Friday 2 April 2021

Sperm whales taught each other how to fend off whaling ships in the 19th century, scientists find

 A scientist from Nova Scotia and his team discovered that sperm whales shared information across the ocean on how to run away — and even fight back — against hunters

In the 18th and 19th centuries, industrial whale hunters in the North Pacific Ocean were having a field day hunting sperm whales. Riding rowboats and brandishing hand-thrown harpoons, the whalers would hunt large gatherings of whales for their oil. The business was booming.

But, according to old fishing logs, their hunts became less and less fruitful, until their yield was reduced by more than half in the span of two years.

Sperm whaling in the North Pacific from the ship Canton on the Japan Grounds in the North Pacific. Four whaling boats harpooned six whales. Three of those whales were killed (exhaling reddish blows) and the other three were lost when the harpoons pulled free or broke. One whaling boat, shown in the lower left, was destroyed. PHOTO BY INK AND WATERCOLOUR BY OLIVER

Now researchers say that the whales had actually learned how to avoid the whalers — and shared this information across the ocean.

Their paper published on March 17 in The Royal Society says that sperm whales shared tips among each other on how to prevent — and even fight back — against whalers in the 19th-century North Pacific, and reduced successful whale killings by 58 percent.

Hal Whitehead, one of the paper’s co-authors and a biology professor at Dalhousie University in Nova Scotia, has been studying whales — primarily sperm whales — and analyzing their behaviours and social systems for almost 40 years. His interest in this study began with the release of a trove of recently digitized documents; thousands of captains’ logs and fishing logs, providing extremely detailed accounts of whaling expeditions around the world.

Most historians focused on the history of the whalers themselves, but Whitehead said what piqued his interest was their descriptions of the whales’ behaviours. Sometime in the 19th century, whalers began complaining that they were catching significantly fewer whales.

Initially, Whitehead said, it was hard to find the culprit, as most of the first whaling expeditions didn’t keep detailed logs.

Sperm whales in the 19th century and beyond have shared information in a form of “culture”, researchers say.

“We don’t have good data sets to do this. The problem is, when we as humans start exploiting anything, we don’t tend to keep very good records of it,” Whitehead said. “This makes it hard to figure out the potential for animals reacting to this, because we don’t have good records.”

So his team, which included U.K. biologist Luke Rendell and data scientist Tim Smith, decided to pay close attention to American whaling expeditions in the North Pacific Ocean in the 19th century. Whitehead said, as one of the more recent areas that whalers began to hunt in, it was a region where the expedition logs were more complete, and at that time it was exclusively the domain of American whalers.

Before hunters encroached on their territory, the only predator sperm whales — who often weigh more than 40,000 kilos — had to fear were killer whales.

“These were the Texaco of this era, these guys killing sperm whales, getting the oil, selling the oil and making huge amounts of money,” Whitehead said.

According to the study, Smith compiled a dataset of 77,749 voyage days, which included 2,405 days where whalers spotted sperm whales.

When they discovered that there was a 58 percent drop in successful sperm whale hunts in an extremely small window of just over two years, Whitehead said he was “pretty well blown apart by that.”

“That was very remarkable,” he said. “I thought there might be a drop, but not that much and not that quickly. Usually, you expect it to increase as they figure out stuff and become more successful. That’s typically how our exploitation of wildlife goes. We become more efficient as we learn how to do it.”

Before hunters encroached on their territory, the only predator sperm whales — who often weigh more than 40,000 kilos — had to fear were killer whales. Typically, sperm whales defend themselves against killer whales by forming a large circle, with their young in the middle, and fight back with either their jaws or tails.

It works pretty well, Whitehead said, but has the opposite effect when confronted with humans.

“This is what they did to their previous enemy,” Whitehead said. “So they now have this new enemy, and this is almost the very worst thing you should do when faced with Captain Ahab. To form a tight group, slow-moving, just sitting there, it’s a wonderful target for someone throwing a harpoon.”

At first, whalers were extremely successful at catching and killing sperm whales. But there soon was a shift — instead of gathering in a circle when hunters arrived, the whales would quickly swim upwind, where the weak rowboats couldn’t follow. Some even attacked the fragile boats instead.

The sperm whales were communicating, the study finds, sharing their findings when new strategies helped fight off their attackers, and soon whales across the entire North Pacific were doing it.

Whitehead said the behaviours of the sperm whales in that area are indicative of their sharing of culture, which he defines as what information a creature passes on to those around them, and which potentially is passed on through generations.

“This pattern is more like agriculture, a new idea which develops and becomes really important,” Whitehead said. “I’m really interested in this diversity of culture in the whales, and this is a wonderful example of it.”

But despite the sudden shift in sperm whale safety in the 19th century, Whitehead said that more advanced whaling technologies — more powerful boats, explosive harpoon guns — eventually became too much for sperm whales to fight, though he said that they tried.

“Of course, none of it works,” he said. “The modern whalers are totally lethal. The whales cannot get away.”

Whitehead said he’s still seeing ways in which communities of sperm whales are sharing their culture to others, including learning how to safely harvest food from fishing lines, and is hopeful they’ll continue to adapt to their rapidly changing environment.

“We’re still affecting the ocean,” he said. “Whether they’re learning about those things and how to deal with them, we don’t know. But hopefully they are.“

(Source: National Post)

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