Researchers eavesdropping on sperm whales living in the eastern Pacific Ocean have discovered that the whales learn to vocalize like others around them. These different clans with their own dialects likely emerged through cultural learning, according to findings published in Nature Communications this week. A similar process is thought to underlie the formation of diverse human cultures, or the behaviors we share with others within the same group.
While male sperm whales (Physeter macrocephalus) are solitary and live closer to the poles, females live in multi-level societies: Individuals within family units group together into larger clans. These massive, toothy cetaceans communicate using a series of clicks (called codas), and researchers have been able to distinguish clans based on similar patterns in their vocal repertoires recorded with hydrophones. However, it’s unclear how different clans emerge in the ocean where there are no physical barriers to separate them.
To investigate, a team led by Dalhousie University’s Maurício Cantor examined a dataset of sperm whale social interactions and vocalizations off the Galápagos Islands spanning 18 years. These whales belonged to three nested social levels: individuals, social units, and vocal clans. Social units consisted of about 12 whales that have lived and moved together for years based on photos of markings on tail flukes; clans contain many social units and thousands of whales with a high similarity in their coda repertoires. The team then created a model that simulates interactions between individual whales to test if clan structure could arise from evolving vocal behavior.
Based on their simulations, clans likely arose when whales preferentially learned the vocalizations of other whales that behave like themselves. Information flow within smaller groups helped maintain clan cohesion. This is one more pillar of support for the idea that animals have culture, Cantor told National Geographic. Other scenarios, such as the genetic inheritance of call structures, can’t explain the patterns observed in the wild.
"We all tend to interact more with likeminded individuals," Cantor tells CBC. "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.”