcamphalala CA, Makola MO, McKechnie AE. Evolution of avian heat tolerance: The role of atmospheric humidity. Ecology 2024; 105:e4279. [PMID: 38501232 DOI: 10.1002/ecy.4279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 11/12/2023] [Accepted: 01/19/2024] [Indexed: 03/20/2024]
Abstract
The role of atmospheric humidity in the evolution of endotherms' thermoregulatory performance remains largely unexplored, despite the fact that elevated humidity is known to impede evaporative cooling capacity. Using a phylogenetically informed comparative framework, we tested the hypothesis that pronounced hyperthermia tolerance among birds occupying humid lowlands evolved to reduce the impact of humidity-impeded scope for evaporative heat dissipation by comparing heat tolerance limits (HTLs; maximum tolerable air temperature), maximum body temperatures (Tbmax), and associated thermoregulatory variables in humid (19.2 g H2O m-3) versus dry (1.1 g H2O m-3) air among 30 species from three climatically distinct sites (arid, mesic montane, and humid lowland). Humidity-associated decreases in evaporative water loss and resting metabolic rate were 27%-38% and 21%-27%, respectively, and did not differ significantly between sites. Decreases in HTLs were significantly larger among arid-zone (mean ± SD = 3.13 ± 1.12°C) and montane species (2.44 ± 1.0°C) compared to lowland species (1.23 ± 1.34°C), with more pronounced hyperthermia among lowland (Tbmax = 46.26 ± 0.48°C) and montane birds (Tbmax = 46.19 ± 0.92°C) compared to arid-zone species (45.23 ± 0.24°C). Our findings reveal a functional link between facultative hyperthermia and humidity-related constraints on evaporative cooling, providing novel insights into how hygric and thermal environments interact to constrain avian performance during hot weather. Moreover, the macrophysiological patterns we report provide further support for the concept of a continuum from thermal specialization to thermal generalization among endotherms, with adaptive variation in body temperature correlated with prevailing climatic conditions.
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Affiliation(s)
- Marc 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
| | - Bianca Coulson
- 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
| | - James C Short
- 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
| | - Celiwe A Ngcamphalala
- Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa
| | - Mathome O Makola
- 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
| | - Andrew 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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2
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Pollock HS, Rutt CL, Cooper WJ, Brawn JD, Cheviron ZA, Luther DA. Equivocal support for the climate variability hypothesis within a Neotropical bird assemblage. Ecology 2024; 105:e4206. [PMID: 37950619 DOI: 10.1002/ecy.4206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 07/03/2023] [Accepted: 10/05/2023] [Indexed: 11/13/2023]
Abstract
The climate variability hypothesis posits that an organism's exposure to temperature variability determines the breadth of its thermal tolerance and has become an important framework for understanding variation in species' susceptibilities to climate change. For example, ectotherms from more thermally stable environments tend to have narrower thermal tolerances and greater sensitivity to projected climate warming. Among endotherms, however, the relationship between climate variability and thermal physiology is less clear, particularly with regard to microclimate variation-small-scale differences within or between habitats. To address this gap, we explored associations between two sources of temperature variation (habitat type and vertical forest stratum) and (1) thermal physiological traits and (2) temperature sensitivity metrics within a diverse assemblage of Neotropical birds (n = 89 species). We used long-term temperature data to establish that daily temperature regimes in open habitats and forest canopy were both hotter and more variable than those in the forest interior and forest understory, respectively. Despite these differences in temperature regime, however, we found little evidence that species' thermal physiological traits or temperature sensitivity varied in association with either habitat type or vertical stratum. Our findings provide two novel and important insights. First, and in contrast to the supporting empirical evidence from ectotherms, the thermal physiology of birds at our study site appears to be largely decoupled from local temperature variation, providing equivocal support for the climate variability hypothesis in endotherms. Second, we found no evidence that the thermal physiology of understory forest birds differed from that of canopy or open-habitat species-an oft-invoked, yet previously untested, mechanism for why these species are so vulnerable to environmental change.
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Affiliation(s)
- Henry S Pollock
- Department of Natural Resources and Environmental Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Cameron L Rutt
- Department of Biology, George Mason University, Fairfax, Virginia, USA
- American Bird Conservancy, The Plains, Virginia, USA
| | | | - Jeffrey D Brawn
- Department of Natural Resources and Environmental Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Zachary A Cheviron
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - David A Luther
- Department of Biology, George Mason University, Fairfax, Virginia, USA
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3
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Subasinghe K, Symonds MRE, Prober SM, Bonnet T, Williams KJ, Ware C, Gardner JL. Spatial variation in avian bill size is associated with temperature extremes in a major radiation of Australian passerines. Proc Biol Sci 2024; 291:20232480. [PMID: 38262606 PMCID: PMC10805599 DOI: 10.1098/rspb.2023.2480] [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: 11/10/2023] [Accepted: 12/13/2023] [Indexed: 01/25/2024] Open
Abstract
Morphology is integral to body temperature regulation. Recent advances in understanding of thermal physiology suggest a role of the avian bill in thermoregulation. To explore the adaptive significance of bill size for thermoregulation we characterized relationships between bill size and climate extremes. Most previous studies focused on climate means, ignoring frequencies of extremes, and do not reflect thermoregulatory costs experienced over shorter time scales. Using 79 species (9847 museum specimens), we explore how bill size variation is associated with temperature extremes in a large and diverse radiation of Australasian birds, Meliphagides, testing a series of predictions. Overall, across the continent, bill size variation was associated with both climate extremes and means and was most strongly associated with winter temperatures; associations at the level of climate zones differed from continent-wide associations and were complex, yet consistent with physiology and a thermoregulatory role for avian bills. Responses to high summer temperatures were nonlinear suggesting they may be difficult to detect in large-scale continental analyses using previous methodologies. We provide strong evidence that climate extremes have contributed to the evolution of bill morphology in relation to thermoregulation and show the importance of including extremes to understand fine-scale trait variation across space.
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Affiliation(s)
- Kalya Subasinghe
- CSIRO Environment, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia
- Department of Zoology and Environmental Management, University of Kelaniya, Kelaniya 11600, Sri Lanka
| | - Matthew R. E. Symonds
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
| | - Suzanne M. Prober
- CSIRO Environment, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia
| | - Timothée Bonnet
- Centre d'Etudes Biologiques de Chizé UMR 7372 Université de la Rochelle-CNRS, 405 route de Prissé la Charrière 79360 Villiers en Bois, France
| | - Kristen J. Williams
- CSIRO Environment, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia
| | - Chris Ware
- CSIRO Environment, University of Tasmania, College Road, Sandy Bay Tas 7005, Australia
| | - Janet L. Gardner
- CSIRO Environment, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia
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4
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Zhao M, Kurtis SM, Humbel EA, Griffith EV, Liu T, Braun EL, Buchholz R, Kimball RT. Bare parts in the Galliformes: the evolution of a multifunctional structure. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231695. [PMID: 38204797 PMCID: PMC10776217 DOI: 10.1098/rsos.231695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 12/08/2023] [Indexed: 01/12/2024]
Abstract
A morphological trait can have multiple functions shaped by varying selective forces. Bare parts in birds, such as wattles, casques and combs, are known to function in both signalling and thermoregulation. Studies have demonstrated such structures are targets of sexual selection via female choice in several species of Galliformes (junglefowl, turkeys and grouse), though other studies have shown some role in thermoregulation (guineafowl). Here, we tested fundamental hypotheses regarding the evolution and maintenance of bare parts in Galliformes. Using a phylogeny that included nearly 90% of species in the order, we evaluated the role of both sexual and natural selection in shaping the function of bare parts across different clades. We found a combination of both environmental and putative sexually selected traits strongly predicted the variation of bare parts for both males and females across Galliformes. When the analysis is restricted to the largest family, Phasianidae (pheasants, junglefowl and allies), sexually selected traits were the primary predictors of bare parts. Our results suggest that bare parts are important for both thermoregulation and sexual signalling across Galliformes but are primarily under strong sexual selection within the Phasianidae.
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Affiliation(s)
- Min Zhao
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Sarah M. Kurtis
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Ellen A. Humbel
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Emily V. Griffith
- Department of Biodiversity, Earth, and Environmental Sciences, Drexel University, Philadelphia, PA 19104, USA
| | - Tong Liu
- College of Life Science, Jilin Agricultural University, Jilin, People's Republic of China
| | - Edward L. Braun
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Richard Buchholz
- Department of Biology, University of Mississippi, University, MS 38677, USA
| | - Rebecca T. Kimball
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
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5
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Grunst ML, Grunst AS, Grémillet D, Kato A, Gentès S, Fort J. Keystone seabird may face thermoregulatory challenges in a warming Arctic. Sci Rep 2023; 13:16733. [PMID: 37794049 PMCID: PMC10550970 DOI: 10.1038/s41598-023-43650-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
Climate change affects the Arctic more than any other region, resulting in evolving weather, vanishing sea ice and altered biochemical cycling, which may increase biotic exposure to chemical pollution. We tested thermoregulatory impacts of these changes on the most abundant Arctic seabird, the little auk (Alle alle). This small diving species uses sea ice-habitats for foraging on zooplankton and resting. We equipped eight little auks with 3D accelerometers to monitor behavior, and ingested temperature recorders to measure body temperature (Tb). We also recorded weather conditions, and collected blood to assess mercury (Hg) contamination. There were nonlinear relationships between time engaged in different behaviors and Tb. Tb increased on sea ice, following declines while foraging in polar waters, but changed little when birds were resting on water. Tb also increased when birds were flying, and decreased at the colony after being elevated during flight. Weather conditions, but not Hg contamination, also affected Tb. However, given our small sample size, further research regarding thermoregulatory effects of Hg is warranted. Results suggest that little auk Tb varies with behavior and weather conditions, and that loss of sea ice due to global warming may cause thermoregulatory and energic challenges during foraging trips at sea.
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Affiliation(s)
- Melissa L Grunst
- Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, 17000, La Rochelle, France.
| | - Andrea S Grunst
- Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, 17000, La Rochelle, France
| | - David Grémillet
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France
- Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch, South Africa
| | - Akiko Kato
- Centre d'Etudes Biologiques de Chizé, CEBC, UMR 7372 CNRS-La Rochelle Université, La Rochelle, France
| | - Sophie Gentès
- Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, 17000, La Rochelle, France
| | - Jérôme Fort
- Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, 17000, La Rochelle, France
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6
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Liu P, Lou Y, Yao J, Wang L, Møller AP, Sun Y. Variation in bill surface area is associated with local climatic factors across populations of the plain laughingthrush. Ecol Evol 2023; 13:e10535. [PMID: 37780534 PMCID: PMC10534077 DOI: 10.1002/ece3.10535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 05/31/2023] [Accepted: 09/01/2023] [Indexed: 10/03/2023] Open
Abstract
Recent studies have found that avian bill and tarsus morphology may have evolved in response to climatic conditions, and these organs play important roles in thermoregulation and water retention in extreme environments. Here, we examined whether bill surface area and tarsus length were associated with climatic conditions in the plain laughingthrush, Garrulax davidi, which mainly occurs in north China and occupies several climatic zones from east to west. We measured bill surface area and tarsus length in 321 adults from 11 populations, almost encompassing all habitat types of the species. We analyzed the relationships among these morphological traits and local climatic factors. Bill surface area was positively correlated with maximum temperature, indicating that bill surface area tended to be larger in hotter environments. Furthermore, we found a negative relationship among bill surface area and winter precipitation, indicating that bill surface area tended to be larger in arid areas. However, we did not find any relationships between tarsus length and climatic factors. These results suggest that local climates may shape the evolution of bill morphology divergence, and summer seems to be the critical season for thermoregulation in this temperate zone passerine.
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Affiliation(s)
- Pengfei Liu
- School of Life Science and TechnologyLongdong UniversityQingyangChina
| | - Yingqiang Lou
- Key Laboratory of Animal Ecology and Conservation BiologyInstitute of Zoology, Chinese Academy of ScienceBeijingChina
| | - Jingxiao Yao
- School of Life Science and TechnologyLongdong UniversityQingyangChina
| | - Linghui Wang
- School of Life Science and TechnologyLongdong UniversityQingyangChina
| | - Anders Pape Møller
- Ecologie Systématique Evolution, Université Paris–Sud, CNRS, AgroParisTechUniversité Paris–SaclayOrsay CedexFrance
| | - Yuehua Sun
- Key Laboratory of Animal Ecology and Conservation BiologyInstitute of Zoology, Chinese Academy of ScienceBeijingChina
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7
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Monge O, Maggini I, Schulze CH, Dullinger S, Fusani L. Physiologically vulnerable or resilient? Tropical birds, global warming, and redistributions. Ecol Evol 2023; 13:e9985. [PMID: 37082319 PMCID: PMC10111238 DOI: 10.1002/ece3.9985] [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: 07/14/2022] [Revised: 02/16/2023] [Accepted: 03/23/2023] [Indexed: 04/22/2023] Open
Abstract
Tropical species are considered to be more threatened by climate change than those of other world regions. This increased sensitivity to warming is thought to stem from the assumptions of low physiological capacity to withstand temperature fluctuations and already living near their limits of heat tolerance under current climatic conditions. For birds, despite thorough documentation of community-level rearrangements, such as biotic attrition and elevational shifts, there is no consistent evidence of direct physiological sensitivity to warming. In this review, we provide an integrative outlook into the physiological response of tropical birds to thermal variation and their capacity to cope with warming. In short, evidence from the literature suggests that the assumed physiological sensitivity to warming attributed to tropical biotas does not seem to be a fundamental characteristic of tropical birds. Tropical birds do possess the physiological capacities to deal with fluctuating temperatures, including high-elevation species, and are prepared to withstand elevated levels of heat, even those living in hot and arid environments. However, there are still many unaddressed points that hinder a more complete understanding of the response of tropical birds to warming, such as cooling capacities when exposed to combined gradients of heat and humidity, the response of montane species to heat, and thermoregulation under increased levels of microclimatic stress in disturbed ecosystems. Further research into how populations and species from different ecological contexts handle warming will increase our understanding of current and future community rearrangements in tropical birds.
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Affiliation(s)
- Otto Monge
- Vienna Doctoral School of Ecology and EvolutionUniversity of ViennaDjerassiplatz 11030ViennaAustria
| | - Ivan Maggini
- Konrad‐Lorenz Institute of EthologyUniversity of Veterinary MedicineSavoyenstrasse 1a1160ViennaAustria
| | - Christian H. Schulze
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 141030ViennaAustria
| | - Stefan Dullinger
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 141030ViennaAustria
| | - Leonida Fusani
- Konrad‐Lorenz Institute of EthologyUniversity of Veterinary MedicineSavoyenstrasse 1a1160ViennaAustria
- Department of Behavioural and Cognitive BiologyUniversity of ViennaAlthanstrasse 141090ViennaAustria
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8
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Freeman NE, Gustafson M, Hefley TJ, Boyle WA. Riding out the storm: depleted fat stores and elevated hematocrit in a small bodied endotherm exposed to severe weather. CONSERVATION PHYSIOLOGY 2023; 11:coad011. [PMID: 36950375 PMCID: PMC10026549 DOI: 10.1093/conphys/coad011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 02/15/2023] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
In the mid-continental grasslands of North America, climate change is increasing the intensity and frequency of extreme weather events. Increasingly severe storms and prolonged periods of elevated temperatures can impose challenges that adversely affect an individual's condition and, ultimately, survival. However, despite mounting evidence that extreme weather events, such as heavy rain storms, can impose short-term physiological challenges, we know little regarding the putative costs of such weather events. To determine the consequences of extreme weather for small endotherms, we tested predictions of the relationships between both severe precipitation events and wet bulb temperatures (an index that combines temperature and humidity) prior to capture with body composition and hematocrit of grasshopper sparrows (Ammodramus savannarum) caught during the breeding season at the Konza Prairie Biological Station, Kansas, USA, between 2014 and 2016. We measured each individual's fat mass, lean mass and total body water using quantitative magnetic resonance in addition to their hematocrit. Individuals exposed to storms in the 24 hours prior to capture had less fat reserves, more lean mass, more water and higher hematocrit than those exposed to moderate weather conditions. Furthermore, individuals stored more fat if they experienced high wet bulb temperatures in the week prior to capture. Overall, the analysis of these data indicate that extreme weather events take a physiological toll on small endotherms, and individuals may be forced to deplete fat stores and increase erythropoiesis to meet the physiological demands associated with surviving a storm. Elucidating the potential strategies used to cope with severe weather may enable us to understand the energetic consequences of increasingly severe weather in a changing world.
