在这个繁忙的假期里，我们中的许多人都在一心多用。北极驯鹿也不例外。
一项新的研究表明，驯鹿可以同时吃饭和睡觉。12月22日发表在《当代生物学》(Current Biology)杂志上的这一节省时间的策略，增加了动物在恶劣条件下捕捉睡眠的巧妙方法的数量(SN: 11/30/23)。
北极驯鹿在夏天非常忙碌——当太阳全天候照耀，食物充足时，它们就会吃东西。像其他反刍动物一样，驯鹿花相当多的时间咀嚼反刍食物，使其更小，更容易消化。在这些反刍声中找时间睡觉可能很难。但如果驯鹿能在吃东西的时候睡觉就不会了。为了弄清楚驯鹿是否真的会睡觉吃东西，神经科学家梅勒妮·弗勒和时间生物学家萨拉·迈耶以及他们的同事们训练了四只欧亚苔原雌性驯鹿(Rangifer tarandus tarandus)，让它们在剃光的皮肤上忍受笔和电极。这个过程包括踢几脚和吃很多地衣，“这对它们来说就像糖果，”苏黎世大学的梅尔说。
研究人员一直在寻找非快速眼动睡眠期间出现的脑电波，这是一种深度的恢复性睡眠阶段。这些波出现在驯鹿反刍时，尽管咀嚼运动本身使得很难说信号是否与常规睡眠时的信号相同。同样来自苏黎世大学的Furrer说:“我们不能仅仅通过观察脑电波来了解细节，因为我们在那里有咀嚼，这稍微扰乱了它。”
不过，其他迹象也表明，吃东西时睡觉。驯鹿在咀嚼时很平静，经常闭着眼睛。“他们处于一种非常放松的状态，类似于非快速眼动睡眠的身体姿势，”Furrer说。反刍的驯鹿也很难被打扰;来自邻近驯鹿的沙沙声不太可能被反刍的驯鹿看到。当驯鹿保持清醒时，它们需要补觉。但研究人员发现，咀嚼的时间减少了恢复性睡眠的时间。
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Together, these strands of evidence “convincingly demonstrate that reindeer are able to sleep while ruminating,” says neurobiologist Niels Rattenborg of the Max Planck Institute for Biological Intelligence in Seewiesen, Germany, who was not involved in the study.
Unlike fur seals, ducks and long-haul flying frigatebirds, the reindeer show signs of sleeping with both sides of their brains while chewing (SN: 6/30/16). Figuring out exactly how reindeer pull this off would be interesting, Rattenborg says. Studying various forms of sleep might lead to insights on sleep walking in people, “a poorly understood and potentially dangerous sleep disorder,” he says.
Neuroscientist and study coauthor Gabi Wagner notes that Indigenous reindeer herders have a concept that roughly translates to “pasture peace.” Reindeer “need time and space to be quiet and to have peace, to ruminate,” says Wagner, of the Norwegian Institute of Bioeconomy Research in Troms?. “This paper for the first time shows that this is a very real, physiological requirement to have enough peace to ruminate undisturbed in order to cover the sleep requirements.”
For now, let’s all be cheered that reindeer can take good care of themselves. Some of them might be busy this Christmas Eve.
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