In the murky waters off the coast of Malaysia, dolphins navigate not with their eyes but with sounds — and it is precisely these sounds that scientists are now recording in order to understand how humans are changing their world.
Saliza Bono, a bioacoustician at the organization MareCet, studies the voices of Indo-Pacific humpback dolphins and Irrawaddy dolphins (Sousa chinensis and Orcaella brevirostris). Her work began with simple curiosity: as a child she saw a dolphin for the first time in Australia and was amazed that this was a mammal breathing with lungs underwater. Later, upon learning about killer whale dialects, she decided to devote her life to bioacoustics.
The coastal waters of Malaysia are home to 27 species of marine mammals. Many of them, like the Ganges river dolphin, are almost blind and depend entirely on echolocation and whistles. Noise from boats and fishing vessels disrupts their communication: when a vessel comes closer than 500 meters, the frequency of their whistles drops sharply and does not immediately recover.
The main threats are bycatch in nets and noise pollution. To combat bycatch, MareCet is testing acoustic pingers: they emit a high-frequency signal audible only to marine mammals and warn dolphins of invisible nets. The fishermen do not lose their catch, and the dolphins do not lose their lives.
Funding remains an acute problem: marine hydrophones are several times more expensive than land-based ones. At the same time, Malaysians' awareness of local dolphins is still low — "if you don't know them, you don't love them," as they say at the organization. Gradually, developers are beginning to consult scientists before starting work in order to assess the acoustic environment.
Dolphins serve as indicators of the ocean's health: their presence shows that the ecosystem is still coping with the pressure.
