一个主要原因是，蝙蝠也能听到雄泡蟾的鸣叫，并且在时刻准备吃掉它们。
A primary reason is that bats are also often listening, waiting, and getting ready to eat... frogs.
对于雄孔雀来说，硕长且沉重的尾屏是个沉重的负担，而过多的羽毛可能也同样拖累了近鸟龙。
And just as their long, heavy trains pose a burden to peacocks, the extravagant feathers of Anchiornis may have been a bit of a drag, literally.
一个种群中所有的雄鲸都唱同一首歌，但是偶尔他们也会发明一首全新的歌。
All the males in one population sing the same song, but occasionally they invent an entirely new one.
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