Humpbacks, when they develop the ability to sing this song, they're listening to other whales and modifying what they sing based on what they're hearing, just like song birds or the dolphin whistles I described.
ザトウクジラは歌う能力を発展させる過程で 他のクジラの歌を聞き 聞いた歌に基づいて 自分の歌を変えるのです 鳴き鳥や 先ほどの鳴き真似するイルカと同じですね