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Testing the heat dissipation limit theory in a breeding passerine

Author:
  • Jan-Åke Nilsson
  • Andreas Nord
Publishing year: 2018
Language: English
Pages:
Publication/Series: Proceedings of the Royal Society B: Biological Sciences
Volume: 285
Issue: 1878
Document type: Journal article
Publisher: Royal Society

Abstract english

The maximum work rate of animals has recently been suggested to be determined by the rate at which excess metabolic heat generated during work can be dissipated (heat dissipation limitation (HDL) theory). As a first step towards testing this theory in wild animals, we experimentally manipulated brood size in breeding marsh tits (Poecile palustris) to change their work rate. Parents feeding nestlings generally operated at above-normal body temperatures. Body temperature in both males and females increased with maximum ambient temperature and with manipulated work rate, sometimes even exceeding 45°C, which is close to suggested lethal levels for birds. Such high body temperatures have previously only been described for birds living in hot and arid regions. Thus, reproductive effort in marsh tits may potentially be limited by the rate of heat dissipation. Females had lower body temperatures, a possible consequence of their brood patch serving as a thermal window facilitating heat dissipation. Because increasing body temperatures are connected to somatic costs, we suggest that the HDL theory may constitute a possible mediator of the trade-off between current and future reproduction. It follows that globally increasing, more stochastic, ambient temperatures may restrict the capacity for sustained work of animals in the future.
The maximum work rate of animals has recently been suggested to be determined by the rate at which excess metabolic heat generated during work can be dissipated (heat dissipation limitation (HDL) theory). As a first step towards testing this theory in wild animals, we experimentally manipulated brood size in breeding marsh tits (Poecile palustris) to change their work rate. Parents feeding nestlings generally operated at above-normal body temperatures. Body temperature in both males and females increased with maximum ambient temperature and with manipulated work rate, sometimes even exceeding 45°C, which is close to suggested lethal levels for birds. Such high body temperatures have previously only been described for birds living in hot and arid regions. Thus, reproductive effort in marsh tits may potentially be limited by the rate of heat dissipation. Females had lower body temperatures, a possible consequence of their brood patch serving as a thermal window facilitating heat dissipation. Because increasing body temperatures are connected to somatic costs, we suggest that the HDL theory may constitute a possible mediator of the trade-off between current and future reproduction. It follows that globally increasing, more stochastic, ambient temperatures may restrict the capacity for sustained work of animals in the future.

Keywords

  • Ecology
  • Evolutionary Biology
  • Zoology
  • Body Temperature
  • heat dissipation
  • hyperthermia
  • heterothermy
  • life history
  • reproductive investment
  • bird
  • body temperature
  • heat dissipation
  • hyperthermia
  • maximum work rate
  • parental effort
  • reproductive cost

Other

Published
  • ISSN: 1471-2954
Andreas Nord
E-mail: andreas [dot] nord [at] biol [dot] lu [dot] se

Researcher

Evolutionary ecology

+4746143537

Ekologihuset, Sölvegatan 37, Lund

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