Partial migration, whereby a proportion of a population migrates between distinct seasonal ranges, is common throughout the animal kingdom. However, studies linking existing theoretical models of migration probability, with empirical data are lacking. The competitive release hypothesis for partial migration predicts that due to density-dependent habitat selection, the proportion of migrants increases as the relative quality and size of the seasonal range increases, but decreases with increasing migration cost and population density. To test this prediction, we developed a quantitative framework to predict the proportion of migrants, using empirical data from 545 individually GPS-marked moose Alces alces from across Fennoscandia, spanning latitudes of 56° to 68°N. Moose contracted their ranges to common and spatially limited winter areas (typically at lower elevation), but expanded them during summer due to an increase in suitable habitat (at highland ranges). As predicted from our model, a better and larger highland range relative to the lowland range corresponded to a higher proportion of migrants in an area. Quantitative predictions coupling the balance of habitat availability of seasonal ranges with the probability of migrating in a large herbivore is a necessary step towards an enhanced understanding of the mechanisms underlying migration at the population level.

中文翻译：

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竞争的季节性释放解释了欧洲驼鹿的部分迁徙

部分迁移，即一部分种群在不同的季节性范围之间迁移，在整个动物王国中都很常见。然而，缺乏将现有迁移概率理论模型与经验数据联系起来的研究。部分迁徙的竞争性释放假设预测，由于密度依赖的栖息地选择，迁徙的比例随着季节范围的相对质量和规模的增加而增加，但随着迁徙成本和人口密度的增加而减少。为了测试这一预测，我们开发了一个定量框架来预测移民的比例，使用来自 545 只单独 GPS 标记的驼鹿Alces alces 的经验数据来自芬诺斯坎迪亚，横跨北纬 56° 至 68°。驼鹿将它们的活动范围缩小到常见且空间有限的冬季地区（通常在较低海拔地区），但由于适宜栖息地的增加（在高地范围内），它们在夏季扩大了活动范围。正如我们的模型所预测的那样，相对于低地范围，更好和更大的高地范围对应于一个地区更高比例的移民。将季节性范围的栖息地可用性与大型食草动物迁徙概率相结合的定量预测是加深对种群水平迁徙机制的理解的必要步骤。