After reducing two 45-minute recordings of whale cries to a series of symbols, Buck and his colleagues used a computer program to study the sequences. Unlike, say, bird calls, which consist primarily of simple, repeated patterns of notes, Buck found that the whales' songs, like human language, appear to have a hierarchical structure.
In speech, such structure allows sentences to be diagrammed and makes English grammar predictable. For example, says Buck, "If I say that I will wear either the red shoes or the blue shoes, once you hear the word 'either,' you know an 'or' is coming."
Researchers still need to show that the humpback sounds have specific meaning before the songs can be considered a language.