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Affiliation(s)
- N E Freeman
- Division of Biology, Kansas State University,
116 Ackert Hall, Manhattan, KS 66506, USA
- School of Natural Sciences, Bangor University,
Deiniol Road, Bangor, Gwynedd, LL57 2DG, UK
| | - M Gustafson
- Division of Biology, Kansas State University,
116 Ackert Hall, Manhattan, KS 66506, USA
- Department of Biological Sciences, Boise State University, 2133 Cesar Chavez Lane, Boise, ID 83725, USA
| | - T J Hefley
- Department of Statistics, Kansas State University, 101 Dickens Hall, Manhattan, KS 66506, USA
| | - W A Boyle
- Division of Biology, Kansas State University,
116 Ackert Hall, Manhattan, KS 66506, USA
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9
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Zuluaga JD, Danner RM. Acute stress and restricted diet reduce bill-mediated heat dissipation in the song sparrow (Melospiza melodia): implications for optimal thermoregulation. J Exp Biol 2023; 226:286688. [PMID: 36651227 DOI: 10.1242/jeb.245316] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 01/11/2023] [Indexed: 01/19/2023]
Abstract
We used thermal imaging to show that two environmental factors - acute stress and diet - influence thermoregulatory performance of a known thermal window, the avian bill. The bill plays important roles in thermoregulation and water balance. Given that heat loss through the bill is adjustable through vasoconstriction and vasodilation, and acute stress can cause vasoconstriction in peripheral body surfaces, we hypothesized that stress may influence the bill's role as a thermal window. We further hypothesized that diet influences heat dissipation from the bill, given that body condition influences the surface temperature of another body region (the eye region). We measured the surface temperature of the bills of song sparrows (Melospiza melodia) before, during and after handling by an observer at 37°C ambient temperature. We fed five birds a restricted diet intended to maintain body mass typical of wild birds, and we fed six birds an unrestricted diet for 5 months prior to experiments. Acute stress caused a decrease in the surface temperature of the bill, resulting in a 32.4% decrease in heat dissipation immediately following acute stress, before recovering over approximately 2.3 min. The initial reduction and subsequent recovery provide partial support for the hemoprotective and thermoprotective hypotheses, which predict a reduction or increase in peripheral blood flow, respectively. Birds with unrestricted diets had larger bills and dissipated more heat, indicating that diet and body condition influence bill-mediated heat dissipation and thermoregulation. These results indicate that stress-induced vascular changes and diet can influence mechanisms of heat loss and potentially inhibit optimal thermoregulation.
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Affiliation(s)
- Juan D Zuluaga
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403-5915, USA
| | - Raymond M Danner
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403-5915, USA.,Smithsonian Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, D.C. 20008, USA
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10
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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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11
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Cestari C, Melo C. Shorebirds adjust resting orientation in response to solar radiation and wind speed. AUSTRAL ECOL 2022. [DOI: 10.1111/aec.13170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- César Cestari
- Instituto de Biologia Universidade Federal de Uberlândia (UFU) Campus Umuarama – Bloco 2D. Avenida Pará, 1720 Uberlândia MG CEP 1720 Brazil
| | - Celine Melo
- Instituto de Biologia Universidade Federal de Uberlândia (UFU) Campus Umuarama – Bloco 2D. Avenida Pará, 1720 Uberlândia MG CEP 1720 Brazil
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12
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Withers PC, Cooper CE, Körtner G, Geiser F. Small Alpine Marsupials Regulate Evaporative Water Loss Suggesting a Thermoregulatory Rather than Water Conservation Role. Physiol Biochem Zool 2022; 95:212-228. [DOI: 10.1086/719735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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13
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Pacheco-Fuentes H, Cooper CE, Withers PC, Griffith SC. Re-evaluating model assumptions suggests that Australian birds are more tolerant of heat and aridity than predicted: a response to Conradie et al. (2020). CONSERVATION PHYSIOLOGY 2022; 10:coac010. [PMID: 35492422 PMCID: PMC9040279 DOI: 10.1093/conphys/coac010] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/05/2021] [Accepted: 02/06/2022] [Indexed: 06/14/2023]
Abstract
Conradie et al. (2020) recently modelled the vulnerability of Australian arid birds to a changing climate. While the approach used by Conradie et al. (2020) is valuable, we argue that key assumptions in their study are poorly supported and the risks of a changing climate to arid zone avifauna are consequently overstated.
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Affiliation(s)
- Hector Pacheco-Fuentes
- Corresponding author: Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia.
| | - Christine E Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, Western Australia 6102 Australia
| | - Philip C Withers
- School of Biological Sciences, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Simon C Griffith
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
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14
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Reher S, Rabarison H, Nowack J, Dausmann KH. Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.779381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Rapid environmental changes are challenging for endothermic species because they have direct and immediate impacts on their physiology by affecting microclimate and fundamental resource availability. Physiological flexibility can compensate for certain ecological perturbations, but our basic understanding of how species function in a given habitat and the extent of their adaptive scope is limited. Here we studied the effect of acute, experimental microclimate change on the thermal physiology of two populations of the widespread Malagasy bat, Macronycteris commersoni. Populations of this species are found roosting under contrasting conditions, i.e., in a constant hot and humid cave or below foliage unprotected from fluctuations in ambient conditions. We exposed free-ranging individuals of each population to the respective opposite condition and thus to novel microclimate within an ecologically realistic scope while measuring metabolic rate and skin temperature. Cave bats in forest setting had a limited capacity to maintain euthermia to the point that two individuals became hypothermic when ambient temperature dropped below their commonly experienced cave temperature. Forest bats on the other hand, had difficulties to dissipate heat in the humid cave set-up. The response to heat, however, was surprisingly uniform and all bats entered torpor combined with hyperthermia at temperatures exceeding their thermoneutral zone. Thus, while we observed potential for flexible compensation of heat through “hot” torpor, both populations showed patterns suggestive of limited potential to cope with acute microclimate changes deviating from their typically occupied roosts. Our study emphasizes that intraspecific variation among populations could be misleading when assessing species’ adaptive scopes, as variation may arise from genetic adaptation, developmental plasticity or phenotypic flexibility, all of which allow for compensatory responses at differing time scales. Disentangling these mechanisms and identifying the basis of variation is vital to make accurate predictions of species’ chances for persisting in ever rapidly changing habitats and climates.
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15
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Schoenjahn J, Pavey CR, Walter GH. Low activity levels are an adaptation to desert-living in the Grey Falcon, an endotherm that specializes in pursuing highly mobile prey. J Therm Biol 2022; 103:103108. [PMID: 35027196 DOI: 10.1016/j.jtherbio.2021.103108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 10/07/2021] [Accepted: 10/08/2021] [Indexed: 10/20/2022]
Abstract
Endothermic animals that live permanently in hot deserts must avoid harmful hyperthermia when their body temperature increases from heat gained through external and internal sources. This is true particularly for endotherms that are exclusively diurnal. We investigated the Grey Falcon (Falco hypoleucos), a predatory Australian endemic restricted to the hot arid/semi-arid zone. To understand how this species' entire population persists exclusively and permanently in this extreme environment we examined its activity levels and compared these with equivalent variables from the Peregrine Falcon (F. peregrinus), a cosmopolitan species that inhabits similar environments without being restricted to them. Further, we compared, across a selected group of Falco species, specific plumage characteristics (measured on museum specimens) that we anticipated would enhance the Grey Falcons' ability to cope with high heat loads. We found no morphological or physiological characteristics that would allow them to cope with heat better than other birds, but the chicks seem to have unusually high thermal tolerances. Grey Falcons do, however, possess a suite of unusual behavioural adaptations that, as we propose, enable them to cope with climatic extremes in arid environments. Specifically, throughout their lives Grey Falcons keep activity levels and thus physical exertion low. This behaviour contrasts strikingly with that of the Peregrine Falcon, which also actively hunts birds in flight. Keeping activity levels low is expected to minimize endogenous heat production and thus ease the Grey Falcon's thermoregulation during periods of high heat load. These birds may rely on low levels of relative humidity for efficient evaporative cooling, and this may explain their absolute restriction to hot arid/semi-arid zones.
