scholarly journals Vocal panting: a novel thermoregulatory mechanism for enhancing heat tolerance in a desert-adapted bird

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Anaïs Pessato ◽  
Andrew E. McKechnie ◽  
Katherine L. Buchanan ◽  
Mylene M. Mariette
Keyword(s):  
Climate Change ◽  
Respiratory Tract ◽  
Heat Tolerance ◽  
Resting Metabolic Rate ◽  
Climate Change Impacts ◽  
Acoustic Signals ◽  
Evaporative Water ◽  
Air Temperatures ◽  
Specific Stage ◽  
Individual Repeatability

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.

scholarly journals Efficient Evaporative Cooling and Pronounced Heat Tolerance in an Eagle-Owl, a Thick-Knee and a Sandgrouse

2021 ◽  
Vol 9 ◽  
Author(s):  
Zenon J. Czenze ◽  
Marc T. Freeman ◽  
Ryno Kemp ◽  
Barry van Jaarsveld ◽  
Blair O. Wolf ◽  
...  
Keyword(s):  
Heat Tolerance ◽  
Resting Metabolic Rate ◽  
Evaporative Cooling ◽  
Heat Exposure ◽  
Cooling Capacity ◽  
Published Data ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Air Temperatures ◽  
Eagle Owl

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.

scholarly journals Climate change increases the likelihood of catastrophic avian mortality events during extreme heat waves

2009 ◽  
Vol 6 (2) ◽  
pp. 253-256 ◽  
Author(s):  
Andrew E. McKechnie ◽  
Blair O. Wolf
Keyword(s):  
Climate Change ◽  
Heat Waves ◽  
Extreme Heat ◽  
Survival Times ◽  
Water Requirements ◽  
Evaporative Water ◽  
Change Models ◽  
Air Temperatures ◽  
Hot Weather

Severe heat waves have occasionally led to catastrophic avian mortality in hot desert environments. Climate change models predict increases in the intensity, frequency and duration of heat waves. A model of avian evaporative water requirements and survival times during the hottest part of day reveals that the predicted increases in maximum air temperatures will result in large fractional increases in water requirements (in small birds, equivalent to 150–200 % of current values), which will severely reduce survival times during extremely hot weather. By the 2080s, desert birds will experience reduced survival times much more frequently during mid-summer, increasing the frequency of catastrophic mortality events.

scholarly journals Could plasticity mediate highlands lizards’ resilience to climate change? A case study of the leopard iguana (Diplolaemus leopardinus) in central andes of Argentina

2021 ◽  
Author(s):  
Nadia Vicenzi ◽  
Leonardo D. Bacigalupe ◽  
Alejandro Laspiur ◽  
Nora Ibargüengoytía ◽  
Paola L. Sassi
Keyword(s):  
Climate Change ◽  
Thermal History ◽  
Heat Waves ◽  
Resting Metabolic Rate ◽  
Physiological Traits ◽  
Main Concern ◽  
Evaporative Water ◽  
Species Vulnerability ◽  
Acclimation Response ◽  
The Impact

The rising temperature predicted is of main concern for ectotherms because its direct impact on their behavior and physiology. Since physiological performance mediates a species’ resilience to warming exposure, physiological plasticity could greatly reduce the susceptibility to climate change. We studied the degree to which Diplolaemus leopardinus’ lizards are able to adjust behavioral and physiological traits in response to short periods of temperature change. We used a split cross design to measure acclimation response of preferred body temperature (Tp), and thermal performance curve of resting metabolic rate (RMR) and evaporative water loss (EWL). Our results showed that plasticity differs among traits; whereas Tp and EWL showed lower values in warm conditions, RMR increased the temperature at which its value is highest. Moreover, RMR was affected by thermal history, showing a great increase in response to cold exposure in the group initially acclimated to warm. The reduction of EWL and the increase in optimal temperature will give lizards the potential to partially mitigate the impact of rising temperatures in the energy cost and water balance. However, the decrease in Tp and the sensitivity to the warm thermal history in RMR could be detrimental to the energy net gain increasing the species vulnerability, especially considering the increase of heat waves predicted for the next fifty years. The integration of acclimation responses in behavioral and physiological traits provides a better understanding of the range of possible responses of lizards to cope with the upcoming climatic and environmental modifications expected due to climate change.

