hmmm.

A mass EXODUS of the 2nd most sentient and intelligent animal on this planet. An unplanned, migration of a significant portion of the entire species population.

Can mean only a few things.

1. Their home is no-longer suitable for life and they are forced to re-locate.

2. They are sensing imminent danger and are fleeing to safer waters.

3. They have coordinated through use of their language, a mass migration out of their own free will, in order to find a new home with better prospects?

4. They are ill or affected by something resulting in mass confusion and un-natural behaviour.