Using recordings made from boats while in the presence of Omura’s whales, along with long-term recordings from remote acoustic recorders mounted on the sea floor, the Madagascar Project has documented for the first time the vocalizations made by Omura’s whales. Even more exciting, the vocalizations occur in what we consider to be a typical rorqual whale song. There are three main features that indicate a vocalization is song:
1. Stereotyped vocalization – this means that the sound is a very recognizable pattern that is similar each time it is produced. The main vocalization that we have recorded is a low frequency call, between 15-50 Hz (below most humans’ hearing), about 8-9 seconds long, and pulsative in form, like a long low rumble.
2. Rhythmic repetition – whenever this call is recorded, it is produced in a series with a very consistent repetition rate of 2 to 3 min, and can go on for hours. We consider each series the vocalization of a single animal repeating the call over and over again. This is an individual whale singing.
3. Chorusing of multiple individuals – the remote recorders frequently record many overlapping series of the vocalization, that be believe are multiple individuals singing in close proximity to each other, in what we call a chorus.
Song is known to be a male breeding display, and although we have much more work to do on the breeding behavior of Omura’s whales, we therefore suspect that the song we have recorded is likely a male behavior and is important in the species mating system. You can see what the song looks like in the spectrogram below.