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Affiliation(s)
- Jonny Schoenjahn
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
| | | | - Gimme H Walter
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
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16
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Coomes C, Derryberry E. High temperatures reduce song production and alter signal salience in songbirds. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.07.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Sabat P, Newsome SD, Pinochet S, Nespolo R, Sanchez-Hernandez JC, Maldonado K, Gerson AR, Sharp ZD, Whiteman JP. Triple Oxygen Isotope Measurements (Δ' 17O) of Body Water Reflect Water Intake, Metabolism, and δ 18O of Ingested Water in Passerines. Front Physiol 2021; 12:710026. [PMID: 34552501 PMCID: PMC8450417 DOI: 10.3389/fphys.2021.710026] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 08/09/2021] [Indexed: 12/02/2022] Open
Abstract
Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations (e.g., drought) that impact water availability. However, relatively few studies have examined variation in the sources of water animals use to maintain water balance, and even fewer have focused on the role of metabolic water. A key reason is methodological limitations. Here, we applied a new method that measures the triple oxygen isotopic composition of a single blood sample to estimate the contribution of metabolic water to the body water pool of three passerine species. This approach relies on Δ'17O, defined as the residual from the tight linear correlation that naturally exists between δ17O and δ18O values. Importantly, Δ'17O is relatively insensitive to key fractionation processes, such as Rayleigh distillation in the water cycle that have hindered previous isotope-based assessments of animal water balance. We evaluated the effects of changes in metabolic rate and water intake on Δ'17O values of captive rufous-collared sparrows (Zonotrichia capensis) and two invertivorous passerine species in the genus Cinclodes from the field. As predicted, colder acclimation temperatures induced increases in metabolic rate, decreases in water intake, and increases in the contribution of metabolic water to the body water pool of Z. capensis, causing a consistent change in Δ'17O. Measurement of Δ'17O also provides an estimate of the δ18O composition of ingested pre-formed (drinking/food) water. Estimated δ18O values of drinking/food water for captive Z. capensis were ~ −11‰, which is consistent with that of tap water in Santiago, Chile. In contrast, δ18O values of drinking/food water ingested by wild-caught Cinclodes were similar to that of seawater, which is consistent with their reliance on marine resources. Our results confirm the utility of this method for quantifying the relative contribution of metabolic versus pre-formed drinking/food water to the body water pool in birds.
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Affiliation(s)
- Pablo Sabat
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.,Center of Applied Ecology and Sustainability (CAPES), Santiago, Chile
| | - Seth D Newsome
- Department of Biology, University of New Mexico, Albuquerque, NM, United States
| | - Stephanie Pinochet
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Roberto Nespolo
- Center of Applied Ecology and Sustainability (CAPES), Santiago, Chile.,Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile.,Millennium Institute for Integrative Biology (iBio), Santiago, Chile
| | | | - Karin Maldonado
- Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ibáñez, Santiago, Chile
| | - Alexander R Gerson
- Biology Department, University of Massachusetts, Amherst, MA, United States
| | - Zachary D Sharp
- Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, United States
| | - John P Whiteman
- Department of Biological Sciences, Old Dominion University, Norfolk, VA, United States
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18
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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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19
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Gilson LN, Cooper CE, Withers PC, Gagnon MM. Two independent approaches to assessing the constancy of evaporative water loss for birds under varying evaporative conditions. Comp Biochem Physiol A Mol Integr Physiol 2021; 261:111041. [PMID: 34298193 DOI: 10.1016/j.cbpa.2021.111041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/28/2021] [Accepted: 07/15/2021] [Indexed: 11/17/2022]
Abstract
We examine here the effects on evaporative water loss, at and below thermoneutrality, of perturbing the evaporative environment for the red-capped parrot (Purpureicephalus spurius) by modifying the ambient relative humidity or the diffusive properties of the ambient environment using a helium‑oxygen mix (helox). We found that evaporative water loss did not change with relative humidity at an ambient temperature of 30 °C, but there was a negative relationship for evaporative water loss with relative humidity at 20 and 25 °C. The evaporative water loss per water vapour pressure deficit between the bird and its ambient environment was not constant with relative humidity, as would be expected for a physical effect (slope = 0); rather there was a significant positive relationship with relative humidity at ambient temperatures of 25 and 30 °C. Consequently, we conclude that the red-capped parrot can physiologically control its EWL over a range of relative humidities. For the first time for a bird species, we also confirmed EWL control using a second methodology to perturb the evaporative environment, and demonstrated that a more diffusive helox atmosphere has no effect on evaporative water loss of live birds, but evaporative water loss was higher for dead birds in helox compared to air. Our results for evaporative water loss and other physiological variables for red-capped parrots are consistent with the hypothesis that evaporative water loss is under physiological control.
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Affiliation(s)
- Lauren Noelle Gilson
- School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia.
| | - Christine Elizabeth Cooper
- School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia.
| | - Philip Carew Withers
- School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia; School of Biological Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009, Australia.
| | - Marthe Monique Gagnon
- School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia.
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20
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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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21
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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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22
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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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23
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Sharpe LL, Bayter C, Gardner JL. Too hot to handle? Behavioural plasticity during incubation in a small, Australian passerine. J Therm Biol 2021; 98:102921. [PMID: 34016345 DOI: 10.1016/j.jtherbio.2021.102921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/25/2021] [Accepted: 03/27/2021] [Indexed: 10/21/2022]
Abstract
Global warming and intensifying extreme heat events may affect avian reproductive success and costs, particularly in hot, arid environments. It is unclear how breeding birds alter their behaviour in response to rapid climate change, and whether such plasticity will be sufficient to offset rising temperatures. We examine whether a small, open-cup nesting, passerine - the Jacky Winter Microeca fascinans - in semi-arid Australia, exhibits similar levels of behavioural plasticity when incubating under high temperatures as low, and how heat impacts upon parental effort, body mass change and reproductive success. At high temperatures, female effort increased. Females doubled nest attendance between 28 °C and 40 °C, switching from incubating to shading eggs at approx. 30 °C. Egg-shading females panted to avoid hyperthermia. Panting increased with temperature and sun exposure. Male breeding effort was linked to temperature extremes. In cold conditions, males provisioned their mates heavily, buffering females from additional energetic costs, and males suffered a loss of body mass. In extreme heat, males helped shade eggs (although they never incubated). The likelihood of male egg-shading increased with temperature, but level of contribution was positively related to sun exposure. Hatching success declined with air temperatures >35 °C. Egg mortality reached 100 at air temperatures >42.5 °C. Parents continued to attend unviable eggs (for up to two weeks), suggesting egg-loss from heat exposure is a recent phenomenon. Although pairs exhibited considerable behavioural plasticity - including positioning nests to maximize afternoon shade - this was insufficient to counter extreme temperatures. In 2019, one hot day (45 °C) effectively terminated reproduction two months early, and was associated with a 50% decrease in reproductive success. The increasing frequency, intensity and earlier arrival of extreme heat events is likely to pose a major threat to avifauna populations in hot, arid environments, due to increased parental costs, reduced reproductive success and direct mortality.
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Affiliation(s)
- Lynda L Sharpe
- Division of Ecology and Evolution, Research School of Biology, Australian National University, RN Robertson Building 46 Sullivans Creek Rd.Acton 2601, Canberra, ACT, Australia.
| | - Camilo Bayter
- Division of Ecology and Evolution, Research School of Biology, Australian National University, RN Robertson Building 46 Sullivans Creek Rd.Acton 2601, Canberra, ACT, Australia
| | - Janet L Gardner
- Division of Ecology and Evolution, Research School of Biology, Australian National University, RN Robertson Building 46 Sullivans Creek Rd.Acton 2601, Canberra, ACT, Australia
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24
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Palmer BJ, Fulbright TE, Grahmann ED, HernÁNdez F, Hehman MW, Wester DB. Vegetation Structural Attributes Providing Thermal Refugia for Northern Bobwhites. J Wildl Manage 2021. [DOI: 10.1002/jwmg.22006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Brandon J. Palmer
- Caesar Kleberg Wildlife Research Institute, Texas A&M University—Kingsville Kingsville TX 78363 USA
| | - Timothy E. Fulbright
- Caesar Kleberg Wildlife Research Institute, Texas A&M University—Kingsville Kingsville TX 78363 USA
| | | | - Fidel HernÁNdez
- Caesar Kleberg Wildlife Research Institute, Texas A&M University—Kingsville Kingsville TX 78363 USA
| | | | - David B. Wester
- Caesar Kleberg Wildlife Research Institute, Texas A&M University—Kingsville Kingsville TX 78363 USA
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25
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Danner RM, Coomes CM, Derryberry EP. Simulated heat waves reduce cognitive and motor performance of an endotherm. Ecol Evol 2021; 11:2261-2272. [PMID: 33717453 PMCID: PMC7920763 DOI: 10.1002/ece3.7194] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 12/07/2020] [Accepted: 12/22/2020] [Indexed: 11/19/2022] Open
Abstract
Heat waves cause mass mortality of animals, including humans, across the globe annually, which has drawn new attention to how animals cope with high air temperatures. Recent field research has explored behavioral responses to high air temperatures, which can influence reproductive success and mortality.Less well studied are the effects of high air temperatures on cognition, which may underlie behavioral changes. Specifically, it is poorly known if cognitive declines occur at high temperatures, and if cognitive and motor components of behavior are similarly affected.We tested how well zebra finches (Taeniopygia guttata castanotis), a model for cognition research, performed two learned foraging tasks (color association and detour-reaching) at mild (22°C) and high (43 and 44°C) air temperatures that occur naturally in their range. We habituated birds to the trial conditions and temperatures on days preceding the test trials and at the trial temperature for 30 min immediately prior to each test trial. Trials lasted less than 10 min. At high air temperatures, zebra finches exhibited heat dissipation behaviors during most tasks, suggesting thermoregulatory challenge.Cognitive performance declined at high air temperatures in two of three measures: Color association was unaffected, but birds missed more food rewards, and did more unproductive behaviors. Motor performance declined at high temperatures on the color association task, including longer times to complete the task, move between food rewards, and process individual seeds. Performance declines varied among components of behavior and among individuals.We combined our behavioral data with existing climate data and predicted that in the austral summer of 2018-2019, zebra finches experienced air temperatures that caused cognitive and motor declines in our captive birds in 34% and 45% of their Australian range, respectively.This study provides novel experimental evidence that high air temperatures cause cognitive and motor performance decline in birds. Further, our results provide insights to how those declines might affect bird ecology and evolution. First, differences in declines among behavioral components may allow identification of behaviors that are most susceptible to decline in the wild. Second, variation in performance declines and heat dissipation behaviors among individuals suggests variability in heat tolerance, which could lead to differential fitness in the wild. Last, these results suggest that high air temperatures cause cognitive declines in the wild and that understanding cognition could help refine predictive models of population persistence.
