Heat loss to water during head immersion in the pekin duck

Abstract

It is widely accepted that the whole-animal metabolic rate is reduced during prolonged submersion in domestic ducks. One line of supporting evidence (body temperature data) relies upon the assumption that overall thermal conductivity of the animal is reduced during head immersion. However, one potential heat exchange surface has not been adequately assessed: the oro-pharyngeal surface. This experiment was designed to determine the extent to which the water serves as a sink for metabolic heat during prolonged head immersion. Heat production (estimated from oxygen consumption) of the resting nonsubmerged ducks was 5.1 ± 0.4 W·kg–1. Underwater endurance time was 7.8 ± 0.6 min. Deep body temperature did not change during submergence. Average rate of heat lost to water was 3.9 ± 0.4 W·kg–1. However, heat loss to water varied substantially as a function of submergence time, being 15 ± 1.7 W·kg–1 in the first minute and declining rapidly to <1.5 W·kg–1 after 4 min of submersion. We conclude that the duck bill serves as a significant heat exchange surface only during the early stages of head immersion, when the cardiovascular response is not fully developed. These data support the hypothesis that heat production is depressed during the later stages of prolonged head immersion in this species. J. Exp. Zool. 278:429–434, 1997. © 1997 Wiley-Liss, Inc.