Abstract
The emu is a large, flightless bird native to Australia. Its habitats range from the high snow country to the arid interior of the continent. Our experiments show that the emu maintains a constant body temperature within the ambient temperature range-5 to 45°C. The males regulate their body temperature about 0.5°C lower than the females. With falling ambient temperature the emu regulates its body temperature initially by reducing conductance and then by increasing heat production. At-5°C the cost of maintaining thermal balance is 2.6 times basal metabolic rate. By sitting down and reducing heat loss from the legs the cost of homeothermy at-5°C is reduced to 1.5 times basal metabolic rate. At high ambient temperatures the emu utilises cutaneous evaporative water loss in addition to panting. At 45°C evaporation is equal to 160% of heat production. Panting accounts for 70% of total evaporation at 45°C. The cost of utilising cutaneous evaporation for the other 30% appears to be an increase in dry conductance.
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Abbreviations
- A r :
-
Effective radiating surface area
- BMR:
-
basal metabolic rate
- C dry :
-
dry conductance
- CEWL:
-
cutaneous evaporative water loss
- EHL:
-
evaporative heat loss
- EWL:
-
evaporative water loss
- FECO2 :
-
fractional concentration of CO2 in excurrent air
- FFH2O :
-
water content of chamber excurrent air
- FEO2 :
-
fractional concentration of O2 in chamber excurrent air
- FICO2 :
-
fractional concentration of CO2 in incurrent air
- FIO2 :
-
fractional concentration of O2 in chamber incurrent air
- MHP:
-
metabolic heat production
- MR:
-
metabolic rate
- REWL:
-
respiratory evaporative water loss
- RH:
-
relative humidity
- RQ:
-
respiratory quotient\((\dot VCO_2 /\dot VO_2 )\);
- SA:
-
surface area
- SEM:
-
standard error of the mean
- SNK:
-
Student-Newman-Keuls multiple range test
- STPD:
-
standard temperature and pressure dry
- T a :
-
ambient temperature(s)
- T b :
-
body temperature(s)
- T e :
-
surface temperature(s)
- \(\dot V\) :
-
flow rate of air into the chamber
- \(\dot VCO_2\) :
-
carbon dioxide production
- \(\dot VO_2\) :
-
oxygen consumption
- \(VP_{H_2 O}\) :
-
vapour pressure of water
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Maloney, S.K., Dawson, T.J. Thermoregulation in a large bird, the emu (Dromaius novaehollandiae). J Comp Physiol B 164, 464–472 (1994). https://doi.org/10.1007/BF00714584
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DOI: https://doi.org/10.1007/BF00714584