Imitation, generally speaking, is a human trait – whereas most animals are born making the sounds they make, humans learn to communicate with one another. While there are some pseudo-exceptions (cats learn to mimic the frequency of crying babies to receive attention), a study in the Journal of the Acoustical Society of America reports unprecedented findings: Killer whales can learn to “speak dolphin” in captivity.

“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. There needs to be some experimental proof so you can say how well they learn and what context promotes learning,” said Dr. Ann Bowles, senior research scientist at the Hubbs-SeaWorld Research Institute.

When orcas are socialized with bottlenose dolphins in captivity, they demonstrate the ability to learn and mimic the sounds of the dolphins. The researchers believe this may foster social interactions between the two species.

Even among their own species, the clicks and whistles they make to communicate can vary across social groups. That is, each group can produce their own “dialect” of sorts that allows them to identify members by sound, varied by duration and frequency. Testing for learning ability across species wasn’t easy, but the researchers found a novel approach.

Luckily, they had three orcas that had been housed with dolphins over a period of several years. A comparison of vocal recordings from both cross-socialized groups and segregates ones showed that in cross-socialized groups, the whales changed their vocal patterns to rely more on clicks and whistles and less on the vocal pulses more commonly used by whales.

What’s more, their learning capacity goes even further: One whale showed the ability to learn new sounds, a chirping sequence the researchers taught only to her dolphin pool-mates by researchers over the course of the experiment.

“Killer whales seem to be really motivated to match the features of their social partners,” said Bowles.

The adaptive advantage of this ability is as yet unknown, if there is one at all. Still, the researchers believe it’s important to study these mechanisms in marine mammals.

“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.”