Largest of the toothed whales, sperm whales are unique and easy to identify. They have unusually large heads (one-third their body length); narrow, almost hidden lower jaws and off-center blows. Their dark brown to dark gray skin often includes narrow white markings around their mouths and the skin on the back of the whale is usually knobby, giving them a prunelike appearance. That bulging forehead (melon) contains spermaceti, a semi-liquid white oil. Early whalers thought the oil was sperm, hence the sperm whales'common name.
The male and female sperm whales differ greatly. Males are typically 30 to 50 percent larger than females and weigh about twice as much. Males' lower jaws have 20 to 30 pairs of large (up to 10 inches long) cone-shaped teeth that are designed for grasping slippery prey such as squid, rather than cutting. Females have smaller and fewer teeth.
In the past, whalers hunted sperm whales for spermaceti, fine oil used to make high-quality candles and lubricants. Estimates vary widely regarding the present population of sperm whales. The American Cetacean Society states, "Most recent estimates suggest a global population of 300,000 animals, down from about 1,100,000 before whaling." The sperm whale population is slow to recover because these animals mature late and have few offspring. Sperm whales are listed on the U.S. Endangered Species List. Hunting of sperm whales is banned nearly worldwide.
The sperm whale was celebrated as the "great white whale" named Moby Dick in Herman Melville's novel of that name.
It is hypothesized that the sharp beaks of consumed squid lodged in the whale's intestine leads to the production of the waxy substance called ambergris. Lumps of ambergris are found in the intestines of dead sperm whales or as flotsam on the sea or sea coast. When fresh, it has a foul smell, but when dried, it has a strong, musklike odor. Its primary use was as a fixative in fine perfumes, and ambergris was once worth its weight in gold. Today it's illegal to possess, buy or sell ambergris in the United States.
Sperm whales "see" in the dark depths of the ocean by using sonar or echolocation. The melon focuses sound waves toward objects and prey. When sound waves echo back, they tell the whales the objects' positions, distances and sizes. Authorities believe that sperm whales can produce a powerful sonic blast by using the spermaceti organ as an amplifier. A strong blast stuns squid, which allows whales to swallow squid whole. (Giant squid may reach 60 feet in length.) Whalers have found sperm whales with no teeth or with broken jaws, yet they have a belly full of squid. Were the squid stunned by a sonic blast?
Sperm whales can dive to 9,850 feet (3000 m) and stay under water for up to two hours.