All whales make
noise, but
humpback whales are notable, as their noises come in "
songs" that take a rhythmic and repetitive structure. The songs last between five and fifteen minutes, and rarely up to thirty. Only
male humpbacks sing, and the song is only produced during
mating season. Curiously, when the song is over
females do not come to the male, and he is left pretty much
alone until he rejoins the
group. For this reason, the
purpose of the song is not known, as it is apparently not for
attracting females, or at least not in any way that
science has found. It is theorized that the song may for warding off
rivals, comforting
mates and
offspring, or even as
sonar to find other groups of
whales.
All of the humpbacks in a pod sing an identical song, which changes with time. A pod's song will become audibly different after a few years. Songs can also be transfered from one population to another. In the study I'm familiar with, two humpbacks from the West coast of Australia ended up on the East coast, with their very different songs. Between the years of 1996 and 1998, the new song spread to the entire 112 whale population of the East coast, showing the songs to be a completely learnable and adaptable behavior.
Whale songs are made up of grunts, squeals, whistles, moans, trills, chirps, and other such noises, which can be produced at anywhere from 45 to 3600 hertz. For comparison, middle C is 262 Hz, and only the most talented operatic sopranos can sing above 1200 Hz. Individual whale noises, when used in song, are known as elements. Elements are produced at about 170 dB, easily louder than most ocean-going vessels.
Phrases are composed of elements repeated in twos or fours, which are themselves repeated to produce themes. There are six to ten themes in any given song. When the whale has sung the last theme, he resurfaces to breathe, and then submerges a few feet and begins again with the first theme.