Caves, crevices and cooling capacity roost microclimate predicts heat tolerance in bats
- Authors: Czenze, Zenon J , Smit, Ben , van Jaarsveld, Barry , Freeman, Marc T , McKechnie, Andrew
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441571 , vital:73899 , https://doi.org/10.1111/1365-2435.13918
- Description: The microsites that animals occupy during the rest phase of their circa-dian activity cycle influence their physiology and behaviour, but relative-ly few studies have examined correlations between interspecific varia-tion in thermal physiology and roost microclimate. Among bats, there is some evidence that species exposed to high roost temperatures (Troost) possess greater heat tolerance and evaporative cooling capacity, but the small number of species for which both thermal physiology and roost microclimate data exist mean that the generality of this pattern remains unclear.
- Full Text:
Heat dissipation behaviour of birds in seasonally hot arid‐zones: are there global patterns?
- Authors: Pattinson, Nicholas B , Thompson, Michelle L , Griego, Michael , Russell, Grace , Mitchell, Nicola J , Martin, Rowan O , Wolf, Blair O , Smit, Ben , Cunningham, Susan J , McKechnie, Andrew , Hockey, Philip A R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441682 , vital:73906 , https://doi.org/10.1111/jav.02350
- Description: Quantifying organismal sensitivity to heat stress provides one means for predicting vulnerability to climate change. Birds are ideal for investigating this approach, as they display quantifiable fitness consequences associated with behavioural and physiological responses to heat stress. We used a recently developed method that examines correlations between readily‐observable behaviours and air temperature (Tair) to investigate interspecific variation in avian responses to heat stress in seasonally hot, arid regions on three continents: the southwestern United States, the Kalahari Desert of southern Africa and the Gascoyne region of western Australia.
- Full Text:
Regularly drinking desert birds have greater evaporative cooling capacity and higher heat tolerance limits than non‐drinking species
- Authors: Czenze, Zenon J , Kemp, Ryno , van Jaarsveld, Barry , Freeman, Marc T , Smit, Ben , Wolf, Blair O , McKechnie, Andrew
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441585 , vital:73900 , https://doi.org/10.1111/1365-2435.13573
- Description: Surface water is a critical resource for many birds inhabiting arid re-gions, but the implications of regular drinking and dependence on sur-face water for the evolution of thermal physiology remain largely unex-plored. We hypothesized that avian thermoregulation in the heat has evolved in tandem with the use of surface water and predicted that (a) regularly drinking species have a greater capacity to elevate rates of evaporative water loss (EWL) compared to non‐drinking species, and (b) heat tolerance limits (HTLs) are higher among drinking species. To test these predictions, we quantified thermoregulatory responses to high air temperature (Ta) in 12 species of passerines from the South African arid zone and combined these with values for an additional five species. We categorized each species as either: (a) water‐dependent, regularly drinking, or (b) water‐independent, occasional‐/non‐drinking.
- Full Text:
The functional significance of facultative hyperthermia varies with body size and phylogeny in birds
- Authors: Gerson, Alexander R , McKechnie, Andrew , Smit, Ben , Whitfield, Maxine C , Smith, Eric K , Talbot, William A , McWhorter, Todd J , Wolf, Blair O
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441609 , vital:73901 , https://doi.org/10.1111/1365-2435.13274
- Description: Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the wa-ter economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa. Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (Tb) above environmental temperatures (Te), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient when Te > Tb, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases in Tb which reduces evaporative heat loss demands and conserves wa-ter. Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat toler-ance and mechanisms of evaporative heat dissipation. We measured resting metabolism, evaporative water loss and real‐time Tb from 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species.
- Full Text: