Study finds South China Sea sperm whales share vocal patterns with Pacific pods

More than 2,000 meters beneath the surface of the South China Sea, sperm whales are using sharp clicking sounds to communicate in the dark.

These clicks, sometimes compared to Morse code, are among the basic sounds sperm whales use to exchange information and recognize one another. In social settings, the whales combine several clicks into short, repeated rhythmic sequences known as codas.

Sperm whales, the largest toothed whales on Earth, are also known to have distinct vocal "dialects." Different groups use different sets of codas, much like regional speech patterns in humans. Scientists say these vocal patterns are learned rather than innate, with young whales going through a babbling-like stage as they try different coda types before mastering those used by their group.

The findings were published online in June in The Journal of the Acoustical Society of America. The study was led by Li Songhai's team at the Institute of Deep-sea Science and Engineering under the Chinese Academy of Sciences, following about seven years of research into the vocal behavior of sperm whales in the South China Sea.

From 2019 to 2025, the team conducted eight scientific expeditions in the region, recording 13 sperm whale sightings and more than 1,200 minutes of acoustic data.

Li said regular sperm whale clicks are produced in the head and reflected multiple times through different structures, creating a series of pulses. By analyzing the length of these pulses, researchers can estimate the body length of individual whales.

The results showed that most sperm whales detected in the South China Sea were relatively small females and immature individuals, suggesting that the warm tropical waters may serve as an important nursing area for the species.

If regular clicks help answer the question of "who is here," codas may help reveal "which group they belong to."

Researchers found that the vocal patterns of sperm whales in the South China Sea are highly similar to those recorded in distant areas including the Galapagos Islands, Peru, Chile, Tonga and Papua New Guinea. The similarity suggests the South China Sea whales may share historical links with sperm whale groups across the wider Pacific.

Sperm whales are listed as vulnerable on the International Union for Conservation of Nature Red List. They face threats from human activities including ship strikes, entanglement in fishing gear and underwater noise.

The study provides important baseline acoustic data for sperm whale conservation in the South China Sea, researchers said.