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Affiliation(s)
- Raymond M. Danner
- Department of Biology and Marine BiologyUniversity of North Carolina WilmingtonWilmingtonNCUSA
| | - Casey M. Coomes
- Department of Ecology and Evolutionary BiologyTulane UniversityNew OrleansLAUSA
- Department of Ecology and Evolutionary BiologyUniversity of TennesseeKnoxvilleTNUSA
| | - Elizabeth P. Derryberry
- Department of Ecology and Evolutionary BiologyTulane UniversityNew OrleansLAUSA
- Department of Ecology and Evolutionary BiologyUniversity of TennesseeKnoxvilleTNUSA
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26
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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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27
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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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28
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Abstract
Temperature is an important environmental factor governing the ability of organisms to grow, survive and reproduce. Thermal performance curves (TPCs), with some caveats, are useful for charting the relationship between body temperature and some measure of performance in ectotherms, and provide a standardized set of characteristics for interspecific comparisons. Endotherms, however, have a more complicated relationship with environmental temperature, as endothermy leads to a decoupling of body temperature from external temperature through use of metabolic heat production, large changes in insulation and variable rates of evaporative heat loss. This has impeded our ability to model endothermic performance in relation to environmental temperature as well as to readily compare performance between species. In this Commentary, we compare the strengths and weaknesses of potential TPC analogues (including other useful proxies for linking performance to temperature) in endotherms and suggest several ways forward in the comparative ecophysiology of endotherms. Our goal is to provide a common language with which ecologists and physiologists can evaluate the effects of temperature on performance. Key directions for improving our understanding of endotherm thermoregulatory physiology include a comparative approach to the study of the level and precision of body temperature, measuring performance directly over a range of body temperatures and building comprehensive mechanistic models of endotherm responses to environmental temperatures. We believe the answer to the question posed in the title could be 'yes', but only if 'performance' is well defined and understood in relation to body temperature variation, and the costs and benefits of endothermy are specifically modelled.
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Affiliation(s)
| | - Katie E Marshall
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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29
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Benham PM, Bowie RCK. The influence of spatially heterogeneous anthropogenic change on bill size evolution in a coastal songbird. Evol Appl 2021; 14:607-624. [PMID: 33664798 PMCID: PMC7896719 DOI: 10.1111/eva.13144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/27/2020] [Accepted: 09/28/2020] [Indexed: 12/25/2022] Open
Abstract
Natural history collections provide an unparalleled resource for documenting population responses to past anthropogenic change. However, in many cases, traits measured on specimens may vary temporally in response to a number of different anthropogenic pressures or demographic processes. While teasing apart these different drivers is challenging, approaches that integrate analyses of spatial and temporal series of specimens can provide a robust framework for examining whether traits exhibit common responses to ecological variation in space and time. We applied this approach to analyze bill morphology variation in California Savannah Sparrows (Passerculus sandwichensis). We found that bill surface area increased in birds from higher salinity tidal marshes that are hotter and drier. Only the coastal subspecies, alaudinus, exhibited a significant increase in bill size through time. As with patterns of spatial variation, alaudinus populations occupying higher salinity tidal marshes that have become warmer and drier over the past century exhibited the greatest increases in bill surface area. We also found a significant negative correlation between bill surface area and total evaporative water loss (TEWL) and estimated that observed increases in bill size could result in a reduction of up to 16.2% in daily water losses. Together, these patterns of spatial and temporal variation in bill size were consistent with the hypothesis that larger bills are favored in freshwater-limited environments as a mechanism of dissipating heat, reducing reliance on evaporative cooling, and increasing water conservation. With museum collections increasingly being leveraged to understand past responses to global change, this work highlights the importance of considering the influence of many different axes of anthropogenic change and of integrating spatial and temporal analyses to better understand the influence of specific human impacts on population change over time.
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Affiliation(s)
- Phred M. Benham
- Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeley, BerkeleyCAUSA
| | - Rauri C. K. Bowie
- Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeley, BerkeleyCAUSA
- Department of Integrative BiologyUniversity of CaliforniaBerkeley, BerkeleyCAUSA
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30
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Oswald KN, Lee ATK, Smit B. Seasonal metabolic adjustments in an avian evolutionary relict restricted to mountain habitat. J Therm Biol 2020; 95:102815. [PMID: 33454043 DOI: 10.1016/j.jtherbio.2020.102815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 11/12/2020] [Accepted: 12/12/2020] [Indexed: 10/22/2022]
Abstract
For endotherms, maintaining body temperature during cold winters is energetically costly.Greater increase in winter maximum thermogenic capacity (Msum) has typically been correlated with improved cold tolerance. However, seasonal studies have shown equivocal direction change in basal metabolic rate (BMR) in winter, perhaps explained by latitude or phylogeny. We examined seasonal metabolic responses in the Cape rockjumper (Chaetops frenatus; "rockjumper"), a range-restricted mountain bird. We hypothesized that, given their mountain habitat preference, rockjumpers would be physiologically specialized for cooler air temperatures compared to other subtropical passerines. We measured body condition (using the ratio of Mb/tarsus), BMR, and Msum, in wild-living rockjumpers during winter and summer (n = 12 adults in winter -- 4 females, 8 males; n = 12 adults in summer -- 6 females, 6 males). We found birds had lesser BMR and thermal conductance, and greater Msum and body condition, in winter compared to summer. These changes may help rockjumpers conserve energy in winter while still allowing birds to produce more metabolic heat during the coldest air temperatures. When compared with existing data on avian seasonal metabolic adjustments, rockjumper BMR fit general patterns observed in passerines, but their Msum was low compared with other members of the oscine Passeriformes. These patterns may be explained by the narrow temperature range of their habitat not requiring cold-adjustment, or perhaps by their basal placement within passerine phylogeny. Further work on the physiological phenotypic plasticity in habitat specialists across different latitudinal zones and taxa is needed to better understand the relationship between metabolism, habitat, and phylogeny.
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Affiliation(s)
- Krista N Oswald
- Department of Zoology and Entomology, Rhodes University, Makhanda, 6139, South Africa; Department of Zoology, Nelson Mandela University, Port Elizabeth, 6031, South Africa.
| | - Alan T K Lee
- Fitzpatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Cape Town, 7701, South Africa; Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa
| | - Ben Smit
- Department of Zoology and Entomology, Rhodes University, Makhanda, 6139, South Africa; Department of Zoology, Nelson Mandela University, Port Elizabeth, 6031, South Africa
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31
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Cooper CE, Withers PC. Two lines of evidence for physiological control of insensible evaporative water loss by a tiny marsupial. J Exp Biol 2020; 223:jeb234450. [PMID: 33097571 DOI: 10.1242/jeb.234450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/16/2020] [Indexed: 11/20/2022]
Abstract
We present two independent lines of evidence that a tiny dasyurid marsupial, the ningaui (Ningaui spp.), has acute physiological control of its insensible evaporative water loss below and within thermoneutrality. Perturbation of the driving force for evaporation by varying relative humidity, and therefore the water vapour pressure deficit between the animal and the ambient air, does not have the expected physical effect on evaporative water loss. Exposure to a helox atmosphere also does not have the expected physical effect of increasing evaporative water loss for live ningauis (despite it having the expected effect of increasing heat loss for live ningauis), but increases evaporative water loss for dead ningauis. We discuss the relative advantages and disadvantages of both experimental approaches for demonstrating physiological control of insensible evaporative water loss. An appreciation of physiological control is important because insensible evaporative water loss contributes to both water and heat balance, is clearly under environmental selection pressure, and potentially impacts the distribution of endotherms and their response to environmental change.
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Affiliation(s)
- Christine Elizabeth Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6845, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009, Australia
| | - Philip Carew Withers
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6845, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009, Australia
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32
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Perez DM, Gardner JL, Medina I. Climate as an Evolutionary Driver of Nest Morphology in Birds: A Review. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.566018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Avian nests are critical for successful reproduction in birds. Nest microclimate can affect egg development, chick growth and fledgling success, suggesting that nest building behavior should be under strong selective pressure to nesting conditions. Given that the internal microclimate of the nest is critical for avian fitness, it is expected that nest morphology is shaped by the local environment. Here we review the relationship between nest morphology and climate across species’ distributions. We collate growing evidence that supports a link between environmental conditions and particular nest traits, within species and across species. We discuss the degree to which phenotypic plasticity in nesting behavior can contribute to observed variation in nest traits, the role of phylogenetic history in determining nest morphology, and which nest traits are likely to be influenced by climatic conditions. Finally, we identify gaps in our understanding of the evolution of nest morphology and suggest topics for future research. Overall, we argue that nests are part of the extended phenotype of a bird, they play a crucial role in their reproductive success, and may be an important factor in determining which species will be able to persist in the face of ongoing climate change.
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33
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Rozen-Rechels D, Valls-Fox H, Mabika CT, Chamaillé-Jammes S. Temperature as a constraint on the timing and duration of African elephant foraging trips. J Mammal 2020. [DOI: 10.1093/jmammal/gyaa129] [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
Abstract
In arid and semiarid environments, water is a key resource that is limited in availability. During the dry season, perennial water sources such as water pans often are far apart and shape the daily movement routines of large herbivores. In hot environments, endotherms face a lethal risk of overheating that can be buffered by evaporative cooling. Behavioral adjustments are an alternative way to reduce thermal constraints on the organism. The trade-off between foraging and reaching water pans has been studied widely in arid environments; however, few studies have looked into how ambient temperature shapes individual trips between two visits to water. In this study, we tracked during the dry season the movement of eight GPS-collared African elephants (Loxodonta africana) cows from different herds in Hwange National Park, Zimbabwe. This species, the largest extant terrestrial animal, is particularly sensitive to heat due to its body size and the absence of sweat glands. We show that most foraging trips depart from water at nightfall, lowering the average temperature experienced during walking. This pattern is conserved across isolated elephant populations in African savannas. We also observed that higher temperatures at the beginning of the trip lead to shorter trips. We conclude that elephants adjust the timing of foraging trips to reduce the thermal constraints, arguing that further considerations of the thermal landscape of endotherms are important to understand their ecology.
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Affiliation(s)
- David Rozen-Rechels
- Sorbonne Université, CNRS, IRD, INRA, Institut d’écologie et des sciences de l’environnement (IEES), Paris, France
| | - Hugo Valls-Fox
- SELMET, Univ de Montpellier, CIRAD, INRA, Montpellier Sup. Agro, Montpellier, France
| | - Cheryl Tinashe Mabika
- Scientific Services, Zimbabwe Parks and Wildlife Management Authority, Hwange National Park, Zimbabwe
| | - Simon Chamaillé-Jammes
- CEFE, Univ de Montpellier, CNRS, EPHE, IRD, Unive Paul Valéry Montpellier 3, Montpellier, France
- Mammal Research Institute, Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield, Pretoria, South Africa
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34
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Lee VK, David JM, Huerkamp MJ. Micro- and Macroenvironmental Conditions and Stability of Terrestrial Models. ILAR J 2020; 60:120-140. [PMID: 33094820 DOI: 10.1093/ilar/ilaa013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 04/28/2020] [Accepted: 05/20/2020] [Indexed: 01/15/2023] Open
Abstract
Environmental variables can have profound effects on the biological responses of research animals and the outcomes of experiments dependent on them. Some of these influences are both predictable and unpredictable in effect, many are challenging to standardize, and all are influenced by the planning and conduct of experiments and the design and operation of the vivarium. Others are not yet known. Within the immediate environment where the research animal resides, in the vivarium and in transit, the most notable of these factors are ambient temperature, relative humidity, gaseous pollutant by-products of animal metabolism and physiology, dust and particulates, barometric pressure, electromagnetic fields, and illumination. Ambient temperatures in the animal housing environment, in particular those experienced by rodents below the thermoneutral zone, may introduce degrees of stress and thermoregulatory compensative responses that may complicate or invalidate study measurements across a broad array of disciplines. Other factors may have more subtle and specific effects. It is incumbent on scientists designing and executing experiments and staff responsible for animal husbandry to be aware of, understand, measure, systematically record, control, and account for the impact of these factors on sensitive animal model systems to ensure the quality and reproducibility of scientific studies.
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Affiliation(s)
- Vanessa K Lee
- Department of Pathology and Laboratory Medicine and Division of Animal Resources, School of Medicine, Emory University, Atlanta, Georgia
| | - John M David
- Translational Medicine Department, Vertex Pharmaceuticals, Boston, Massachusetts
| | - Michael J Huerkamp
- Department of Pathology and Laboratory Medicine and Division of Animal Resources, School of Medicine, Emory University, Atlanta, Georgia
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35
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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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36
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Pollock HS, Brawn JD, Cheviron ZA. Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13693] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Henry S. Pollock
- Department of Natural Resources and Environmental Sciences University of Illinois at Urbana‐Champaign Champaign IL USA
| | - Jeffrey D. Brawn
- Department of Natural Resources and Environmental Sciences University of Illinois at Urbana‐Champaign Champaign IL USA
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37
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Cooper CE, Withers PC, Körtner G, Geiser F. Does control of insensible evaporative water loss by two species of mesic parrot have a thermoregulatory role? J Exp Biol 2020; 223:jeb229930. [PMID: 32747451 DOI: 10.1242/jeb.229930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/29/2020] [Indexed: 12/20/2022]
Abstract
Insensible evaporative water loss (EWL) at or below thermoneutrality is generally assumed to be a passive physical process. However, some arid zone mammals and a single arid zone bird can control their insensible water loss, so we tested the hypothesis that the same is the case for two parrot species from a mesic habitat. We investigated red-rumped parrots (Psephotus haematonotus) and eastern rosellas (Platycercus eximius), measuring their EWL, and other physiological variables, at a range of relative humidities at ambient temperatures of 20 and 30°C (below and at thermoneutrality). We found that, despite a decrease in EWL with increasing relative humidity, rates of EWL were not fully accounted for by the water vapour deficit between the animal and its environment, indicating that the insensible EWL of both parrots was controlled. It is unlikely that this deviation from physical expectations was regulation with a primary role for water conservation because our mesic-habitat parrots had equivalent regulatory ability as the arid habitat budgerigar (Melopsittacus undulatus). This, together with our observations of body temperature and metabolic rate, instead support the hypothesis that acute physiological control of insensible water loss serves a thermoregulatory purpose for endotherms. Modification of both cutaneous and respiratory avenues of evaporation may be involved, possibly via modification of expired air temperature and humidity, and surface resistance.
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Affiliation(s)
- Christine Elizabeth Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6102, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009, Australia
- Centre for Behavioural and Physiology Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Philip Carew Withers
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6102, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009, Australia
- Centre for Behavioural and Physiology Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Gerhard Körtner
- Centre for Behavioural and Physiology Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiology Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
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38
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Ruth JM, Talbot WA, Smith EK. Behavioral Response to High Temperatures in a Desert Grassland Bird: Use of Shrubs as Thermal Refugia. WEST N AM NATURALIST 2020. [DOI: 10.3398/064.080.0215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Janet M. Ruth
- U.S. Geological Survey, Fort Collins Science Center, New Mexico Landscapes Field Station, Albuquerque, NM 87131
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39
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Tapper S, Nocera JJ, Burness G. Heat dissipation capacity influences reproductive performance in an aerial insectivore. J Exp Biol 2020; 223:jeb222232. [PMID: 32321750 DOI: 10.1242/jeb.222232] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/08/2020] [Indexed: 12/26/2022]
Abstract
Climatic warming is predicted to increase the frequency of extreme weather events, which may reduce an individual's capacity for sustained activity because of thermal limits. We tested whether the risk of overheating may limit parental provisioning of an aerial insectivorous bird in population decline. For many seasonally breeding birds, parents are thought to operate close to an energetic ceiling during the 2-3 week chick-rearing period. The factors determining the ceiling remain unknown, although it may be set by an individual's capacity to dissipate body heat (the heat dissipation limitation hypothesis). Over two breeding seasons we experimentally trimmed the ventral feathers of female tree swallows (Tachycineta bicolor) to provide a thermal window. We then monitored maternal and paternal provisioning rates, nestling growth rates and fledging success. We found the effect of our experimental treatment was context dependent. Females with an enhanced capacity to dissipate heat fed their nestlings at higher rates than controls when conditions were hot, but the reverse was true under cool conditions. Control females and their mates both reduced foraging under hot conditions. In contrast, male partners of trimmed females maintained a constant feeding rate across temperatures, suggesting attempts to match the feeding rate of their partners. On average, nestlings of trimmed females were heavier than controls, but did not have a higher probability of fledging. We suggest that removal of a thermal constraint allowed females to increase provisioning rates, but additionally provided nestlings with a thermal advantage via increased heat transfer during maternal brooding. Our data provide support for the heat dissipation limitation hypothesis and suggest that depending on temperature, heat dissipation capacity can influence reproductive success in aerial insectivores.
