Sperm Whales: Physeteridae

The family of sperm whales contains the largest toothed whale—the giant sperm whale—and two smaller toothed whales. All are dark gray above, lighter gray on the belly, and have erupted (visible) teeth only in the lower jaw. Although these animals range in size and weight from 9 feet (2.7 meters) and 600 pounds (270 kilograms), to 60 feet (18.3 meters) and 125,000 pounds (57,000 kilograms), they have other physical features in common.

All members of this family have a spermaceti (spur-mah-CEE-tee) organ in their forehead. This produces a waxy substance called spermaceti. At the animal's body temperature, it is a clear yellowish liquid. After processing, it becomes a white waxy solid. It was prized in the 1800s and 1900s for making smoke-free candles and soap and as a way to waterproof cloth (called oilskins). Later it was used in cosmetics, ointments, as a lubricant for watches and machinery, and in automatic transmission fluid. Today it has been replaced by human-made oils and waxes.

The purpose of the spermaceti organ is not clear. Some scientists think that it helps the whale regulate its buoyancy, or ability to sink or float, during dives. Others believe that it is used to focus the sounds made for echolocation (eck-oh-loh-KAY-shun) and communication. Echolocation involves making sounds that bounce off objects. Sense organs pick up the echo or reflected sound and use information about the timing, direction, and strength to determine the location of objects. Echolocation allows whales to find food in water so deep that there is no natural sunlight.

Members of the sperm whale family share other physical characteristics. Their heads are asymmetrical, meaning that if they were divided in half along the long axis of the body, the features in the right half would look different from the features in the left half. This is not common in mammals. As a result, a single S-shaped blowhole that allows the whale to breathe is located on the left side of the body. The left nasal passage is used for breathing, but the right one is narrower and is thought to be used to produce sounds.