Whalers’ logbooks show rapid drop in strike rate in north Pacific due to changes in cetacean behaviour
Wed 17 Mar 2021 07.01 GMT Last modified on Thu 18 Mar 2021 14.38 GMT
A remarkable new study on how whales behaved when attacked by humans in the 19th century has implications for the way they react to changes wreaked by humans in the 21st century.
The paper, published by the Royal Society on Wednesday, is authored by Hal Whitehead and Luke Rendell, pre-eminent scientists working with cetaceans, and Tim D Smith, a data scientist, and their research addresses an age-old question: if whales are so smart, why did they hang around to be killed? The answer? They didn’t.
Using newly digitised logbooks detailing the hunting of sperm whales in the north Pacific, the authors discovered that within just a few years, the strike rate of the whalers’ harpoons fell by 58%. This simple fact leads to an astonishing conclusion: that information about what was happening to them was being collectively shared among the whales, who made vital changes to their behaviour. As their culture made fatal first contact with ours, they learned quickly from their mistakes.
“Sperm whales have a traditional way of reacting to attacks from orca,” notes Hal Whitehead, who spoke to the Guardian from his house overlooking the ocean in Halifax, Nova Scotia, where he teaches at Dalhousie University. Before humans, orca were their only predators, against whom sperm whales form defensive circles, their powerful tails held outwards to keep their assailants at bay. But such techniques “just made it easier for the whalers to slaughter them”, says Whitehead.
It was a frighteningly rapid killing, and it accompanied other threats to the ironically named Pacific. From whaling and sealing stations to missionary bases, western culture was imported to an ocean that had remained largely untouched. As Herman Melville, himself a whaler in the Pacific in 1841, would write in Moby-Dick (1851): “The moot point is, whether Leviathan can long endure so wide a chase, and so remorseless a havoc.”
Sperm whales are highly socialised animals, able to communicate over great distances. They associate in clans defined by the dialect pattern of their sonar clicks. Their culture is matrilinear, and information about the new dangers may have been passed on in the same way whale matriarchs share knowledge about feeding grounds. Sperm whales also possess the largest brain on the planet. It is not hard to imagine that they understood what was happening to them.
The hunters themselves realised the whales’ efforts to escape. They saw that the animals appeared to communicate the threat within their attacked groups. Abandoning their usual defensive formations, the whales swam upwind to escape the hunters’ ships, themselves wind-powered. ‘This was cultural evolution, much too fast for genetic evolution,’ says Whitehead.
And in turn, it evokes another irony. Now, just as whales are beginning to recover from the industrial destruction by 20th-century whaling fleets – whose steamships and grenade harpoons no whale could evade – they face new threats created by our technology. ‘They’re having to learn not to get hit by ships, cope with the depredations of longline fishing, the changing source of their food due to climate change,’ says Whitehead. Perhaps the greatest modern peril is noise pollution, one they can do nothing to evade.
Whitehead and Randall have written persuasively of whale culture, expressed in localised feeding techniques as whales adapt to shifting sources, or in subtle changes in humpback song whose meaning remains mysterious. The same sort of urgent social learning the animals experienced in the whale wars of two centuries ago is reflected in the way they negotiate today’s uncertain world and what we’ve done to it.
As Whitehead observes, whale culture is many millions of years older than ours. Perhaps we need to learn from them as they learned from us. After all, it was the whales that provoked Melville to his prophesies in Moby-Dick. “We account the whale immortal in his species, however perishable in individuality,” he wrote, “and if ever the world is to be again flooded … then the eternal whale will still survive, and … spout his frothed defiance to the skies.”
• This article was amended on 18 March 2021 to make clear the status of “Dalhousie” as a university, not a placename.