Sperm whale clicks are by far the loudest sounds recorded from any biological source. Sperm whales use echolocation to find food, and they produce echolocation clicks almost continuously while foraging.

In echolocation, an animal makes a sound that travels through the water, bounces off an object and comes back as an echo. Sperm whale clicks bounce around inside the whale's head, so the time between pulses in a click can be used to estimate the size of its head and body.

The same sounds help answer how deep a sperm whale can dive. A sperm whale can dive deeper than 3,000 feet (about 1,000 metres). Listening with microphones in the western North Atlantic showed foraging dives with bottom phases at depths of 400-800, 800-1200, or more than 1200 m, and analysis of stomach contents suggests sperm whales can dive beyond 3,000 m (1.9 miles).

Sperm whales are the only living members of their genus, and the pygmy and dwarf sperm whales of the genus Kogia are thought to be their closest relatives. A giant extinct sperm whale from the Middle Miocene of Peru, about 12 to 13 million years old, was described from a skull with teeth and a jaw. That fossil sperm whale had a head 3 m long, and its teeth were more than 36 cm long.

Commercial whaling from about 1800 to the 1980s greatly reduced sperm whale numbers around the world, and the International Whaling Commission placed a moratorium on commercial whaling in 1986. A 2022 study found that whaling, by affecting the sex ratio or the social cohesion of females, reduced sperm whale recovery rates well after whaling ceased.

In 2002 scientists scaled up surveys of 24% of the habitat to estimate about 360,000 sperm whales worldwide. A 2022 population model estimated about 844,761 sperm whales in 2022, down from about 1,949,698 before whaling, with much uncertainty about these numbers.

Eastern Caribbean sperm whale social units shrank by about 4.5% a year from about 2010, and the study found no well-substantiated cause. In the eastern Caribbean, the number of adult sperm whales fell in 12 of 16 social units followed from 2005 to 2015.

Southern Ocean sperm whales release iron-rich faeces into the sunlit surface water, an estimated 50 tonnes of iron each year. Scientists estimate that the 12,000 sperm whales of the Southern Ocean remove about 200,000 more tonnes of carbon from the atmosphere than they add by breathing.

NOAA says sperm whales are expected to be more resilient to climate change than species with narrower habitats, because their feeding range is likely the greatest of any species on earth. As of November 2026, NOAA also says their populations are still recovering and their numbers are likely increasing.

Codas are stereotyped sequences of 3 to 40 broadband clicks. Sperm whales exchange codas when socialising or between long, deep foraging dives, and certain features of codas may be unique to each whale in a group, so individuals can be told apart.

Sperm whale codas fall into six acoustic clans, five in the Pacific and one in the Caribbean, whose ranges span thousands of kilometres. Whales in the eastern Caribbean were found to share 21 coda types, and two of them made up 65% of the codas recorded.

Researchers found that sperm whale codas have two features that depend on context, which they named rubato and ornamentation.

A 2024 study proposed a sperm whale phonetic alphabet in which 18 rhythm types and 5 tempo types combine with rubato and ornamentation. The study estimated that the sperm whale coda system could carry up to twice the information per coda that earlier work assumed.

The 2024 coda study did not look at what the codas mean. It says playback experiments with wild whales are needed to link features to meaning.

Project CETI is a nonprofit program that uses machine learning, robotics and underwater acoustics to try to understand and translate sperm whale communication.

Words to know

• echolocation: finding by sound
• codas: click patterns
• genus: group
• moratorium: official pause
• rubato: stretched timing