Risso’s dolphins – such as this one swimming off the coast of southern California – can not only distinguish between the calls of killer whales and other, non-threatening, cetaceans, they also seem to be able to discern intent conveyed in each call.
Scientists led by Matthew Bowers of Duke University in the US played recordings of calls by killer whales and baleen whales to a group of four of the dolphins.
The dolphins all reacted to the killer whale calls, but did so very strongly only to a certain subset. In a paper published in The Journal of Experimental Biology, the scientists suggest that the animals can distinguish between killer whale vocalisations that do not contain a threat (or perhaps statement of intent), and those that do.