Endangered Spotlight: Sperm Whale (Physeter catodon)

Sperm whales. Photo: NOAA

By Stefan Marti and Mary Jane Schramm

Despite being the largest toothed animals on the planet and inhabiting all of the world’s oceans, sperm whales are seldom seen by the naked human eye.  This is because they spend 90% of their lives deep underwater, searching for food in the ocean darkness.

Although sperm whales live and feed in our Sanctuary, the rare times we do spot them, they are either beyond the edge of the Continental Shelf or dead and washed ashore.  This happened last March when a 40-ton whale washed up in Pt .Reyes. They have a complex social structure, with females forming distinctive groups, while adult males lead a far more solitary existence.

Physical Description

Although Herman Melville’s Moby Dick was a white whale, most sperm whales are dark gray to brownish-gray in color. Occasionally, the interior of the mouth is bright white, and some whales have white patches on the belly.

The species is distinguished by its extremely large head, which takes up to 25 to 35% of its total body length. Much of its exceptionally large brain is given over to processing acoustic signals. Its flippers are paddle-shaped and small compared to the size of the body, and its fluke is triangular in shape. It has a small rounded dorsal fin.

Male whales are considerably larger than females, reaching 50 feet in length and weighing up to 45 tons.  Females reach 36 feet and weigh up to 15 tons.

Unlike other whales, where the blowhole shoots straight up, the sperm whale's blowhole is at an angle on the left side of its head. This causes its blow to shoot out to the left and forward, and makes them even harder to spot in the ocean, as their spray only shoots 6 to 8 feet up in the air, and is easily missed from a distance. When the whale dives, it closes the blowhole to keep the water out.

Because of their ability to store oxygen in their blood and muscles, adult sperm whales can stay submerged well over an hour without taking a breath. They have been tracked by sonar diving to depths of 3,900 feet. Equally amazing is how fast they reach that depth; some have descended at 550 feet per minute.

Hunting

Deep underwater, where there is no light, sperm whales hunt using echolocation. The whale produces a series of loud clicks which travel through the water and bounce off objects. The reflected sound bounces back to the whale, which interprets the echo. Using this technique, many kinds of whales and dolphins can "see" in complete darkness.

With echolocation, sperm whales can determine the size, direction and distance of the prey—usually giant squid or fish. The only problem is that echolocation can also give away the presence of the whale if the prey hears it. Lucky for sperm whales, the giant squid can't hear.

Endangered Status

The sperm whale gets its name from the spermaceti organ, an extremely powerful, highly directional sonar system, which fills most of its huge head. During the 18th and 19th centuries, New England whalers sought out the sperm whale for the valuable spermaceti oil, which makes an exceptionally fine lubricant.  From 1800 to 1987, somewhere between 500,000 and 1,000,000 sperm whales were killed by humans.  In 1970, the sperm whale became protected under the Endangered Species Act and the Marine Mammal Protection Act.

Today, because of their general offshore distribution, sperm whales have one of the most stable populations of all whales. And if you are lucky, you may spot one of their crooked sprays on a FMSA whale watching trip.