Well, Why are Sperm Whales Called Sperm Whales?

Written by Cindy Rasmussen
Published: November 23, 2021


You may think that the sperm whale got its name from the shape of its body or some mating habit, but the truth is sperm whales are named for something entirely different. The name “sperm whale” comes from the substance found in an organ in the whale’s head that is full of spermaceti oil. This oil has a white semi-liquid appearance and early whalers in the early 19th century believed it was the whale’s stash of sperm. They were incorrect but the name stuck.

Why do sperm whales have spermaceti oil?

Sperm whales in a social gathering, <a href=
Sperm whales in a social gathering, Indian Ocean, Mauritius.

Sperm whales are the largest of the toothed whales. They can grow to be 52 feet long and weigh up to 90,000lbs. Scientists are still unsure why they have a “head full of oil” but have a few speculations. The spermaceti organ is enormous and located in the top half of the whale’s head and continues back to almost half of the whale’s body covering 40% of its body. This organ holds 530 gallons of spermaceti oil! Think about a dunk tank at the fair, those typically hold 500 gallons of water, similar to the amount of oil present in the sperm whale!

So why do sperm whales have that much spermaceti oil? Two hypotheses exist and may work in tandem. The first idea is that it is used similar to a melon in dolphins, used to transmit and focus sound. Toothed whales, as opposed to baleen whales, use echolocation as a tool to locate prey, avoid predators and to navigate. They send out noises or clicks and then wait for the noise to bounce off objects and send back a noise wave.

Another theory as to the purpose of the giant vat of spermaceti oil is that it is used as a buoyancy system assisting in the whales deep dives and returns to the surface. Sperm whales are some of the deepest diving animals on the planet and can routinely make dives of 3,000 feet. The purpose of these dives is to find food and their favorite food, the giant squid. Sperm whales are mammals and therefore breathe air; they do not have gills, so they have to return to the surface of the ocean to get air. So how can they dive so deep? They have large lungs that can hold enough oxygen to support a 90 minute dive!

What did whalers use spermaceti oil for?

Sperm whale and her calf swimming at the surface, Indian Ocean, Mauritius.
Sperm whale and her calf swimming at the surface, Indian Ocean, Mauritius.

The value in the spermaceti oil was that when it cooled it made a waxy substance that could be used in a variety of products. It was originally valued because it was thin and could resist pressure and temperatures, making it an ideal substance to make candles. Whalers sold it for use as lighting in oil lamps and as a lubricant and later for use in making cosmetics, detergents and soap. During the industrial revolution much of the machinery required lubricants to make sure everything ran smoothly and the whale oil provided exactly what they need for this.

Why not change the name of the sperm whale now that we know?

Sperm whale, Indian Ocean
Sperm whale, Indian Ocean

There are all kinds of animals that have been misnamed and few lawyers fighting on their behalf. Think about the cousin of the sperm whale, the killer whale. Killer whales are actually a part of the dolphin family and may not appreciate their aggressive namesake. The whale shark is actually a shark, not a whale and may be upset with having to always explain that. For now the sperm whale name will have to deal with its namesake.