Sperm whales live in structured clans similar to early humans, according to new research.
Hal Whitehead, the sole author of the study and a professor at Dalhousie University, said the clan systems are matrilineal and average roughly 20,000 females per clan.
The discovery will help understand the marine mammals’ cultural system and non-vocal behaviour, he said.
“We often, as biologists, try to make sense of what we see by comparing species. And as we looked for parallels with the clans, the closest thing we could find was what some people call ethnolinguistic groups,” he said. “Some people just call them clans of humans.”
Whitehead’s research paper, published in the Royal Society Open Science journal on Jan. 10, said the clans are determined by vocalizations called “codas” that involve distinct sequences of clicks.
‘Morse code-like’ patterns
The paper references Taylor Hersh, one of Whitehead’s former students, for discovering seven female-led clans among the estimated 300,000 sperm whales in the Pacific Ocean, with each clan using a different dialect.
“I think the thing we were most excited about was finding that the different clans did seem to have these preferred vocalizations,” Hersh said.
When two clans overlap geographically, the whales are believed to change codas, just as humans who encounter different cultural groups look for things that distinguish “us from them,” she said.
Hersh, who is now a postdoctoral researcher at Oregon State University, analyzed dozens of sperm whale dialects, describing them as a “Morse code-like patterned series of clicks.”
‘A whole way of life’
Whitehead first discovered two clans using different dialects in the early 2000s, during a research trip to the Galapagos Islands with a colleague. He described one group going “click click click click,” and the other “click click click pause click.”
Two decades later, Whitehead said they still don’t know why sperm whales only socialize with members of their own clan and not with members from another one.
But his research paper says the dialects mark social divisions, and that culture is the only feasible explanation for differences between clans.
Whitehead said the clans act in a “democratic” system when hunting, navigating, communicating and making decisions. When attacked, they defend themselves communally and protect the young by putting them in the centre of the group, similar to hunter-gatherers.
“It’s a really exciting thing because the young sperm whale is not only learning to make the click patterns, but learning a whole way of life from the members of his family and the other members of his clan,” he said.
Whitehead said his research is motivated in part by understanding how humans ended up with “extraordinary social structures,” and learning how another group of animals manage their lives.
“We can think about the things that we have in common with sperm whales,” he said. “We’re learning all the time, and that makes us human. Without that, we really couldn’t do anything. With sperm whales, it’s the same.”