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Affiliation(s)
- Simon Tapper
- Environmental and Life Sciences Graduate Program, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada, K9L 0G2
| | - Joseph J Nocera
- University of New Brunswick, Forestry and Environmental Management, Fredericton, NB, Canada, E3B 5A3
| | - Gary Burness
- Department of Biology, Trent University, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada, K9L 0G2
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40
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Bat thermoregulation in the heat: Limits to evaporative cooling capacity in three southern African bats. J Therm Biol 2020; 89:102542. [PMID: 32364970 DOI: 10.1016/j.jtherbio.2020.102542] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 02/07/2020] [Accepted: 02/13/2020] [Indexed: 12/16/2022]
Abstract
High environmental temperatures pose significant physiological challenges related to energy and water balance for small endotherms. Although there is a growing literature on the effect of high temperatures on birds, comparable data are scarcer for bats. Those data that do exist suggest that roost microsite may predict tolerance of high air temperatures. To examine this possibility further, we quantified the upper limits to heat tolerance and evaporative cooling capacity in three southern African bat species inhabiting the same hot environment but using different roost types (crevice, foliage or cave). We used flow-through respirometry and compared heat tolerance limits (highest air temperature (Ta) tolerated before the onset of severe hyperthermia), body temperature (Tb), evaporative water loss, metabolic rate, and maximum cooling capacity (i.e., evaporative heat loss/metabolic heat production). Heat tolerance limits for the two bats roosting in more exposed sites, Taphozous mauritianus (foliage-roosting) and Eptesicus hottentotus (crevice-roosting), were Ta = ~44 °C and those individuals defended maximum Tb between 41 °C and 43 °C. The heat tolerance limit for the bat roosting in a more buffered site, Rousettus aegyptiacus (cave-roosting), was Ta = ~38 °C with a corresponding Tb of ~38 °C. These interspecific differences, together with a similar trend for higher evaporative cooling efficiency in species occupying warmer roost microsites, add further support to the notion that ecological factors like roost choice may have profound influences on physiological traits related to thermoregulation.
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41
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Thonis A, Ceballos RM, Tuen AA, Lovegrove BG, Levesque DL. Small Tropical Mammals Can Take the Heat: High Upper Limits of Thermoneutrality in a Bornean Treeshrew. Physiol Biochem Zool 2020; 93:199-209. [PMID: 32196407 DOI: 10.1086/708467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Tropical ectotherms are generally believed to be more vulnerable to global heating than temperate species. Currently, however, we have insufficient knowledge of the thermoregulatory physiology of equatorial tropical mammals, particularly of small diurnal mammals, to enable similar predictions. In this study, we measured the resting metabolic rates (via oxygen consumption) of wild-caught lesser treeshrews (Tupaia minor, order Scandentia) over a range of ambient temperatures. We predicted that, similar to other treeshrews, T. minor would exhibit more flexibility in body temperature regulation and a wider thermoneutral zone compared with other small mammals because these thermoregulatory traits provide both energy and water savings at high ambient temperatures. Basal metabolic rate was on average 1.03±0.10 mL O2 h-1 g-1, which is within the range predicted for a 65-g mammal. We calculated the lower critical temperature of the thermoneutral zone at 31.0°C (95% confidence interval: 29.3°-32.7°C), but using metabolic rates alone, we could not determine the upper critical temperature at ambient temperatures as high as 36°C. The thermoregulatory characteristics of lesser treeshrews provide a means of saving energy and water at temperatures well in excess of their current environmental temperatures. Our research highlights the knowledge gaps in our understanding of the energetics of mammals living in high-temperature environments, specifically in the equatorial tropics, and questions the purported lack of variance in the upper critical temperatures of the thermoneutral zone in mammals, emphasizing the importance of further research in the tropics.
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McKechnie AE, Wolf BO. The Physiology of Heat Tolerance in Small Endotherms. Physiology (Bethesda) 2020; 34:302-313. [PMID: 31389778 DOI: 10.1152/physiol.00011.2019] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Understanding the heat tolerances of small mammals and birds has taken on new urgency with the advent of climate change. Here, we review heat tolerance limits, pathways of evaporative heat dissipation that permit the defense of body temperature during heat exposure, and mechanisms operating at tissue, cellular, and molecular levels.
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Affiliation(s)
- Andrew E McKechnie
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria, South Africa.,DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, South Africa
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, Albuquerque, New Mexico
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Boyce AJ, Mouton JC, Lloyd P, Wolf BO, Martin TE. Metabolic rate is negatively linked to adult survival but does not explain latitudinal differences in songbirds. Ecol Lett 2020; 23:642-652. [PMID: 31990148 DOI: 10.1111/ele.13464] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 01/02/2020] [Indexed: 01/11/2023]
Abstract
Survival rates vary dramatically among species and predictably across latitudes, but causes of this variation are unclear. The rate-of-living hypothesis posits that physiological damage from metabolism causes species with faster metabolic rates to exhibit lower survival rates. However, whether increased survival commonly observed in tropical and south temperate latitudes is associated with slower metabolic rate remains unclear. We compared metabolic rates and annual survival rates that we measured across 46 species, and from literature data across 147 species of birds in northern, southern and tropical latitudes. High metabolic rates were associated with lower survival but survival varied substantially among latitudinal regions independent of metabolism. The inability of metabolic rate to explain latitudinal variation in survival suggests (1) species may evolve physiological mechanisms that mitigate physiological damage from cellular metabolism and (2) extrinsic rather than intrinsic sources of mortality are the primary causes of latitudinal differences in survival.
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Affiliation(s)
- Andy J Boyce
- Montana Cooperative Wildlife Research Unit, Wildlife Biology Program, University of Montana, Missoula, MT, USA
| | - James C Mouton
- Montana Cooperative Wildlife Research Unit, Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - Penn Lloyd
- FitzPatrick Institute of African Ornithology, Department of Science and Technology/National Research Foundation Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa
| | - Blair O Wolf
- Department of Biology, University of New Mexico, Albuquerque, NM, USA
| | - Thomas E Martin
- U.S. Geological Survey, Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT, USA
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44
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Cook TR, Martin R, Roberts J, Häkkinen H, Botha P, Meyer C, Sparks E, Underhill LG, Ryan PG, Sherley RB. Parenting in a warming world: thermoregulatory responses to heat stress in an endangered seabird. CONSERVATION PHYSIOLOGY 2020; 8:coz109. [PMID: 31976077 PMCID: PMC6970236 DOI: 10.1093/conphys/coz109] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/19/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
The frequency of extreme weather events, including heat waves, is increasing with climate change. The thermoregulatory demands resulting from hotter weather can have catastrophic impacts on animals, leading to mass mortalities. Although less dramatic, animals also experience physiological costs below, but approaching, critical temperature thresholds. These costs may be particularly constraining during reproduction, when parents must balance thermoregulation against breeding activities. Such challenges should be acute among seabirds, which often nest in locations exposed to high solar radiation and predation risk. The globally endangered bank cormorant Phalacrocorax neglectus breeds in southern Africa in the winter, giving little scope for poleward or phenological shifts in the face of increasing temperatures. Physiological studies of endangered species sensitive to human disturbance, like the bank cormorant, are challenging, because individuals cannot be captured for experimental research. Using a novel, non-invasive, videographic approach, we investigated the thermoregulatory responses of this seabird across a range of environmental temperatures at three nesting colonies. The time birds spent gular fluttering, a behaviour enhancing evaporative heat loss, increased with temperature. Crouching or standing birds spent considerably less time gular fluttering than birds sitting on nests (ca 30% less at 22°C), showing that postural adjustments mediate exposure to heat stress and enhance water conservation. Crouching or standing, however, increases the vulnerability of eggs and chicks to suboptimal temperatures and/or expose nest contents to predation, suggesting that parents may trade-off thermoregulatory demands against offspring survival. We modelled thermoregulatory responses under future climate scenarios and found that nest-bound bank cormorants will gular flutter almost continuously for several hours a day by 2100. The associated increase in water loss may lead to dehydration, forcing birds to prioritize survival over breeding, a trade-off that would ultimately deteriorate the conservation status of this species.
