1
|
Porter CK, Cortes KM, Levy O, Riddell EA. The effects of humidity on thermoregulatory physiology of a small songbird. J Exp Biol 2024; 227:jeb247357. [PMID: 38853754 DOI: 10.1242/jeb.247357] [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: 01/17/2024] [Accepted: 05/31/2024] [Indexed: 06/11/2024]
Abstract
Scholander-Irving curves describe the relationship between ambient temperature and metabolic rate and are fundamental to understanding the energetic demands of homeothermy. However, Scholander-Irving curves are typically measured in dry air, which is not representative of the humidity many organisms experience in nature. Consequently, it is unclear (1) whether Scholander-Irving curves (especially below thermoneutrality) are altered by humidity, given the effects of humidity on thermal properties of air, and (2) whether physiological responses associated with Scholander-Irving curves in the lab reflect organismal performance in humid field conditions. We used laboratory experiments and biophysical models to test the effects of humidity on the thermoregulatory physiology of tree swallows (Tachycineta bicolor). We also tested whether physiological responses measured under lab conditions were correlated with field body temperatures and nestling provisioning rates. We found that humidity reduced rates of evaporative water loss but did not have large effects on body temperature or metabolic rate, suggesting that swallows can decouple evaporative cooling, body temperature and metabolic rate. Although the effect of humidity on metabolic rate in the lab was small, our biophysical models indicated that energetic costs of thermoregulation were ∼8% greater in simulations that used metabolic rates from birds in humid compared with dry conditions. Finally, we found mixed evidence that physiological responses measured in the lab under humid or dry conditions were associated with body temperature and nest provisioning rates in the field. Our results help clarify the effect of humidity on endotherm thermoregulation, which may help forecast organismal responses to environmental change.
Collapse
Affiliation(s)
- Cody K Porter
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Kevin M Cortes
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Ofir Levy
- Faculty of Life Sciences, School of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Eric A Riddell
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
- Department of Biology, University of North Carolina - Chapel Hill, Chapel Hill, NC 27599, USA
| |
Collapse
|
2
|
Ding C, Newbold T, Ameca EI. Assessing the global vulnerability of dryland birds to heatwaves. GLOBAL CHANGE BIOLOGY 2024; 30:e17136. [PMID: 38273501 DOI: 10.1111/gcb.17136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 12/11/2023] [Accepted: 12/19/2023] [Indexed: 01/27/2024]
Abstract
As global average surface temperature increases, extreme climatic events such as heatwaves are becoming more frequent and intense, which can drive biodiversity responses such as rapid population declines and/or shifts in species distributions and even local extirpations. However, the impacts of extreme climatic events are largely ignored in conservation plans. Birds are known to be susceptible to heatwaves, especially in dryland ecosystems. Understanding which birds are most vulnerable to heatwaves, and where these birds occur, can offer a scientific basis for adaptive management and conservation. We assessed the relative vulnerability of 1196 dryland bird species to heatwaves using a trait-based approach. Among them, 888 bird species are estimated to be vulnerable to heatwaves (170 highly vulnerable, eight extremely vulnerable), of which ~91% are currently considered non-threatened by the IUCN, which suggests that many species will likely become newly threatened with intensifying climate change. We identified the top three hotspot areas of heatwave-vulnerable species in Australia (208 species), Southern Africa (125 species) and Eastern Africa (99 species). Populations of vulnerable species recorded in the Living Planet Database were found to be declining significantly faster than those of non-vulnerable species (p = .048) after heatwaves occurred. In contrast, no significant difference in population trends between vulnerable and non-vulnerable species was detected when no heatwave occurred (p = .34). This suggests that our vulnerability framework correctly identified vulnerable species and that heatwaves are already impacting the population trends of these species. Our findings will help prioritize heatwave-vulnerable birds in dryland ecosystems in risk mitigation and adaptation management as the frequency of heatwaves accelerates in the coming decades.
Collapse
Affiliation(s)
- Chenchen Ding
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, China
- Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Tim Newbold
- Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Eric I Ameca
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, China
- Climate Change Specialist Group, Species Survival Commission, International Union for Conservation of Nature, Gland, Switzerland
| |
Collapse
|
3
|
Navarrete L, Lübcker N, Alvarez F, Nespolo R, Sanchez-Hernandez JC, Maldonado K, Sharp ZD, Whiteman JP, Newsome SD, Sabat P. A multi-isotope approach reveals seasonal variation in the reliance on marine resources, production of metabolic water, and ingestion of seawater by two species of coastal passerine to maintain water balance. Front Ecol Evol 2023. [DOI: 10.3389/fevo.2023.1120271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (δ16O, δ17O, δ18O) and bulk tissue carbon (δ13C) and nitrogen (δ15N) isotopes of feathers and blood to estimate the proportional contribution of marine resources, seawater, and metabolic water used by two species of unique songbirds (genus Cinclodes) to maintain their water balance in a seasonal coastal environment. We also assessed the physiological adjustments that these birds use to maintain their water balance. In agreement with previous work on these species, δ13C and δ15N data show that the coastal resident and invertivore C. nigrofumosus consumes a diet rich in marine resources, while the diet of migratory C. oustaleti shifts seasonally between marine (winter) to freshwater aquatic resources (summer). Triple-oxygen isotope analysis (Δ17O) of blood plasma, basal metabolic rate (BMR), and total evaporative water loss (TEWL) revealed that ~25% of the body water pool of both species originated from metabolic water, while the rest originated from a mix of seawater and fresh water. Δ17O measurements suggest that the contribution of metabolic water tends to increase in summer in C. nigrofumosus, which is coupled with a significant increase in BMR and TEWL. The two species had similar BMR and TEWL during the austral winter when they occur sympatrically in coastal environments. We also found a positive and significant association between the use of marine resources as measured by δ13C and δ15N values and the estimated δ18O values of ingested (pre-formed) water in both species, which indicates that Cinclodes do not directly drink seawater but rather passively ingest when consuming marine invertebrates. Finally, results obtained from physiological parameters and the isotope-based estimates of marine (food and water) resource use are consistent, supporting the use of the triple-oxygen isotopes to quantify the contribution of water sources to the total water balance of free-ranging birds.
