 At first it started as a couple of whales, and now it seems like there's maybe a third and a fourth whale getting in on the chorus or the exchange. And what's hard to hear by ear, and one of the reasons why this is neat in our new study, is that they're varying the duration of those rhythms. Even if they're making the same click, click, click, click, click, they're changing how long that sound is, and the whale that's speaking with them is matching that duration very accurately.