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Type: Journal article
Title: Avian thermoregulation in the heat: efficient evaporative cooling allows for extreme heat tolerance in four southern hemisphere columbids
Author: McKechnie, A.
Whitfield, M.
Smit, B.
Gerson, A.
Smith, E.
Talbot, W.
McWhorter, T.
Wolf, B.
Citation: The Journal of Experimental Biology, 2016; 219(14):2145-2155
Publisher: Company of Biologists
Issue Date: 2016
ISSN: 0022-0949
Statement of
Andrew E. McKechnie, Maxine C. Whitfield, Ben Smit, Alexander R. Gerson, Eric Krabbe Smith, William A. Talbot, Todd J. McWhorter and Blair O. Wolf
Abstract: Birds show phylogenetic variation in the relative importance of respiratory versus cutaneous evaporation, but the consequences for heat tolerance and evaporative cooling capacity remain unclear. We measured evaporative water loss (EWL), resting metabolic rate (RMR) and body temperature (Tb) in four arid-zone columbids from southern Africa [Namaqua dove (Oena capensis, ∼37 g), laughing dove (Spilopelia senegalensis, ∼89 g) and Cape turtle dove (Streptopelia capicola, ∼148 g)] and Australia [crested pigeon (Ocyphaps lophotes), ∼186 g] at air temperatures (Ta) of up to 62°C. There was no clear relationship between body mass and maximum Ta tolerated during acute heat exposure. Maximum Tb at very high Ta was 43.1±1.0, 43.7±0.8, 44.7±0.3 and 44.3±0.8°C in Namaqua doves, laughing doves, Cape turtle doves and crested pigeons, respectively. In all four species, RMR increased significantly at Ta above thermoneutrality, but the increases were relatively modest with RMR at Ta=56°C being 32, 60, 99 and 11% higher, respectively, than at Ta=35°C. At the highest Ta values reached, evaporative heat loss was equivalent to 466, 227, 230 and 275% of metabolic heat production. The maximum ratio of evaporative heat loss to metabolic production observed in Namaqua doves, 4.66, exceeds by a substantial margin previous values reported for birds. Our results support the notion that cutaneous evaporation provides a highly efficient mechanism of heat dissipation and an enhanced ability to tolerate extremely high Ta.
Keywords: Body temperature; columbiformes; cutaneous evaporative water loss; hyperthermia; passeriformes; respiratory evaporative water loss
Rights: © 2016. Published by The Company of Biologists Ltd.
DOI: 10.1242/jeb.138776
Appears in Collections:Animal and Veterinary Sciences publications
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