Collapse
|
4
|
Cabello-Vergel J, González-Medina E, Parejo M, Abad-Gómez JM, Playà-Montmany N, Patón D, Sánchez-Guzmán JM, Masero JA, Gutiérrez JS, Villegas A. Heat tolerance limits of Mediterranean songbirds and their current and future vulnerabilities to temperature extremes. J Exp Biol 2022; 225:285906. [PMID: 36408945 PMCID: PMC9789400 DOI: 10.1242/jeb.244848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 11/09/2022] [Indexed: 11/22/2022]
Abstract
Songbirds are one of the groups most vulnerable to extreme heat events. Although several recent studies have assessed their physiological responses to heat, most of them have focused solely on arid-zone species. We investigated thermoregulatory responses to heat in eight small-sized songbirds occurring in the Mediterranean Basin, where heatwaves are becoming more frequent and intense. Specifically, we determined their heat tolerance limits (HTLs) and evaporative cooling efficiency, and evaluated their current and future vulnerabilities to heat in southwestern Iberia, a Mediterranean climate warming hotspot. To do this, we exposed birds to an increasing profile of air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), evaporative cooling efficiency (the ratio between evaporative heat loss and metabolic heat production) and body temperature (Tb). HTL ranged between 40 and 46°C across species, and all species showed rapid increases in RMR, EWL and Tb in response to increasing Ta. However, only the crested lark (Galerida cristata) achieved an evaporative cooling efficiency greater than 1. The studied songbirds currently experience summer Ta maxima that surpass the upper critical temperatures of their thermoneutral zone and even their HTL. Our estimates indicate that five of the eight species will experience moderate risk of lethal dehydration by the end of the century. We argue that the limited heat tolerance and evaporative cooling efficiency of small-sized Mediterranean songbirds make them particularly vulnerable to heatwaves, which will be exacerbated under future climate change scenarios.
Collapse
Affiliation(s)
- Julián Cabello-Vergel
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Author for correspondence ()
| | - Erick González-Medina
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Manuel Parejo
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - José M. Abad-Gómez
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Núria Playà-Montmany
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Daniel Patón
- Ecology Department, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Juan M. Sánchez-Guzmán
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - José A. Masero
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Jorge S. Gutiérrez
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| | - Auxiliadora Villegas
- Conservation Biology Research Group, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain,Ecology in the Anthropocene, Associated Unit CSIC-UEX, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
| |
Collapse
|
5
|
Mota FMM, Heming NM, Morante-Filho JC, Talora DC. Amount of bird suitable areas under climate change is modulated by morphological, ecological and geographical traits. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.987204] [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
Biodiversity is already experiencing the effects of climate change through range expansion, retraction, or relocation, potentializing negative effects of other threats. Future projections already indicate richness reduction and composition modifications of bird communities due to global warming, which may disrupt the provision of key ecological services to ecosystem maintenance. Here, we systematically review the effect of morphological, ecological, and geographical traits on the amount of future suitable area for birds worldwide. Specifically, we tested whether body mass, diet, habitat type, movement pattern, range size, and biogeographic realm affect birds' suitable area. Our search returned 75 studies that modeled the effects of climate change on 1,991 bird species. Our analyses included 1,661 species belonging to 128 families, representing 83% of the total, for which we were able to acquire all the six traits. The proportion of birds' suitable area was affected by range size, body mass, habitat type, and biogeographic realm, while diet and movement pattern showed lower relative importance and were not included in our final model. Contrary to expectations, the proportion of birds' suitable area was negatively related to range size, which may be explained by higher climatic stability predicted in certain areas that harbor species with restricted distribution. In contrast, we observed that birds presenting higher body mass will show an increase of the proportion of suitable area in the future. This is expected due to the high exposure of smaller birds to environmental changes and their difficulty to keep thermoregulation. Our results also indicated a low proportion of suitable area to forest-dependent birds, which is in accordance with their higher vulnerability due to specific requirements for reproduction and feeding. Finally, the proportion of suitable area was low for birds from Oceania, which is expected since the region encompasses small islands isolated from continents, preventing their species from reaching new suitable areas. Our study highlights that different traits should be considered when assessing extinction risk of species based on future projections, helping to improve bird conservation, especially the most vulnerable to climate change.
Collapse
|
6
|
Nelson SD, Keever AC, Wightman PH, Bakner NW, Argabright CM, Byrne ME, Collier BA, Chamberlain MJ, Cohen BS. Fine‐scale resource selection and behavioral tradeoffs of eastern wild turkey broods. J Wildl Manage 2022. [DOI: 10.1002/jwmg.22222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Stefan D. Nelson
- College of Arts and Science Tennessee Technological University Cookeville TN 38505 USA
| | - Allison C. Keever
- College of Arts and Science Tennessee Technological University Cookeville TN 38505 USA
| | - Patrick H. Wightman
- Warnell School of Forestry and Natural Resources University of Georgia Athens GA 30602 USA
| | - Nicholas W. Bakner
- Warnell School of Forestry and Natural Resources University of Georgia Athens GA 30602 USA
| | - Chad M. Argabright
- School of Renewable Natural Resources Louisiana State University Baton Rouge LA 70803 USA
| | - Michael E. Byrne
- School of Natural Resources University of Missouri Columbia MO 65211 USA
| | - Bret A. Collier
- School of Renewable Natural Resources Louisiana State University Baton Rouge LA 70803 USA
| | - Michael J. Chamberlain
- Warnell School of Forestry and Natural Resources University of Georgia Athens GA 30602 USA
| | - Bradley S. Cohen
- College of Arts and Science Tennessee Technological University Cookeville TN 38505 USA
| |
Collapse
|
7
|
Pessato A, McKechnie AE, Mariette MM. A prenatal acoustic signal of heat affects thermoregulation capacities at adulthood in an arid-adapted bird. Sci Rep 2022; 12:5842. [PMID: 35393484 PMCID: PMC8991222 DOI: 10.1038/s41598-022-09761-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/01/2022] [Indexed: 11/16/2022] Open
Abstract
Understanding animal physiological adaptations for tolerating heat, and the causes of inter-individual variation, is key for predicting climate change impacts on biodiversity. Recently, a novel mechanism for transgenerational heat adaptation was identified in a desert-adapted bird, where parents acoustically signal hot conditions to embryos. Prenatal exposure to "heat-calls" adaptively alters zebra finch development and their thermal preferences in adulthood, suggesting a long-term shift towards a heat-adapted phenotype. However, whether such acoustic experience improves long-term thermoregulatory capacities is unknown. We measured metabolic rate (MR), evaporative water loss (EWL) and body temperature in adults exposed to a stepped profile of progressively higher air temperatures (Ta) between 27 and 44 °C. Remarkably, prenatal acoustic experience affected heat tolerance at adulthood, with heat-call exposed individuals more likely to reach the highest Ta in morning trials. This was despite MR and EWL reaching higher levels at the highest Ta in heat-call individuals, partly driven by a stronger metabolic effect of moderate activity. At lower Ta, however, heat-call exposed individuals had greater relative water economy, as expected. They also better recovered mass lost during morning trials. We therefore provide the first evidence that prenatal acoustic signals have long-term consequences for heat tolerance and physiological adaptation to heat.
