Killer Whales Learn the Language of Dolphins: Communication Cross-Species

When it comes to communication, the animal kingdom is filled with sound. From barks to gobbles to shrieks, animals innately know how to communicate to one another. Yet a few species, including humans, can imitate new sounds and use them in appropriate social contexts. Known as vocal learning, this is one of the underpinnings of language. Now, scientists have found that killer whales possess this particular ability and can actually learn cross-species.

Before now, scientists have seen vocal learning in bats, some birds and cetaceans. Studying large marine mammals, though, has been a challenge. In this case, the scientists found that killer whales (Orcinus orca) can actually learn from other species. When they socialized with bottlenose dolphins, the killer whales shifted the types of sounds they made to more closely match their social partners.

"There's been an idea for a long time that killer whales learn their dialect, but it isn't enough to say they all have different dialects so therefore they learn," said Ann Bowles, one of the researchers, in a news release. "There needs to be some experimental proof so you can say how well they learn and what context promotes learning."

In this case, the researchers compared old recordings of vocalizations patterns of killer whales that had been held with bottlenose dolphins to vocalizations of killer whales in same-species groups. In this way, the scientists evaluated the degree to which killer whales learned vocalization patterns from dolphins.

So what did they find? It turns out that all three killer whales that had been housed with dolphins for several years shifted the proportions of different call types in their repertoire to more closely match the distribution found in dolphins. For example, they produced more clicks and whistles and fewer pulsed calls. In addition, the scientists found that killer whales can learn completely new sounds; one killer whale living with dolphins learned how to produce a chirp sequence that humans had taught her dolphin pool-mates.

"It's important to understand how they acquire [their vocalization patterns], and lifelong, to what degree they can change it, because there are a number of different [cetacean] populations on the decline right now," said Bowles. "And where killer whales go, we can expect other small whale species to go-it's a broader question."

The findings are published in The Journal of the Acoustical Society of America.