Sperm whales live in clans with distinctive cultures, much like those of humans, a study has found.
Using underwater microphones and drone surveys, Hal Whitehead, a sperm whale scientist at Dalhousie University, in Halifax, Canada, examined the sounds the animals made and their feeding habits and found they organised themselves into groups of up to around 20,000.
The paper, published in the Royal Society Open Science journal, said the clans were defined by variations in their vocalisations – distinctive, morse code-like sequences of clicks known as “codas”.
Acting like human dialects, these enabled Whitehead and his colleagues to establish the existence of seven such clans in the Pacific Ocean – with a total of 300,000 sperm whales.
“This is a huge number for culturally defined entities outside modern human ethnolinguistic groups,” Whitehead said. The clans might meet but they never interbred, he added. Their sense of identity appeared, in human terms, almost tribal, recognising and maintaining their differences while being of the same species.
Sperm whales have the biggest brains on the planet. The animals can reach 15 metres in length, weigh up to 45 tonnes, and are able to dive for up to two hours in search of food, mostly squid. They are present in oceans around the world.
Whitehead noted that the clans appeared to be “almost entirely female-based”. Males visited females occasionally and for only a few hours at a time. Their “only important transfer is of sperm”. Designated females undertook “alloparental” care, looking out for calves while their mothers dived for food.
While underlining how different whales were from humans, the paper suggested intriguing correspondences. Sperm whale society appeared to use consensus, rather than top-down leadership, to reach communal decisions.
With thousands of animals travelling at the same time, searching for fast-changing food sources and constantly aware of predators (killer whales will prey on sperm whale calves), these debates can be very important. Whitehead said he had seen whales “taking up to an hour or more to make a 90-degree turn” as they tried to agree where to go.
The democracy of whales was a “slow and messy” business, Whitehead observed, just like our own.
He said he believed that studying the evolution of these large populations would give clues to “human social evolution at the largest scales” in ways that “have few parallels elsewhere”.
The study suggested there may be evidence of how human activity had affected the whales. Sperm whales were widely hunted in the 18th, 19th and 20th centuries. In the 20th century alone, 700,000 died in hunts carried out by Britain, Norway, the Netherlands, Russia, Japan, Canada and Australia, among other nations. Up until 1971, sperm whale oil was used in the automatic transmissions of most American cars.
Population numbers have recovered since the 1982 moratorium on the killing of great whales. But as sperm whales can reach up to 80 years in age, it is possible that individuals may retain traumatic memories of 20th-century hunts, the paper suggested.
Whitehead told the Guardian that genetics in populations subjected to “intense modern whaling” showed evidence of reduced fertility and fragmented family units. Even the physical size of the animals had reduced.
Whitehead, who has been studying sperm whales at sea since 1985, said he liked the term “whale nations” as a way to express the scale of the separate clans. He looked to human history and prehistory, as a way of understanding the whales’ evolution, comparing a discrete whale clan in a closed area, such as the Mediterranean, to that of the human population on an isolated island, such as Australia.
Conversely, in larger areas, such as the Pacific, where two or more clans share the same environment, “culture is the only tenable explanation for the differences between clans”, like a country shared by humans speaking different languages.
Whitehead acknowledged that research into the whales’ deeper prehistory – since the species evolved 24m years ago – may be as difficult as the study of human prehistory. But he said he believed “patterns in genetics and linguistics, coupled with measures of environmental change” could reveal “an extraordinary amount”.
“I suppose one could say that [the whales’] history starts when we humans started writing about them,” he said. “The prehistory of sperm whales is likely to be fascinating, but will be much harder to picture than for humans.”
