How deep can a sperm whale dive, and how can researchers possibly learn this about an animal that spends most of its life far out of sight below the surface? A sperm whale can dive deeper than 3,000 feet (about 1,000 metres), and an analysis of stomach contents suggests that sperm whales can dive beyond 3,000 m (1.9 miles).

One effective way to follow a diving whale is simply to listen to it. Listening to sperm whales 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.

Listening works because sperm whales are so persistent in their use of sound. In echolocation, an animal makes a sound that travels through the water, bounces off an object and comes back as an echo, and sperm whales produce echolocation clicks almost continuously while foraging, which makes listening a good way to study them.

The clicks reveal considerably more than a whale's location. 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, and the clicks themselves are by far the loudest sounds recorded from any biological source.

Whales also use clicks to communicate with one another. Codas are stereotyped sequences of 3 to 40 broadband clicks, and sperm whales exchange codas when socialising or between long, deep foraging dives.

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

The whales also influence the ocean well beyond their own social groups. Southern Ocean sperm whales release iron-rich faeces into the sunlit surface water, an estimated 50 tonnes of iron each year.

Sperm whales are hard to count because they spend long periods under water and can be missed during sightings. In 2002 scientists scaled up surveys of 24% of the habitat to estimate about 360,000 sperm whales worldwide.

Commercial whaling from about 1800 to the 1980s greatly reduced sperm whale numbers around the world, and sperm whale hunting reached two peaks, one in the 1840s and one in the 1960s. The International Whaling Commission placed a moratorium on commercial whaling in 1986.

Another estimate looks back to the years before whaling. 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.

Numbers have also fallen in some places. In the eastern Caribbean, the number of adult sperm whales fell in 12 of 16 social units followed from 2005 to 2015.

As of November 2026, the sperm whale is listed as endangered under the Endangered Species Act in the United States and as vulnerable on the IUCN Red List.

NOAA says that sperm whale populations are still recovering and that their numbers are likely increasing, as of November 2026. The recovery plan for the sperm whale, published in December 2010, aims to delist the species, with an interim goal of moving it from endangered to threatened.

Words to know

• foraging: looking for food
• echolocation: finding by sound
• codas: click patterns
• clans: coda groups
• moratorium: official pause