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Affiliation(s)
- Timothée R Cook
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
- BLOOM Association, 62 Bis Avenue Parmentier, 75011 Paris, France
| | - Rowan Martin
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
| | - Jennifer Roberts
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
| | - Henry Häkkinen
- Centre for Ecology and Conservation, University of Exeter, Penryn, TR10 9FE UK
| | - Philna Botha
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
- Animal Demography Unit, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa
| | - Corlia Meyer
- Centre for Research on Evaluation, Science and Technology, Stellenbosch University, Stellenbosch 7600, South Africa
| | - Emilee Sparks
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
| | - Leslie G Underhill
- Animal Demography Unit, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa
| | - Peter G Ryan
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
| | - Richard B Sherley
- Centre for Ecology and Conservation, University of Exeter, Penryn, TR10 9FE UK
- Environment and Sustainability Institute, University of Exeter, Penryn TR10 9FE, UK
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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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46
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Cooper CE, Withers PC, Turner JM. Physiological implications of climate change for a critically endangered Australian marsupial. AUST J ZOOL 2020. [DOI: 10.1071/zo20067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Extreme weather events (e.g. heatwaves and droughts) can expose animals to environmental conditions outside of their zones of physiological tolerance, and even resistance, and impact long-term viability of populations and species. We examined the thermal and hygric physiology of the critically endangered western ringtail possum (Pseudocheirus occidentalis), a member of a family of marsupial folivores (Pseudocheiridae) that appear particularly vulnerable to environmental extremes. Basal metabolic rate and other standard physiological variables measured at an ambient temperature of 30°C conformed to values for other marsupials. At lower temperatures, body temperature decreased slightly, and metabolic rate increased significantly at 5°C. At higher temperatures, possums experienced mild hyperthermia and increased evaporative heat loss by licking rather than panting. Their point of relative water economy (–8.7°C) was more favourable than other pseudocheirid possums and the koala (Phascolarctos cinereus). We predict that western ringtail possums should tolerate low ambient temperatures well and be more physiologically tolerant of hot and dry conditions than common (Pseudocheirus peregrinus) and particularly green (Pseudochirops archeri) ringtail possums, and koalas. Our physiological data can be incorporated into mechanistic species distribution models to test our hypothesis that western ringtail possums should physiologically tolerate the climate of habitat further inland than their current distribution, and withstand moderate impacts of climate change in the south-west of Western Australia.
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47
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Gardner JL, Amano T, Peters A, Sutherland WJ, Mackey B, Joseph L, Stein J, Ikin K, Little R, Smith J, Symonds MRE. Australian songbird body size tracks climate variation: 82 species over 50 years. Proc Biol Sci 2019; 286:20192258. [PMID: 31771472 DOI: 10.1098/rspb.2019.2258] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The observed variation in the body size responses of endotherms to climate change may be explained by two hypotheses: the size increases with climate variability (the starvation resistance hypothesis) and the size shrinks as mean temperatures rise (the heat exchange hypothesis). Across 82 Australian passerine species over 50 years, shrinking was associated with annual mean temperature rise exceeding 0.012°C driven by rising winter temperatures for arid and temperate zone species. We propose the warming winters hypothesis to explain this response. However, where average summer temperatures exceeded 34°C, species experiencing annual rise over 0.0116°C tended towards increasing size. Results suggest a broad-scale physiological response to changing climate, with size trends probably reflecting the relative strength of selection pressures across a climatic regime. Critically, a given amount of temperature change will have varying effects on phenotype depending on the season in which it occurs, masking the generality of size patterns associated with temperature change. Rather than phenotypic plasticity, and assuming body size is heritable, results suggest selective loss or gain of particular phenotypes could generate evolutionary change but may be difficult to detect with current warming rates.
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Affiliation(s)
- Janet L Gardner
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.,School of Biological Sciences, Monash University, Clayton, Victoria 3168, Australia
| | - Tatsuya Amano
- School of Biological Sciences, University of Queensland, Brisbane, 4072 Queensland, Australia
| | - Anne Peters
- School of Biological Sciences, Monash University, Clayton, Victoria 3168, Australia
| | - William J Sutherland
- Department of Zoology, University of Cambridge, The David Attenborough Building, Pembroke Street, Cambridge CB2 3QZ, UK
| | - Brendan Mackey
- Griffith Climate Change Response Program, Griffith University, Gold Coast Campus, Queensland 4222, Australia
| | - Leo Joseph
- Australian National Wildlife Collection, CSIRO National Research Collections Australia, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia
| | - John Stein
- The Fenner School of Environment and Society, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - Karen Ikin
- The Fenner School of Environment and Society, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - Roellen Little
- School of Biological Sciences, Monash University, Clayton, Victoria 3168, Australia
| | - Jesse Smith
- School of Biological Sciences, Monash University, Clayton, Victoria 3168, Australia
| | - Matthew R E Symonds
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
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Rozen‐Rechels D, Dupoué A, Lourdais O, Chamaillé‐Jammes S, Meylan S, Clobert J, Le Galliard J. When water interacts with temperature: Ecological and evolutionary implications of thermo-hydroregulation in terrestrial ectotherms. Ecol Evol 2019; 9:10029-10043. [PMID: 31534711 PMCID: PMC6745666 DOI: 10.1002/ece3.5440] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 06/17/2019] [Indexed: 02/06/2023] Open
Abstract
The regulation of body temperature (thermoregulation) and of water balance (defined here as hydroregulation) are key processes underlying ecological and evolutionary responses to climate fluctuations in wild animal populations. In terrestrial (or semiterrestrial) ectotherms, thermoregulation and hydroregulation closely interact and combined temperature and water constraints should directly influence individual performances. Although comparative physiologists traditionally investigate jointly water and temperature regulation, the ecological and evolutionary implications of these coupled processes have so far mostly been studied independently. Here, we revisit the concept of thermo-hydroregulation to address the functional integration of body temperature and water balance regulation in terrestrial ectotherms. We demonstrate how thermo-hydroregulation provides a framework to investigate functional adaptations to joint environmental variation in temperature and water availability, and potential physiological and/or behavioral conflicts between thermoregulation and hydroregulation. We extend the classical cost-benefit model of thermoregulation in ectotherms to highlight the adaptive evolution of optimal thermo-hydroregulation strategies. Critical gaps in the parameterization of this conceptual optimality model and guidelines for future empirical research are discussed. We show that studies of thermo-hydroregulation refine our mechanistic understanding of physiological and behavioral plasticity, and of the fundamental niche of the species. This is illustrated with relevant and recent examples of space use and dispersal, resource-based trade-offs, and life-history tactics in insects, amphibians, and nonavian reptiles.
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Affiliation(s)
- David Rozen‐Rechels
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
| | - Andréaz Dupoué
- UMR 5321 CNRS-Université Toulouse III Paul SabatierStation d'Écologie Théorique et ExpérimentaleMoulisFrance
| | - Olivier Lourdais
- UMR 7372 CNRS-ULRCentre d'Études Biologiques de ChizéVilliers en BoisFrance
- School of Life SciencesArizona State UniversityTempeAZUSA
| | - Simon Chamaillé‐Jammes
- CNRS, Univ Montpellier, EPHE, IRD, Univ Paul Valéry Montpellier 3Centre d'Écologie Fonctionnelle et ÉvolutiveMontpellierFrance
| | - Sandrine Meylan
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
- Sorbonne UniversitéESPE de ParisParisFrance
| | - Jean Clobert
- UMR 5321 CNRS-Université Toulouse III Paul SabatierStation d'Écologie Théorique et ExpérimentaleMoulisFrance
| | - Jean‐François Le Galliard
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
- École normale supérieure, CNRS, UMS 3194Centre de recherche en écologie expérimentale et prédictive (CEREEP‐Ecotron IleDeFrance), Département de biologiePSL Research UniversitySaint‐Pierre‐lès‐NemoursFrance
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49
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High air temperatures induce temporal, spatial and social changes in the foraging behaviour of wild zebra finches. Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.01.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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50
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van Dyk M, Noakes MJ, McKechnie AE. Interactions between humidity and evaporative heat dissipation in a passerine bird. J Comp Physiol B 2019; 189:299-308. [DOI: 10.1007/s00360-019-01210-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 02/14/2019] [Accepted: 02/17/2019] [Indexed: 12/01/2022]
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