Had a thought this morning.
You know that whale song has some characteristics which are not easily explained.
- All whales seem to sing the same song, regardless of where they are
- The song changes subtly from year to year
- Whales can stop singing for hours or days at a time and then pick up the song again right where they left off
- There is some evidence that whales all over the world sing in unison
What if whale song is not communication whale-to-whale? What if they're harmonizing with sounds the earth is making, sounds we can't hear?
The sounds could be movement of magma inside the earth, or cosmic rays hitting the ionosphere. Maybe it isn't "sound" at all but some other vibration our senses don't pick up -- like the sense that makes animals jumpy before an earthquake?
This would explain why recording whale song and playing it back to them elicits no reaction. Out of context, without the earth sounds synchronized, the song has no purpose.