Variability within species is key for adaptability and biological evolution. To understand individualities in the context of animal movement, we focused on one of the most remarkable migrations—the journey of the endangered European eel from their birthplace in the Sargasso Sea to freshwater environments. Laboratory observations unveiled a continuum of diverse phenotypes of migrating eels: Some displayed a heightened tendency to swim against a constant water flow, while others a greater propensity to climb obstacles. Looking for the biological underpinnings of this migratory diversity, we characterized the eels’ individual differences in traits of four key domains: life history, physiology, behavior, and cognition, among which we found significant variance and interconnectedness. Upon reducing this variance to its primary multivariate axes, we found that these predict the migratory types. Eels with 1) low exploration, high activity, low boldness, and high lateralization; 2) strong lateralization, enhanced quantitative abilities, short problem-solving time, high boldness, and low growth rates; or 3) enhanced problem-solving, reduced spatial learning, high cognitive flexibility, and shorter time to solve the cognitive tasks were more likely to display the climbing migratory type. Field sampling revealed how specific traits’ combinations seemed to influence the distribution of eels once they begin to settle in the freshwater environment. Our study underscores the impressive diversity of individuals during this critical migration, emphasizing an intrinsic connection to multidomain trait variance. Preserving this diversity becomes paramount, as it likely contributes to the resilience and adaptability of endangered migratory species.

中文翻译：

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鳗鱼的个体迁徙行为源于一种复杂的综合症，涉及认知、行为、生理和生活史


物种内部的变异性是适应性和生物进化的关键。为了了解动物运动背景下的个体，我们专注于最引人注目的迁徙之一——濒临灭绝的欧洲鳗鱼从它们在马尾藻海的出生地到淡水环境的旅程。实验室观察揭示了迁徙鳗鱼不同表型的连续体：一些表现出更强的逆流游泳的倾向，而另一些则更倾向于攀爬障碍物。为了寻找这种迁徙多样性的生物学基础，我们表征了鳗鱼在生活史、生理学、行为和认知四个关键领域特征的个体差异，其中我们发现了显着的差异和相互关联性。在将此方差减少到其主要多变量轴后，我们发现这些轴可以预测迁移类型。鳗鱼 1） 低探索、高活性、低大胆和高偏侧化;2） 强偏侧化、增强定量能力、解决问题时间短、大胆度高、增长率低;或 3） 解决问题能力增强、空间学习减少、认知灵活性高、解决认知任务的时间更短更有可能表现出攀爬迁移型。实地采样揭示了一旦鳗鱼开始在淡水环境中定居，特定性状的组合似乎如何影响它们的分布。我们的研究强调了这一关键迁移过程中个体令人印象深刻的多样性，强调了与多域性状方差的内在联系。保护这种多样性变得至关重要，因为它可能有助于提高濒危迁徙物种的复原力和适应性。