People in different countries often speak different languages. And even within a community, different groups may have distinct dialects or slang. Turns out, the same is true of pilot whales.

“Short-finned pilot whales are actually often referred to as the ‘canaries of the ocean’ because they have such sing-songy type whistles,” said Amy Van Cise, a postdoctoral scholar at Woods Hole Oceanographic Institution and the lead author on a new study documenting distinct dialects among pilot whales.

Their creaking and clicking calls sound a lot like dolphin noises, which makes sense because pilot whales are actually a kind of dolphin, she explained.

Twenty years of data collected near Hawaii shows that pilot whales spend their entire lives in small social groups, which are made up of their immediate family members. They also spend time with their extended families, such as aunts, uncles and cousins. There’s not any sign of inbreeding, so they do leave the group to breed, it appears.

Van Cise used a large database of recorded pilot whale calls for the study.

“We went through and manually identified every single [pilot whale] call we found in every single recording,” Van Cise said. “It was a good bit of time.”

What they found was that each family had its own distinct set of calls. Some of the groups shared certain calls, but it was clear that every group had a dialect.

This is useful when two or more groups of 70 to 100 whales come into contact with each other. When it's time to go, they all have to figure out who they’re supposed to leave with.

“These animals are living in an area where there are no barriers to mixing at all. They share the exact same space, and yet they have to maintain their own groups,” she said.

The whales are taught the dialects by family members, Van Cise said, showing a real learning capacity among marine mammals. This is not unexpected. Orcas in captivity have even been known to learn to make dolphin sounds, mimicking the nearby animals that they can hear.

There may be some evolutionary strategy at work among the social groups of pilot whales, Van Cise said. It's not yet clear what that strategy is.

“As far as we know, there's no geographic, oceanographic, or ecological barrier that would stop these animals from mixing with each other,” she said. “They are simply choosing not to mix.”