Body surface rewarming in fully and partially hypothermic king penguins

Agnès Lewden,Florent Chauvet,Dominic J Mccafferty,Andreas Nord,Batshéva Bonnet,André Ancel

doi:10.1007/s00360-020-01294-1

Abstract

Penguins face a major thermal transition when returning to land in a hypothermic state after a foraging trip. Uninsulated appendages (flippers and feet) could provide flexible heat exchange during subsequent rewarming. Here, we tested the hypothesis that peripheral vasodilation could be delayed during this recovery stage. To this end, we designed an experiment to examine patterns of surface rewarming in fully hypothermic (the cloaca and peripheral regions (here; flippers, feet and the breast) < 37 °C) and partially hypothermic (cloaca at normothermia ≥ 37 °C, but periphery at hypothermia) king penguins (Aptenodytes patagonicus) when they rewarmed in the laboratory. Both groups rewarmed during the 21 min observation period, but the temperature changes were larger in fully than in partially hypothermic birds. Moreover, we observed a 5 min delay of peripheral temperature in fully compared to partially hypothermic birds, suggesting that this process was impacted by low internal temperature. To investigate whether our laboratory data were applicable to field conditions, we also recorded surface temperatures of free-ranging penguins after they came ashore to the colony. Initial surface temperatures were lower in these birds compared to in those that rewarmed in the laboratory, and changed less over a comparable period of time on land. This could be explained both by environmental conditions and possible handling-induced thermogenesis in the laboratory. Nevertheless, this study demonstrated that appendage vasodilation is flexibly used during rewarming and that recovery may be influenced by both internal temperature and environmental conditions when penguins transition from sea to land.

Highlights

Seabirds and pinnipeds spend a large part of their lives at sea but periodically come to land for reproduction, moult or rest (Feltz and Fay 1966; Ling 1970; Croxall 1982; Hammond et al 1988; Watts 1992, 1996)
Journal of Comparative Physiology B (2020) 190:597–609 that substantially reduces the rate of heat loss compared to water (Bullard and Rapp 1970; Nadel 1984; Ponganis 2015) and air temperatures are often higher than sea temperatures
Reduced appendage temperature is achieved by massive peripheral vasoconstriction and countercurrent heat exchange in the appendages (Pabst et al 1999; Williams and Worthy 2002)

Summary

Introduction

Seabirds and pinnipeds spend a large part of their lives at sea but periodically come to land for reproduction, moult or rest (Feltz and Fay 1966; Ling 1970; Croxall 1982; Hammond et al 1988; Watts 1992, 1996). (e.g., thermal conductivity) that substantially reduces the rate of heat loss compared to water (Bullard and Rapp 1970; Nadel 1984; Ponganis 2015) and air temperatures are often higher than sea temperatures. To reduce the rate of heat loss at sea, the body trunk of marine endotherms is well insulated by dense pelage or a thick layer of subcutaneous fat. Reduced appendage temperature is achieved by massive peripheral vasoconstriction and countercurrent heat exchange in the appendages (Pabst et al 1999; Williams and Worthy 2002) The latter is important, because the appendages are relatively fat free, and at most insulated by short feathers or hair. Vasoconstriction may reduce heat loss from the flippers to only 2–6% of total body heat loss in 0 °C water, compared to 19–48% without vasoconstriction at 24 °C (Kvadsheim and Folkow 1997)

Objectives

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Conclusion