Sperm Whales
Physeter macrocephalus
A sperm whale's head is roughly a third of its body and holds the largest brain of any animal that has ever existed. They hunt in darkness, at depths where sunlight never reaches, using sound.
They were also the species that built the whaling industry. The oil in their heads burned cleaner and brighter than anything else available in the nineteenth century, and the hunt for it drove ships around the world.
- Length
- Males up to 60 ft (18 m); females smaller
- Weight
- Up to 45 tons
- Dive depth
- Recorded to 7,380 ft (2,250 m)
- Dive duration
- Typically 30–60 min; up to 90
- Diet
- Deep-water squid and fish
Conservation status
- US Endangered Species Act
- Endangered (listed 1970)
- IUCN Red List
- Vulnerable
Global numbers have been estimated at roughly 736,000 — far more than the great whales in real crisis, but well below pre-whaling levels. Some isolated groups are in much worse shape: the genetically distinct Mediterranean population is assessed as Endangered with fewer than 2,500 animals.
Hunting in the dark
Sperm whales feed far below the reach of light, mostly on squid. They find it by echolocation, producing clicks that are among the loudest sounds made by any animal.
A typical foraging dive goes to between 1,000 and 2,000 metres and lasts thirty to sixty minutes. Dives have been recorded to around 2,250 metres and durations of up to ninety minutes. They are not quite the deepest-diving mammal — that record belongs to Cuvier's beaked whale, at close to 3,000 metres — but few animals come near them.
The organ they were named for
The forehead of a sperm whale contains the spermaceti organ, a mass of waxy oil. Whalers who first cut into it thought it was seminal fluid, which is where the name comes from.
Its actual function appears to be acoustic — focusing and directing the clicks the animal hunts with. To the whaling industry it was simply the finest oil in the world: it burned without smoke or smell, and it lubricated machinery at temperatures that ruined other oils. Sperm whale oil lit street lamps and lighthouses, and later found its way into everything from watches to automatic transmissions.
Societies of females
Females and their young live in stable social units of roughly ten animals, and those units associate with others they know. Members share the care of calves — a calf cannot follow its mother to feeding depth, so adults take turns staying at the surface with it while the others hunt.
Males leave these groups as they mature and range toward the poles, living largely alone and returning to warmer waters to breed. Like orcas, sperm whale groups have distinctive patterns of clicks, called codas, that differ between clans.
What hunting them cost
Sperm whales were hunted through the nineteenth century by sail and harpoon, then far more efficiently through the twentieth by factory ships. Estimates suggest the species was reduced to a fraction of its original numbers.
They are still recovering, and recovery is slow — a female produces a single calf every four to six years. Today the pressures are entanglement, ship strikes, plastic and other debris, and underwater noise, which matters enormously to an animal that lives by sound.
Sources
Population figures and listing statuses change. These were checked in August 2026 — follow the links above for the current position.