Collapse
Affiliation(s)
- Anaïs Pessato
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, Geelong, 3216, Australia.
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0001, South Africa
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, Geelong, 3216, Australia.
- Doñana Biological Station EBD-CSIC, 41092, Seville, Spain.
| |
Collapse
|
8
|
Czenze ZJ, Freeman MT, Kemp R, van Jaarsveld B, Wolf BO, McKechnie AE. Efficient Evaporative Cooling and Pronounced Heat Tolerance in an Eagle-Owl, a Thick-Knee and a Sandgrouse. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.799302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Avian evaporative cooling and the maintenance of body temperature (Tb) below lethal limits during heat exposure has received more attention in small species compared to larger-bodied taxa. Here, we examined thermoregulation at air temperatures (Tair) approaching and exceeding normothermic Tb in three larger birds that use gular flutter, thought to provide the basis for pronounced evaporative cooling capacity and heat tolerance. We quantified Tb, evaporative water loss (EWL) and resting metabolic rate (RMR) in the ∼170-g Namaqua sandgrouse (Pterocles namaqua), ∼430-g spotted thick-knee (Burhinus capensis) and ∼670-g spotted eagle-owl (Bubo africanus), using flow-through respirometry and a stepped Tair profile with very low chamber humidities. All three species tolerated Tair of 56–60°C before the onset of severe hyperthermia, with maximum Tb of 43.2°C, 44.3°C, and 44.2°C in sandgrouse, thick-knees and eagle-owls, respectively. Evaporative scope (i.e., maximum EWL/minimum thermoneutral EWL) was 7.4 in sandgrouse, 12.9 in thick-knees and 7.8 in eagle-owls. The relationship between RMR and Tair varied substantially among species: whereas thick-knees and eagle-owls showed clear upper critical limits of thermoneutrality above which RMR increased rapidly and linearly, sandgrouse did not. Maximum evaporative heat loss/metabolic heat production ranged from 2.8 (eagle-owls) to 5.5 (sandgrouse), the latter the highest avian value yet reported. Our data reveal some larger species with gular flutter possess pronounced evaporative cooling capacity and heat tolerance and, when taken together with published data, show thermoregulatory performance varies widely among species larger than 250 g. Our data for Namaqua sandgrouse reveal unexpectedly pronounced variation in the metabolic costs of evaporative cooling within the genus Pterocles.
Collapse
|
9
|
Playà‐Montmany N, González‐Medina E, Cabello‐Vergel J, Parejo M, Abad‐Gómez JM, Sánchez‐Guzmán JM, Villegas A, Masero JA. The thermoregulatory role of relative bill and leg surface areas in a Mediterranean population of Great tit ( Parus major). Ecol Evol 2021; 11:15936-15946. [PMID: 34824801 PMCID: PMC8601919 DOI: 10.1002/ece3.8263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 09/15/2021] [Accepted: 10/07/2021] [Indexed: 11/07/2022] Open
Abstract
There is growing evidence on the role of legs and bill as 'thermal windows' in birds coping with heat stress. However, there is a lack of empirical work examining the relationship between the relative bill and/or leg surface areas and key thermoregulatory traits such as the limits of the thermoneutral zone (TNZ) or the cooling efficiency at high temperatures. Here, we explored this relationship in a Mediterranean population of Great tit (Parus major) facing increasing thermal stress in its environment. The lower and upper critical limits of the TNZ were found to be 17.7 ± 1.6ºC and 34.5 ± 0.7°C, respectively, and the basal metabolic rate was 0.96 ± 0.12 ml O2 min-1 on average. The evaporative water loss (EWL) inflection point was established at 31.85 ± 0.27°C and was not significantly different from the value of the upper critical limit. No significant relationship was observed between the relative bill or tarsi size and TNZ critical limits, breadth, mass-independent VO2, or mass-independent EWL at any environmental temperature (from 10 to 40°C). However, Great tit males (but not females) with larger tarsi areas (a proxy of leg surface area) showed higher cooling efficiencies at 40°C. We found no support for the hypothesis that the bill surface area plays a significant role as a thermal window in Great tits, but the leg surface areas may play a role in males' physiological responses to high temperatures. On the one hand, we argue that the studied population occupies habitats with available microclimates and fresh water for drinking during summer, so active heat dissipation by EWL might be favored instead of dry heat loss through the bill surface. Conversely, male dominance behaviors could imply a greater dependence on cutaneous EWL through the upper leg surfaces as a consequence of higher exposure to harsh environmental conditions than faced by females.
Collapse
Affiliation(s)
- Núria Playà‐Montmany
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Erick González‐Medina
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Julián Cabello‐Vergel
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Manuel Parejo
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - José M. Abad‐Gómez
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Juan M. Sánchez‐Guzmán
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Auxiliadora Villegas
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - José A. Masero
- Conservation Biology Research GroupFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
- Ecology in the AnthropoceneAssociated Unit CSIC‐UEXFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Riddell EA, Iknayan KJ, Hargrove L, Tremor S, Patton JL, Ramirez R, Wolf BO, Beissinger SR. Exposure to climate change drives stability or collapse of desert mammal and bird communities. Science 2021; 371:633-636. [DOI: 10.1126/science.abd4605] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 01/05/2021] [Indexed: 12/15/2022]
Affiliation(s)
- E. A. Riddell
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50010, USA
| | - K. J. Iknayan
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA
- San Francisco Estuary Institute, Richmond, CA 94804, USA
| | - L. Hargrove
- Department of Birds and Mammals, San Diego Natural History Museum, San Diego, CA 92101, USA
| | - S. Tremor
- Department of Birds and Mammals, San Diego Natural History Museum, San Diego, CA 92101, USA
| | - J. L. Patton
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA
| | - R. Ramirez
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - B. O. Wolf
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - S. R. Beissinger
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA
| |
Collapse
|
14
|
O'Connor RS, Le Pogam A, Young KG, Robitaille F, Choy ES, Love OP, Elliott KH, Hargreaves AL, Berteaux D, Tam A, Vézina F. Limited heat tolerance in an Arctic passerine: Thermoregulatory implications for cold-specialized birds in a rapidly warming world. Ecol Evol 2021; 11:1609-1619. [PMID: 33613993 PMCID: PMC7882984 DOI: 10.1002/ece3.7141] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 12/28/2022] Open
Abstract
Arctic animals inhabit some of the coldest environments on the planet and have evolved physiological mechanisms for minimizing heat loss under extreme cold. However, the Arctic is warming faster than the global average and how well Arctic animals tolerate even moderately high air temperatures (T a) is unknown.Using flow-through respirometry, we investigated the heat tolerance and evaporative cooling capacity of snow buntings (Plectrophenax nivalis; ≈31 g, N = 42), a cold specialist, Arctic songbird. We exposed buntings to increasing T a and measured body temperature (T b), resting metabolic rate (RMR), rates of evaporative water loss (EWL), and evaporative cooling efficiency (the ratio of evaporative heat loss to metabolic heat production).Buntings had an average (±SD) T b of 41.3 ± 0.2°C at thermoneutral T a and increased T b to a maximum of 43.5 ± 0.3°C. Buntings started panting at T a of 33.2 ± 1.7°C, with rapid increases in EWL starting at T a = 34.6°C, meaning they experienced heat stress when air temperatures were well below their body temperature. Maximum rates of EWL were only 2.9× baseline rates at thermoneutral T a, a markedly lower increase than seen in more heat-tolerant arid-zone species (e.g., ≥4.7× baseline rates). Heat-stressed buntings also had low evaporative cooling efficiencies, with 95% of individuals unable to evaporatively dissipate an amount of heat equivalent to their own metabolic heat production.Our results suggest that buntings' well-developed cold tolerance may come at the cost of reduced heat tolerance. As the Arctic warms, and this and other species experience increased periods of heat stress, a limited capacity for evaporative cooling may force birds to increasingly rely on behavioral thermoregulation, such as minimizing activity, at the expense of diminished performance or reproductive investment.
