Sperm Whale (Physeter macrocephalus): Facts, Size and Diving

What does a sperm whale look like?

The sperm whale is hard to mistake for any other animal. Its enormous, box-shaped head makes up a quarter to a third of its body length, and a long, narrow lower jaw hangs beneath it. The skin is dark gray to brownish gray and often deeply wrinkled behind the head, which whale watchers compare to a prune. The lips and the inside of the mouth are often white.

Instead of a tall dorsal fin, the sperm whale has a low, thick hump about two-thirds of the way along its back, followed by a row of smaller bumps. The tail flukes are broad, thick and triangular, and the whale often lifts them high into the air as it starts a deep dive. Nicks and scars along the edge of the flukes let researchers recognize individual whales from photographs.

The single blowhole sits near the front of the head and is shifted to the left. As a result, the sperm whale’s spout is bushy and angled forward and to the left at about 45 degrees, so experienced observers can identify the species from a long way off.

The lower jaw holds about 18–26 cone-shaped teeth on each side, each weighing up to about 1 kg (2.2 lb). They fit into sockets in the upper jaw, whose own small teeth rarely break through the gums.

How big is a sperm whale?

The sperm whale is one of the most extreme examples among mammals of a size difference between the sexes. Mature males are typically 30–50% longer than females and about three times as heavy.

Calves are born at about 3.5–4.5 m (11–15 ft) long. Females stop growing at around 11 m (36 ft) and rarely exceed 12 m (39 ft), but males keep growing until they are about 50 years old.

Whaling records include claims of sperm whales 20 m (66 ft) long or more, and the whale that sank the whaleship Essex was said to measure about 26 m (85 ft). Most such figures are thought to be exaggerations or measurements taken along the curve of the body. About 95% of sperm whales in whaling records measured under 16 m (52 ft).

The spermaceti organ and the largest brain on Earth

The whale’s name comes from spermaceti, a liquid wax inside its head that early whalers mistook for semen. The spermaceti organ, a tough barrel of tissue called the case, can hold about 1,900 liters (500 US gallons) of this oil. Below it lies the “junk”, a stack of oil-filled compartments that works like the melon on a dolphin’s forehead.

Together, these structures make the most powerful sound system in the animal kingdom. Air pushed through a pair of lips at the front of the nose, called phonic lips, produces a click. The sound travels back through the spermaceti organ, bounces off an air sac in front of the skull and is focused forward through the junk. Sperm whale clicks have been measured at up to 236 decibels underwater, the loudest sound recorded from any animal, as explained in loudest animals.

Other ideas about the spermaceti organ are still debated. Some researchers suggested that the whale cools or warms the wax to sink or rise more easily, or that males use their massive heads as battering rams, but the sound-making role is by far the best supported.

Behind the organ sits the largest brain known for any animal, living or extinct. It averages about 7 kg (15.6 lb), more than five times the weight of a human brain. Compared with the size of the whale’s body, though, the brain is not unusually large, and size alone says little about intelligence.

Where do sperm whales live?

Sperm whales live in every ocean, from the equator to the edges of the Arctic and Antarctic pack ice, one of the widest ranges of any mammal. They prefer deep, ice-free water more than 1,000 m (3,300 ft) deep and are most common along continental slopes, around underwater canyons and near oceanic islands where the seabed drops away steeply. They live in the Mediterranean but not in the Black Sea.

Males and females lead different lives. Females and their young stay in tropical and warm-temperate waters all year, while adult males travel to cold, food-rich waters at high latitudes, such as off Norway, Alaska and the Antarctic, and return to warmer seas to breed.

Good places to see them include the Azores, the Caribbean island of Dominica, Kaikōura in New Zealand and Andenes in northern Norway, where deep water lies close to shore. Guides often use underwater microphones to listen for the whales’ clicks before they surface.

What do sperm whales eat?

Sperm whales eat mostly squid. In many studies, the bulk of their prey is medium-sized deep-sea squid weighing well under 1 kg (2.2 lb), but they also eat giant squid, colossal squid in the Antarctic, octopuses, deep-sea fish, rays and sharks. NOAA estimates that a sperm whale eats about 3–3.5% of its body weight each day. How the famous clashes with giant squid really work is covered in Do sperm whales fight giant squid?