scholarly journals Climate change impacts and potential benefits of drought and heat tolerance in chickpea in South Asia and East Africa

2014 ◽  
Vol 52 ◽  
pp. 123-137 ◽  
Author(s):  
Piara Singh ◽  
S. Nedumaran ◽  
K.J. Boote ◽  
P.M. Gaur ◽  
K. Srinivas ◽  
...  
Keyword(s):  
Climate Change ◽  
South Asia ◽  
East Africa ◽  
Heat Tolerance ◽  
Climate Change Impacts ◽  
Potential Benefits

scholarly journals Thermoregulation in desert birds: scaling and phylogenetic variation in heat tolerance and evaporative cooling

2021 ◽  
Vol 224 (Suppl 1) ◽  
pp. jeb229211
Author(s):  
Andrew E. McKechnie ◽  
Alexander R. Gerson ◽  
Blair O. Wolf
Keyword(s):  
Heat Tolerance ◽  
Heat Dissipation ◽  
Arid Zone ◽  
Resting Metabolic Rate ◽  
Heat Exposure ◽  
Published Data ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Data Set ◽  
The Difference

ABSTRACTEvaporative heat dissipation is a key aspect of avian thermoregulation in hot environments. We quantified variation in avian thermoregulatory performance at high air temperatures (Ta) using published data on body temperature (Tb), evaporative water loss (EWL) and resting metabolic rate (RMR) measured under standardized conditions of very low humidity in 56 arid-zone species. Maximum Tb 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 Tb and the difference between maximum and normothermic Tb decreased significantly with body mass (Mb). 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 (Tuc) varied by >20°C and maximum RMR during acute heat exposure scaled to Mb0.75 in both the overall data set and among passerines. The slope of RMR at Ta>Tuc increased significantly with Mb 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.

scholarly journals Initiative use of climate change hotspots for targeting adaptation sites in Indonesia

2021 ◽  
Vol 893 (1) ◽  
pp. 012035
Author(s):  
Ikrom Mustofa ◽  
Perdinan ◽  
Syafararisa Dian Pratiwi ◽  
Suvany Aprilia ◽  
Raden Eliasar Prabowo Tjahjono ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Change Adaptation ◽  
Air Temperature ◽  
Climate Model ◽  
Climate Change Impacts ◽  
Base Temperature ◽  
Economic Sectors ◽  
Air Temperatures ◽  
Wide Range ◽  
Increasing Temperature

Abstract Designing climate change adaptation actions are considerably a challenge, as the actions should be targeted uniquely addressing climate change impacts. One of the challenges is to determine climate change adaptation sites. The complexity raises considering climate change impact a wide range of economic sectors, which require a lot of resources to conduct a comprehensive climate change assessments. This study proposes the use of climate change hotspots as an initiative to firstly consider the potential targeted sites. The target of global efforts to maintain air temperature under 2°C was employed as a clue to prioritize areas that air temperature is increasing beyond the thresholds to which can affect human activities. This study employed spatial and threshold analysis to develop climate change hotspots of projected temperature change for 2021-2050 over Indonesia. The thresholds were defined by considering the effects of base temperature of 32 °C, 35 °C, and 38 °C on agriculture, environment, and human health in combination with elevated temperature from 0.75 to 2 °C. The initiative method was applied to the baseline and projected air temperature obtained from higher resolution of climate model outputs simulated under representative carbon pathway scenario of 4.5 (RCP 4.5 and 8.5) as a case study. The maps of climate change hotspots provide the potential targeted areas for climate change adaptation actions. Referring to the target of suppressing global temperatures below 2°C, we identified the distribution of climate change hotspots in Indonesia with a scenario of increasing temperature of 2°C from baseline conditions so that future air temperatures will be more than 35°C. The maps can also be combined with the other maps related to climate change analyses, which are available in Indonesia such as SIDIK to refine the priority areas and/or more general geographic information such as city location. As an example, the overlay of climate change hotspots and city location can provide early anticipation on which city will experience urban heat island. The development of climate change hotspots nationally is also expected to initiate climate change services that can be provided to the end users to ease them in defining suitable actions to adapt to the impacts of climate change.

