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.

中文翻译：

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完全和部分低温的王企鹅的体表复温

企鹅在觅食之旅后以低温状态返回陆地时面临重大的热转变。非绝缘附件（鳍状肢和脚）可以在随后的复温过程中提供灵活的热交换。在这里，我们测试了在此恢复阶段可能延迟外周血管舒张的假设。为此，我们设计了一个实验来检查完全低温（泄殖腔和外围区域（这里；脚蹼、脚和乳房）<37°C）和部分低温（正常体温下的泄殖腔≥37°C，但在体温过低时的外围）王企鹅（Aptenodytes patagonicus）在实验室复温时。两组在 21 分钟的观察期内均复温，但完全体温变化大于部分低温鸟类。而且，与部分体温过低的鸟类相比，我们观察到外周温度完全延迟了 5 分钟，这表明该过程受到内部温度低的影响。为了调查我们的实验室数据是否适用于野外条件，我们还记录了自由放养的企鹅在登陆殖民地后的表面温度。这些鸟的初始表面温度低于那些在实验室中重新加热的鸟，并且在陆地上的可比时间段内变化较小。这可以通过环境条件和实验室中可能的处理引起的产热来解释。尽管如此，