Weaned southern elephant seals (SES) quickly transition from terrestrial to aquatic life after a 5- to 6-week post-weaning period. At sea, juveniles and adult elephant seals present extreme, continuous diving behaviour. Previous studies have highlighted the importance of the post-weaning period for weanlings to prepare for the physiological challenges of their future sea life. However, very little is known about how their body condition during this period may influence the development of their behaviour and brain activities. To characterise changes in the behavioural and brain activity of weanlings prior to ocean departure, we implemented a multi-logger approach combining measurements of movements (related to behaviour), pressure (related to diving), and brain electrical activity. As pups age, the amount of time allocated to resting decreases in favour of physical activity. Most resting (9.6 ± 1.2 h/day) takes place during daytime, with periods of slow-wave sleep representing 4.9 ± 0.9 h/day during the first 2 weeks. Furthermore, an increasing proportion of physical activity transitions from land to shore. Additionally, pups in poorer condition (lean group) are more active earlier than those in better condition (corpulent group). Finally, at weaning, clear circadian activity with two peaks at dawn and dusk is observed, and this pattern remains unchanged during the 4 weeks on land. This circadian pattern matches the one observed in adults at sea, with more prey catches at dawn and dusk, raising the question of whether it is endogenous or triggered by the mother during lactation.

中文翻译：

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从陆地到海洋：南象海豹幼崽在第一次出海前需要一个月的时间来掌握水生技能

断奶的南象海豹 (SES) 在断奶后 5 至 6 周后迅速从陆地生活过渡到水生生活。在海上，幼年和成年象海豹表现出极端、持续的潜水行为。先前的研究强调了断奶后阶段对于断奶仔鱼为未来海洋生活的生理挑战做好准备的重要性。然而，人们对这一时期的身体状况如何影响他们的行为和大脑活动的发展知之甚少。为了表征断奶仔猪在离开海洋之前的行为和大脑活动的变化，我们实施了一种多记录器方法，结合了运动（与行为相关）、压力（与潜水相关）和脑电活动的测量。随着幼犬年龄的增长，分配给休息的时间减少，有利于体力活动。大多数休息（9.6 ± 1.2 小时/天）发生在白天，前两周的慢波睡眠时间为 4.9 ± 0.9 小时/天。此外，越来越多的身体活动从陆地转移到海岸。此外，状况较差的幼犬（瘦弱组）比状况较好的幼犬（肥胖组）更早活跃。最后，在断奶时，观察到清晰的昼夜节律活动，在黎明和黄昏有两个高峰，并且这种模式在陆地上的 4 周内保持不变。这种昼夜节律模式与在海上观察到的成年人的昼夜节律模式相匹配，黎明和黄昏时捕获的猎物更多，这引发了一个问题：这种昼夜节律模式是内源性的还是由母亲在哺乳期间触发的。