They hunt in total darkness using echolocation. A typical foraging dive reaches about 400–1,200 m (1,300–3,900 ft) and lasts around 45 minutes. The whale clicks steadily as it searches, then speeds up into a rapid “creak” as it closes in on prey. Tags show that sperm whales sometimes hunt upside down, perhaps to see squid outlined against the faint light above. After a dive, the whale typically spends about 9 minutes breathing at the surface before going down again. Record depths and the tricks whales use to survive them are explained in How deep can whales dive?

Exactly how they catch squid is uncertain. Well-fed sperm whales have been found with missing teeth or deformed jaws, so many scientists think they mainly suck prey into the mouth. In the Gulf of Alaska, some whales have learned to shake sablefish off fishing lines.

Clicks, codas and communication

Sperm whales use four main kinds of clicks. Regular clicks are for echolocation, creaks are rapid bursts used when homing in on prey, slow clicks are made by adult males, especially on breeding grounds, and codas are short, rhythmic patterns, usually of about 3 to 12 clicks, used for communication.

Codas are learned within the family. Groups of families that share the same coda “dialect” form vocal clans, and whales from different clans tend not to mix even where their ranges overlap. Around Dominica, where a long-term research project has followed families since 2005, there are two main clans. In 2024, researchers analyzing thousands of recorded codas reported that whales vary the rhythm and tempo of codas in subtle, combinable ways, but what the codas mean is still unknown.

Family life and behavior

Female sperm whales live in stable family groups called social units, which NOAA puts at about 12 females and their young on average, and members may stay together for decades. When mothers dive, other members of the unit stay near the surface with the calves, a form of babysitting, and calves may suckle from females other than their mother.

Young males leave their family between about 4 and 21 years of age. They join loose groups of males of similar size, called bachelor groups, which shrink as the males age. The largest males are usually alone and visit the families mainly to breed.

When orcas threaten a group, the adults gather around the calves. Often they form a circle with their heads pointing inward and their powerful tails outward, known as the marguerite formation after the daisy-like shape. Sperm whales also take short naps while hanging vertically just below the surface, described in How do whales sleep?

Reproduction and lifespan

Females become mature at around 9 years of age. Pregnancy lasts 14–16 months and produces a single calf, usually once every five to seven years and sometimes much less often. Calves start eating solid food before they are a year old but keep nursing for several years.

Males become sexually mature between about 10 and 20 years old, but most do not breed successfully until their late twenties, when they are big enough to compete. Sperm whales can live 60–70 years or more. Scientists estimate their age by counting growth layers in the teeth, much like tree rings.

Predators and threats

Healthy adult males have no natural predators. Orcas sometimes attack family groups, usually trying to separate and kill a calf, and pilot whales and false killer whales occasionally harass them.

People are the bigger threat. Sperm whales can be hit by ships while resting at the surface, become tangled in fishing gear, swallow plastic and other debris, and be disturbed by underwater noise from shipping and industry. The small population in the Mediterranean Sea is assessed separately by the IUCN as Endangered.

Whaling, Moby-Dick and conservation status

Sperm whales were hunted heavily from the 18th century onward. Spermaceti made fine candles and lamp oil, sperm oil lubricated machinery, and ambergris, a rare substance from the whale’s gut, was prized by perfumers, as explained in What is ambergris? At least 770,000 sperm whales were killed in the 20th century alone, most of them between 1946 and 1980.

Whaling also produced the sperm whale’s fearsome image. On 20 November 1820, a large bull rammed and sank the Nantucket whaleship Essex in the Pacific, an event that helped inspire Herman Melville’s 1851 novel Moby-Dick. The fictional white whale also drew on tales of a real pale sperm whale nicknamed Mocha Dick.

The International Whaling Commission gave sperm whales full protection in 1985, and commercial whaling largely ended in the 1980s. The IUCN now lists the species as Vulnerable, the United States lists it as endangered, and international trade in its products is banned under CITES Appendix I. A 2002 estimate put the world population at about 360,000, around a third of pre-whaling numbers. Because females have so few calves, recovery is slow.