Animals that occupy temperate and polar regions have specialized traits that help them survive in harsh, highly seasonal environments. One particularly important adaptation is seasonal coat colour (SCC) moulting. Over 20 species of birds and mammals distributed across the northern hemisphere undergo complete, biannual colour change from brown in the summer to completely white in the winter. But as climate change decreases duration of snow cover, seasonally winter white species (including the snowshoe hare Lepus americanus, Arctic fox Vulpes lagopus and willow ptarmigan Lagopus lagopus) become highly contrasted against dark snowless backgrounds. The negative consequences of camouflage mismatch and adaptive potential is of high interest for conservation. Here we provide the first comprehensive review across birds and mammals of the adaptive value and mechanisms underpinning SCC moulting. We found that across species, the main function of SCC moults is seasonal camouflage against snow, and photoperiod is the main driver of the moult phenology. Next, although many underlying mechanisms remain unclear, mammalian species share similarities in some aspects of hair growth, neuroendocrine control, and the effects of intrinsic and extrinsic factors on moult phenology. The underlying basis of SCC moults in birds is less understood and differs from mammals in several aspects. Lastly, our synthesis suggests that due to limited plasticity in SCC moulting, evolutionary adaptation will be necessary to mediate future camouflage mismatch and a detailed understanding of the SCC moulting will be needed to manage populations effectively under climate change.

中文翻译：

---

哺乳动物和鸟类季节性换色的功能和潜在机制：是什么让它们在变暖的世界中发生变化？

生活在温带和极地地区的动物具有特殊的特征，可以帮助它们在严酷、季节性强的环境中生存。一种特别重要的适应是季节性毛色 (SCC) 换羽。分布在北半球的 20 多种鸟类和哺乳动物每半年经历一次完整的颜色变化，从夏季的棕色到冬季的完全白色。但随着气候变化减少积雪持续时间，季节性冬季白色物种（包括雪兔美洲兔、北极狐 Vulpes lagopus 和柳树雷鸟 Lagopus lagopus）与深色无雪背景形成鲜明对比。伪装不匹配和适应性潜力的负面后果是保护的高度兴趣。在这里，我们对鸟类和哺乳动物的适应性价值和支持 SCC 换羽的机制进行了首次全面审查。我们发现，在不同物种中，SCC 换羽的主要功能是对雪的季节性伪装，而光周期是换羽物候的主要驱动因素。其次，虽然许多潜在机制仍不清楚，但哺乳动物物种在毛发生长、神经内分泌控制以及内在和外在因素对换羽物候的影响的某些方面有相似之处。鸟类 SCC 蜕皮的潜在基础知之甚少，并且在几个方面与哺乳动物不同。最后，我们的综合表明，由于 SCC 换羽的可塑性有限，