Sperm whales live in clans with distinctive cultures, much like those of humans, a study has found.
Using underwater microphones and drone footage, Hal Whitehead, a sperm whale scientist at Dalhousie University, in Halifax, Canada, examined the sounds the animals made and their feeding habits and found that they organized themselves into groups of up to about 20,000.
The paperpublished in the Royal Society Open Science journal, said the strains were defined by variations in their vocalizations – distinctive, Morse code-like sequences of clicks known as “codas”.
These acted like human dialects and this allowed Whitehead and his colleagues to establish the existence of seven such tribes in the Pacific Ocean – with a total of 300,000 sperm whales.
“This is a large number for culturally defined entities outside of modern human ethnolinguistic groups,” Whitehead said. The tribes may meet, but they never interbreed, he added. Their sense of identity appeared, in human terms, almost tribal, recognizing and maintaining their differences while being of the same species.
Sperm whales have the largest brains on the planet. The animals can reach 15 meters in length, weigh up to 45 tons, and can 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 only for a few hours at a time. Their “only important transmission is from sperm”. Designated females undertook “allo-parental” care, watching out for calves while their mothers dived for food.
While underscoring how different whales are from humans, the paper suggested interesting similarities. Sperm whale society appears to have used consensus, rather than top-down leadership, to make communal decisions.
With thousands of animals traveling at the same time, searching for rapidly 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 has seen whales “take up to an hour or more to make a 90-degree turn” as they try to agree where to go.
The democracy of whales was a “slow and messy” business, Whitehead noted, just like our own.
He said he believed that studying the evolution of these large populations would provide clues to “human social evolution on the grandest scales” in ways that “have few parallels elsewhere”.
The study suggested that there may be evidence of how human activities have 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 others. Until 1971, sperm whale oil was used in the automatic transmission of most American cars.
Population numbers have recovered since the 1982 moratorium about killing large whales. But since sperm whales can live up to 80 years, it’s 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” show evidence of reduced fertility and fragmented family units. Even the physical size of the animals reduced.
Whitehead, who has studied sperm whales at sea since 1985, said he likes the term “whale nations” as a way to express the range of the separate tribes. He looked at human history and prehistory as a way of understanding cetacean evolution, comparing a discrete whale tribe in an enclosed area, such as the Mediterranean, with that of the human population on an isolated island , like Australia.
Conversely, in larger areas, such as the Pacific, where two or more tribes share the same environment, “culture is the only tenable explanation for the differences between tribes,” such as a land shared by people who speak different languages.
Whitehead acknowledged that research into the whales’ deeper prehistory – since the species evolved 24 million years ago – could be as difficult as the study of human prehistory. But he said he believed “patterns in genetics and linguistics, together with measures of environmental change” could reveal “an extraordinary amount”.
“I suppose one could say that [the whales’] history begins when our people began to write about them,” he said. “The prehistory of sperm whales is likely to be fascinating, but it will be much more difficult to imagine than for humans.”