A mysterious organ in the sperm whale's head gives it the power to sink ships

A survivor of the shipwreck that inspired the novel Moby Dick had a theory about how a sperm whale could destroy a vessel many times its size – 200 years later, he's been proved right.

On the morning of 20 November 1820, 15-year-old Thomas Nickerson had just escaped from one whale punching a hole in the side of his boat. Rowing quickly back to the main whaling ship as the boat took on water, Nickerson and his companions thought they were safe.

But, taking the helm of the whaleship Essex, Nickerson saw another, much larger whale speeding straight towards them. Alerting Owen Chase, the ship's first mate, there was shouting and alarm among the crew followed by "a tremendous crash", Nickerson wrote 50 years later. 

The whale struck the Essex with such force that all the men were knocked off their feet. The whale swam 900ft (270m) away from the boat, turned around sharply and came back at its utmost speed. With that second collision, it stove in the entire bow. The whaleship Essex was sunk. 

If it sounds like a novel, it's because the shipwreck of the Essex inspired Herman Melville's Moby Dick. Today, 175 years after publication of the book, research has revealed the mystery of how a sperm whale can take down a ship several times its size. As it turns out, the answer was correctly predicted more than 200 years ago by none other than Chase, the first mate of the Essex. 

Ironically, the whales' superpower seems to reside in the same place as the precious oil chased by the whalers: inside its head.

A mysterious cranial organ

Sperm whales have a huge head. In fact, their heads make up around a third of their overall body length. Weighing up to 9kg (20lbs), they boast the biggest brain of all animals on Earth.

Within the forehead is a large fatty, squishy organ called the spermaceti – unique to their species. This organ is filled with an oily substance also called spermaceti, which gained its name because whalers thought it was semen.

The spermaceti was highly sought after by whalers as the oil provided a high-quality fuel, and could be congealed into products like soaps and candles. During the 18th and 19th Centuries, around 300,000 sperm whales were killed worldwide.

Despite this extensive harvesting of the sperm whales' spermaceti, we still don't fully understand its function.

One theory sees the spermaceti as a combat tool.

"This wasn't originally our hypothesis, it was Owen Chase's", says retired evolutionary biologist Dave Carrier. "An 18th-Century whaler argued that the forehead was a weapon, and we set out to test........

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