Collapse
Affiliation(s)
- Ryan S. O'Connor
- Département de Biologie, Chimie et GéographieUniversité du Québec à RimouskiRimouskiQCCanada
- Groupe de recherche sur les environnements nordiques BORÉASRimouskiCanada
- Centre d'études nordiquesRimouskiCanada
- Centre de la science de la biodiversité du QuébecRimouskiCanada
| | - Audrey Le Pogam
- Département de Biologie, Chimie et GéographieUniversité du Québec à RimouskiRimouskiQCCanada
- Groupe de recherche sur les environnements nordiques BORÉASRimouskiCanada
- Centre d'études nordiquesRimouskiCanada
- Centre de la science de la biodiversité du QuébecRimouskiCanada
| | - Kevin G. Young
- Department of BiologyAdvanced Facility for Avian ResearchWestern UniversityLondonONCanada
| | - Francis Robitaille
- Département de Biologie, Chimie et GéographieUniversité du Québec à RimouskiRimouskiQCCanada
| | - Emily S. Choy
- Department of Natural Resource SciencesMcGill UniversityQCCanada
| | - Oliver P. Love
- Department of Integrative BiologyUniversity of WindsorWindsorONCanada
| | - Kyle H. Elliott
- Department of Natural Resource SciencesMcGill UniversityQCCanada
| | | | - Dominique Berteaux
- Département de Biologie, Chimie et GéographieUniversité du Québec à RimouskiRimouskiQCCanada
- Groupe de recherche sur les environnements nordiques BORÉASRimouskiCanada
- Centre d'études nordiquesRimouskiCanada
- Centre de la science de la biodiversité du QuébecRimouskiCanada
| | - Andrew Tam
- Department of National Defence, 8 Wing EnvironmentAstraONCanada
| | - François Vézina
- Département de Biologie, Chimie et GéographieUniversité du Québec à RimouskiRimouskiQCCanada
- Groupe de recherche sur les environnements nordiques BORÉASRimouskiCanada
- Centre d'études nordiquesRimouskiCanada
- Centre de la science de la biodiversité du QuébecRimouskiCanada
| |
Collapse
|
15
|
Szafrańska PA, Andreasson F, Nord A, Nilsson JÅ. Deep body and surface temperature responses to hot and cold environments in the zebra finch. J Therm Biol 2020; 94:102776. [PMID: 33292974 DOI: 10.1016/j.jtherbio.2020.102776] [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] [Received: 03/17/2020] [Revised: 10/26/2020] [Accepted: 10/29/2020] [Indexed: 10/23/2022]
Abstract
Global warming increasingly challenges thermoregulation in endothermic animals, particularly in hot and dry environments where low water availability and high temperature increase the risk of hyperthermia. In birds, un-feathered body parts such as the head and bill work as 'thermal windows', because heat flux is higher compared to more insulated body regions. We studied how such structures were used in different thermal environments, and if heat flux properties change with time in a given temperature. We acclimated zebra finches (Taeniopygia guttata) to two different ambient temperatures, 'cold' (5 °C) and 'hot' (35 °C), and measured the response in core body temperature using a thermometer, and head surface temperature using thermal imaging. Birds in the hot treatment had 10.3 °C higher head temperature than those in the cold treatment. Thermal acclimation also resulted in heat storage in the hot group: core body temperature was 1.1 °C higher in the 35 °C group compared to the 5 °C group. Hence, the thermal gradient from core to shell was 9.03 °C smaller in the hot treatment. Dry heat transfer rate from the head was significantly lower in the hot compared to the cold treatment after four weeks of thermal acclimation. This reflects constraints on changes to peripheral circulation and maximum body temperature. Heat dissipation capacity from the head region increased with acclimation time in the hot treatment, perhaps because angiogenesis was required to reach peak heat transfer rate. We have shown that zebra finches meet high environmental temperature by heat storage, which saves water and energy, and by peripheral vasodilation in the head, which facilitates dry heat loss. These responses will not exclude the need for evaporative cooling, but will lessen the amount of energy expend on body temperature reduction in hot environments.
Collapse
Affiliation(s)
- Paulina Anna Szafrańska
- Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland; Department of Biology, Lund University, Lund, Sweden.
| | | | - Andreas Nord
- Department of Biology, Lund University, Lund, Sweden.
| | | |
Collapse
|
16
|
Lowney AM, Bolopo D, Krochuk BA, Thomson RL. The Large Communal Nests of Sociable Weavers Provide Year-Round Insulated Refuge for Weavers and Pygmy Falcons. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.570006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
17
|
Pessato A, McKechnie AE, Buchanan KL, Mariette MM. Vocal panting: a novel thermoregulatory mechanism for enhancing heat tolerance in a desert-adapted bird. Sci Rep 2020; 10:18914. [PMID: 33144650 PMCID: PMC7609653 DOI: 10.1038/s41598-020-75909-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/15/2020] [Indexed: 01/06/2023] Open
Abstract
Animals thriving in hot deserts rely on extraordinary adaptations and thermoregulatory capacities to cope with heat. Uncovering such adaptations, and how they may be favoured by selection, is essential for predicting climate change impacts. Recently, the arid-adapted zebra finch was discovered to program their offspring’s development for heat, by producing ‘heat-calls’ during incubation in hot conditions. Intriguingly, heat-calls always occur during panting; and, strikingly, avian evaporative cooling mechanisms typically involve vibrating an element of the respiratory tract, which could conceivably produce sound. Therefore, we tested whether heat-call emission results from a particular thermoregulatory mechanism increasing the parent’s heat tolerance. We repeatedly measured resting metabolic rate, evaporative water loss (EWL) and heat tolerance in adult wild-derived captive zebra finches (n = 44) at increasing air temperatures up to 44 °C. We found high within-individual repeatability in thermoregulatory patterns, with heat-calling triggered at an individual-specific stage of panting. As expected for thermoregulatory mechanisms, both silent panting and heat-calling significantly increased EWL. However, only heat-calling resulted in greater heat tolerance, demonstrating that “vocal panting” brings a thermoregulatory benefit to the emitter. Our findings therefore not only improve our understanding of the evolution of passerine thermal adaptations, but also highlight a novel evolutionary precursor for acoustic signals.
