But important questions remain, he says. For example, male humpback whales sometimes sing as they move in and out of competitive groups, but researchers don't know what role the songs play in mating.

但重要的问题还是，他说，比如，雄性驼背鲸有时候在进入或离开一个竞争性群体时唱歌，但研究者不清楚唱歌在其中起什么作用。

youdao

The rate at which an epidemic spreads to lower-risk groups depends a great deal on whether different groups mate mainly among themselves (assortative mating) or whether they mate a lot with other people (disassortative mating).

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