State University of New York, College of Environmental Science and Forestry, Syracuse, New York, USA.
National Park Service, Arctic Inventory and Monitoring Program, Gates of the Arctic National Park and Preserve, Fairbanks, Alaska, USA.
Glob Chang Biol. 2024 Nov;30(11):e17589. doi: 10.1111/gcb.17589.
Long-distance migrations are a striking, and strikingly successful, adaptation for highly mobile terrestrial animals in seasonal environments. However, it remains an open question whether migratory animals are more resilient or less resilient to rapidly changing environments. Furthermore, the mechanisms by which animals adapt or modify their migrations are poorly understood. We describe a dramatic shift of over 500 km in the wintering range of the Western Arctic Herd, a large caribou (Rangifer tarandus) herd in northwestern Alaska, an area that is undergoing some of the most rapid warming on Earth. Between 2012 and 2020, caribou switched from reliably wintering in maritime tundra in the southwesternmost portion of their range to more frequently wintering in mountainous areas to the east. Analysis of this range shift, in conjunction with nearly 200 documented mortality events, revealed that it was both broadly adaptive and likely driven by collective memory of poor winter conditions. Before the range shift, overwinter survival in the maritime tundra was high, routinely surpassing 95%, but falling to around 80% even as fewer animals wintered there. Meanwhile, in the increasingly used mountainous portion of the range, survival was intermediate and less variable across years compared to the extremes in the southern winter ranges. Thus, the shift only imperfectly mitigated overall increased mortality rates. The range shift has also been accompanied by changes in seasonal patterns of survival that are consistent with poorer nutritional intake in winter. Unexpectedly, the strongest single predictor of an individual's probability of migrating south was the overall survival of animals in the south in the preceding winter, suggesting that the range shift is in part driven by collective memory. Our results demonstrate the importance and use of collective decision making and memory for a highly mobile species for improving fitness outcomes in a dynamic, changing environment.
长距离迁徙是高度适应季节性环境的移动性陆地动物的一种显著且成功的适应方式。然而，迁徙动物对快速变化的环境更具弹性还是更不具弹性，仍然是一个悬而未决的问题。此外，动物适应或改变其迁徙的机制还知之甚少。我们描述了阿拉斯加西北部一个大型驯鹿（Rangifer tarandus）群——西北极鹿群——越冬范围的剧烈变化，超过 500 公里。这个地区正在经历地球上最快的变暖之一。在 2012 年至 2020 年期间，驯鹿从可靠地在其范围最西南部分的沿海冻原越冬，转变为更频繁地在东部山区越冬。对这种范围变化的分析，结合近 200 次有记录的死亡事件，表明它是广泛适应的，并且可能是由对恶劣冬季条件的集体记忆驱动的。在范围变化之前，在沿海冻原越冬的存活率很高，通常超过 95%，但当更少的动物在那里越冬时，存活率下降到 80%左右。与此同时，在越来越多被使用的山区范围内，与南部冬季范围的极端情况相比，存活率居中且每年变化较小。因此，这种转变只是不完全缓解了整体死亡率的增加。范围变化还伴随着季节性生存模式的变化，这与冬季营养摄入较差一致。出乎意料的是，个体向南迁徙的概率的最强单一预测因子是前一年南方动物的整体存活率，这表明范围变化部分是由集体记忆驱动的。我们的研究结果表明，对于一个高度移动的物种来说，集体决策和记忆对于在动态、变化的环境中提高适应性结果具有重要性和实用性。
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