Collapse
Affiliation(s)
- Anaïs Pessato
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia.
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa.,DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0001, South Africa
| | - Katherine L Buchanan
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia
| | - Mylene M Mariette
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University Geelong, Geelong, VIC, 3216, Australia.
| |
Collapse
|
18
|
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
| | | |
Collapse
|
19
|
Gerson AR, DeSimone JG, Black EC, Dick MF, Groom DJ. Metabolic reduction after long-duration flight is not related to fat-free mass loss or flight duration in a migratory passerine. J Exp Biol 2020; 223:jeb215384. [PMID: 32778563 DOI: 10.1242/jeb.215384] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 07/31/2020] [Indexed: 01/19/2023]
Abstract
Migratory birds catabolize large quantities of protein during long flights, resulting in dramatic reductions in organ and muscle mass. One of the many hypotheses to explain this phenomenon is that decrease in lean mass is associated with reduced resting metabolism, saving energy after flight during refueling. However, the relationship between lean body mass and resting metabolic rate remains unclear. Furthermore, the coupling of lean mass with resting metabolic rate and with peak metabolic rate before and after long-duration flight have not previously been explored. We flew migratory yellow-rumped warblers (Setophaga coronata) in a wind tunnel under one of two humidity regimes to manipulate the rate of lean mass loss in flight, decoupling flight duration from total lean mass loss. Before and after long-duration flights, we measured resting and peak metabolism, and also measured fat mass and lean body mass using quantitative magnetic resonance. Flight duration ranged from 28 min to 600 min, and birds flying under dehydrating conditions lost more fat-free mass than those flying under humid conditions. After flight, there was a 14% reduction in resting metabolism but no change in peak metabolism. Interestingly, the reduction in resting metabolism was unrelated to flight duration or to change in fat-free body mass, indicating that protein metabolism in flight is unlikely to have evolved as an energy-saving measure to aid stopover refueling, but metabolic reduction itself is likely to be beneficial to migratory birds arriving in novel habitats.
Collapse
Affiliation(s)
- Alexander R Gerson
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Joely G DeSimone
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Elizabeth C Black
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Morag F Dick
- Advanced Facility for Avian Research, Department of Biology, University of Western Ontario, London, ON, Canada, N6A 5B7
| | - Derrick J Groom
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| |
Collapse
|
20
|
|
21
|
Freeman MT, Czenze ZJ, Schoeman K, McKechnie AE. Extreme hyperthermia tolerance in the world's most abundant wild bird. Sci Rep 2020; 10:13098. [PMID: 32753751 PMCID: PMC7403380 DOI: 10.1038/s41598-020-69997-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 06/26/2020] [Indexed: 11/09/2022] Open
Abstract
The thermal tolerances of vertebrates are generally restricted to body temperatures below 45–47 °C, and avian and mammalian critical thermal maxima seldom exceed 46 °C. We investigated thermoregulation at high air temperatures in the red-billed quelea (Quelea quelea), an African passerine bird that occurs in flocks sometimes numbering millions of individuals. Our data reveal this species can increase its body temperature to extremely high levels: queleas exposed to air temperature > 45 °C increased body temperature to 48.0 ± 0.7 °C without any apparent ill-effect, with individual values as high as 49.1 °C. These values exceed known avian lethal limits, with tolerance of body temperature > 48 °C unprecedented among birds and mammals.
Collapse
Affiliation(s)
- M T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Z J Czenze
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - K Schoeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa.,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - A E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, South Africa. .,DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
| |
Collapse
|
22
|
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
| | | | | |
Collapse
|
23
|
Czenze ZJ, Kemp R, Jaarsveld B, Freeman MT, Smit B, Wolf BO, McKechnie AE. Regularly drinking desert birds have greater evaporative cooling capacity and higher heat tolerance limits than non‐drinking species. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13573] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zenon J. Czenze
- South African Research Chair in Conservation Physiology 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 Pretoria South Africa
| | - Ryno Kemp
- South African Research Chair in Conservation Physiology 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 Pretoria South Africa
| | - Barry Jaarsveld
- South African Research Chair in Conservation Physiology 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 Pretoria South Africa
| | - Marc T. Freeman
- South African Research Chair in Conservation Physiology 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 Pretoria South Africa
| | - Ben Smit
- Department of Zoology and Entomology Rhodes University Grahamstown South Africa
| | - Blair O. Wolf
- UNM Biology Department University of New Mexico Albuquerque NM USA
| | - Andrew E. McKechnie
- South African Research Chair in Conservation Physiology 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 Pretoria South Africa
| |
Collapse
|
24
|
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.
Collapse
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
| |
Collapse
|
25
|
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.
Collapse
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.
