Phys.org, August 2011
“If – and that is a big if – we are witnessing the horizontal spread of this behaviour, then I would assume that it spreads by an associate of a ‘conching’ dolphin closely observing the behaviour and then imitating it,” Mr. Allen said.
https://phys.org/news/2011-08-ingenious-fishing-method-dolphins.html
https://phys.org/news/2011-08-ingenious-fishing-method-dolphins.html