Depicted as predictable movements, migrations can, however, show important interannual variations, making the conservation of migratory species particularly challenging. Plasticity in migratory behaviour allows individuals to adjust their migratory tactics to maximize their fitness. Destination of migration, and therefore migration patterns, may vary according to climatic and environmental conditions encountered during migration or at the arrival site but also according to competition. In northern‐Québec and Labrador, Canada, fall migration patterns of caribou from the Rivière‐George (RGH) and the Rivière‐aux‐Feuilles (RFH) herds have varied greatly during the last decades. Meanwhile, both herds have shown large fluctuations in abundance. We assessed the influence of environmental factors and changes in population size on wintering area selection. Based on 649 fall migrations of 284 females equipped with ARGOS collars, we used a machine‐learning algorithm, the random forests, to assess how climate, resources and population size affected the selection of four different wintering areas. Individuals followed over several years switched to a different wintering area 45% of the time between consecutive years, and this probability increased at high population size. The main determinant of wintering area selection was the population size for both herds, suggesting intra‐ and inter‐herd competition for wintering areas. The long migrations of RGH toward the western wintering areas, also used by RFH, were favoured when the herd was abundant and when the availability of resources was low at the departure. The migrations of RFH toward the south‐western area increased as RGH declined, possibly because the past presence of RGH in this area reduced access for caribou from RFH. These results highlight the flexibility in the migratory behaviour of caribou in response to variation in competition. Our study is the first to suggest that wintering area selection can be determined by competition between populations of the same ungulate species.

中文翻译：

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在哪里度过冬天？种内竞争和气候在决定迁徙驯鹿选择越冬地区中的作用

然而，被描述为可预测的移动，迁移可能显示重要的年际变化，这使得对迁徙物种的保护特别具有挑战性。迁徙行为的可塑性使个人可以调整其迁徙策略，以最大程度地提高其适应能力。迁移的目的地以及迁移方式可能会根据迁移过程中或到达地点遇到的气候和环境条件而有所不同，但也会因竞争而异。在加拿大魁北克北部和拉布拉多，驯鹿从里维耶尔·乔治（RGH）和里维埃勒·奥弗尔（RFH）牧群的秋季迁徙模式在过去几十年间变化很大。同时，这两个群体的丰度都有很大的波动。我们评估了环境因素和人口规模变化对越冬地区选择的影响。基于284名配备ARGOS项圈的雌性动物的649例秋季迁徙，我们使用了机器学习算法（即随机森林）来评估气候，资源和人口规模如何影响四个不同越冬区域的选择。连续数年追踪的个体在连续几年之间有45％的时间切换到不同的越冬区域，并且这种概率在高人口规模下会增加。越冬地区选择的主要决定因素是这两个种群的人口规模，这表明越冬地区的内部和内部竞争。当牧群丰富且出发时资源匮乏时，RFH也使用了RGH向西部越冬地区的长期迁徙。随着RGH的下降，RFH向西南地区的迁移增加，可能是因为RGH过去在该地区的存在减少了来自RFH的驯鹿的进入。这些结果突出了驯鹿对竞争变化的迁徙行为的灵活性。我们的研究首次表明越冬地区的选择可以通过相同有蹄类动物的种群之间的竞争来决定。