| |
Collapse
|
26
|
Cooling requirements fueled the collapse of a desert bird community from climate change. Proc Natl Acad Sci U S A 2019; 116:21609-21615. [PMID: 31570585 PMCID: PMC6815107 DOI: 10.1073/pnas.1908791116] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Climate change—especially accelerated warming and drying—threatens to increase extinction risk, yet there is little evidence that physiological limitations have contributed to species declines. This study links species-specific water requirements for cooling body temperature to the collapse of a Mojave Desert bird community over the past century from climate change. Species occupying the hottest, driest sites were less likely to persist. Birds with the greatest water requirements for cooling their body temperature experienced the largest declines. Large-bodied carnivores and insectivores were especially vulnerable to cooling costs because they obtain water primarily from their food. Climate warming increases the evaporative cooling demand for birds, which will affect geographic patterns in body size and future extinction risk. Climate change threatens global biodiversity by increasing extinction risk, yet few studies have uncovered a physiological basis of climate-driven species declines. Maintaining a stable body temperature is a fundamental requirement for homeothermic animals, and water is a vital resource that facilitates thermoregulation through evaporative cooling, especially in hot environments. Here, we explore the potential for thermoregulatory costs to underlie the community collapse of birds in the Mojave Desert over the past century in response to climate change. The probability of persistence was lowest for species occupying the warmest and driest sites, which imposed the greatest cooling costs. We developed a general model of heat flux to evaluate whether water requirements for evaporative cooling contributed to species’ declines by simulating thermoregulatory costs in the Mojave Desert for 50 bird species representing the range of observed declines. Bird species’ declines were positively associated with climate-driven increases in water requirements for evaporative cooling and exacerbated by large body size, especially for species with animal-based diets. Species exhibiting reductions in body size across their range saved up to 14% in cooling costs and experienced less decline than species without size reductions, suggesting total cooling costs as a mechanism underlying Bergmann’s rule. Reductions in body size, however, are unlikely to offset the 50 to 78% increase in cooling costs threatening desert birds from future climate change. As climate change spreads warm, dry conditions across the planet, water requirements are increasingly likely to drive population declines, providing a physiological basis for climate-driven extinctions.
Collapse
|
27
|
Riddell EA, Roback EY, Wells CE, Zamudio KR, Sears MW. Thermal cues drive plasticity of desiccation resistance in montane salamanders with implications for climate change. Nat Commun 2019; 10:4091. [PMID: 31501425 PMCID: PMC6733842 DOI: 10.1038/s41467-019-11990-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 08/06/2019] [Indexed: 01/21/2023] Open
Abstract
Organisms rely upon external cues to avoid detrimental conditions during environmental change. Rapid water loss, or desiccation, is a universal threat for terrestrial plants and animals, especially under climate change, but the cues that facilitate plastic responses to avoid desiccation are unclear. We integrate acclimation experiments with gene expression analyses to identify the cues that regulate resistance to water loss at the physiological and regulatory level in a montane salamander (Plethodon metcalfi). Here we show that temperature is an important cue for developing a desiccation-resistant phenotype and might act as a reliable cue for organisms across the globe. Gene expression analyses consistently identify regulation of stem cell differentiation and embryonic development of vasculature. The temperature-sensitive blood vessel development suggests that salamanders regulate water loss through the regression and regeneration of capillary beds in the skin, indicating that tissue regeneration may be used for physiological purposes beyond replacing lost limbs.
Collapse
Affiliation(s)
- Eric A Riddell
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA.
| | - Emma Y Roback
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA.,Biology Department, Grinnell College, 1116 Eighth Ave, Grinnell, IA, 50112, USA
| | - Christina E Wells
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA
| | - Kelly R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, E145 Corson Hall, Ithaca, NY, 14853, USA
| | - Michael W Sears
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA
| |
Collapse
|
28
|
Chronic, sublethal effects of high temperatures will cause severe declines in southern African arid-zone birds during the 21st century. Proc Natl Acad Sci U S A 2019; 116:14065-14070. [PMID: 31235571 DOI: 10.1073/pnas.1821312116] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Birds inhabiting hot, arid regions are among the terrestrial organisms most vulnerable to climate change. The potential for increasingly frequent and intense heat waves to cause lethal dehydration and hyperthermia is well documented, but the consequences of sublethal fitness costs associated with chronic exposure to sustained hot weather remain unclear. Using data for species occurring in southern Africa's Kalahari Desert, we mapped exposure to acute lethal risks and chronic sublethal fitness costs under past, present, and future climates. For inactive birds in shaded microsites, the risks of lethal dehydration and hyperthermia will remain low during the 21st century. In contrast, exposure to conditions associated with chronic, sublethal costs related to progressive body mass loss, reduced nestling growth rates, or increased breeding failure will expand dramatically. For example, by the 2080s the region will experience 10-20 consecutive days per year on which Southern Pied Babblers (Turdoides bicolor) will lose ∼4% of body mass per day, conditions under which this species' persistence will be extremely unlikely. Similarly, exposure to air temperature maxima associated with delayed fledging, reduced fledgling size, and breeding failure will increase several-fold in Southern Yellow-billed Hornbills (Tockus leucomelas) and Southern Fiscals (Lanius collaris). Our analysis reveals that sublethal costs of chronic heat exposure are likely to drive large declines in avian diversity in the southern African arid zone by the end of the century.
Collapse
|
29
|
Nilsson JÅ, Nord A. Testing the heat dissipation limit theory in a breeding passerine. Proc Biol Sci 2019; 285:rspb.2018.0652. [PMID: 29769365 DOI: 10.1098/rspb.2018.0652] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 04/19/2018] [Indexed: 11/12/2022] Open
Abstract
The maximum work rate of animals has recently been suggested to be determined by the rate at which excess metabolic heat generated during work can be dissipated (heat dissipation limitation (HDL) theory). As a first step towards testing this theory in wild animals, we experimentally manipulated brood size in breeding marsh tits (Poecile palustris) to change their work rate. Parents feeding nestlings generally operated at above-normal body temperatures. Body temperature in both males and females increased with maximum ambient temperature and with manipulated work rate, sometimes even exceeding 45°C, which is close to suggested lethal levels for birds. Such high body temperatures have previously only been described for birds living in hot and arid regions. Thus, reproductive effort in marsh tits may potentially be limited by the rate of heat dissipation. Females had lower body temperatures, a possible consequence of their brood patch serving as a thermal window facilitating heat dissipation. Because increasing body temperatures are connected to somatic costs, we suggest that the HDL theory may constitute a possible mediator of the trade-off between current and future reproduction. It follows that globally increasing, more stochastic, ambient temperatures may restrict the capacity for sustained work of animals in the future.
