They follow the sun in a daily migration that feeds their passengers and ensures their own survival. (?
它们每天跟着阳光迁移，不仅确保了自己生命的延续，而且也成为过往‘旅客’的美餐。
But daily vertical movements by zooplankton in the ocean—upward by night to seek food, downward by day to escape predators—can also be considered migration.
但是海洋中浮游动物每天的垂直运动——夜里上浮以寻找食物，白天下潜以躲避捕食者——也可以被视作迁徒。
Fear of predators doesn't just affect the penguins' daily activities, however. It also influences the birds' migration patterns, Ainley and Ballard report this week in Polar Biology.
Ainley和Ballard在本周的《极地生物学》中指出，害怕被捕食已经影响到企鹅的日常活动，甚至它们的迁徙规律。
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