Avian thermoregulation in the heat: evaporative cooling in desert birds from three continents

  • DATE

    23 August 2017

  • TIME

    11:00 - 12:00

  • VENUE

    MRI seminar room (Botany 1-5)

The ability of some birds to survive and breed in the hottest and driest habitats on the planet, despite diurnal habits and high mass-specific energy and water requirements, has intrigued ecological physiologists for nearly a century. Central to this field of enquiry has been the study of evaporative cooling, the only mechanism whereby birds can defend body temperature below environmental temperature. We developed a novel technique for quantifying avian heat tolerance and evaporative cooling capacity, and used this approach to investigate thermoregulatory capacity in arid-zone avifaunas from three continents. For each of 37 species, we measured the interactions between body temperature, evaporative water loss and resting metabolic rate at high air temperatures. Our data reveal that the efficiency and scaling of heat tolerance vary greatly among higher taxa. Some species can dissipate up to ~500 % of metabolic heat production via evaporation. We also documented substantial variation within orders, as well as intraspecific variation among populations within species. Not all taxa showed an upper critical limit of thermoneutrality; in species with well-developed cutaneous evaporative heat dissipation and/or gular flutter, resting metabolic rate often remained at minimal levels even at air temperatures above 50 °C. More recently, we have used these data to model increases in water requirements associated with climate change. These models reveal that many species will be subject to greatly increased water requirements in future, and some desert specialists may lose large parts of their ranges on account of conditions that exceed their physiological tolerance limits.

  • Contact: Dr Heike Lutermann: 012 420-4627

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