Sperm whale 'dialects' suggest cultural learning
Young whales appear to learn from adults who talk like their own social group
Whadd'ya at? Ow ya goin'? If you were at a picnic with a bunch of Newfoundlanders or Australians, those are the greetings you might fling around.
Similarly, scientists who eavesdrop on sperm whales – Moby Dick's species — have found they also have distinct "dialects." And a new study suggests like human dialects, they arise through cultural learning.
"Cultural transmission seems key to the partitioning of sperm whales into… clans," the researchers wrote in a paper published today in the journal Nature Communications.
Sperm whales live around the world, mainly in deeper waters far offshore. The solitary males live in colder areas, and roam in Canadian waters in areas where the ocean depth is more than 1000 metres, says Mauricio Cantor, the Dalhousie University PhD. student who led the new study with Hal Whitehead, a Dalhousie biology professor.
The females live in warmer, more southern waters, in loose family groups of around seven to 12 whales – sisters, aunts, grandmothers, cousins, and the occasional unrelated friend and their calves. Sometimes, they meet up with other families for gatherings of up to 200 whales, similar to human picnics or festivals. These can last from a few hours to a few days.
The whales that gather in these groups, called clans, have distinct "dialects" of patterns of clicks called codas that are distinct from the clicks they use in echolocation when they're hunting for food. They use codas talk to each other when they surface between dives.
"They kind of communicate with Morse code," said Cantor, adding that the sound of each click is similar, but the rhythm and tempo varies, along with the length of pauses between them.
If you listen to the example below, you'll hear up to 10 whales from the microphone, some closer and some farther away from the microphone, making a distinctive coda.
Researchers don't yet know what the whales are saying. But they know that among a given clan, whales make some of the same patterns of clicks.
Cantor and his colleagues recorded 18 years of "conversations" among sperm whales near the Galapagos Islands from a boat equipped with underwater microphones. They found the whales in that region belong to two or three clans, each with a different coda.
Dialects not tied to geography
While regional variations in song are sometimes seen in birds, the variations in sperm whale codas isn't tied to geography.
"What is really interesting is they all use the same waters at the same time," Cantor said, "so they could potentially hear or listen to all these codas, but they choose to stick with their own pattern."
Cantor and his colleagues wondered how those different dialects might have arisen. Some possibilities were that:
- They were due to genetic differences.
- Mothers taught the codas to their calves.
- Young whales learned the codas from other, unrelated whales.
The researchers ran computer simulations of virtual groups of whales over 1,000 years to see what kinds of factors would generate the types of patterns they saw in the actual data they collected.
What they found was that in order to create clans with distinct dialects, young whales had to learn codas not just from their mothers, but also other adults. But that wasn't enough – the young whales also had to prefer to learn codas:
- Most similar to those used by their own family.
- Most commonly used by whales in their social group.
"Which is similar to what we see in human populations," Cantor said. "I just find really, really fascinating that an animal that is completely different and lives in a completely different environment - they have some striking similarities with our societies… Our findings suggest another line of evidence for animal culture."
He added that scientists still debate whether animals are capable of having culture, but if it's proven that they do, we might be more motivated to help conserve other species.
"We all tend to interact more with likeminded individuals," he said. "If we figure out somehow that we're not as different [from] other animals, maybe we can improve our relationship with the natural world or with nature."