When lemming population density reached a certain level they became restless with anxiety, so that if one of them deliberately or accidentally fell into the sea others would follow suit.
當鼠口密度達到一定比例時，老鼠會焦躁不安，只要有一隻受不了或不小心掉進海裡去，其他的就一窩蜂跟著下去。