Here are excerpts from an interesting Wikipedia article on "songs" of Humpback Whales", followed by a picture and sound from the same article, combined as a "movie":

"Two groups of whales, the Humpback Whale and the subspecies of Blue Whale found in the Indian Ocean, are known to produce a series of repetitious sounds at varying frequencies. This is known as whale song. Male humpback whales perform these vocalizations only during the mating season, and so it is believed the purpose of songs is to aid sexual selection. The whale will repeat the same song, which last up to 30 or so minutes, over and over again over the course of hours or even days. All the whales in an area sing virtually the same song at any point in time and the song is constantly and slowly evolving over time. For example, over the course of a month a particular unit that started as an "upsweep" (increasing in frequency) might slowly flatten to become a constant note."

WHICH STATEMENTS BEST CHARACTERIZES WHALE SONGS AS THE TYPE OF COMMUNICATION THAT PINKER CALLS "VARIATIONS ON A THEME"?