Collapse
Affiliation(s)
- Jan-Åke Nilsson
- Department of Biology, Section of Evolutionary Ecology, Lund University, Ecology Building, 223 62 Lund, Sweden
| | - Andreas Nord
- Department of Biology, Section of Evolutionary Ecology, Lund University, Ecology Building, 223 62 Lund, Sweden
| |
Collapse
|
30
|
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]
|
31
|
Kline HN, Fulbright TE, Grahmann ED, Hernández F, Wester DB, Brennan LA, Hehman MW. Temperature influences resource use by chestnut-bellied scaled quail. Ecosphere 2019. [DOI: 10.1002/ecs2.2599] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Holley N. Kline
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | - Timothy E. Fulbright
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | - Eric D. Grahmann
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | - Fidel Hernández
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | - David B. Wester
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | - Leonard A. Brennan
- Caesar Kleberg Wildlife Research Institute; Texas A&M University-Kingsville; MSC 218 Kingsville Texas 78363 USA
| | | |
Collapse
|
32
|
Gerson AR, McKechnie AE, Smit B, Whitfield MC, Smith EK, Talbot WA, McWhorter TJ, Wolf BO. The functional significance of facultative hyperthermia varies with body size and phylogeny in birds. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13274] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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 InstituteDepartment of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Ben Smit
- DST‐NRF Centre of Excellence at the FitzPatrick InstituteDepartment of Zoology and Entomology Rhodes University Grahamstown South Africa
| | - Maxine C. Whitfield
- DST‐NRF Centre of Excellence at the FitzPatrick InstituteDepartment of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Eric K. Smith
- Department of Biology University of New Mexico Albuquerque New Mexico
| | - William A. Talbot
- Department of Biology University of New Mexico Albuquerque New Mexico
| | - Todd J. McWhorter
- School of Animal and Veterinary Sciences University of Adelaide Adelaide South Australia Australia
| | - Blair O. Wolf
- Department of Biology University of New Mexico Albuquerque New Mexico
| |
Collapse
|
33
|
Kemp R, McKechnie AE. Thermal physiology of a range-restricted desert lark. J Comp Physiol B 2018; 189:131-141. [PMID: 30488103 DOI: 10.1007/s00360-018-1190-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/27/2018] [Accepted: 11/05/2018] [Indexed: 11/30/2022]
Abstract
Much recent work on avian physiological adaptation to desert environments has focused on larks (Passeriformes: Alaudidae). We tested the prediction that the threatened red lark (Calendulauda burra), a species restricted to very arid parts of South Africa and which is not known to drink, exhibits highly efficient evaporative cooling and makes pronounced use of facultative hyperthermia when exposed to high air temperatures (Ta). We also predicted that C. burra possesses similarly low basal metabolic rate (BMR) and total evaporative water loss (EWL) at moderate Ta as reported for species from the deserts of the Middle East. Rest-phase thermoregulation in C. burra was characterized by an unusually low lower critical limit of thermoneutrality at Ta = ~ 21 °C and a BMR of 0.317 ± 0.047 W, the lowest BMR relative to allometrically-expected values yet reported in any lark. During the diurnal active phase, red larks were able to tolerate Ta up to 50 °C, with the onset of panting occurring at Ta = 38 °C. Maximum EWL was 1.475 ± 0.107 g h- 1 at Ta = 50 °C, equivalent to 620% of minimum EWL at thermoneutrality. The maximum ratio of evaporative heat dissipation to metabolic heat production was 1.58, a value towards the lower end of the range reported for passerines. Our data support the prediction that C. burra shows metabolic traits similar to those of other larks inhabiting extremely arid climates, but not the notion that evaporative cooling at high Ta in this species is more efficient than in most passerines.
Collapse
Affiliation(s)
- Ryno Kemp
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria, 0028, South Africa
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, P.O. Box 754, Pretoria, 0001, South Africa
| | - Andrew E McKechnie
- DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, Private Bag X20, Pretoria, 0028, South Africa.
- South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, P.O. Box 754, Pretoria, 0001, South Africa.
| |
Collapse
|
34
|
Harrison JF. Approaches for testing hypotheses for the hypometric scaling of aerobic metabolic rate in animals. Am J Physiol Regul Integr Comp Physiol 2018; 315:R879-R894. [DOI: 10.1152/ajpregu.00165.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypometric scaling of aerobic metabolism [larger organisms have lower mass-specific metabolic rates (MR/g)] is nearly universal for interspecific comparisons among animals, yet we lack an agreed upon explanation for this pattern. If physiological constraints on the function of larger animals occur and limit MR/g, these should be observable as direct constraints on animals of extant species and/or as evolved responses to compensate for the proposed constraint. There is evidence for direct constraints and compensatory responses to O2 supply constraint in skin-breathing animals, but not in vertebrates with gas-exchange organs. The duration of food retention in the gut is longer for larger birds and mammals, consistent with a direct constraint on nutrient uptake across the gut wall, but there is little evidence for evolving compensatory responses to gut transport constraints in larger animals. Larger placental mammals (but not marsupials or birds) show evidence of greater challenges with heat dissipation, but there is little evidence for compensatory adaptations to enhance heat loss in larger endotherms, suggesting that metabolic rate (MR) more generally balances heat loss for thermoregulation in endotherms. Size-dependent patterns in many molecular, physiological, and morphological properties are consistent with size-dependent natural selection, such as stronger selection for neurolocomotor performance and growth rate in smaller animals and stronger selection for safety and longevity in larger animals. Hypometric scaling of MR very likely arises from different mechanisms in different taxa and conditions, consistent with the diversity of scaling slopes for MR.
Collapse
Affiliation(s)
- Jon F. Harrison
- School of Life Sciences, Arizona State University, Tempe, Arizona
| |
Collapse
|
35
|
Medina I, Newton E, Kearney MR, Mulder RA, Porter WP, Stuart-Fox D. Reflection of near-infrared light confers thermal protection in birds. Nat Commun 2018; 9:3610. [PMID: 30190466 PMCID: PMC6127310 DOI: 10.1038/s41467-018-05898-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 07/31/2018] [Indexed: 12/25/2022] Open
Abstract
Biologists have focused their attention on the optical functions of light reflected at ultraviolet and human-visible wavelengths. However, most radiant energy in sunlight occurs in 'unseen' near-infrared (NIR) wavelengths. The capacity to reflect solar radiation at NIR wavelengths may enable animals to control heat gain and remain within their critical thermal limits. Here, using a continent-wide phylogenetic analysis of Australian birds, we show that species occupying hot, arid environments reflect more radiant energy in NIR wavelengths than species in thermally benign environments, even when controlling for variation in visible colour. Biophysical models confirm that smaller species gain a greater advantage from high NIR reflectivity in hot, arid environments, reducing water loss from compensatory evaporative cooling by up to 2% body mass per hour. These results highlight the importance of NIR reflectivity for thermal protection, which may become increasingly critical as the frequency of extreme climatic events increases.