scholarly journals Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance

2017 ◽  
Author(s):  
Ben Smit ◽  
Maxine C. Whitfield ◽  
William A. Talbot ◽  
Alexander R. Gerson ◽  
Andrew E. McKechnie ◽  
...  
Keyword(s):  
Heat Tolerance ◽  
Heat Dissipation ◽  
Resting Metabolic Rate ◽  
Evaporative Cooling ◽  
Cooling Capacity ◽  
Evaporative Heat Loss ◽  
Cooling Efficiency ◽  
Evaporative Water ◽  
Cutaneous Evaporation ◽  
Hot Environments

AbstractLittle 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: 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 (RMR) and evaporative water loss (EWL) increased by quantitatively similar magnitudes in all three species, although maximum rates of EWL 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.Summary statementWe show that avian evaporative cooling efficiency and heat tolerance display substantial taxonomic variation that are, unexpectedly, not systematically related to the use of panting versus gular flutter processes.

scholarly journals Limited heat tolerance in a cold-adapted seabird: implications of a warming Arctic

2021 ◽  
Vol 224 (13) ◽  
Author(s):  
Emily S. Choy ◽  
Ryan S. O'Connor ◽  
H. Grant Gilchrist ◽  
Anna L. Hargreaves ◽  
Oliver P. Love ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Heat Tolerance ◽  
Water Loss ◽  
Resting Metabolic Rate ◽  
Evaporative Cooling ◽  
Evaporative Water Loss ◽  
Cooling Efficiency ◽  
Direct Effects ◽  
Evaporative Water ◽  
Rate Of Increase

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.

scholarly journals Seasonal physiological responses to heat in an alpine range-restricted bird: the Cape Rockjumper

2018 ◽  
Author(s):  
Krista N Oswald ◽  
Alan TK Lee ◽  
Ben Smit
Keyword(s):  
Physiological Stress ◽  
Resting Metabolic Rate ◽  
Evaporative Cooling ◽  
Cooling Capacity ◽  
Cooling Efficiency ◽  
Evaporative Water ◽  
Air Temperatures ◽  
Functional Value ◽  
Summer Temperatures ◽  
Physiological Adjustments

AbstractHot, dry summer conditions impose physiological stress on endotherms, yet we have a poor understanding of how endotherms seasonally adjust their costs of thermoregulation under hot conditions. We determined whether seasonal phenotypic plasticity in evaporative cooling capacity at high temperatures explained how the range-restricted Cape Rockjumper (Chaetops frenatus; hereafter “Rockjumper”), copes with hot and dry summer temperatures of the temperate mountain peaks of southwest South Africa. We measured evaporative water loss (EWL), resting metabolic rate (RMR), and body temperature (Tb) at high air temperatures (30 to 42°C) of individuals from a wild population of Rockjumpers during winter and summer (n = 11 winter, 4 females, 7 males; n = 10 summer, 6 females, 4 males). We found Rockjumper evaporative cooling in summer imposes higher EWL (i.e. greater water costs) compared to winter, although an accompanying lack of change in RMR resulted in increased summer cooling efficiency. These patterns are similar to those observed in species that inhabit regions where summer temperatures are routinely hot but not water stressed. Our findings show that avian seasonal physiological adjustments to heat can be diverse. Further seasonal studies on thermoregulation in the heat will greatly improve our knowledge of the functional value traits such as evaporative cooling efficiency and heat tolerance hold and how they contribute to the physiological stress organisms experience in heterogenous environments.

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