complete data FOTS6639.xlsx

Data from: Seasonal variation in the thermal responses to changing environmental temperature in the world's northernmost landbird, by Nord A, Folkow LP. J Exp. Biol.<br>Abstract: Arctic homeotherms counter challenges at high latitudes using a combination of seasonal adjustments in pelage/plumage, fat deposition, and intricate thermoregulatory adaptations. However, there are still gaps in our understanding of their thermal responses to cold, particularly in Arctic birds. Here, we have studied the potential use of local heterothermy (i.e., tissue cooling that can contribute to lower heat loss rate) in Svalbard ptarmigan (Lagopus muta hyperborea), the world's northernmost landbird. We exposed birds kept under simulated Svalbard photoperiod to low ambient temperatures (Ta; between 0 and -30oC) during three seasons (early winter, late winter, summer), whilst recording resting metabolic rate (RMR), core temperature (Tc) and several cutaneous temperatures. Leg skin temperature varied the most, but still only by up to ~15oC, whereas body trunk skin temperature changed &lt; 1oC when Ta decreased from 0 to -30oC. At the same time, Tc increased by 0.9oC, concomitant with increased RMR. This was likely driven by triggering of cerebral thermosensors in response to cooling of the poorly insulated head, the skin of which was 5.4oC colder at -30oC than at 0oC. Thermal conductance in winter was higher in yearling birds, probably because they were time/resource constrained from acquiring a high-quality plumage and sufficient fat reserves due to concomitant body growth. In conclusion, Svalbard ptarmigan do not employ extensive local heterothermy for cold protection, but instead rely on efficient thermogenesis combined with excellent body insulation. Hence, cold defence in the world's northernmost landbird is not mechanistically much different from that of lower latitude relatives.

数据来源：《全球最北陆生鸟类对环境温度变化的热响应季节差异》，作者Nord A、Folkow LP，发表于《实验生物学杂志》（J Exp. Biol.）。
北极恒温动物通过被毛/羽毛的季节性调整、脂肪沉积以及复杂的体温调节适应策略，应对高纬度地区的生存挑战。然而，学界对其耐寒热响应的认知仍存在缺口，针对北极鸟类的相关研究尤为匮乏。本研究以全球最北的陆生鸟类——斯瓦尔巴岩雷鸟（Lagopus muta hyperborea）为对象，探究其局部异温性（local heterothermy，即可降低热散失率的组织降温现象）的潜在应用。本研究将饲养于模拟斯瓦尔巴光周期条件下的岩雷鸟，于初冬、晚冬和夏季三个季节暴露于0℃至-30℃的环境温度（ambient temperature, Ta）中，同时记录其静息代谢率（resting metabolic rate, RMR）、核心体温（core temperature, Tc）以及多处皮肤温度。结果显示，腿部皮肤温度波动幅度最大，但也仅变化约15℃；而当环境温度从0℃降至-30℃时，躯干皮肤温度的变化不足1℃。与此同时，核心体温上升0.9℃，并伴随静息代谢率的升高。该现象或由脑部温度感受器被激活所引发，该激活源于隔热性能欠佳的头部皮肤降温：当环境温度为-30℃时，头部皮肤温度较0℃时低5.4℃。冬季时，一岁龄岩雷鸟的热传导率更高，这可能是由于其正处于身体生长阶段，受时间与资源限制，无法获得高质量羽毛与充足的脂肪储备。综上，斯瓦尔巴岩雷鸟并未通过大范围局部异温性来抵御寒冷，而是依靠高效的产热能力与优异的身体隔热性能实现防寒。因此，这种全球最北陆生鸟类的防寒机制，与低纬度亲缘物种并无显著差异。