Collapse
Affiliation(s)
- Iliana Medina
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
| | - Elizabeth Newton
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Michael R Kearney
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Raoul A Mulder
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Warren P Porter
- Department of Zoology, The University of Wisconsin Madison, Madison, WI, 53706, USA
| | - Devi Stuart-Fox
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia
| |
Collapse
|
36
|
Talbot WA, Gerson AR, Smith EK, McKechnie AE, Wolf BO. Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls. J Exp Biol 2018; 221:221/12/jeb171108. [DOI: 10.1242/jeb.171108] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 04/17/2018] [Indexed: 11/20/2022]
Abstract
ABSTRACT
The thermoregulatory responses of owls to heat stress have been the subject of few studies. Although nocturnality buffers desert-dwelling owls from significant heat stress during activity, roost sites in tree and cactus cavities or in deep shade provide only limited refuge from high environmental temperatures during the day. We measured thermoregulatory responses to acute heat stress in two species of small owls, the elf owl (Micrathene whitneyi) and the western screech-owl (Megascops kennicottii), which occupy the Sonoran Desert of southwestern North America, an area of extreme heat and aridity. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limits (HTL; the maximum Ta reached). Comparatively low RMR values were observed in both species, Tb approximated Ta at 40°C and mild hyperthermia occurred as Ta was increased toward the HTL. Elf owls and screech-owls reached HTLs of 48 and 52°C, respectively, and RMR increased to 1.5 and 1.9 times thermoneutral values. Rates of EWL at the HTL allowed for the dissipation of 167–198% of metabolic heat production (MHP). Gular flutter was used as the primary means of evaporative heat dissipation and produced large increases in evaporative heat loss (44–100%), accompanied by only small increases (<5%) in RMR. These small, cavity-nesting owls have thermoregulatory capacities that are intermediate between those of the open-ground nesting nightjars and the passerines that occupy the same ecosystem.
Collapse
Affiliation(s)
- William A. Talbot
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | | | - Eric Krabbe Smith
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | - Andrew E. McKechnie
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Blair O. Wolf
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| |
Collapse
|
37
|
McWhorter TJ, Gerson AR, Talbot WA, Smith EK, McKechnie AE, Wolf BO. Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots. ACTA ACUST UNITED AC 2018; 221:jeb.168930. [PMID: 29440360 DOI: 10.1242/jeb.168930] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 02/01/2018] [Indexed: 11/20/2022]
Abstract
Avian orders differ in their thermoregulatory capabilities and tolerance of high environmental temperatures. Evaporative heat loss, and the primary avenue whereby it occurs, differs amongst taxa. Although Australian parrots (Psittaciformes) have been impacted by mass mortality events associated with extreme weather events (heat waves), their thermoregulatory physiology has not been well characterized. We quantified the upper limits to thermoregulation under extremely hot conditions in two Australian parrots: the mulga parrot (Psephotellus varius; ∼55 g) and the galah (Eolophus roseicapilla; ∼265 g). At air temperatures (Ta) exceeding body temperature (Tb), both species showed increases in Tb to maximum values around 43-44°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss to levels equivalent to 700-1000% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.71 to 1.79, consistent with the known range for parrots, similar to the corresponding range in passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (the maximum Ta tolerated) ranged from 44 to 55°C, similar to the range reported for passerines, but lower than that reported for columbids and caprimulgids. Our data suggest that heat tolerance in parrots is similar to that in passerines. We argue that understanding how thermoregulatory capacity and heat tolerance vary across avian orders is vital for predicting how climate change and the associated increase in frequency of extreme weather events may impact avian populations in the future.
Collapse
Affiliation(s)
- Todd J McWhorter
- School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, South Australia 5371, Australia
| | - Alexander R Gerson
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - William A Talbot
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | - Eric Krabbe Smith
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | - Andrew E McKechnie
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.,South African Research Chair in Conservation Physiology, National Zoological Gardens of South Africa, P.O. Box 754, Pretoria 0001, South Africa
| | - Blair O Wolf
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| |
Collapse
|
38
|
Smit B, Whitfield MC, Talbot WA, Gerson AR, McKechnie AE, Wolf BO. Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance. ACTA ACUST UNITED AC 2018; 221:jeb.174870. [PMID: 29440359 DOI: 10.1242/jeb.174870] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 02/01/2018] [Indexed: 11/20/2022]
Abstract
Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
Collapse
Affiliation(s)
- Ben Smit
- Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown 6040, South Africa
| | - Maxine C Whitfield
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - William A Talbot
- UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | - Alexander R Gerson
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Andrew E McKechnie
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.,South African Research Chair in Conservation Physiology, National Zoological Gardens of South Africa, P.O. Box 754, Pretoria 0001, South Africa
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| |
Collapse
|
39
|
Price ER, Dzialowski EM. Development of endothermy in birds: patterns and mechanisms. J Comp Physiol B 2017; 188:373-391. [DOI: 10.1007/s00360-017-1135-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/25/2017] [Accepted: 10/29/2017] [Indexed: 02/08/2023]
|
40
|
Talbot WA, McWhorter TJ, Gerson AR, McKechnie AE, Wolf BO. Avian thermoregulation in the heat: evaporative cooling capacity of arid-zone Caprimulgiformes from two continents. ACTA ACUST UNITED AC 2017; 220:3488-3498. [PMID: 28760832 DOI: 10.1242/jeb.161653] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/20/2017] [Indexed: 11/20/2022]
Abstract
Birds in the order Caprimulgiformes (nightjars and allies) have a remarkable capacity for thermoregulation over a wide range of environmental temperatures, exhibiting pronounced heterothermy in cool conditions and extreme heat tolerance at high environmental temperatures. We measured thermoregulatory responses to acute heat stress in three species of Caprimulgiformes that nest in areas of extreme heat and aridity, the common poorwill (Phalaenoptilus nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in the mallee woodlands of South Australia. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limit (HTL; the maximum Ta reached). Comparatively low RMR values were observed in all species (0.35, 0.36 and 0.40 W for the poorwill, nighthawk and owlet-nightjar, respectively), with Tb approximating Ta at 40°C and mild hyperthermia occurring as Ta reached the HTL. Nighthawks and poorwills reached HTLs of 60 and 62°C, respectively, whereas the owlet-nightjar had a HTL of 52°C. RMR increased gradually above minima at Ta of 42, 42 and 35°C, and reached 1.7, 1.9 and 2.0 times minimum resting values at HTLs in the poorwill, nighthawk and owlet-nightjar, respectively. EWL increased rapidly and linearly as Ta exceeded Tb and resulted in maximum rates of evaporative heat dissipation equivalent to 237-424% of metabolic heat production. Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50-123%) accompanied by only small increments in RMR (<5%). The cavity-nesting/roosting owlet-nightjar had a lower HTL and less efficient evaporative cooling compared with the species that nest and/or roost on open desert surfaces. The high efficiency of gular flutter for evaporative cooling, combined with mild hyperthermia, provides the physiological basis for defending Tb well below Ta in extreme heat and is comparable to the efficient cooling observed in arid-zone columbids in which cutaneous EWL is the predominant cooling pathway.
Collapse
Affiliation(s)
- William A Talbot
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| | - Todd J McWhorter
- School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, SA 5371, Australia
| | - Alexander R Gerson
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Andrew E McKechnie
- DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Blair O Wolf
- Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA
| |
Collapse
|